path: root/control-spec.txt

                   TC: A Tor control protocol (Version 1)

Table of Contents

    0. Scope
    1. Protocol outline
        1.1. Forward-compatibility
    2. Message format
        2.1. Description format
            2.1.1. Notes on an escaping bug
        2.2. Commands from controller to Tor
        2.3. Replies from Tor to the controller
        2.4. General-use tokens
    3. Commands
        3.1. SETCONF
        3.2. RESETCONF
        3.3. GETCONF
        3.4. SETEVENTS
        3.5. AUTHENTICATE
        3.6. SAVECONF
        3.7. SIGNAL
        3.8. MAPADDRESS
        3.9. GETINFO
        3.10. EXTENDCIRCUIT
        3.11. SETCIRCUITPURPOSE
        3.12. SETROUTERPURPOSE
        3.13. ATTACHSTREAM
        3.14. POSTDESCRIPTOR
        3.15. REDIRECTSTREAM
        3.16. CLOSESTREAM
        3.17. CLOSECIRCUIT
        3.18. QUIT
        3.19. USEFEATURE
        3.20. RESOLVE
        3.21. PROTOCOLINFO
        3.22. LOADCONF
        3.23. TAKEOWNERSHIP
        3.24. AUTHCHALLENGE
        3.25. DROPGUARDS
        3.26. HSFETCH
        3.27. ADD_ONION
        3.28. DEL_ONION
        3.29. HSPOST
        3.30. ONION_CLIENT_AUTH_ADD
        3.31. ONION_CLIENT_AUTH_REMOVE
        3.32. ONION_CLIENT_AUTH_VIEW
        3.33. DROPOWNERSHIP
        3.34. DROPTIMEOUTS
    4. Replies
        4.1. Asynchronous events
            4.1.1. Circuit status changed
            4.1.2. Stream status changed
            4.1.3. OR Connection status changed
            4.1.4. Bandwidth used in the last second
            4.1.5. Log messages
            4.1.6. New descriptors available
            4.1.7. New Address mapping
            4.1.8. Descriptors uploaded to us in our role as authoritative dirserver
            4.1.9. Our descriptor changed
            4.1.10. Status events
            4.1.11. Our set of guard nodes has changed
            4.1.12. Network status has changed
            4.1.13. Bandwidth used on an application stream
            4.1.14. Per-country client stats
            4.1.15. New consensus networkstatus has arrived
            4.1.16. New circuit buildtime has been set
            4.1.17. Signal received
            4.1.18. Configuration changed
            4.1.19. Circuit status changed slightly
            4.1.20. Pluggable transport launched
            4.1.21. Bandwidth used on an OR or DIR or EXIT connection
            4.1.22. Bandwidth used by all streams attached to a circuit
            4.1.23. Per-circuit cell stats
            4.1.24. Token buckets refilled
            4.1.25. HiddenService descriptors
            4.1.26. HiddenService descriptors content
            4.1.27. Network liveness has changed
            4.1.28. Pluggable Transport Logs
            4.1.29. Pluggable Transport Status
    5. Implementation notes
        5.1. Authentication
        5.2. Don't let the buffer get too big
        5.3. Backward compatibility with v0 control protocol
        5.4. Tor config options for use by controllers
        5.5. Phases from the Bootstrap status event
            5.5.1. Overview of Bootstrap reporting.
            5.5.2. Phases in Bootstrap Stage 1
            5.5.3. Phases in Bootstrap Stage 2
            5.5.4. Phases in Bootstrap Stage 3
        5.6 Bootstrap phases reported by older versions of Tor

0. Scope

  This document describes an implementation-specific protocol that is used
  for other programs (such as frontend user-interfaces) to communicate with a
  locally running Tor process.  It is not part of the Tor onion routing
  protocol.

  This protocol replaces version 0 of TC, which is now deprecated.  For
  reference, TC is described in "control-spec-v0.txt".  Implementors are
  recommended to avoid using TC directly, but instead to use a library that
  can easily be updated to use the newer protocol.  (Version 0 is used by Tor
  versions 0.1.0.x; the protocol in this document only works with Tor
  versions in the 0.1.1.x series and later.)

      The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
      NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED",  "MAY", and
      "OPTIONAL" in this document are to be interpreted as described in
      RFC 2119.

1. Protocol outline

  TC is a bidirectional message-based protocol.  It assumes an underlying
  stream for communication between a controlling process (the "client"
  or "controller") and a Tor process (or "server").  The stream may be
  implemented via TCP, TLS-over-TCP, a Unix-domain socket, or so on,
  but it must provide reliable in-order delivery.  For security, the
  stream should not be accessible by untrusted parties.

  In TC, the client and server send typed messages to each other over the
  underlying stream.  The client sends "commands" and the server sends
  "replies".

  By default, all messages from the server are in response to messages from
  the client.  Some client requests, however, will cause the server to send
  messages to the client indefinitely far into the future.  Such
  "asynchronous" replies are marked as such.

  Servers respond to messages in the order messages are received.

1.1. Forward-compatibility

  This is an evolving protocol; new client and server behavior will be
  allowed in future versions.  To allow new backward-compatible behavior
  on behalf of the client, we may add new commands and allow existing
  commands to take new arguments in future versions.  To allow new
  backward-compatible server behavior, we note various places below
  where servers speaking a future version of this protocol may insert
  new data, and note that clients should/must "tolerate" unexpected
  elements in these places.  There are two ways that we do this:

  * Adding a new field to a message:

    For example, we might say "This message has three space-separated
    fields; clients MUST tolerate more fields."  This means that a
    client MUST NOT crash or otherwise fail to parse the message or
    other subsequent messages when there are more than three fields, and
    that it SHOULD function at least as well when more fields are
    provided as it does when it only gets the fields it accepts.  The
    most obvious way to do this is by ignoring additional fields; the
    next-most-obvious way is to report additional fields verbatim to the
    user, perhaps as part of an expert UI.

  * Adding a new possible value to a list of alternatives:

    For example, we might say "This field will be OPEN, CLOSED, or
    CONNECTED.  Clients MUST tolerate unexpected values."  This means
    that a client MUST NOT crash or otherwise fail to parse the message
    or other subsequent messages when there are unexpected values, and
    that it SHOULD try to handle the rest of the message as well as it
    can.  The most obvious way to do this is by pretending that each
    list of alternatives has an additional "unrecognized value" element,
    and mapping any unrecognized values to that element; the
    next-most-obvious way is to create a separate "unrecognized value"
    element for each unrecognized value.

    Clients SHOULD NOT "tolerate" unrecognized alternatives by
    pretending that the message containing them is absent.  For example,
    a stream closed for an unrecognized reason is nevertheless closed,
    and should be reported as such.

    (If some list of alternatives is given, and there isn't an explicit
    statement that clients must tolerate unexpected values, clients still
    must tolerate unexpected values. The only exception would be if there
    were an explicit statement that no future values will ever be added.)

2. Message format

2.1. Description format

  The message formats listed below use ABNF as described in RFC 2234.
  The protocol itself is loosely based on SMTP (see RFC 2821).

  We use the following nonterminals from RFC 2822: atom, qcontent

  We define the following general-use nonterminals:

     QuotedString = DQUOTE *qcontent DQUOTE

  There are explicitly no limits on line length.  All 8-bit characters
  are permitted unless explicitly disallowed.  In QuotedStrings,
  backslashes and quotes must be escaped; other characters need not be
  escaped.

  Wherever CRLF is specified to be accepted from the controller, Tor MAY also
  accept LF.  Tor, however, MUST NOT generate LF instead of CRLF.
  Controllers SHOULD always send CRLF.

2.1.1. Notes on an escaping bug

     CString = DQUOTE *qcontent DQUOTE

  Note that although these nonterminals have the same grammar, they
  are interpreted differently.  In a QuotedString, a backslash
  followed by any character represents that character.  But
  in a CString, the escapes "\n", "\t", "\r", and the octal escapes
  "\0" ... "\377" represent newline, tab, carriage return, and the
  256 possible octet values respectively.

  The use of CString in this document reflects a bug in Tor;
  they should have been QuotedString instead.  In the future, they
  may migrate to use QuotedString instead.  If they do, the
  QuotedString implementation will never place a backslash before a
  "n", "t", "r", or digit, to ensure that old controllers don't get
  confused.

  For future-proofing, controller implementors MAY use the following
  rules to be compatible with buggy Tor implementations and with
  future ones that implement the spec as intended:

    Read \n \t \r and \0 ... \377 as C escapes.
    Treat a backslash followed by any other character as that character.

  Currently, many of the QuotedString instances below that Tor
  outputs are in fact CStrings.  We intend to fix this in future
  versions of Tor, and document which ones were broken.  (See
  bugtracker ticket #14555 for a bit more information.)

  Note that this bug exists only in strings generated by Tor for the
  Tor controller; Tor should parse input QuotedStrings from the
  controller correctly.


2.2. Commands from controller to Tor

    Command = Keyword OptArguments CRLF / "+" Keyword OptArguments CRLF CmdData
    Keyword = 1*ALPHA
    OptArguments = [ SP *(SP / VCHAR) ]

  A command is either a single line containing a Keyword and arguments, or a
  multiline command whose initial keyword begins with +, and whose data
  section ends with a single "." on a line of its own.  (We use a special
  character to distinguish multiline commands so that Tor can correctly parse
  multi-line commands that it does not recognize.) Specific commands and
  their arguments are described below in section 3.

2.3. Replies from Tor to the controller

    Reply = SyncReply / AsyncReply
    SyncReply = *(MidReplyLine / DataReplyLine) EndReplyLine
    AsyncReply = *(MidReplyLine / DataReplyLine) EndReplyLine

    MidReplyLine = StatusCode "-" ReplyLine
    DataReplyLine = StatusCode "+" ReplyLine CmdData
    EndReplyLine = StatusCode SP ReplyLine
    ReplyLine = [ReplyText] CRLF
    ReplyText = XXXX
    StatusCode = 3DIGIT

  Unless specified otherwise, multiple lines in a single reply from
  Tor to the controller are guaranteed to share the same status
  code. Specific replies are mentioned below in section 3, and
  described more fully in section 4.

  [Compatibility note:  versions of Tor before 0.2.0.3-alpha sometimes
  generate AsyncReplies of the form "*(MidReplyLine / DataReplyLine)".
  This is incorrect, but controllers that need to work with these
  versions of Tor should be prepared to get multi-line AsyncReplies with
  the final line (usually "650 OK") omitted.]

2.4. General-use tokens

  ; CRLF means, "the ASCII Carriage Return character (decimal value 13)
  ; followed by the ASCII Linefeed character (decimal value 10)."
  CRLF = CR LF

  ; How a controller tells Tor about a particular OR.  There are four
  ; possible formats:
  ;    $Fingerprint -- The router whose identity key hashes to the fingerprint.
  ;        This is the preferred way to refer to an OR.
  ;    $Fingerprint~Nickname -- The router whose identity key hashes to the
  ;        given fingerprint, but only if the router has the given nickname.
  ;    $Fingerprint=Nickname -- The router whose identity key hashes to the
  ;        given fingerprint, but only if the router is Named and has the given
  ;        nickname.
  ;    Nickname -- The Named router with the given nickname, or, if no such
  ;        router exists, any router whose nickname matches the one given.
  ;        This is not a safe way to refer to routers, since Named status
  ;        could under some circumstances change over time.
  ;
  ; The tokens that implement the above follow:

  ServerSpec = LongName / Nickname
  LongName   = Fingerprint [ "~" Nickname ]

  ; For tors older than 0.3.1.3-alpha, LongName may have included an equal
  ; sign ("=") in lieu of a tilde ("~").  The presence of an equal sign
  ; denoted that the OR possessed the "Named" flag:

  LongName   = Fingerprint [ ( "=" / "~" ) Nickname ]

  Fingerprint = "$" 40*HEXDIG
  NicknameChar = "a"-"z" / "A"-"Z" / "0" - "9"
  Nickname = 1*19 NicknameChar

  ; What follows is an outdated way to refer to ORs.
  ; Feature VERBOSE_NAMES replaces ServerID with LongName in events and
  ; GETINFO results. VERBOSE_NAMES can be enabled starting in Tor version
  ; 0.1.2.2-alpha and it is always-on in 0.2.2.1-alpha and later.
  ServerID = Nickname / Fingerprint


  ; Unique identifiers for streams or circuits.  Currently, Tor only
  ; uses digits, but this may change
  StreamID = 1*16 IDChar
  CircuitID = 1*16 IDChar
  ConnID = 1*16 IDChar
  QueueID = 1*16 IDChar
  IDChar = ALPHA / DIGIT

  Address = ip4-address / ip6-address / hostname   (XXXX Define these)

  ; A "CmdData" section is a sequence of octets concluded by the terminating
  ; sequence CRLF "." CRLF.  The terminating sequence may not appear in the
  ; body of the data.  Leading periods on lines in the data are escaped with
  ; an additional leading period as in RFC 2821 section 4.5.2.
  CmdData = *DataLine "." CRLF
  DataLine = CRLF / "." 1*LineItem CRLF / NonDotItem *LineItem CRLF
  LineItem = NonCR / 1*CR NonCRLF
  NonDotItem = NonDotCR / 1*CR NonCRLF

  ; ISOTime, ISOTime2, and ISOTime2Frac are time formats as specified in
  ; ISO8601.
  ;  example ISOTime:      "2012-01-11 12:15:33"
  ;  example ISOTime2:     "2012-01-11T12:15:33"
  ;  example ISOTime2Frac: "2012-01-11T12:15:33.51"
  IsoDatePart = 4*DIGIT "-" 2*DIGIT "-" 2*DIGIT
  IsoTimePart = 2*DIGIT ":" 2*DIGIT ":" 2*DIGIT
  ISOTime  = IsoDatePart " " IsoTimePart
  ISOTime2 = IsoDatePart "T" IsoTimePart
  ISOTime2Frac = IsoTime2 [ "." 1*DIGIT ]

  ; Numbers
  LeadingDigit = "1" - "9"
  UInt = LeadingDigit *Digit

3. Commands

  All commands are case-insensitive, but most keywords are case-sensitive.

3.1. SETCONF

  Change the value of one or more configuration variables.  The syntax is:

    "SETCONF" 1*(SP keyword ["=" value]) CRLF
    value = String / QuotedString

  Tor behaves as though it had just read each of the key-value pairs
  from its configuration file.  Keywords with no corresponding values have
  their configuration values reset to 0 or NULL (use RESETCONF if you want
  to set it back to its default).  SETCONF is all-or-nothing: if there
  is an error in any of the configuration settings, Tor sets none of them.

  Tor responds with a "250 OK" reply on success.
  If some of the listed keywords can't be found, Tor replies with a
  "552 Unrecognized option" message. Otherwise, Tor responds with a
  "513 syntax error in configuration values" reply on syntax error, or a
  "553 impossible configuration setting" reply on a semantic error.

  Some configuration options (e.g. "Bridge") take multiple values. Also,
  some configuration keys (e.g. for hidden services and for entry
  guard lists) form a context-sensitive group where order matters (see
  GETCONF below). In these cases, setting _any_ of the options in a
  SETCONF command is taken to reset all of the others. For example,
  if two ORListenAddress values are configured, and a SETCONF command
  arrives containing a single ORListenAddress value, the new command's
  value replaces the two old values.

  Sometimes it is not possible to change configuration options solely by
  issuing a series of SETCONF commands, because the value of one of the
  configuration options depends on the value of another which has not yet
  been set. Such situations can be overcome by setting multiple configuration
  options with a single SETCONF command (e.g. SETCONF ORPort=443
  ORListenAddress=9001).

3.2. RESETCONF

  Remove all settings for a given configuration option entirely, assign
  its default value (if any), and then assign the String provided.
  Typically the String is left empty, to simply set an option back to
  its default. The syntax is:

    "RESETCONF" 1*(SP keyword ["=" String]) CRLF

  Otherwise it behaves like SETCONF above.

3.3. GETCONF

  Request the value of zero or more configuration variable(s).
  The syntax is:

    "GETCONF" *(SP keyword) CRLF

  If all of the listed keywords exist in the Tor configuration, Tor replies
  with a series of reply lines of the form:

      250 keyword=value

  If any option is set to a 'default' value semantically different from an
  empty string, Tor may reply with a reply line of the form:

      250 keyword

  Value may be a raw value or a quoted string.  Tor will try to use unquoted
  values except when the value could be misinterpreted through not being
  quoted. (Right now, Tor supports no such misinterpretable values for
  configuration options.)

  If some of the listed keywords can't be found, Tor replies with a
  "552 unknown configuration keyword" message.

  If an option appears multiple times in the configuration, all of its
  key-value pairs are returned in order.

  If no keywords were provided, Tor responds with "250 OK" message.

  Some options are context-sensitive, and depend on other options with
  different keywords.  These cannot be fetched directly.  Currently there
  is only one such option: clients should use the "HiddenServiceOptions"
  virtual keyword to get all HiddenServiceDir, HiddenServicePort,
  HiddenServiceVersion, and HiddenserviceAuthorizeClient option settings.

3.4. SETEVENTS

  Request the server to inform the client about interesting events.  The
  syntax is:

     "SETEVENTS" [SP "EXTENDED"] *(SP EventCode) CRLF

     EventCode = 1*(ALPHA / "_")  (see section 4.1.x for event types)

  Any events *not* listed in the SETEVENTS line are turned off; thus, sending
  SETEVENTS with an empty body turns off all event reporting.

  The server responds with a "250 OK" reply on success, and a "552
  Unrecognized event" reply if one of the event codes isn't recognized.  (On
  error, the list of active event codes isn't changed.)

  If the flag string "EXTENDED" is provided, Tor may provide extra
  information with events for this connection; see 4.1 for more information.
  NOTE: All events on a given connection will be provided in extended format,
  or none.
  NOTE: "EXTENDED" was first supported in Tor 0.1.1.9-alpha; it is
  always-on in Tor 0.2.2.1-alpha and later.

  Each event is described in more detail in Section 4.1.

3.5. AUTHENTICATE

  Sent from the client to the server.  The syntax is:

     "AUTHENTICATE" [ SP 1*HEXDIG / QuotedString ] CRLF

  This command is used to authenticate to the server. The provided string is
  one of the following:

     * (For the HASHEDPASSWORD authentication method; see 3.21)
       The original password represented as a QuotedString.

     * (For the COOKIE is authentication method; see 3.21)
       The contents of the cookie file, formatted in hexadecimal

     * (For the SAFECOOKIE authentication method; see 3.21)
       The HMAC based on the AUTHCHALLENGE message, in hexadecimal.

  The server responds with "250 OK" on success or "515 Bad authentication" if
  the authentication cookie is incorrect.  Tor closes the connection on an
  authentication failure.

  The authentication token can be specified as either a quoted ASCII string,
  or as an unquoted hexadecimal encoding of that same string (to avoid escaping
  issues).

  For information on how the implementation securely stores authentication
  information on disk, see section 5.1.

  Before the client has authenticated, no command other than
  PROTOCOLINFO, AUTHCHALLENGE, AUTHENTICATE, or QUIT is valid.  If the
  controller sends any other command, or sends a malformed command, or
  sends an unsuccessful AUTHENTICATE command, or sends PROTOCOLINFO or
  AUTHCHALLENGE more than once, Tor sends an error reply and closes
  the connection.

  To prevent some cross-protocol attacks, the AUTHENTICATE command is still
  required even if all authentication methods in Tor are disabled.  In this
  case, the controller should just send "AUTHENTICATE" CRLF.

  (Versions of Tor before 0.1.2.16 and 0.2.0.4-alpha did not close the
  connection after an authentication failure.)

3.6. SAVECONF

  Sent from the client to the server.  The syntax is:

     "SAVECONF" [SP "FORCE"] CRLF

  Instructs the server to write out its config options into its torrc. Server
  returns "250 OK" if successful, or "551 Unable to write configuration
  to disk" if it can't write the file or some other error occurs.

  If the %include option is used on torrc, SAVECONF will not write the
  configuration to disk. If the flag string "FORCE" is provided, the
  configuration will be overwritten even if %include is used. Using %include
  on defaults-torrc does not affect SAVECONF. (Introduced in 0.3.1.1-alpha.)

  See also the "getinfo config-text" command, if the controller wants
  to write the torrc file itself.

  See also the "getinfo config-can-saveconf" command, to tell if the FORCE
  flag will be required. (Also introduced in 0.3.1.1-alpha.)

3.7. SIGNAL

  Sent from the client to the server. The syntax is:

     "SIGNAL" SP Signal CRLF

     Signal = "RELOAD" / "SHUTDOWN" / "DUMP" / "DEBUG" / "HALT" /
              "HUP" / "INT" / "USR1" / "USR2" / "TERM" / "NEWNYM" /
              "CLEARDNSCACHE" / "HEARTBEAT" / "ACTIVE" / "DORMANT"

  The meaning of the signals are:

      RELOAD    -- Reload: reload config items.
      SHUTDOWN  -- Controlled shutdown: if server is an OP, exit immediately.
                   If it's an OR, close listeners and exit after
                   ShutdownWaitLength seconds.
      DUMP      -- Dump stats: log information about open connections and
                   circuits.
      DEBUG     -- Debug: switch all open logs to loglevel debug.
      HALT      -- Immediate shutdown: clean up and exit now.
      CLEARDNSCACHE -- Forget the client-side cached IPs for all hostnames.
      NEWNYM    -- Switch to clean circuits, so new application requests
                   don't share any circuits with old ones.  Also clears
                   the client-side DNS cache.  (Tor MAY rate-limit its
                   response to this signal.)
      HEARTBEAT -- Make Tor dump an unscheduled Heartbeat message to log.
      DORMANT   -- Tell Tor to become "dormant".  A dormant Tor will
                   try to avoid CPU and network usage until it receives
                   user-initiated network request.  (Don't use this
                   on relays or hidden services yet!)
      ACTIVE    -- Tell Tor to stop being "dormant", as if it had received
                   a user-initiated network request.

  The server responds with "250 OK" if the signal is recognized (or simply
  closes the socket if it was asked to close immediately), or "552
  Unrecognized signal" if the signal is unrecognized.

  Note that not all of these signals have POSIX signal equivalents.  The
  ones that do are as below.  You may also use these POSIX names for the
  signal that have them.

      RELOAD: HUP
      SHUTDOWN: INT
      HALT: TERM
      DUMP: USR1
      DEBUG: USR2

  [SIGNAL DORMANT and SIGNAL ACTIVE were added in 0.4.0.1-alpha.]

3.8. MAPADDRESS

  Sent from the client to the server.  The syntax is:

    "MAPADDRESS" 1*(Address "=" Address SP) CRLF

  The first address in each pair is an "original" address; the second is a
  "replacement" address.  The client sends this message to the server in
  order to tell it that future SOCKS requests for connections to the original
  address should be replaced with connections to the specified replacement
  address.  If the addresses are well-formed, and the server is able to
  fulfill the request, the server replies with a 250 message:

    250-OldAddress1=NewAddress1
    250 OldAddress2=NewAddress2

  containing the source and destination addresses.  If request is
  malformed, the server replies with "512 syntax error in command
  argument".  If the server can't fulfill the request, it replies with
  "451 resource exhausted".

  The client may decline to provide a body for the original address, and
  instead send a special null address ("0.0.0.0" for IPv4, "::0" for IPv6, or
  "." for hostname), signifying that the server should choose the original
  address itself, and return that address in the reply.  The server
  should ensure that it returns an element of address space that is unlikely
  to be in actual use.  If there is already an address mapped to the
  destination address, the server may reuse that mapping.

  If the original address is already mapped to a different address, the old
  mapping is removed.  If the original address and the destination address
  are the same, the server removes any mapping in place for the original
  address.

  Example:

    C: MAPADDRESS 1.2.3.4=torproject.org
    S: 250 1.2.3.4=torproject.org

    C: GETINFO address-mappings/control
    S: 250-address-mappings/control=1.2.3.4 torproject.org NEVER
    S: 250 OK

    C: MAPADDRESS 1.2.3.4=1.2.3.4
    S: 250 1.2.3.4=1.2.3.4

    C: GETINFO address-mappings/control
    S: 250-address-mappings/control=
    S: 250 OK

  {Note: This feature is designed to be used to help Tor-ify applications
  that need to use SOCKS4 or hostname-less SOCKS5.  There are three
  approaches to doing this:

     1. Somehow make them use SOCKS4a or SOCKS5-with-hostnames instead.
     2. Use tor-resolve (or another interface to Tor's resolve-over-SOCKS
        feature) to resolve the hostname remotely.  This doesn't work
        with special addresses like x.onion or x.y.exit.
     3. Use MAPADDRESS to map an IP address to the desired hostname, and then
        arrange to fool the application into thinking that the hostname
        has resolved to that IP.

  This functionality is designed to help implement the 3rd approach.}

  Mappings set by the controller last until the Tor process exits:
  they never expire. If the controller wants the mapping to last only
  a certain time, then it must explicitly un-map the address when that
  time has elapsed.

  MapAddress replies MAY contain mixed status codes.

  Example:

    C: MAPADDRESS xxx=@@@ 0.0.0.0=bogus1.google.com
    S: 512-syntax error: invalid address '@@@'
    S: 250 127.199.80.246=bogus1.google.com

3.9. GETINFO

  Sent from the client to the server.  The syntax is as for GETCONF:

    "GETINFO" 1*(SP keyword) CRLF

  Unlike GETCONF, this message is used for data that are not stored in the Tor
  configuration file, and that may be longer than a single line.  On success,
  one ReplyLine is sent for each requested value, followed by a final 250 OK
  ReplyLine.  If a value fits on a single line, the format is:

      250-keyword=value
  If a value must be split over multiple lines, the format is:

      250+keyword=
      value
      .
  The server sends a 551 or 552 error on failure.

  Recognized keys and their values include:

    "version" -- The version of the server's software, which MAY include the
      name of the software, such as "Tor 0.0.9.4".  The name of the software,
      if absent, is assumed to be "Tor".

    "config-file" -- The location of Tor's configuration file ("torrc").

    "config-defaults-file" -- The location of Tor's configuration
      defaults file ("torrc.defaults").  This file gets parsed before
      torrc, and is typically used to replace Tor's default
      configuration values. [First implemented in 0.2.3.9-alpha.]

    "config-text" -- The contents that Tor would write if you send it
      a SAVECONF command, so the controller can write the file to
      disk itself. [First implemented in 0.2.2.7-alpha.]

    "exit-policy/default" -- The default exit policy lines that Tor will
      *append* to the ExitPolicy config option.

    "exit-policy/reject-private/default" -- The default exit policy lines
      that Tor will *prepend* to the ExitPolicy config option when
      ExitPolicyRejectPrivate is 1.

    "exit-policy/reject-private/relay" -- The relay-specific exit policy
      lines that Tor will *prepend* to the ExitPolicy config option based
      on the current values of ExitPolicyRejectPrivate and
      ExitPolicyRejectLocalInterfaces. These lines are based on the public
      addresses configured in the torrc and present on the relay's
      interfaces. Will send 552 error if the server is not running as
      onion router. Will send 551 on internal error which may be transient.

    "exit-policy/ipv4"
    "exit-policy/ipv6"
    "exit-policy/full" -- This OR's exit policy, in IPv4-only, IPv6-only, or
      all-entries flavors. Handles errors in the same way as "exit-policy/
      reject-private/relay" does.

    "desc/id/<OR identity>" or "desc/name/<OR nickname>" -- the latest
      server descriptor for a given OR.  (Note that modern Tor clients
      do not download server descriptors by default, but download
      microdescriptors instead.  If microdescriptors are enabled, you'll
      need to use "md" instead.)

    "md/all" -- all known microdescriptors for the entire Tor network.
      Each microdescriptor is terminated by a newline.
      [First implemented in 0.3.5.1-alpha]

    "md/id/<OR identity>" or "md/name/<OR nickname>" -- the latest
      microdescriptor for a given OR. Empty if we have no microdescriptor for
      that OR (because we haven't downloaded one, or it isn't in the
      consensus). [First implemented in 0.2.3.8-alpha.]

    "desc/download-enabled" -- "1" if we try to download router descriptors;
      "0" otherwise. [First implemented in 0.3.2.1-alpha]

    "md/download-enabled" -- "1" if we try to download microdescriptors;
      "0" otherwise. [First implemented in 0.3.2.1-alpha]

    "dormant" -- A nonnegative integer: zero if Tor is currently active and
      building circuits, and nonzero if Tor has gone idle due to lack of use
      or some similar reason.  [First implemented in 0.2.3.16-alpha]

    "desc-annotations/id/<OR identity>" -- outputs the annotations string
      (source, timestamp of arrival, purpose, etc) for the corresponding
      descriptor. [First implemented in 0.2.0.13-alpha.]

    "extra-info/digest/<digest>"  -- the extrainfo document whose digest (in
      hex) is <digest>.  Only available if we're downloading extra-info
      documents.

    "ns/id/<OR identity>" or "ns/name/<OR nickname>" -- the latest router
      status info (v3 directory style) for a given OR.  Router status
      info is as given in dir-spec.txt, and reflects the latest
      consensus opinion about the
      router in question. Like directory clients, controllers MUST
      tolerate unrecognized flags and lines.  The published date and
      descriptor digest are those believed to be best by this Tor,
      not necessarily those for a descriptor that Tor currently has.
      [First implemented in 0.1.2.3-alpha.]
      [In 0.2.0.9-alpha this switched from v2 directory style to v3]

    "ns/all" -- Router status info (v3 directory style) for all ORs we
      that the consensus has an opinion about, joined by newlines.
      [First implemented in 0.1.2.3-alpha.]
      [In 0.2.0.9-alpha this switched from v2 directory style to v3]

    "ns/purpose/<purpose>" -- Router status info (v3 directory style)
      for all ORs of this purpose. Mostly designed for /ns/purpose/bridge
      queries.
      [First implemented in 0.2.0.13-alpha.]
      [In 0.2.0.9-alpha this switched from v2 directory style to v3]
      [In versions before 0.4.1.1-alpha we set the Running flag on
       bridges when /ns/purpose/bridge is accessed]
      [In 0.4.1.1-alpha we set the Running flag on bridges when the
       bridge networkstatus file is written to disk]

    "desc/all-recent" -- the latest server descriptor for every router that
      Tor knows about.  (See md note about "desc/id" and "desc/name" above.)

    "network-status" -- [Deprecated in 0.3.1.1-alpha, removed
      in 0.4.5.1-alpha.]

    "address-mappings/all"
    "address-mappings/config"
    "address-mappings/cache"
    "address-mappings/control" -- a \r\n-separated list of address
      mappings, each in the form of "from-address to-address expiry".
      The 'config' key returns those address mappings set in the
      configuration; the 'cache' key returns the mappings in the
      client-side DNS cache; the 'control' key returns the mappings set
      via the control interface; the 'all' target returns the mappings
      set through any mechanism.
      Expiry is formatted as with ADDRMAP events, except that "expiry" is
      always a time in UTC or the string "NEVER"; see section 4.1.7.
      First introduced in 0.2.0.3-alpha.

    "addr-mappings/*" -- as for address-mappings/*, but without the
      expiry portion of the value.  Use of this value is deprecated
      since 0.2.0.3-alpha; use address-mappings instead.

    "address" -- the best guess at our external IP address. If we
      have no guess, return a 551 error. (Added in 0.1.2.2-alpha)

    "address/v4"
    "address/v6"
      the best guess at our respective external IPv4 or IPv6 address.
      If we have no guess, return a 551 error. (Added in 0.4.5.1-alpha)

    "fingerprint" -- the contents of the fingerprint file that Tor
      writes as a relay, or a 551 if we're not a relay currently.
      (Added in 0.1.2.3-alpha)

    "circuit-status"
      A series of lines as for a circuit status event. Each line is of
      the form described in section 4.1.1, omitting the initial
      "650 CIRC ".  Note that clients must be ready to accept additional
      arguments as described in section 4.1.

    "stream-status"
      A series of lines as for a stream status event.  Each is of the form:
         StreamID SP StreamStatus SP CircuitID SP Target CRLF

    "orconn-status"
      A series of lines as for an OR connection status event.  In Tor
      0.1.2.2-alpha with feature VERBOSE_NAMES enabled and in Tor
      0.2.2.1-alpha and later by default, each line is of the form:
         LongName SP ORStatus CRLF

     In Tor versions 0.1.2.2-alpha through 0.2.2.1-alpha with feature
     VERBOSE_NAMES turned off and before version 0.1.2.2-alpha, each line
     is of the form:
         ServerID SP ORStatus CRLF

    "entry-guards"
      A series of lines listing the currently chosen entry guards, if any.
      In Tor 0.1.2.2-alpha with feature VERBOSE_NAMES enabled and in Tor
      0.2.2.1-alpha and later by default, each line is of the form:
         LongName SP Status [SP ISOTime] CRLF

     In Tor versions 0.1.2.2-alpha through 0.2.2.1-alpha with feature
     VERBOSE_NAMES turned off and before version 0.1.2.2-alpha, each line
     is of the form:
         ServerID2 SP Status [SP ISOTime] CRLF
         ServerID2 = Nickname / 40*HEXDIG

      The definition of Status is the same for both:
         Status = "up" / "never-connected" / "down" /
                  "unusable" / "unlisted"

      [From 0.1.1.4-alpha to 0.1.1.10-alpha, entry-guards was called
       "helper-nodes". Tor still supports calling "helper-nodes", but it
        is deprecated and should not be used.]

      [Older versions of Tor (before 0.1.2.x-final) generated 'down' instead
       of unlisted/unusable. Between 0.1.2.x-final and 0.2.6.3-alpha,
       'down' was never generated.]

      [XXXX ServerID2 differs from ServerID in not prefixing fingerprints
       with a $.  This is an implementation error.  It would be nice to add
       the $ back in if we can do so without breaking compatibility.]

    "traffic/read" -- Total bytes read (downloaded).

    "traffic/written" -- Total bytes written (uploaded).

    "uptime" -- Uptime of the Tor daemon (in seconds).  Added in
       0.3.5.1-alpha.

    "accounting/enabled"
    "accounting/hibernating"
    "accounting/bytes"
    "accounting/bytes-left"
    "accounting/interval-start"
    "accounting/interval-wake"
    "accounting/interval-end"
      Information about accounting status.  If accounting is enabled,
      "enabled" is 1; otherwise it is 0.  The "hibernating" field is "hard"
      if we are accepting no data; "soft" if we're accepting no new
      connections, and "awake" if we're not hibernating at all.  The "bytes"
      and "bytes-left" fields contain (read-bytes SP write-bytes), for the
      start and the rest of the interval respectively.  The 'interval-start'
      and 'interval-end' fields are the borders of the current interval; the
      'interval-wake' field is the time within the current interval (if any)
      where we plan[ned] to start being active. The times are UTC.

    "config/names"
      A series of lines listing the available configuration options. Each is
      of the form:
         OptionName SP OptionType [ SP Documentation ] CRLF
         OptionName = Keyword
         OptionType = "Integer" / "TimeInterval" / "TimeMsecInterval" /
           "DataSize" / "Float" / "Boolean" / "Time" / "CommaList" /
           "Dependent" / "Virtual" / "String" / "LineList"
         Documentation = Text
      Note: The incorrect spelling "Dependant" was used from the time this key
      was introduced in Tor 0.1.1.4-alpha until it was corrected in Tor
      0.3.0.2-alpha.  It is recommended that clients accept both spellings.

    "config/defaults"
      A series of lines listing default values for each configuration
      option. Options which don't have a valid default don't show up
      in the list.  Introduced in Tor 0.2.4.1-alpha.
         OptionName SP OptionValue CRLF
         OptionName = Keyword
         OptionValue = Text

    "info/names"
      A series of lines listing the available GETINFO options.  Each is of
      one of these forms:
         OptionName SP Documentation CRLF
         OptionPrefix SP Documentation CRLF
         OptionPrefix = OptionName "/*"
      The OptionPrefix form indicates a number of options beginning with the
      prefix. So if "config/*" is listed, other options beginning with
      "config/" will work, but "config/*" itself is not an option.

    "events/names"
      A space-separated list of all the events supported by this version of
      Tor's SETEVENTS.

    "features/names"
      A space-separated list of all the features supported by this version
      of Tor's USEFEATURE.

    "signal/names"
      A space-separated list of all the values supported by the SIGNAL
      command.

    "ip-to-country/ipv4-available"
    "ip-to-country/ipv6-available"
      "1" if the relevant geoip or geoip6 database is present; "0" otherwise.
      This field was added in Tor 0.3.2.1-alpha.

    "ip-to-country/*"
      Maps IP addresses to 2-letter country codes.  For example,
      "GETINFO ip-to-country/18.0.0.1" should give "US".

    "process/pid" -- Process id belonging to the main tor process.
    "process/uid" -- User id running the tor process, -1 if unknown (this is
     unimplemented on Windows, returning -1).
    "process/user" -- Username under which the tor process is running,
     providing an empty string if none exists (this is unimplemented on
     Windows, returning an empty string).
    "process/descriptor-limit" -- Upper bound on the file descriptor limit, -1
     if unknown

    "dir/status-vote/current/consensus" [added in Tor 0.2.1.6-alpha]
    "dir/status-vote/current/consensus-microdesc" [added in Tor 0.4.3.1-alpha]
    "dir/status/authority"
    "dir/status/fp/<F>"
    "dir/status/fp/<F1>+<F2>+<F3>"
    "dir/status/all"
    "dir/server/fp/<F>"
    "dir/server/fp/<F1>+<F2>+<F3>"
    "dir/server/d/<D>"
    "dir/server/d/<D1>+<D2>+<D3>"
    "dir/server/authority"
    "dir/server/all"
      A series of lines listing directory contents, provided according to the
      specification for the URLs listed in Section 4.4 of dir-spec.txt.  Note
      that Tor MUST NOT provide private information, such as descriptors for
      routers not marked as general-purpose.  When asked for 'authority'
      information for which this Tor is not authoritative, Tor replies with
      an empty string.

      Note that, as of Tor 0.2.3.3-alpha, Tor clients don't download server
      descriptors anymore, but microdescriptors.  So, a "551 Servers
      unavailable" reply to all "GETINFO dir/server/*" requests is actually
      correct.  If you have an old program which absolutely requires server
      descriptors to work, try setting UseMicrodescriptors 0 or
      FetchUselessDescriptors 1 in your client's torrc.

    "status/circuit-established"
    "status/enough-dir-info"
    "status/good-server-descriptor"
    "status/accepted-server-descriptor"
    "status/..."
      These provide the current internal Tor values for various Tor
      states. See Section 4.1.10 for explanations. (Only a few of the
      status events are available as getinfo's currently. Let us know if
      you want more exposed.)
    "status/reachability-succeeded/or"
      0 or 1, depending on whether we've found our ORPort reachable.
    "status/reachability-succeeded/dir"
      0 or 1, depending on whether we've found our DirPort reachable.
      1 if there is no DirPort, and therefore no need for a reachability
      check.
    "status/reachability-succeeded"
      "OR=" ("0"/"1") SP "DIR=" ("0"/"1")
      Combines status/reachability-succeeded/*; controllers MUST ignore
      unrecognized elements in this entry.
    "status/bootstrap-phase"
      Returns the most recent bootstrap phase status event
      sent. Specifically, it returns a string starting with either
      "NOTICE BOOTSTRAP ..." or "WARN BOOTSTRAP ...". Controllers should
      use this getinfo when they connect or attach to Tor to learn its
      current bootstrap state.
    "status/version/recommended"
      List of currently recommended versions.
    "status/version/current"
      Status of the current version. One of: new, old, unrecommended,
      recommended, new in series, obsolete, unknown.
    "status/clients-seen"
      A summary of which countries we've seen clients from recently,
      formatted the same as the CLIENTS_SEEN status event described in
      Section 4.1.14. This GETINFO option is currently available only
      for bridge relays.
    "status/fresh-relay-descs"
      Provides fresh server and extra-info descriptors for our relay. Note
      this is *not* the latest descriptors we've published, but rather what we
      would generate if we needed to make a new descriptor right now.

    "net/listeners/*"

      A quoted, space-separated list of the locations where Tor is listening
      for connections of the specified type. These can contain IPv4
      network address...

        "127.0.0.1:9050" "127.0.0.1:9051"

      ... or local unix sockets...

        "unix:/home/my_user/.tor/socket"

      ... or IPv6 network addresses:

        "[2001:0db8:7000:0000:0000:dead:beef:1234]:9050"

      [New in Tor 0.2.2.26-beta.]

    "net/listeners/or"

      Listeners for OR connections. Talks Tor protocol as described in
      tor-spec.txt.

    "net/listeners/dir"

      Listeners for Tor directory protocol, as described in dir-spec.txt.

    "net/listeners/socks"

      Listeners for onion proxy connections that talk SOCKS4/4a/5 protocol.

    "net/listeners/trans"

      Listeners for transparent connections redirected by firewall, such as
      pf or netfilter.

    "net/listeners/natd"

      Listeners for transparent connections redirected by natd.

    "net/listeners/dns"

      Listeners for a subset of DNS protocol that Tor network supports.

    "net/listeners/control"

      Listeners for Tor control protocol, described herein.

    "net/listeners/extor"

      Listeners corresponding to Extended ORPorts for integration with
      pluggable transports. See proposals 180 and 196.

    "net/listeners/httptunnel"

      Listeners for onion proxy connections that leverage HTTP CONNECT
      tunnelling.

      [The extor and httptunnel lists were added in 0.3.2.12, 0.3.3.10, and
      0.3.4.6-rc.]

    "dir-usage"
      A newline-separated list of how many bytes we've served to answer
      each type of directory request. The format of each line is:
         Keyword 1*SP Integer 1*SP Integer
      where the first integer is the number of bytes written, and the second
      is the number of requests answered.

      [This feature was added in Tor 0.2.2.1-alpha, and removed in
       Tor 0.2.9.1-alpha. Even when it existed, it only provided
       useful output when the Tor client was built with either the
       INSTRUMENT_DOWNLOADS or RUNNING_DOXYGEN compile-time options.]

    "bw-event-cache"
      A space-separated summary of recent BW events in chronological order
      from oldest to newest.  Each event is represented by a comma-separated
      tuple of "R,W", R is the number of bytes read, and W is the number of
      bytes written.  These entries each represent about one second's worth
      of traffic.
      [New in Tor 0.2.6.3-alpha]

     "consensus/valid-after"
     "consensus/fresh-until"
     "consensus/valid-until"
      Each of these produces an ISOTime describing part of the lifetime of
      the current (valid, accepted) consensus that Tor has.
      [New in Tor 0.2.6.3-alpha]

    "hs/client/desc/id/<ADDR>"
      Prints the content of the hidden service descriptor corresponding to
      the given <ADDR> which is an onion address without the ".onion" part.
      The client's cache is queried to find the descriptor. The format of
      the descriptor is described in section 1.3 of the rend-spec.txt
      document.

      If <ADDR> is unrecognized or if not found in the cache, a 551 error is
      returned.

      [New in Tor 0.2.7.1-alpha]
      [HS v3 support added 0.3.3.1-alpha]

    "hs/service/desc/id/<ADDR>"
      Prints the content of the hidden service descriptor corresponding to
      the given <ADDR> which is an onion address without the ".onion" part.
      The service's local descriptor cache is queried to find the descriptor.
      The format of the descriptor is described in section 1.3 of the
      rend-spec.txt document.

      If <ADDR> is unrecognized or if not found in the cache, a 551 error is
      returned.

      [New in Tor 0.2.7.2-alpha]
      [HS v3 support added 0.3.3.1-alpha]

    "onions/current"
    "onions/detached"
      A newline-separated list of the Onion ("Hidden") Services created
      via the "ADD_ONION" command. The 'current' key returns Onion Services
      belonging to the current control connection. The 'detached' key
      returns Onion Services detached from the parent control connection
      (as in, belonging to no control connection).
      The format of each line is:
         HSAddress
      [New in Tor 0.2.7.1-alpha.]
      [HS v3 support added 0.3.3.1-alpha]

    "network-liveness"
      The string "up" or "down", indicating whether we currently believe the
      network is reachable.

    "downloads/"
      The keys under downloads/ are used to query download statuses; they all
      return either a sequence of newline-terminated hex encoded digests, or
      a "serialized download status" as follows:

       SerializedDownloadStatus =
         -- when do we plan to next attempt to download this object?
         "next-attempt-at" SP ISOTime CRLF
         -- how many times have we failed since the last success?
         "n-download-failures" SP UInt CRLF
         -- how many times have we tried to download this?
         "n-download-attempts" SP UInt CRLF
         -- according to which schedule rule will we download this?
         "schedule" SP DownloadSchedule CRLF
         -- do we want to fetch this from an authority, or will any cache do?
         "want-authority" SP DownloadWantAuthority CRLF
         -- do we increase our download delay whenever we fail to fetch this,
         -- or whenever we attempt fetching this?
         "increment-on" SP DownloadIncrementOn CRLF
         -- do we increase the download schedule deterministically, or at
         -- random?
         "backoff" SP DownloadBackoff CRLF
         [
           -- with an exponential backoff, where are we in the schedule?
           "last-backoff-position" Uint CRLF
           -- with an exponential backoff, what was our last delay?
           "last-delay-used UInt CRLF
         ]

      where

      DownloadSchedule =
        "DL_SCHED_GENERIC" / "DL_SCHED_CONSENSUS" / "DL_SCHED_BRIDGE"
      DownloadWantAuthority =
        "DL_WANT_ANY_DIRSERVER" / "DL_WANT_AUTHORITY"
      DownloadIncrementOn =
        "DL_SCHED_INCREMENT_FAILURE" / "DL_SCHED_INCREMENT_ATTEMPT"
      DownloadBackoff =
        "DL_SCHED_DETERMINISTIC" / "DL_SCHED_RANDOM_EXPONENTIAL"

      The optional last two lines must be present if DownloadBackoff is
      "DL_SCHED_RANDOM_EXPONENTIAL" and must be absent if DownloadBackoff
      is "DL_SCHED_DETERMINISTIC".

      In detail, the keys supported are:

      "downloads/networkstatus/ns"
        The SerializedDownloadStatus for the NS-flavored consensus for
        whichever bootstrap state Tor is currently in.

      "downloads/networkstatus/ns/bootstrap"
        The SerializedDownloadStatus for the NS-flavored consensus at
        bootstrap time, regardless of whether we are currently bootstrapping.

      "downloads/networkstatus/ns/running"

        The SerializedDownloadStatus for the NS-flavored consensus when
        running, regardless of whether we are currently bootstrapping.

      "downloads/networkstatus/microdesc"
        The SerializedDownloadStatus for the microdesc-flavored consensus for
        whichever bootstrap state Tor is currently in.

      "downloads/networkstatus/microdesc/bootstrap"
        The SerializedDownloadStatus for the microdesc-flavored consensus at
        bootstrap time, regardless of whether we are currently bootstrapping.

      "downloads/networkstatus/microdesc/running"
        The SerializedDownloadStatus for the microdesc-flavored consensus when
        running, regardless of whether we are currently bootstrapping.

      "downloads/cert/fps"

        A newline-separated list of hex-encoded digests for authority
        certificates for which we have download status available.

      "downloads/cert/fp/<Fingerprint>"
        A SerializedDownloadStatus for the default certificate for the
        identity digest <Fingerprint> returned by the downloads/cert/fps key.

      "downloads/cert/fp/<Fingerprint>/sks"
        A newline-separated list of hex-encoded signing key digests for the
        authority identity digest <Fingerprint> returned by the
        downloads/cert/fps key.

      "downloads/cert/fp/<Fingerprint>/<SKDigest>"
        A SerializedDownloadStatus for the certificate for the identity
        digest <Fingerprint> returned by the downloads/cert/fps key and signing
        key digest <SKDigest> returned by the downloads/cert/fp/<Fingerprint>/
        sks key.

      "downloads/desc/descs"
        A newline-separated list of hex-encoded router descriptor digests
        [note, not identity digests - the Tor process may not have seen them
        yet while downloading router descriptors].  If the Tor process is not
        using a NS-flavored consensus, a 551 error is returned.

      "downloads/desc/<Digest>"
        A SerializedDownloadStatus for the router descriptor with digest
        <Digest> as returned by the downloads/desc/descs key.  If the Tor
        process is not using a NS-flavored consensus, a 551 error is returned.

      "downloads/bridge/bridges"
        A newline-separated list of hex-encoded bridge identity digests.  If
        the Tor process is not using bridges, a 551 error is returned.

      "downloads/bridge/<Digest>"
        A SerializedDownloadStatus for the bridge descriptor with identity
        digest <Digest> as returned by the downloads/bridge/bridges key.  If
        the Tor process is not using bridges, a 551 error is returned.

    "sr/current"
    "sr/previous"
      The current or previous shared random value, as received in the
      consensus, base-64 encoded.  An empty value means that either
      the consensus has no shared random value, or Tor has no consensus.

    "current-time/local"
    "current-time/utc"
      The current system or UTC time, as returned by the system, in ISOTime2
      format.  (Introduced in 0.3.4.1-alpha.)

    "stats/ntor/requested"
    "stats/ntor/assigned"
      The NTor circuit onion handshake rephist values which are requested or
      assigned.  (Introduced in 0.4.5.1-alpha)

    "stats/tap/requested"
    "stats/tap/assigned"
      The TAP circuit onion handshake rephist values which are requested or
      assigned.  (Introduced in 0.4.5.1-alpha)

    "config-can-saveconf"
      0 or 1, depending on whether it is possible to use SAVECONF without the
      FORCE flag. (Introduced in 0.3.1.1-alpha.)

    "limits/max-mem-in-queues"
      The amount of memory that Tor's out-of-memory checker will allow
      Tor to allocate (in places it can see) before it starts freeing memory
      and killing circuits. See the MaxMemInQueues option for more
      details. Unlike the option, this value reflects Tor's actual limit, and
      may be adjusted depending on the available system memory rather than on
      the MaxMemInQueues option. (Introduced in 0.2.5.4-alpha)

  Examples:

     C: GETINFO version desc/name/moria1
     S: 250+desc/name/moria=
     S: [Descriptor for moria]
     S: .
     S: 250-version=Tor 0.1.1.0-alpha-cvs
     S: 250 OK

3.10. EXTENDCIRCUIT

  Sent from the client to the server.  The format is:

      "EXTENDCIRCUIT" SP CircuitID
                      [SP ServerSpec *("," ServerSpec)]
                      [SP "purpose=" Purpose] CRLF

  This request takes one of two forms: either the CircuitID is zero, in
  which case it is a request for the server to build a new circuit,
  or the CircuitID is nonzero, in which case it is a request for the
  server to extend an existing circuit with that ID according to the
  specified path.

  If the CircuitID is 0, the controller has the option of providing
  a path for Tor to use to build the circuit. If it does not provide
  a path, Tor will select one automatically from high capacity nodes
  according to path-spec.txt.

  If CircuitID is 0 and "purpose=" is specified, then the circuit's
  purpose is set. Two choices are recognized: "general" and
  "controller". If not specified, circuits are created as "general".

  If the request is successful, the server sends a reply containing a
  message body consisting of the CircuitID of the (maybe newly created)
  circuit. The syntax is "250" SP "EXTENDED" SP CircuitID CRLF.

3.11. SETCIRCUITPURPOSE

  Sent from the client to the server.  The format is:

      "SETCIRCUITPURPOSE" SP CircuitID SP "purpose=" Purpose CRLF

  This changes the circuit's purpose. See EXTENDCIRCUIT above for details.

3.12. SETROUTERPURPOSE

  Sent from the client to the server.  The format is:

      "SETROUTERPURPOSE" SP NicknameOrKey SP Purpose CRLF

  This changes the descriptor's purpose. See +POSTDESCRIPTOR below
  for details.

  NOTE: This command was disabled and made obsolete as of Tor
  0.2.0.8-alpha. It doesn't exist anymore, and is listed here only for
  historical interest.

3.13. ATTACHSTREAM

  Sent from the client to the server.  The syntax is:

     "ATTACHSTREAM" SP StreamID SP CircuitID [SP "HOP=" HopNum] CRLF

  This message informs the server that the specified stream should be
  associated with the specified circuit.  Each stream may be associated with
  at most one circuit, and multiple streams may share the same circuit.
  Streams can only be attached to completed circuits (that is, circuits that
  have sent a circuit status 'BUILT' event or are listed as built in a
  GETINFO circuit-status request).

  If the circuit ID is 0, responsibility for attaching the given stream is
  returned to Tor.

  If HOP=HopNum is specified, Tor will choose the HopNumth hop in the
  circuit as the exit node, rather than the last node in the circuit.
  Hops are 1-indexed; generally, it is not permitted to attach to hop 1.

  Tor responds with "250 OK" if it can attach the stream, 552 if the
  circuit or stream didn't exist, 555 if the stream isn't in an
  appropriate state to be attached (e.g. it's already open), or 551 if
  the stream couldn't be attached for another reason.

  {Implementation note: Tor will close unattached streams by itself,
  roughly two minutes after they are born. Let the developers know if
  that turns out to be a problem.}

  {Implementation note: By default, Tor automatically attaches streams to
  circuits itself, unless the configuration variable
  "__LeaveStreamsUnattached" is set to "1".  Attempting to attach streams
  via TC when "__LeaveStreamsUnattached" is false may cause a race between
  Tor and the controller, as both attempt to attach streams to circuits.}

  {Implementation note: You can try to attachstream to a stream that
  has already sent a connect or resolve request but hasn't succeeded
  yet, in which case Tor will detach the stream from its current circuit
  before proceeding with the new attach request.}

3.14. POSTDESCRIPTOR

  Sent from the client to the server. The syntax is:

    "+POSTDESCRIPTOR" [SP "purpose=" Purpose] [SP "cache=" Cache]
                      CRLF Descriptor CRLF "." CRLF

  This message informs the server about a new descriptor. If Purpose is
  specified, it must be either "general", "controller", or "bridge",
  else we return a 552 error. The default is "general".

  If Cache is specified, it must be either "no" or "yes", else we
  return a 552 error. If Cache is not specified, Tor will decide for
  itself whether it wants to cache the descriptor, and controllers
  must not rely on its choice.

  The descriptor, when parsed, must contain a number of well-specified
  fields, including fields for its nickname and identity.

  If there is an error in parsing the descriptor, the server must send a
  "554 Invalid descriptor" reply. If the descriptor is well-formed but
  the server chooses not to add it, it must reply with a 251 message
  whose body explains why the server was not added. If the descriptor
  is added, Tor replies with "250 OK".

3.15. REDIRECTSTREAM

  Sent from the client to the server. The syntax is:

    "REDIRECTSTREAM" SP StreamID SP Address [SP Port] CRLF

  Tells the server to change the exit address on the specified stream.  If
  Port is specified, changes the destination port as well.  No remapping
  is performed on the new provided address.

  To be sure that the modified address will be used, this event must be sent
  after a new stream event is received, and before attaching this stream to
  a circuit.

  Tor replies with "250 OK" on success.

3.16. CLOSESTREAM

  Sent from the client to the server.  The syntax is:

    "CLOSESTREAM" SP StreamID SP Reason *(SP Flag) CRLF

  Tells the server to close the specified stream.  The reason should be one
  of the Tor RELAY_END reasons given in tor-spec.txt, as a decimal.  Flags is
  not used currently; Tor servers SHOULD ignore unrecognized flags.  Tor may
  hold the stream open for a while to flush any data that is pending.

  Tor replies with "250 OK" on success, or a 512 if there aren't enough
  arguments, or a 552 if it doesn't recognize the StreamID or reason.

3.17. CLOSECIRCUIT

   The syntax is:

     "CLOSECIRCUIT" SP CircuitID *(SP Flag) CRLF
     Flag = "IfUnused"

  Tells the server to close the specified circuit.   If "IfUnused" is
  provided, do not close the circuit unless it is unused.

  Other flags may be defined in the future; Tor SHOULD ignore unrecognized
  flags.

  Tor replies with "250 OK" on success, or a 512 if there aren't enough
  arguments, or a 552 if it doesn't recognize the CircuitID.

3.18. QUIT

  Tells the server to hang up on this controller connection. This command
  can be used before authenticating.

3.19. USEFEATURE

  Adding additional features to the control protocol sometimes will break
  backwards compatibility. Initially such features are added into Tor and
  disabled by default. USEFEATURE can enable these additional features.

  The syntax is:

    "USEFEATURE" *(SP FeatureName) CRLF
    FeatureName = 1*(ALPHA / DIGIT / "_" / "-")

  Feature names are case-insensitive.

  Once enabled, a feature stays enabled for the duration of the connection
  to the controller. A new connection to the controller must be opened to
  disable an enabled feature.

  Features are a forward-compatibility mechanism; each feature will eventually
  become a standard part of the control protocol. Once a feature becomes part
  of the protocol, it is always-on. Each feature documents the version it was
  introduced as a feature and the version in which it became part of the
  protocol.

  Tor will ignore a request to use any feature that is always-on. Tor will give
  a 552 error in response to an unrecognized feature.

  EXTENDED_EVENTS

     Same as passing 'EXTENDED' to SETEVENTS; this is the preferred way to
     request the extended event syntax.

     This feature was first introduced in 0.1.2.3-alpha.  It is always-on
     and part of the protocol in Tor 0.2.2.1-alpha and later.

  VERBOSE_NAMES

     Replaces ServerID with LongName in events and GETINFO results. LongName
     provides a Fingerprint for all routers, an indication of Named status,
     and a Nickname if one is known. LongName is strictly more informative
     than ServerID, which only provides either a Fingerprint or a Nickname.

     This feature was first introduced in 0.1.2.2-alpha. It is always-on and
     part of the protocol in Tor 0.2.2.1-alpha and later.

3.20. RESOLVE

  The syntax is

    "RESOLVE" *Option *Address CRLF
    Option = "mode=reverse"
    Address = a hostname or IPv4 address

  This command launches a remote hostname lookup request for every specified
  request (or reverse lookup if "mode=reverse" is specified).  Note that the
  request is done in the background: to see the answers, your controller will
  need to listen for ADDRMAP events; see 4.1.7 below.

  [Added in Tor 0.2.0.3-alpha]

3.21. PROTOCOLINFO

  The syntax is:

    "PROTOCOLINFO" *(SP PIVERSION) CRLF

  The server reply format is:

    "250-PROTOCOLINFO" SP PIVERSION CRLF *InfoLine "250 OK" CRLF

    InfoLine = AuthLine / VersionLine / OtherLine

     AuthLine = "250-AUTH" SP "METHODS=" AuthMethod *("," AuthMethod)
                       *(SP "COOKIEFILE=" AuthCookieFile) CRLF
     VersionLine = "250-VERSION" SP "Tor=" TorVersion OptArguments CRLF

     AuthMethod =
      "NULL"           / ; No authentication is required
      "HASHEDPASSWORD" / ; A controller must supply the original password
      "COOKIE"         / ; ... or supply the contents of a cookie file
      "SAFECOOKIE"       ; ... or prove knowledge of a cookie file's contents

     AuthCookieFile = QuotedString
     TorVersion = QuotedString

     OtherLine = "250-" Keyword OptArguments CRLF

    PIVERSION: 1*DIGIT

  This command tells the controller what kinds of authentication are
  supported.

  Tor MAY give its InfoLines in any order; controllers MUST ignore InfoLines
  with keywords they do not recognize.  Controllers MUST ignore extraneous
  data on any InfoLine.

  PIVERSION is there in case we drastically change the syntax one day. For
  now it should always be "1".  Controllers MAY provide a list of the
  protocolinfo versions they support; Tor MAY select a version that the
  controller does not support.

  AuthMethod is used to specify one or more control authentication
  methods that Tor currently accepts.

  AuthCookieFile specifies the absolute path and filename of the
  authentication cookie that Tor is expecting and is provided iff the
  METHODS field contains the method "COOKIE" and/or "SAFECOOKIE".
  Controllers MUST handle escape sequences inside this string.

  All authentication cookies are 32 bytes long.  Controllers MUST NOT
  use the contents of a non-32-byte-long file as an authentication
  cookie.

  If the METHODS field contains the method "SAFECOOKIE", every
  AuthCookieFile must contain the same authentication cookie.

  The COOKIE authentication method exposes the user running a
  controller to an unintended information disclosure attack whenever
  the controller has greater filesystem read access than the process
  that it has connected to.  (Note that a controller may connect to a
  process other than Tor.)  It is almost never safe to use, even if
  the controller's user has explicitly specified which filename to
  read an authentication cookie from.  For this reason, the COOKIE
  authentication method has been deprecated and will be removed from
  a future version of Tor.

  The VERSION line contains the Tor version.

  [Unlike other commands besides AUTHENTICATE, PROTOCOLINFO may be used (but
  only once!) before AUTHENTICATE.]

  [PROTOCOLINFO was not supported before Tor 0.2.0.5-alpha.]

3.22. LOADCONF

  The syntax is:

    "+LOADCONF" CRLF ConfigText CRLF "." CRLF

  This command allows a controller to upload the text of a config file
  to Tor over the control port.  This config file is then loaded as if
  it had been read from disk.

  [LOADCONF was added in Tor 0.2.1.1-alpha.]

3.23. TAKEOWNERSHIP

  The syntax is:

    "TAKEOWNERSHIP" CRLF

  This command instructs Tor to shut down when this control
  connection is closed.  This command affects each control connection
  that sends it independently; if multiple control connections send
  the TAKEOWNERSHIP command to a Tor instance, Tor will shut down when
  any of those connections closes.

  (As of Tor 0.2.5.2-alpha, Tor does not wait a while for circuits to
  close when shutting down because of an exiting controller.  If you
  want to ensure a clean shutdown--and you should!--then send "SIGNAL
  SHUTDOWN" and wait for the Tor process to close.)

  This command is intended to be used with the
  __OwningControllerProcess configuration option.  A controller that
  starts a Tor process which the user cannot easily control or stop
  should 'own' that Tor process:

    * When starting Tor, the controller should specify its PID in an
      __OwningControllerProcess on Tor's command line.  This will
      cause Tor to poll for the existence of a process with that PID,
      and exit if it does not find such a process.  (This is not a
      completely reliable way to detect whether the 'owning
      controller' is still running, but it should work well enough in
      most cases.)

    * Once the controller has connected to Tor's control port, it
      should send the TAKEOWNERSHIP command along its control
      connection.  At this point, *both* the TAKEOWNERSHIP command and
      the __OwningControllerProcess option are in effect: Tor will
      exit when the control connection ends *and* Tor will exit if it
      detects that there is no process with the PID specified in the
      __OwningControllerProcess option.

    * After the controller has sent the TAKEOWNERSHIP command, it
      should send "RESETCONF __OwningControllerProcess" along its
      control connection.  This will cause Tor to stop polling for the
      existence of a process with its owning controller's PID; Tor
      will still exit when the control connection ends.

  [TAKEOWNERSHIP was added in Tor 0.2.2.28-beta.]

3.24. AUTHCHALLENGE

  The syntax is:

    "AUTHCHALLENGE" SP "SAFECOOKIE"
                    SP ClientNonce
                    CRLF

    ClientNonce = 2*HEXDIG / QuotedString

  This command is used to begin the authentication routine for the
  SAFECOOKIE method of authentication.

  If the server accepts the command, the server reply format is:

    "250 AUTHCHALLENGE"
            SP "SERVERHASH=" ServerHash
            SP "SERVERNONCE=" ServerNonce
            CRLF

    ServerHash = 64*64HEXDIG
    ServerNonce = 64*64HEXDIG

  The ClientNonce, ServerHash, and ServerNonce values are
  encoded/decoded in the same way as the argument passed to the
  AUTHENTICATE command.  ServerNonce MUST be 32 bytes long.

  ServerHash is computed as:

    HMAC-SHA256("Tor safe cookie authentication server-to-controller hash",
                CookieString | ClientNonce | ServerNonce)

  (with the HMAC key as its first argument)

  After a controller sends a successful AUTHCHALLENGE command, the
  next command sent on the connection must be an AUTHENTICATE command,
  and the only authentication string which that AUTHENTICATE command
  will accept is:

    HMAC-SHA256("Tor safe cookie authentication controller-to-server hash",
                CookieString | ClientNonce | ServerNonce)

  [Unlike other commands besides AUTHENTICATE, AUTHCHALLENGE may be
  used (but only once!) before AUTHENTICATE.]

  [AUTHCHALLENGE was added in Tor 0.2.3.13-alpha.]

3.25. DROPGUARDS

  The syntax is:

    "DROPGUARDS" CRLF

  Tells the server to drop all guard nodes. Do not invoke this command
  lightly; it can increase vulnerability to tracking attacks over time.

  Tor replies with "250 OK" on success.

  [DROPGUARDS was added in Tor 0.2.5.2-alpha.]

3.26. HSFETCH

  The syntax is:

    "HSFETCH" SP (HSAddress / "v" Version "-" DescId)
              *[SP "SERVER=" Server] CRLF

    HSAddress = 16*Base32Character / 56*Base32Character
    Version = "2" / "3"
    DescId = 32*Base32Character
    Server = LongName

  This command launches hidden service descriptor fetch(es) for the given
  HSAddress or DescId.

  HSAddress can be version 2 or version 3 addresses. DescIDs can only be
  version 2 IDs. Version 2 addresses consist of 16*Base32Character and
  version 3 addresses consist of 56*Base32Character.

  If a DescId is specified, at least one Server MUST also be provided,
  otherwise a 512 error is returned. If no DescId and Server(s) are specified,
  it behaves like a normal Tor client descriptor fetch. If one or more
  Server are given, they are used instead triggering a fetch on each of them
  in parallel.

  The caching behavior when fetching a descriptor using this command is
  identical to normal Tor client behavior.

  Details on how to compute a descriptor id (DescId) can be found in
  rend-spec.txt section 1.3.

  If any values are unrecognized, a 513 error is returned and the command is
  stopped. On success, Tor replies "250 OK" then Tor MUST eventually follow
  this with both a HS_DESC and HS_DESC_CONTENT events with the results. If
  SERVER is specified then events are emitted for each location.

  Examples are:

     C: HSFETCH v2-gezdgnbvgy3tqolbmjrwizlgm5ugs2tl
        SERVER=9695DFC35FFEB861329B9F1AB04C46397020CE31
     S: 250 OK

     C: HSFETCH ajkhdsfuygaesfaa
     S: 250 OK

     C: HSFETCH vww6ybal4bd7szmgncyruucpgfkqahzddi37ktceo3ah7ngmcopnpyyd
     S: 250 OK

  [HSFETCH was added in Tor 0.2.7.1-alpha]
  [HS v3 support added 0.4.1.1-alpha]

3.27. ADD_ONION

  The syntax is:

    "ADD_ONION" SP KeyType ":" KeyBlob
            [SP "Flags=" Flag *("," Flag)]
            [SP "MaxStreams=" NumStreams]
            1*(SP "Port=" VirtPort ["," Target])
            *(SP "ClientAuth=" ClientName [":" ClientBlob]) CRLF
            *(SP "ClientAuthV3=" V3Key) CRLF

    KeyType =
     "NEW"     / ; The server should generate a key of algorithm KeyBlob
     "RSA1024" / ; The server should use the 1024 bit RSA key provided
                   in as KeyBlob (v2).
     "ED25519-V3"; The server should use the ed25519 v3 key provided in as
                   KeyBlob (v3).

    KeyBlob =
     "BEST"    / ; The server should generate a key using the "best"
                   supported algorithm (KeyType == "NEW").
                   [As of 0.4.2.3-alpha, ED25519-V3 is used]
     "RSA1024" / ; The server should generate a 1024 bit RSA key
                   (KeyType == "NEW") (v2).
     "ED25519-V3"; The server should generate an ed25519 private key
                   (KeyType == "NEW") (v3).
     String      ; A serialized private key (without whitespace)

    Flag =
     "DiscardPK" / ; The server should not include the newly generated
                     private key as part of the response.
     "Detach"    / ; Do not associate the newly created Onion Service
                     to the current control connection.
     "BasicAuth" / ; Client authorization is required using the "basic"
                     method (v2 only).
     "V3Auth"    / ; Version 3 client authorization is required (v3 only).

     "NonAnonymous" /; Add a non-anonymous Single Onion Service. Tor
                       checks this flag matches its configured hidden
                       service anonymity mode.
     "MaxStreamsCloseCircuit"; Close the circuit is the maximum streams
                               allowed is reached.

    NumStreams = A value between 0 and 65535 which is used as the maximum
                 streams that can be attached on a rendezvous circuit. Setting
                 it to 0 means unlimited which is also the default behavior.

    VirtPort = The virtual TCP Port for the Onion Service (As in the
               HiddenServicePort "VIRTPORT" argument).

    Target = The (optional) target for the given VirtPort (As in the
             optional HiddenServicePort "TARGET" argument).

    ClientName = An identifier 1 to 16 characters long, using only
                 characters in A-Za-z0-9+-_ (no spaces) (v2 only).

    ClientBlob = Authorization data for the client, in an opaque format
                 specific to the authorization method (v2 only).

    V3Key = The client's base32-encoded x25519 public key, using only the key
            part of rend-spec-v3.txt section G.1.2 (v3 only).

  The server reply format is:

    "250-ServiceID=" ServiceID CRLF
    ["250-PrivateKey=" KeyType ":" KeyBlob CRLF]
    *("250-ClientAuth=" ClientName ":" ClientBlob CRLF)
    "250 OK" CRLF

    ServiceID = The Onion Service address without the trailing ".onion"
                suffix

  Tells the server to create a new Onion ("Hidden") Service, with the
  specified private key and algorithm.  If a KeyType of "NEW" is selected,
  the server will generate a new keypair using the selected algorithm.
  The "Port" argument's VirtPort and Target values have identical
  semantics to the corresponding HiddenServicePort configuration values.

  The server response will only include a private key if the server was
  requested to generate a new keypair, and also the "DiscardPK" flag was
  not specified. (Note that if "DiscardPK" flag is specified, there is no
  way to recreate the generated keypair and the corresponding Onion
  Service at a later date).

  If client authorization is enabled using the "BasicAuth" flag (which is v2
  only), the service will not be accessible to clients without valid
  authorization data (configured with the "HidServAuth" option).  The list of
  authorized clients is specified with one or more "ClientAuth" parameters.
  If "ClientBlob" is not specified for a client, a new credential will be
  randomly generated and returned.

  Tor instances can either be in anonymous hidden service mode, or
  non-anonymous single onion service mode. All hidden services on the same
  tor instance have the same anonymity. To guard against unexpected loss
  of anonymity, Tor checks that the ADD_ONION "NonAnonymous" flag matches
  the current hidden service anonymity mode. The hidden service anonymity
  mode is configured using the Tor options HiddenServiceSingleHopMode and
  HiddenServiceNonAnonymousMode. If both these options are 1, the
  "NonAnonymous" flag must be provided to ADD_ONION. If both these options
  are 0 (the Tor default), the flag must NOT be provided.

  Once created the new Onion Service will remain active until either the
  Onion Service is removed via "DEL_ONION", the server terminates, or the
  control connection that originated the "ADD_ONION" command is closed.
  It is possible to override disabling the Onion Service on control
  connection close by specifying the "Detach" flag.

  It is the Onion Service server application's responsibility to close
  existing client connections if desired after the Onion Service is
  removed.

  (The KeyBlob format is left intentionally opaque, however for "RSA1024"
  keys it is currently the Base64 encoded DER representation of a PKCS#1
  RSAPrivateKey, with all newlines removed. For a "ED25519-V3" key is
  the Base64 encoding of the concatenation of the 32-byte ed25519 secret
  scalar in little-endian and the 32-byte ed25519 PRF secret.)

  [Note: The ED25519-V3 format is not the same as, e.g., SUPERCOP
  ed25519/ref, which stores the concatenation of the 32-byte ed25519
  hash seed concatenated with the 32-byte public key, and which derives
  the secret scalar and PRF secret by expanding the hash seed with
  SHA-512.  Our key blinding scheme is incompatible with storing
  private keys as seeds, so we store the secret scalar alongside the
  PRF secret, and just pay the cost of recomputing the public key when
  importing an ED25519-V3 key.]

  Examples:

     C: ADD_ONION NEW:BEST Flags=DiscardPK Port=80
     S: 250-ServiceID=exampleoniont2pqglbny66wpovyvao3ylc23eileodtevc4b75ikpad
     S: 250 OK

     C: ADD_ONION RSA1024:[Blob Redacted] Port=80,192.168.1.1:8080
     S: 250-ServiceID=sampleonion12456
     S: 250 OK

     C: ADD_ONION NEW:BEST Port=22 Port=80,8080
     S: 250-ServiceID=sampleonion4t2pqglbny66wpovyvao3ylc23eileodtevc4b75ikpad
     S: 250-PrivateKey=ED25519-V3:[Blob Redacted]
     S: 250 OK

     C: ADD_ONION NEW:RSA1024 Flags=DiscardPK,BasicAuth Port=22
        ClientAuth=alice:[Blob Redacted] ClientAuth=bob
     S: 250-ServiceID=testonion1234567
     S: 250-ClientAuth=bob:[Blob Redacted]
     S: 250 OK

     C: ADD_ONION NEW:ED25519-V3 ClientAuthV3=[Blob Redacted] Port=22
     S: 250-ServiceID=n35etu3yjxrqjpntmfziom5sjwspoydchmelc4xleoy4jk2u4lziz2yd
     S: 250-ClientAuthV3=[Blob Redacted]
     S: 250 OK

  Examples with Tor in anonymous onion service mode:

     C: ADD_ONION NEW:BEST Flags=DiscardPK Port=22
     S: 250-ServiceID=exampleoniont2pqglbny66wpovyvao3ylc23eileodtevc4b75ikpad
     S: 250 OK

     C: ADD_ONION NEW:BEST Flags=DiscardPK,NonAnonymous Port=22
     S: 512 Tor is in anonymous hidden service mode

  Examples with Tor in non-anonymous onion service mode:

     C: ADD_ONION NEW:BEST Flags=DiscardPK Port=22
     S: 512 Tor is in non-anonymous hidden service mode

     C: ADD_ONION NEW:BEST Flags=DiscardPK,NonAnonymous Port=22
     S: 250-ServiceID=exampleoniont2pqglbny66wpovyvao3ylc23eileodtevc4b75ikpad
     S: 250 OK

  [ADD_ONION was added in Tor 0.2.7.1-alpha.]
  [MaxStreams and MaxStreamsCloseCircuit were added in Tor 0.2.7.2-alpha]
  [ClientAuth was added in Tor 0.2.9.1-alpha. It is v2 only.]
  [NonAnonymous was added in Tor 0.2.9.3-alpha.]
  [HS v3 support added 0.3.3.1-alpha]
  [ClientV3Auth support added 0.4.6.1-alpha]

3.28. DEL_ONION

  The syntax is:

    "DEL_ONION" SP ServiceID CRLF

    ServiceID = The Onion Service address without the trailing ".onion"
                suffix

  Tells the server to remove an Onion ("Hidden") Service, that was
  previously created via an "ADD_ONION" command.  It is only possible to
  remove Onion Services that were created on the same control connection
  as the "DEL_ONION" command, and those that belong to no control
  connection in particular (The "Detach" flag was specified at creation).

  If the ServiceID is invalid, or is neither owned by the current control
  connection nor a detached Onion Service, the server will return a 552.

  It is the Onion Service server application's responsibility to close
  existing client connections if desired after the Onion Service has been
  removed via "DEL_ONION".

  Tor replies with "250 OK" on success, or a 512 if there are an invalid
  number of arguments, or a 552 if it doesn't recognize the ServiceID.

  [DEL_ONION was added in Tor 0.2.7.1-alpha.]
  [HS v3 support added 0.3.3.1-alpha]

3.29. HSPOST

  The syntax is:

    "+HSPOST" *[SP "SERVER=" Server] [SP "HSADDRESS=" HSAddress]
              CRLF Descriptor CRLF "." CRLF

    Server = LongName
    HSAddress = 56*Base32Character
    Descriptor =  The text of the descriptor formatted as specified
    in rend-spec.txt section 1.3.

  The "HSAddress" key is optional and only applies for v3 descriptors. A 513
  error is returned if used with v2.

  This command launches a hidden service descriptor upload to the specified
  HSDirs. If one or more Server arguments are provided, an upload is triggered
  on each of them in parallel. If no Server options are provided, it behaves
  like a normal HS descriptor upload and will upload to the set of responsible
  HS directories.

  If any value is unrecognized, a 552 error is returned and the command is
  stopped. If there is an error in parsing the descriptor, the server
  must send a "554 Invalid descriptor" reply.

  On success, Tor replies "250 OK" then Tor MUST eventually follow
  this with a HS_DESC event with the result for each upload location.

  Examples are:

     C: +HSPOST SERVER=9695DFC35FFEB861329B9F1AB04C46397020CE31
        [DESCRIPTOR]
        .
     S: 250 OK

  [HSPOST was added in Tor 0.2.7.1-alpha]

3.30. ONION_CLIENT_AUTH_ADD

  The syntax is:

    "ONION_CLIENT_AUTH_ADD" SP HSAddress
                            SP KeyType ":" PrivateKeyBlob
                            [SP "ClientName=" Nickname]
                            [SP "Flags=" TYPE] CRLF

    HSAddress = 56*Base32Character
    KeyType = "x25519" is the only one supported right now
    PrivateKeyBlob = base64 encoding of x25519 key

  Tells the connected Tor to add client-side v3 client auth credentials for the
  onion service with "HSAddress". The "PrivateKeyBlob" is the x25519 private
  key that should be used for this client, and "Nickname" is an optional
  nickname for the client.

  FLAGS is a comma-separated tuple of flags for this new client. For now, the
  currently supported flags are:

    "Permanent" - This client's credentials should be stored in the filesystem.
                  If this is not set, the client's credentials are ephemeral
                  and stored in memory.

  If client auth credentials already existed for this service, replace them
  with the new ones.

  If Tor has cached onion service descriptors that it has been unable to
  decrypt in the past (due to lack of client auth credentials), attempt to
  decrypt those descriptors as soon as this command succeeds.

  On success, "250 OK" is returned. Otherwise, the following error codes exist:

    251 - Client auth credentials for this onion service already existed and replaced.
    252 - Added client auth credentials and successfully decrypted a cached descriptor.
    451 - We reached authorized client capacity
    512 - Syntax error in "HSAddress", or "PrivateKeyBlob" or "Nickname"
    551 - Client with with this "Nickname" already exists
    552 - Unrecognized KeyType

  [ONION_CLIENT_AUTH_ADD was added in Tor 0.4.3.1-alpha]

3.31. ONION_CLIENT_AUTH_REMOVE

  The syntax is:

    "ONION_CLIENT_AUTH_REMOVE" SP HSAddress

   KeyType = "x25519" is the only one supported right now

  Tells the connected Tor to remove the client-side v3 client auth credentials
  for the onion service with "HSAddress".

  On success "250 OK" is returned. Otherwise, the following error codes exist:

    512 - Syntax error in "HSAddress".
    251 - Client credentials for "HSAddress" did not exist.

  [ONION_CLIENT_AUTH_REMOVE was added in Tor 0.4.3.1-alpha]

3.32. ONION_CLIENT_AUTH_VIEW

  The syntax is:

    "ONION_CLIENT_AUTH_VIEW" [SP HSAddress] CRLF

  Tells the connected Tor to list all the stored client-side v3 client auth
  credentials for "HSAddress". If no "HSAddress" is provided, list all the
  stored client-side v3 client auth credentials.

  The server reply format is:

    "250-ONION_CLIENT_AUTH_VIEW" [SP HSAddress] CRLF
    *("250-CLIENT" SP HSAddress SP KeyType ":" PrivateKeyBlob
                  [SP "ClientName=" Nickname]
                  [SP "Flags=" FLAGS] CRLF)
    "250 OK" CRLF

    HSAddress = The onion address under which this credential is stored
    KeyType = "x25519" is the only one supported right now
    PrivateKeyBlob = base64 encoding of x25519 key

  "Nickname" is an optional nickname for this client, which can be set either
  through the ONION_CLIENT_AUTH_ADD command, or it's the filename of this
  client if the credentials are stored in the filesystem.

  FLAGS is a comma-separated field of flags for this client, the currently
  supported flags are:

      "Permanent" - This client's credentials are stored in the filesystem.

  On success "250 OK" is returned. Otherwise, the following error codes exist:

    512 - Syntax error in "HSAddress".

  [ONION_CLIENT_AUTH_VIEW was added in Tor 0.4.3.1-alpha]

3.33. DROPOWNERSHIP

  The syntax is:

    "DROPOWNERSHIP" CRLF

  This command instructs Tor to relinquish ownership of its control
  connection. As such tor will not shut down when this control
  connection is closed.

  This method is idempotent. If the control connection does not
  already have ownership this method returns successfully, and
  does nothing.

  The controller can call TAKEOWNERSHIP again to re-establish
  ownership.

  [DROPOWNERSHIP was added in Tor 0.4.0.0-alpha]

3.34. DROPTIMEOUTS

  The syntax is:
    "DROPTIMEOUTS" CRLF

  Tells the server to drop all circuit build times. Do not invoke this command
  lightly; it can increase vulnerability to tracking attacks over time.

  Tor replies with "250 OK" on success. Tor also emits the BUILDTIMEOUT_SET
  RESET event right after this "250 OK".

  [DROPTIMEOUTS was added in Tor 0.4.5.0-alpha.]

4. Replies

  Reply codes follow the same 3-character format as used by SMTP, with the
  first character defining a status, the second character defining a
  subsystem, and the third designating fine-grained information.

  The TC protocol currently uses the following first characters:

    2yz   Positive Completion Reply
       The command was successful; a new request can be started.

    4yz   Temporary Negative Completion reply
       The command was unsuccessful but might be reattempted later.

    5yz   Permanent Negative Completion Reply
       The command was unsuccessful; the client should not try exactly
       that sequence of commands again.

    6yz   Asynchronous Reply
       Sent out-of-order in response to an earlier SETEVENTS command.

  The following second characters are used:

    x0z   Syntax
       Sent in response to ill-formed or nonsensical commands.

    x1z   Protocol
       Refers to operations of the Tor Control protocol.

    x5z   Tor
       Refers to actual operations of Tor system.

  The following codes are defined:

     250 OK
     251 Operation was unnecessary
         [Tor has declined to perform the operation, but no harm was done.]

     451 Resource exhausted

     500 Syntax error: protocol

     510 Unrecognized command
     511 Unimplemented command
     512 Syntax error in command argument
     513 Unrecognized command argument
     514 Authentication required
     515 Bad authentication

     550 Unspecified Tor error

     551 Internal error
               [Something went wrong inside Tor, so that the client's
                request couldn't be fulfilled.]

     552 Unrecognized entity
               [A configuration key, a stream ID, circuit ID, event,
                mentioned in the command did not actually exist.]

     553 Invalid configuration value
         [The client tried to set a configuration option to an
           incorrect, ill-formed, or impossible value.]

     554 Invalid descriptor

     555 Unmanaged entity

     650 Asynchronous event notification

  Unless specified to have specific contents, the human-readable messages
  in error replies should not be relied upon to match those in this document.

4.1. Asynchronous events

  These replies can be sent after a corresponding SETEVENTS command has been
  received.  They will not be interleaved with other Reply elements, but they
  can appear between a command and its corresponding reply.  For example,
  this sequence is possible:

     C: SETEVENTS CIRC
     S: 250 OK
     C: GETCONF SOCKSPORT ORPORT
     S: 650 CIRC 1000 EXTENDED moria1,moria2
     S: 250-SOCKSPORT=9050
     S: 250 ORPORT=0

  But this sequence is disallowed:

     C: SETEVENTS CIRC
     S: 250 OK
     C: GETCONF SOCKSPORT ORPORT
     S: 250-SOCKSPORT=9050
     S: 650 CIRC 1000 EXTENDED moria1,moria2
     S: 250 ORPORT=0

  Clients MUST tolerate more arguments in an asynchronous reply than
  expected, and MUST tolerate more lines in an asynchronous reply than
  expected.  For instance, a client that expects a CIRC message like:

      650 CIRC 1000 EXTENDED moria1,moria2

  must tolerate:

      650-CIRC 1000 EXTENDED moria1,moria2 0xBEEF
      650-EXTRAMAGIC=99
      650 ANONYMITY=high

  If clients receives extended events (selected by USEFEATUERE
  EXTENDED_EVENTS in Tor 0.1.2.2-alpha..Tor-0.2.1.x, and always-on in
  Tor 0.2.2.x and later), then each event line as specified below may be
  followed by additional arguments and additional lines.  Additional
  lines will be of the form:

      "650" ("-"/" ") KEYWORD ["=" ARGUMENTS] CRLF

  Additional arguments will be of the form

      SP KEYWORD ["=" ( QuotedString / * NonSpDquote ) ]

  Clients MUST tolerate events with arguments and keywords they do not
  recognize, and SHOULD process those events as if any unrecognized
  arguments and keywords were not present.

  Clients SHOULD NOT depend on the order of keyword=value arguments,
  and SHOULD NOT depend on there being no new keyword=value arguments
  appearing between existing keyword=value arguments, though as of this
  writing (Jun 2011) some do.  Thus, extensions to this protocol should
  add new keywords only after the existing keywords, until all
  controllers have been fixed.  At some point this "SHOULD NOT" might
  become a "MUST NOT".

4.1.1. Circuit status changed

   The syntax is:

     "650" SP "CIRC" SP CircuitID SP CircStatus [SP Path]
          [SP "BUILD_FLAGS=" BuildFlags] [SP "PURPOSE=" Purpose]
          [SP "HS_STATE=" HSState] [SP "REND_QUERY=" HSAddress]
          [SP "TIME_CREATED=" TimeCreated]
          [SP "REASON=" Reason [SP "REMOTE_REASON=" Reason]]
          [SP "SOCKS_USERNAME=" EscapedUsername]
          [SP "SOCKS_PASSWORD=" EscapedPassword]
          CRLF

      CircStatus =
               "LAUNCHED" / ; circuit ID assigned to new circuit
               "BUILT"    / ; all hops finished, can now accept streams
               "GUARD_WAIT" / ; all hops finished, waiting to see if a
                              ;  circuit with a better guard will be usable.
               "EXTENDED" / ; one more hop has been completed
               "FAILED"   / ; circuit closed (was not built)
               "CLOSED"     ; circuit closed (was built)

      Path = LongName *("," LongName)
        ; In Tor versions 0.1.2.2-alpha through 0.2.2.1-alpha with feature
        ; VERBOSE_NAMES turned off and before version 0.1.2.2-alpha, Path
        ; is as follows:
        ; Path = ServerID *("," ServerID)

      BuildFlags = BuildFlag *("," BuildFlag)
      BuildFlag = "ONEHOP_TUNNEL" / "IS_INTERNAL" /
                  "NEED_CAPACITY" / "NEED_UPTIME"

      Purpose = "GENERAL" / "HS_CLIENT_INTRO" / "HS_CLIENT_REND" /
                "HS_SERVICE_INTRO" / "HS_SERVICE_REND" / "TESTING" /
                "CONTROLLER" / "MEASURE_TIMEOUT" /
                "HS_VANGUARDS" / "PATH_BIAS_TESTING" /
                "CIRCUIT_PADDING"

      HSState = "HSCI_CONNECTING" / "HSCI_INTRO_SENT" / "HSCI_DONE" /
                "HSCR_CONNECTING" / "HSCR_ESTABLISHED_IDLE" /
                "HSCR_ESTABLISHED_WAITING" / "HSCR_JOINED" /
                "HSSI_CONNECTING" / "HSSI_ESTABLISHED" /
                "HSSR_CONNECTING" / "HSSR_JOINED"

      EscapedUsername = QuotedString
      EscapedPassword = QuotedString

      HSAddress = 16*Base32Character / 56*Base32Character
      Base32Character = ALPHA / "2" / "3" / "4" / "5" / "6" / "7"

      TimeCreated = ISOTime2Frac
      Seconds = 1*DIGIT
      Microseconds = 1*DIGIT

      Reason = "NONE" / "TORPROTOCOL" / "INTERNAL" / "REQUESTED" /
               "HIBERNATING" / "RESOURCELIMIT" / "CONNECTFAILED" /
               "OR_IDENTITY" / "OR_CONN_CLOSED" / "TIMEOUT" /
               "FINISHED" / "DESTROYED" / "NOPATH" / "NOSUCHSERVICE" /
               "MEASUREMENT_EXPIRED"

   The path is provided only when the circuit has been extended at least one
   hop.

   The "BUILD_FLAGS" field is provided only in versions 0.2.3.11-alpha
   and later.  Clients MUST accept build flags not listed above.
   Build flags are defined as follows:

      ONEHOP_TUNNEL   (one-hop circuit, used for tunneled directory conns)
      IS_INTERNAL     (internal circuit, not to be used for exiting streams)
      NEED_CAPACITY   (this circuit must use only high-capacity nodes)
      NEED_UPTIME     (this circuit must use only high-uptime nodes)

   The "PURPOSE" field is provided only in versions 0.2.1.6-alpha and
   later, and only if extended events are enabled (see 3.19).  Clients
   MUST accept purposes not listed above.  Purposes are defined as
   follows:

      GENERAL         (circuit for AP and/or directory request streams)
      HS_CLIENT_INTRO (HS client-side introduction-point circuit)
      HS_CLIENT_REND  (HS client-side rendezvous circuit; carries AP streams)
      HS_SERVICE_INTRO (HS service-side introduction-point circuit)
      HS_SERVICE_REND (HS service-side rendezvous circuit)
      TESTING         (reachability-testing circuit; carries no traffic)
      CONTROLLER      (circuit built by a controller)
      MEASURE_TIMEOUT (circuit being kept around to see how long it takes)
      HS_VANGUARDS    (circuit created ahead of time when using
                      HS vanguards, and later repurposed as needed)
      PATH_BIAS_TESTING (circuit used to probe whether our circuits are
                      being deliberately closed by an attacker)
      CIRCUIT_PADDING (circuit that is being held open to disguise its
                      true close time)

   The "HS_STATE" field is provided only for hidden-service circuits,
   and only in versions 0.2.3.11-alpha and later.  Clients MUST accept
   hidden-service circuit states not listed above.  Hidden-service
   circuit states are defined as follows:

      HSCI_*      (client-side introduction-point circuit states)
        HSCI_CONNECTING          (connecting to intro point)
        HSCI_INTRO_SENT          (sent INTRODUCE1; waiting for reply from IP)
        HSCI_DONE                (received reply from IP relay; closing)

      HSCR_*      (client-side rendezvous-point circuit states)
        HSCR_CONNECTING          (connecting to or waiting for reply from RP)
        HSCR_ESTABLISHED_IDLE    (established RP; waiting for introduction)
        HSCR_ESTABLISHED_WAITING (introduction sent to HS; waiting for rend)
        HSCR_JOINED              (connected to HS)

      HSSI_*      (service-side introduction-point circuit states)
        HSSI_CONNECTING          (connecting to intro point)
        HSSI_ESTABLISHED         (established intro point)

      HSSR_*      (service-side rendezvous-point circuit states)
        HSSR_CONNECTING          (connecting to client's rend point)
        HSSR_JOINED              (connected to client's RP circuit)

   The "SOCKS_USERNAME" and "SOCKS_PASSWORD" fields indicate the credentials
   that were used by a SOCKS client to connect to Tor's SOCKS port and
   initiate this circuit. (Streams for SOCKS clients connected with different
   usernames and/or passwords are isolated on separate circuits if the
   IsolateSOCKSAuth flag is active; see Proposal 171.) [Added in Tor
   0.4.3.1-alpha.]

   The "REND_QUERY" field is provided only for hidden-service-related
   circuits, and only in versions 0.2.3.11-alpha and later.  Clients
   MUST accept hidden service addresses in formats other than that
   specified above. [Added in Tor 0.4.3.1-alpha.]

   The "TIME_CREATED" field is provided only in versions 0.2.3.11-alpha and
   later.  TIME_CREATED is the time at which the circuit was created or
   cannibalized. [Added in Tor 0.4.3.1-alpha.]

   The "REASON" field is provided only for FAILED and CLOSED events, and only
   if extended events are enabled (see 3.19).  Clients MUST accept reasons
   not listed above. [Added in Tor 0.4.3.1-alpha.]  Reasons are as given in
   tor-spec.txt, except for:

      NOPATH              (Not enough nodes to make circuit)
      MEASUREMENT_EXPIRED (As "TIMEOUT", except that we had left the circuit
                           open for measurement purposes to see how long it
                           would take to finish.)
      IP_NOW_REDUNDANT    (Closing a circuit to an introduction point that
                           has become redundant, since some other circuit
                           opened in parallel with it has succeeded.)

   The "REMOTE_REASON" field is provided only when we receive a DESTROY or
   TRUNCATE cell, and only if extended events are enabled.  It contains the
   actual reason given by the remote OR for closing the circuit. Clients MUST
   accept reasons not listed above.  Reasons are as listed in tor-spec.txt.
   [Added in Tor 0.4.3.1-alpha.]

4.1.2. Stream status changed

    The syntax is:

      "650" SP "STREAM" SP StreamID SP StreamStatus SP CircuitID SP Target
          [SP "REASON=" Reason [ SP "REMOTE_REASON=" Reason ]]
          [SP "SOURCE=" Source] [ SP "SOURCE_ADDR=" Address ":" Port ]
          [SP "PURPOSE=" Purpose] [SP "SOCKS_USERNAME=" EscapedUsername]
          [SP "SOCKS_PASSWORD=" EscapedPassword]
          [SP "CLIENT_PROTOCOL=" ClientProtocol] [SP "NYM_EPOCH=" NymEpoch]
          [SP "SESSION_GROUP=" SessionGroup] [SP "ISO_FIELDS=" IsoFields]
          CRLF

      StreamStatus =
               "NEW"          / ; New request to connect
               "NEWRESOLVE"   / ; New request to resolve an address
               "REMAP"        / ; Address re-mapped to another
               "SENTCONNECT"  / ; Sent a connect cell along a circuit
               "SENTRESOLVE"  / ; Sent a resolve cell along a circuit
               "SUCCEEDED"    / ; Received a reply; stream established
               "FAILED"       / ; Stream failed and not retriable
               "CLOSED"       / ; Stream closed
               "DETACHED"     / ; Detached from circuit; still retriable
               "CONTROLLER_WAIT"  ; Waiting for controller to use ATTACHSTREAM
                                  ; (new in 0.4.5.1-alpha)
               "XOFF_SENT"  ; XOFF has been sent for this stream
                            ; (new in 0.4.7.5-alpha)
               "XOFF_RECV"  ; XOFF has been received for this stream
                            ; (new in 0.4.7.5-alpha)
               "XON_SENT"  ; XON has been sent for this stream
                           ; (new in 0.4.7.5-alpha)
               "XON_RECV"  ; XON has been received for this stream
                           ; (new in 0.4.7.5-alpha)

       Target = TargetAddress ":" Port
       Port = an integer from 0 to 65535 inclusive
       TargetAddress = Address / "(Tor_internal)"

       EscapedUsername = QuotedString
       EscapedPassword = QuotedString

       ClientProtocol =
               "SOCKS4"      /
               "SOCKS5"      /
               "TRANS"       /
               "NATD"        /
               "DNS"         /
               "HTTPCONNECT" /
               "UNKNOWN"

       NymEpoch = a nonnegative integer
       SessionGroup = an integer

       IsoFields = a comma-separated list of IsoField values

       IsoField =
               "CLIENTADDR" /
               "CLIENTPORT" /
               "DESTADDR" /
               "DESTPORT" /
               the name of a field that is valid for STREAM events

  The circuit ID designates which circuit this stream is attached to.  If
  the stream is unattached, the circuit ID "0" is given.  The target
  indicates the address which the stream is meant to resolve or connect to;
  it can be "(Tor_internal)" for a virtual stream created by the Tor program
  to talk to itself.

      Reason = "MISC" / "RESOLVEFAILED" / "CONNECTREFUSED" /
               "EXITPOLICY" / "DESTROY" / "DONE" / "TIMEOUT" /
               "NOROUTE" / "HIBERNATING" / "INTERNAL"/ "RESOURCELIMIT" /
               "CONNRESET" / "TORPROTOCOL" / "NOTDIRECTORY" / "END" /
               "PRIVATE_ADDR"

   The "REASON" field is provided only for FAILED, CLOSED, and DETACHED
   events, and only if extended events are enabled (see 3.19).  Clients MUST
   accept reasons not listed above.  Reasons are as given in tor-spec.txt,
   except for:

      END          (We received a RELAY_END cell from the other side of this
                    stream.)
      PRIVATE_ADDR (The client tried to connect to a private address like
                    127.0.0.1 or 10.0.0.1 over Tor.)
      [XXXX document more. -NM]

   The "REMOTE_REASON" field is provided only when we receive a RELAY_END
   cell, and only if extended events are enabled.  It contains the actual
   reason given by the remote OR for closing the stream. Clients MUST accept
   reasons not listed above.  Reasons are as listed in tor-spec.txt.

   "REMAP" events include a Source if extended events are enabled:

      Source = "CACHE" / "EXIT"

   Clients MUST accept sources not listed above.  "CACHE" is given if
   the Tor client decided to remap the address because of a cached
   answer, and "EXIT" is given if the remote node we queried gave us
   the new address as a response.

   The "SOURCE_ADDR" field is included with NEW and NEWRESOLVE events if
   extended events are enabled.  It indicates the address and port
   that requested the connection, and can be (e.g.) used to look up the
   requesting program.

      Purpose = "DIR_FETCH" / "DIR_UPLOAD" / "DNS_REQUEST" /
                "USER" /  "DIRPORT_TEST"

   The "PURPOSE" field is provided only for NEW and NEWRESOLVE events, and
   only if extended events are enabled (see 3.19).  Clients MUST accept
   purposes not listed above.  The purposes above are defined as:

       "DIR_FETCH" -- This stream is generated internally to Tor for
         fetching directory information.
       "DIR_UPLOAD" -- An internal stream for uploading information to
         a directory authority.
       "DIRPORT_TEST" -- A stream we're using to test our own directory
         port to make sure it's reachable.
       "DNS_REQUEST" -- A user-initiated DNS request.
       "USER" -- This stream is handling user traffic, OR it's internal
         to Tor, but it doesn't match one of the purposes above.

   The "SOCKS_USERNAME" and "SOCKS_PASSWORD" fields indicate the credentials
   that were used by a SOCKS client to connect to Tor's SOCKS port and
   initiate this stream. (Streams for SOCKS clients connected with different
   usernames and/or passwords are isolated on separate circuits if the
   IsolateSOCKSAuth flag is active; see Proposal 171.)

   The "CLIENT_PROTOCOL" field indicates the protocol that was used by a client
   to initiate this stream. (Streams for clients connected with different
   protocols are isolated on separate circuits if the IsolateClientProtocol
   flag is active.)  Controllers MUST tolerate unrecognized client protocols.

   The "NYM_EPOCH" field indicates the nym epoch that was active when a client
   initiated this stream. The epoch increments when the NEWNYM signal is
   received. (Streams with different nym epochs are isolated on separate
   circuits.)

   The "SESSION_GROUP" field indicates the session group of the listener port
   that a client used to initiate this stream. By default, the session group is
   different for each listener port, but this can be overridden for a listener
   via the "SessionGroup" option in torrc. (Streams with different session
   groups are isolated on separate circuits.)

   The "ISO_FIELDS" field indicates the set of STREAM event fields for which
   stream isolation is enabled for the listener port that a client used to
   initiate this stream.  The special values "CLIENTADDR", "CLIENTPORT",
   "DESTADDR", and "DESTPORT", if their correspondingly named fields are not
   present, refer to the Address and Port components of the "SOURCE_ADDR" and
   Target fields.

4.1.3. OR Connection status changed

  The syntax is:

    "650" SP "ORCONN" SP (LongName / Target) SP ORStatus [ SP "REASON="
             Reason ] [ SP "NCIRCS=" NumCircuits ] [ SP "ID=" ConnID ] CRLF

    ORStatus = "NEW" / "LAUNCHED" / "CONNECTED" / "FAILED" / "CLOSED"

        ; In Tor versions 0.1.2.2-alpha through 0.2.2.1-alpha with feature
        ; VERBOSE_NAMES turned off and before version 0.1.2.2-alpha, OR
        ; Connection is as follows:
        "650" SP "ORCONN" SP (ServerID / Target) SP ORStatus [ SP "REASON="
                 Reason ] [ SP "NCIRCS=" NumCircuits ] CRLF

  NEW is for incoming connections, and LAUNCHED is for outgoing
  connections. CONNECTED means the TLS handshake has finished (in
  either direction). FAILED means a connection is being closed that
  hasn't finished its handshake, and CLOSED is for connections that
  have handshaked.

  A LongName or ServerID is specified unless it's a NEW connection, in
  which case we don't know what server it is yet, so we use Address:Port.

  If extended events are enabled (see 3.19), optional reason and
  circuit counting information is provided for CLOSED and FAILED
  events.

      Reason = "MISC" / "DONE" / "CONNECTREFUSED" /
               "IDENTITY" / "CONNECTRESET" / "TIMEOUT" / "NOROUTE" /
               "IOERROR" / "RESOURCELIMIT" / "PT_MISSING"

  NumCircuits counts both established and pending circuits.

  The ORStatus values are as follows:

     NEW -- We have received a new incoming OR connection, and are starting
       the server-side handshake.
     LAUNCHED -- We have launched a new outgoing OR connection, and are
       starting the client-side handshake.
     CONNECTED -- The OR connection has been connected and the handshake is
       done.
     FAILED -- Our attempt to open the OR connection failed.
     CLOSED -- The OR connection closed in an unremarkable way.

  The Reason values for closed/failed OR connections are:

     DONE -- The OR connection has shut down cleanly.
     CONNECTREFUSED -- We got an ECONNREFUSED while connecting to the target
        OR.
     IDENTITY -- We connected to the OR, but found that its identity was
        not what we expected.
     CONNECTRESET -- We got an ECONNRESET or similar IO error from the
        connection with the OR.
     TIMEOUT -- We got an ETIMEOUT or similar IO error from the connection
        with the OR, or we're closing the connection for being idle for too
        long.
     NOROUTE -- We got an ENOTCONN, ENETUNREACH, ENETDOWN, EHOSTUNREACH, or
        similar error while connecting to the OR.
     IOERROR -- We got some other IO error on our connection to the OR.
     RESOURCELIMIT -- We don't have enough operating system resources (file
        descriptors, buffers, etc) to connect to the OR.
     PT_MISSING -- No pluggable transport was available.
     MISC -- The OR connection closed for some other reason.

  [First added ID parameter in 0.2.5.2-alpha]

4.1.4. Bandwidth used in the last second

  The syntax is:

     "650" SP "BW" SP BytesRead SP BytesWritten *(SP Type "=" Num) CRLF
     BytesRead = 1*DIGIT
     BytesWritten = 1*DIGIT
     Type = "DIR" / "OR" / "EXIT" / "APP" / ...
     Num = 1*DIGIT

  BytesRead and BytesWritten are the totals. [In a future Tor version,
  we may also include a breakdown of the connection types that used
  bandwidth this second (not implemented yet).]

4.1.5. Log messages

  The syntax is:

     "650" SP Severity SP ReplyText CRLF

  or

     "650+" Severity CRLF Data 650 SP "OK" CRLF

     Severity = "DEBUG" / "INFO" / "NOTICE" / "WARN"/ "ERR"

  Some low-level logs may be sent from signal handlers, so their destination
  logs must be signal-safe. These low-level logs include backtraces,
  logging function errors, and errors in code called by logging functions.
  Signal-safe logs are never sent as control port log events.

  Control port message trace debug logs are never sent as control port log
  events, to avoid modifying control output when debugging.

4.1.6. New descriptors available

  This event is generated when new router descriptors (not microdescs or
  extrainfos or anything else) are received.

  Syntax:

     "650" SP "NEWDESC" 1*(SP LongName) CRLF
        ; In Tor versions 0.1.2.2-alpha through 0.2.2.1-alpha with feature
        ; VERBOSE_NAMES turned off and before version 0.1.2.2-alpha, it
        ; is as follows:
        "650" SP "NEWDESC" 1*(SP ServerID) CRLF

4.1.7. New Address mapping

  These events are generated when a new address mapping is entered in
  Tor's address map cache, or when the answer for a RESOLVE command is
  found.  Entries can be created by a successful or failed DNS lookup,
  a successful or failed connection attempt, a RESOLVE command,
  a MAPADDRESS command, the AutomapHostsOnResolve feature, or the
  TrackHostExits feature.

  Syntax:

     "650" SP "ADDRMAP" SP Address SP NewAddress SP Expiry
       [SP "error=" ErrorCode] [SP "EXPIRES=" UTCExpiry] [SP "CACHED=" Cached]
       [SP "STREAMID=" StreamId] CRLF

     NewAddress = Address / "<error>"
     Expiry = DQUOTE ISOTime DQUOTE / "NEVER"

     ErrorCode = "yes" / "internal" / "Unable to launch resolve request"
     UTCExpiry = DQUOTE IsoTime DQUOTE

     Cached = DQUOTE "YES" DQUOTE / DQUOTE "NO" DQUOTE
     StreamId = DQUOTE StreamId DQUOTE

  Error and UTCExpiry are only provided if extended events are enabled.
  The values for Error are mostly useless.  Future values will be
  chosen to match 1*(ALNUM / "_"); the "Unable to launch resolve request"
  value is a bug in Tor before 0.2.4.7-alpha.

  Expiry is expressed as the local time (rather than UTC).  This is a bug,
  left in for backward compatibility; new code should look at UTCExpiry
  instead.  (If Expiry is "NEVER", UTCExpiry is omitted.)

  Cached indicates whether the mapping will be stored until it expires, or if
  it is just a notification in response to a RESOLVE command.

  StreamId is the global stream identifier of the stream or circuit from which
  the address was resolved.

4.1.8. Descriptors uploaded to us in our role as authoritative dirserver

  [NOTE: This feature was removed in Tor 0.3.2.1-alpha.]

  Tor generates this event when it's a directory authority, and
  somebody has just uploaded a server descriptor.

  Syntax:

     "650" "+" "AUTHDIR_NEWDESCS" CRLF Action CRLF Message CRLF
       Descriptor CRLF "." CRLF "650" SP "OK" CRLF
     Action = "ACCEPTED" / "DROPPED" / "REJECTED"
     Message = Text

  The Descriptor field is the text of the server descriptor; the Action
  field is "ACCEPTED" if we're accepting the descriptor as the new
  best valid descriptor for its router, "REJECTED" if we aren't taking
  the descriptor and we're complaining to the uploading relay about
  it, and "DROPPED" if we decide to drop the descriptor without
  complaining.  The Message field is a human-readable string
  explaining why we chose the Action.  (It doesn't contain newlines.)

4.1.9. Our descriptor changed

  Syntax:

     "650" SP "DESCCHANGED" CRLF

  [First added in 0.1.2.2-alpha.]

4.1.10. Status events

  Status events (STATUS_GENERAL, STATUS_CLIENT, and STATUS_SERVER) are sent
  based on occurrences in the Tor process pertaining to the general state of
  the program.  Generally, they correspond to log messages of severity Notice
  or higher.  They differ from log messages in that their format is a
  specified interface.

  Syntax:

     "650" SP StatusType SP StatusSeverity SP StatusAction
                                         [SP StatusArguments] CRLF

     StatusType = "STATUS_GENERAL" / "STATUS_CLIENT" / "STATUS_SERVER"
     StatusSeverity = "NOTICE" / "WARN" / "ERR"
     StatusAction = 1*ALPHA
     StatusArguments = StatusArgument *(SP StatusArgument)
     StatusArgument = StatusKeyword '=' StatusValue
     StatusKeyword = 1*(ALNUM / "_")
     StatusValue = 1*(ALNUM / '_')  / QuotedString

     StatusAction is a string, and StatusArguments is a series of
     keyword=value pairs on the same line.  Values may be space-terminated
     strings, or quoted strings.

     These events are always produced with EXTENDED_EVENTS and
     VERBOSE_NAMES; see the explanations in the USEFEATURE section
     for details.

     Controllers MUST tolerate unrecognized actions, MUST tolerate
     unrecognized arguments, MUST tolerate missing arguments, and MUST
     tolerate arguments that arrive in any order.

     Each event description below is accompanied by a recommendation for
     controllers.  These recommendations are suggestions only; no controller
     is required to implement them.

  Compatibility note: versions of Tor before 0.2.0.22-rc incorrectly
  generated "STATUS_SERVER" as "STATUS_SEVER".  To be compatible with those
  versions, tools should accept both.

  Actions for STATUS_GENERAL events can be as follows:

     CLOCK_JUMPED
     "TIME=NUM"
       Tor spent enough time without CPU cycles that it has closed all
       its circuits and will establish them anew. This typically
       happens when a laptop goes to sleep and then wakes up again. It
       also happens when the system is swapping so heavily that Tor is
       starving. The "time" argument specifies the number of seconds Tor
       thinks it was unconscious for (or alternatively, the number of
       seconds it went back in time).

       This status event is sent as NOTICE severity normally, but WARN
       severity if Tor is acting as a server currently.

       {Recommendation for controller: ignore it, since we don't really
       know what the user should do anyway. Hm.}

     DANGEROUS_VERSION
     "CURRENT=version"
     "REASON=NEW/OBSOLETE/UNRECOMMENDED"
     "RECOMMENDED=\"version, version, ...\""
       Tor has found that directory servers don't recommend its version of
       the Tor software.  RECOMMENDED is a comma-and-space-separated string
       of Tor versions that are recommended.  REASON is NEW if this version
       of Tor is newer than any recommended version, OBSOLETE if
       this version of Tor is older than any recommended version, and
       UNRECOMMENDED if some recommended versions of Tor are newer and
       some are older than this version. (The "OBSOLETE" reason was called
       "OLD" from Tor 0.1.2.3-alpha up to and including 0.2.0.12-alpha.)

       {Controllers may want to suggest that the user upgrade OLD or
       UNRECOMMENDED versions.  NEW versions may be known-insecure, or may
       simply be development versions.}

     TOO_MANY_CONNECTIONS
     "CURRENT=NUM"
       Tor has reached its ulimit -n or whatever the native limit is on file
       descriptors or sockets.  CURRENT is the number of sockets Tor
       currently has open.  The user should really do something about
       this. The "current" argument shows the number of connections currently
       open.

       {Controllers may recommend that the user increase the limit, or
       increase it for them.  Recommendations should be phrased in an
       OS-appropriate way and automated when possible.}

     BUG
     "REASON=STRING"
       Tor has encountered a situation that its developers never expected,
       and the developers would like to learn that it happened. Perhaps
       the controller can explain this to the user and encourage her to
       file a bug report?

       {Controllers should log bugs, but shouldn't annoy the user in case a
       bug appears frequently.}

     CLOCK_SKEW
       SKEW="+" / "-" SECONDS
       MIN_SKEW="+" / "-" SECONDS.
       SOURCE="DIRSERV:" IP ":" Port /
              "NETWORKSTATUS:" IP ":" Port /
              "OR:" IP ":" Port /
              "CONSENSUS"
         If "SKEW" is present, it's an estimate of how far we are from the
         time declared in the source.  (In other words, if we're an hour in
         the past, the value is -3600.)  "MIN_SKEW" is present, it's a lower
         bound.  If the source is a DIRSERV, we got the current time from a
         connection to a dirserver.  If the source is a NETWORKSTATUS, we
         decided we're skewed because we got a v2 networkstatus from far in
         the future.  If the source is OR, the skew comes from a NETINFO
         cell from a connection to another relay.  If the source is
         CONSENSUS, we decided we're skewed because we got a networkstatus
         consensus from the future.

         {Tor should send this message to controllers when it thinks the
         skew is so high that it will interfere with proper Tor operation.
         Controllers shouldn't blindly adjust the clock, since the more
         accurate source of skew info (DIRSERV) is currently
         unauthenticated.}

     BAD_LIBEVENT
     "METHOD=" libevent method
     "VERSION=" libevent version
     "BADNESS=" "BROKEN" / "BUGGY" / "SLOW"
     "RECOVERED=" "NO" / "YES"
        Tor knows about bugs in using the configured event method in this
        version of libevent.  "BROKEN" libevents won't work at all;
        "BUGGY" libevents might work okay; "SLOW" libevents will work
        fine, but not quickly.  If "RECOVERED" is YES, Tor managed to
        switch to a more reliable (but probably slower!) libevent method.

        {Controllers may want to warn the user if this event occurs, though
        generally it's the fault of whoever built the Tor binary and there's
        not much the user can do besides upgrade libevent or upgrade the
        binary.}

     DIR_ALL_UNREACHABLE
       Tor believes that none of the known directory servers are
       reachable -- this is most likely because the local network is
       down or otherwise not working, and might help to explain for the
       user why Tor appears to be broken.

       {Controllers may want to warn the user if this event occurs; further
       action is generally not possible.}

  Actions for STATUS_CLIENT events can be as follows:

     BOOTSTRAP
     "PROGRESS=" num
     "TAG=" Keyword
     "SUMMARY=" String
     ["WARNING=" String]
     ["REASON=" Keyword]
     ["COUNT=" num]
     ["RECOMMENDATION=" Keyword]
     ["HOST=" QuotedString]
     ["HOSTADDR=" QuotedString]

       Tor has made some progress at establishing a connection to the
       Tor network, fetching directory information, or making its first
       circuit; or it has encountered a problem while bootstrapping. This
       status event is especially useful for users with slow connections
       or with connectivity problems.

       "Progress" gives a number between 0 and 100 for how far through
       the bootstrapping process we are. "Summary" is a string that can
       be displayed to the user to describe the *next* task that Tor
       will tackle, i.e., the task it is working on after sending the
       status event. "Tag" is a string that controllers can use to
       recognize bootstrap phases, if they want to do something smarter
       than just blindly displaying the summary string; see Section 5
       for the current tags that Tor issues.

       The StatusSeverity describes whether this is a normal bootstrap
       phase (severity notice) or an indication of a bootstrapping
       problem (severity warn).

       For bootstrap problems, we include the same progress, tag, and
       summary values as we would for a normal bootstrap event, but we
       also include "warning", "reason", "count", and "recommendation"
       key/value combos. The "count" number tells how many bootstrap
       problems there have been so far at this phase. The "reason"
       string lists one of the reasons allowed in the ORCONN event. The
       "warning" argument string with any hints Tor has to offer about
       why it's having troubles bootstrapping.

       The "reason" values are long-term-stable controller-facing tags to
       identify particular issues in a bootstrapping step.  The warning
       strings, on the other hand, are human-readable. Controllers
       SHOULD NOT rely on the format of any warning string. Currently
       the possible values for "recommendation" are either "ignore" or
       "warn" -- if ignore, the controller can accumulate the string in
       a pile of problems to show the user if the user asks; if warn,
       the controller should alert the user that Tor is pretty sure
       there's a bootstrapping problem.

       The "host" value is the identity digest (in hex) of the node we're
       trying to connect to; the "hostaddr" is an address:port combination,
       where 'address' is an ipv4 or ipv6 address.

       Currently Tor uses recommendation=ignore for the first
       nine bootstrap problem reports for a given phase, and then
       uses recommendation=warn for subsequent problems at that
       phase. Hopefully this is a good balance between tolerating
       occasional errors and reporting serious problems quickly.

     ENOUGH_DIR_INFO
       Tor now knows enough network-status documents and enough server
       descriptors that it's going to start trying to build circuits now.
      [Newer versions of Tor (0.2.6.2-alpha and later):
       If the consensus contains Exits (the typical case), Tor will build
       both exit and internal circuits. If not, Tor will only build internal
       circuits.]

       {Controllers may want to use this event to decide when to indicate
       progress to their users, but should not interrupt the user's browsing
       to tell them so.}

     NOT_ENOUGH_DIR_INFO
       We discarded expired statuses and server descriptors to fall
       below the desired threshold of directory information. We won't
       try to build any circuits until ENOUGH_DIR_INFO occurs again.

       {Controllers may want to use this event to decide when to indicate
       progress to their users, but should not interrupt the user's browsing
       to tell them so.}

     CIRCUIT_ESTABLISHED
       Tor is able to establish circuits for client use. This event will
       only be sent if we just built a circuit that changed our mind --
       that is, prior to this event we didn't know whether we could
       establish circuits.

       {Suggested use: controllers can notify their users that Tor is
       ready for use as a client once they see this status event. [Perhaps
       controllers should also have a timeout if too much time passes and
       this event hasn't arrived, to give tips on how to troubleshoot.
       On the other hand, hopefully Tor will send further status events
       if it can identify the problem.]}

     CIRCUIT_NOT_ESTABLISHED
     "REASON=" "EXTERNAL_ADDRESS" / "DIR_ALL_UNREACHABLE" / "CLOCK_JUMPED"
       We are no longer confident that we can build circuits. The "reason"
       keyword provides an explanation: which other status event type caused
       our lack of confidence.

       {Controllers may want to use this event to decide when to indicate
       progress to their users, but should not interrupt the user's browsing
       to do so.}
       [Note: only REASON=CLOCK_JUMPED is implemented currently.]

     CONSENSUS_ARRIVED
        Tor has received and validated a new consensus networkstatus.
        (This event can be delayed a little while after the consensus
        is received, if Tor needs to fetch certificates.)

     DANGEROUS_PORT
     "PORT=" port
     "RESULT=" "REJECT" / "WARN"
       A stream was initiated to a port that's commonly used for
       vulnerable-plaintext protocols. If the Result is "reject", we
       refused the connection; whereas if it's "warn", we allowed it.

       {Controllers should warn their users when this occurs, unless they
       happen to know that the application using Tor is in fact doing so
       correctly (e.g., because it is part of a distributed bundle). They
       might also want some sort of interface to let the user configure
       their RejectPlaintextPorts and WarnPlaintextPorts config options.}

     DANGEROUS_SOCKS
     "PROTOCOL=" "SOCKS4" / "SOCKS5"
     "ADDRESS=" IP:port
       A connection was made to Tor's SOCKS port using one of the SOCKS
       approaches that doesn't support hostnames -- only raw IP addresses.
       If the client application got this address from gethostbyname(),
       it may be leaking target addresses via DNS.

       {Controllers should warn their users when this occurs, unless they
       happen to know that the application using Tor is in fact doing so
       correctly (e.g., because it is part of a distributed bundle).}

     SOCKS_UNKNOWN_PROTOCOL
       "DATA=string"
       A connection was made to Tor's SOCKS port that tried to use it
       for something other than the SOCKS protocol. Perhaps the user is
       using Tor as an HTTP proxy?   The DATA is the first few characters
       sent to Tor on the SOCKS port.

       {Controllers may want to warn their users when this occurs: it
       indicates a misconfigured application.}

     SOCKS_BAD_HOSTNAME
      "HOSTNAME=QuotedString"
       Some application gave us a funny-looking hostname. Perhaps
       it is broken? In any case it won't work with Tor and the user
       should know.

       {Controllers may want to warn their users when this occurs: it
       usually indicates a misconfigured application.}

  Actions for STATUS_SERVER can be as follows:

     EXTERNAL_ADDRESS
     "ADDRESS=IP"
     "HOSTNAME=NAME"
     "METHOD=CONFIGURED/CONFIGURED_ORPORT/DIRSERV/RESOLVED/
             INTERFACE/GETHOSTNAME"
       Our best idea for our externally visible IP has changed to 'IP'.  If
       'HOSTNAME' is present, we got the new IP by resolving 'NAME'.  If the
       method is 'CONFIGURED', the IP was given verbatim as the Address
       configuration option.  If the method is 'CONFIGURED_ORPORT', the IP was
       given verbatim in the ORPort configuration option. If the method is
       'RESOLVED', we resolved the Address configuration option to get the IP.
       If the method is 'GETHOSTNAME', we resolved our hostname to get the IP.
       If the method is 'INTERFACE', we got the address of one of our network
       interfaces to get the IP.  If the method is 'DIRSERV', a directory
       server told us a guess for what our IP might be.

       {Controllers may want to record this info and display it to the user.}

     CHECKING_REACHABILITY
     "ORADDRESS=IP:port"
     "DIRADDRESS=IP:port"
       We're going to start testing the reachability of our external OR port
       or directory port.

       {This event could affect the controller's idea of server status, but
       the controller should not interrupt the user to tell them so.}

     REACHABILITY_SUCCEEDED
     "ORADDRESS=IP:port"
     "DIRADDRESS=IP:port"
       We successfully verified the reachability of our external OR port or
       directory port (depending on which of ORADDRESS or DIRADDRESS is
       given.)

       {This event could affect the controller's idea of server status, but
       the controller should not interrupt the user to tell them so.}

     GOOD_SERVER_DESCRIPTOR
       We successfully uploaded our server descriptor to at least one
       of the directory authorities, with no complaints.

       {Originally, the goal of this event was to declare "every authority
       has accepted the descriptor, so there will be no complaints
       about it." But since some authorities might be offline, it's
       harder to get certainty than we had thought. As such, this event
       is equivalent to ACCEPTED_SERVER_DESCRIPTOR below. Controllers
       should just look at ACCEPTED_SERVER_DESCRIPTOR and should ignore
       this event for now.}

     SERVER_DESCRIPTOR_STATUS
     "STATUS=" "LISTED" / "UNLISTED"
       We just got a new networkstatus consensus, and whether we're in
       it or not in it has changed. Specifically, status is "listed"
       if we're listed in it but previous to this point we didn't know
       we were listed in a consensus; and status is "unlisted" if we
       thought we should have been listed in it (e.g. we were listed in
       the last one), but we're not.

       {Moving from listed to unlisted is not necessarily cause for
       alarm. The relay might have failed a few reachability tests,
       or the Internet might have had some routing problems. So this
       feature is mainly to let relay operators know when their relay
       has successfully been listed in the consensus.}

       [Not implemented yet. We should do this in 0.2.2.x. -RD]

     NAMESERVER_STATUS
     "NS=addr"
     "STATUS=" "UP" / "DOWN"
     "ERR=" message
        One of our nameservers has changed status.

        {This event could affect the controller's idea of server status, but
        the controller should not interrupt the user to tell them so.}

     NAMESERVER_ALL_DOWN
        All of our nameservers have gone down.

        {This is a problem; if it happens often without the nameservers
        coming up again, the user needs to configure more or better
        nameservers.}

     DNS_HIJACKED
        Our DNS provider is providing an address when it should be saying
        "NOTFOUND"; Tor will treat the address as a synonym for "NOTFOUND".

        {This is an annoyance; controllers may want to tell admins that their
        DNS provider is not to be trusted.}

     DNS_USELESS
        Our DNS provider is giving a hijacked address instead of well-known
        websites; Tor will not try to be an exit node.

        {Controllers could warn the admin if the relay is running as an
        exit node: the admin needs to configure a good DNS server.
        Alternatively, this happens a lot in some restrictive environments
        (hotels, universities, coffeeshops) when the user hasn't registered.}

     BAD_SERVER_DESCRIPTOR
     "DIRAUTH=addr:port"
     "REASON=string"
        A directory authority rejected our descriptor.  Possible reasons
        include malformed descriptors, incorrect keys, highly skewed clocks,
        and so on.

        {Controllers should warn the admin, and try to cope if they can.}

     ACCEPTED_SERVER_DESCRIPTOR
     "DIRAUTH=addr:port"
        A single directory authority accepted our descriptor.
        // actually notice

       {This event could affect the controller's idea of server status, but
       the controller should not interrupt the user to tell them so.}

     REACHABILITY_FAILED
     "ORADDRESS=IP:port"
     "DIRADDRESS=IP:port"
       We failed to connect to our external OR port or directory port
       successfully.

       {This event could affect the controller's idea of server status.  The
       controller should warn the admin and suggest reasonable steps to take.}

     HIBERNATION_STATUS
     "STATUS=" "AWAKE" | "SOFT" | "HARD"
       Our bandwidth based accounting status has changed, and we are now
       relaying traffic/rejecting new connections/hibernating.

       {This event could affect the controller's idea of server status.  The
       controller MAY inform the admin, though presumably the accounting was
       explicitly enabled for a reason.}

       [This event was added in tor 0.2.9.0-alpha.]

4.1.11. Our set of guard nodes has changed

  Syntax:

     "650" SP "GUARD" SP Type SP Name SP Status ... CRLF
     Type = "ENTRY"
     Name = ServerSpec
       (Identifies the guard affected)
     Status = "NEW" | "UP" | "DOWN" | "BAD" | "GOOD" | "DROPPED"

  The ENTRY type indicates a guard used for connections to the Tor
  network.

  The Status values are:

    "NEW"  -- This node was not previously used as a guard; now we have
              picked it as one.
    "DROPPED" -- This node is one we previously picked as a guard; we
              no longer consider it to be a member of our guard list.
    "UP"   -- The guard now seems to be reachable.
    "DOWN" -- The guard now seems to be unreachable.
    "BAD"  -- Because of flags set in the consensus and/or values in the
              configuration, this node is now unusable as a guard.
    "BAD_L2" -- This layer2 guard has expired or got removed from the
              consensus. This node is removed from the layer2 guard set.
    "GOOD" -- Because of flags set in the consensus and/or values in the
              configuration, this node is now usable as a guard.

  Controllers must accept unrecognized types and unrecognized statuses.

4.1.12. Network status has changed

  Syntax:

     "650" "+" "NS" CRLF 1*NetworkStatus "." CRLF "650" SP "OK" CRLF

  The event is used whenever our local view of a relay status changes.
  This happens when we get a new v3 consensus (in which case the entries
  we see are a duplicate of what we see in the NEWCONSENSUS event,
  below), but it also happens when we decide to mark a relay as up or
  down in our local status, for example based on connection attempts.

  [First added in 0.1.2.3-alpha]

4.1.13. Bandwidth used on an application stream

  The syntax is:

     "650" SP "STREAM_BW" SP StreamID SP BytesWritten SP BytesRead SP
              Time CRLF
     BytesWritten = 1*DIGIT
     BytesRead = 1*DIGIT
     Time = ISOTime2Frac

  BytesWritten and BytesRead are the number of bytes written and read
  by the application since the last STREAM_BW event on this stream.

  Note that from Tor's perspective, *reading* a byte on a stream means
  that the application *wrote* the byte. That's why the order of "written"
  vs "read" is opposite for stream_bw events compared to bw events.

  The Time field is provided only in versions 0.3.2.1-alpha and later. It
  records when Tor created the bandwidth event.

  These events are generated about once per second per stream; no events
  are generated for streams that have not written or read. These events
  apply only to streams entering Tor (such as on a SOCKSPort, TransPort,
  or so on). They are not generated for exiting streams.

4.1.14. Per-country client stats

  The syntax is:

     "650" SP "CLIENTS_SEEN" SP TimeStarted SP CountrySummary SP
     IPVersions CRLF

  We just generated a new summary of which countries we've seen clients
  from recently. The controller could display this for the user, e.g.
  in their "relay" configuration window, to give them a sense that they
  are actually being useful.

  Currently only bridge relays will receive this event, but once we figure
  out how to sufficiently aggregate and sanitize the client counts on
  main relays, we might start sending these events in other cases too.

  TimeStarted is a quoted string indicating when the reported summary
  counts from (in UTCS).

  The CountrySummary keyword has as its argument a comma-separated,
  possibly empty set of "countrycode=count" pairs. For example (without
  linebreak),
  650-CLIENTS_SEEN TimeStarted="2008-12-25 23:50:43"
  CountrySummary=us=16,de=8,uk=8

  The IPVersions keyword has as its argument a comma-separated set of
  "protocol-family=count" pairs. For example,
  IPVersions=v4=16,v6=40

  Note that these values are rounded, not exact.  The rounding
  algorithm is specified in the description of "geoip-client-origins"
  in dir-spec.txt.

4.1.15. New consensus networkstatus has arrived

  The syntax is:

     "650" "+" "NEWCONSENSUS" CRLF 1*NetworkStatus "." CRLF "650" SP
     "OK" CRLF

  A new consensus networkstatus has arrived. We include NS-style lines for
  every relay in the consensus. NEWCONSENSUS is a separate event from the
  NS event, because the list here represents every usable relay: so any
  relay *not* mentioned in this list is implicitly no longer recommended.

  [First added in 0.2.1.13-alpha]

4.1.16. New circuit buildtime has been set

  The syntax is:

     "650" SP "BUILDTIMEOUT_SET" SP Type SP "TOTAL_TIMES=" Total SP
        "TIMEOUT_MS=" Timeout SP "XM=" Xm SP "ALPHA=" Alpha SP
        "CUTOFF_QUANTILE=" Quantile SP "TIMEOUT_RATE=" TimeoutRate SP
        "CLOSE_MS=" CloseTimeout SP "CLOSE_RATE=" CloseRate
        CRLF
     Type = "COMPUTED" / "RESET" / "SUSPENDED" / "DISCARD" / "RESUME"
     Total = Integer count of timeouts stored
     Timeout = Integer timeout in milliseconds
     Xm = Estimated integer Pareto parameter Xm in milliseconds
     Alpha = Estimated floating point Paredo parameter alpha
     Quantile = Floating point CDF quantile cutoff point for this timeout
     TimeoutRate = Floating point ratio of circuits that timeout
     CloseTimeout = How long to keep measurement circs in milliseconds
     CloseRate = Floating point ratio of measurement circuits that are closed

  A new circuit build timeout time has been set. If Type is "COMPUTED",
  Tor has computed the value based on historical data. If Type is "RESET",
  initialization or drastic network changes have caused Tor to reset
  the timeout back to the default, to relearn again. If Type is
  "SUSPENDED", Tor has detected a loss of network connectivity and has
  temporarily changed the timeout value to the default until the network
  recovers. If type is "DISCARD", Tor has decided to discard timeout
  values that likely happened while the network was down. If type is
  "RESUME", Tor has decided to resume timeout calculation.

  The Total value is the count of circuit build times Tor used in
  computing this value. It is capped internally at the maximum number
  of build times Tor stores (NCIRCUITS_TO_OBSERVE).

  The Timeout itself is provided in milliseconds. Internally, Tor rounds
  this value to the nearest second before using it.

  [First added in 0.2.2.7-alpha]

4.1.17. Signal received

  The syntax is:

     "650" SP "SIGNAL" SP Signal CRLF

     Signal = "RELOAD" / "DUMP" / "DEBUG" / "NEWNYM" / "CLEARDNSCACHE"

  A signal has been received and actions taken by Tor. The meaning of each
  signal, and the mapping to Unix signals, is as defined in section 3.7.
  Future versions of Tor MAY generate signals other than those listed here;
  controllers MUST be able to accept them.

  If Tor chose to ignore a signal (such as NEWNYM), this event will not be
  sent.  Note that some options (like ReloadTorrcOnSIGHUP) may affect the
  semantics of the signals here.

  Note that the HALT (SIGTERM) and SHUTDOWN (SIGINT) signals do not currently
  generate any event.

  [First added in 0.2.3.1-alpha]

4.1.18. Configuration changed

  The syntax is:

     StartReplyLine *(MidReplyLine) EndReplyLine

     StartReplyLine = "650-CONF_CHANGED" CRLF
     MidReplyLine = "650-" KEYWORD ["=" VALUE] CRLF
     EndReplyLine = "650 OK"

  Tor configuration options have changed (such as via a SETCONF or RELOAD
  signal). KEYWORD and VALUE specify the configuration option that was changed.
  Undefined configuration options contain only the KEYWORD.

4.1.19. Circuit status changed slightly

  The syntax is:

    "650" SP "CIRC_MINOR" SP CircuitID SP CircEvent [SP Path]
          [SP "BUILD_FLAGS=" BuildFlags] [SP "PURPOSE=" Purpose]
          [SP "HS_STATE=" HSState] [SP "REND_QUERY=" HSAddress]
          [SP "TIME_CREATED=" TimeCreated]
          [SP "OLD_PURPOSE=" Purpose [SP "OLD_HS_STATE=" HSState]] CRLF

    CircEvent =
             "PURPOSE_CHANGED" / ; circuit purpose or HS-related state changed
             "CANNIBALIZED"      ; circuit cannibalized

  Clients MUST accept circuit events not listed above.

  The "OLD_PURPOSE" field is provided for both PURPOSE_CHANGED and
  CANNIBALIZED events.  The "OLD_HS_STATE" field is provided whenever
  the "OLD_PURPOSE" field is provided and is a hidden-service-related
  purpose.

  Other fields are as specified in section 4.1.1 above.

  [First added in 0.2.3.11-alpha]

4.1.20. Pluggable transport launched

  The syntax is:

    "650" SP "TRANSPORT_LAUNCHED" SP Type SP Name SP TransportAddress SP Port
    Type = "server" | "client"
    Name = The name of the pluggable transport
    TransportAddress = An IPv4 or IPv6 address on which the pluggable
                       transport is listening for connections
    Port = The TCP port on which it is listening for connections.

    A pluggable transport called 'Name' of type 'Type' was launched
    successfully and is now listening for connections on 'Address':'Port'.

4.1.21. Bandwidth used on an OR or DIR or EXIT connection

  The syntax is:

     "650" SP "CONN_BW" SP "ID=" ConnID SP "TYPE=" ConnType
              SP "READ=" BytesRead SP "WRITTEN=" BytesWritten CRLF

     ConnType = "OR" /  ; Carrying traffic within the tor network. This can
                          either be our own (client) traffic or traffic we're
                          relaying within the network.
                "DIR" / ; Fetching tor descriptor data, or transmitting
                          descriptors we're mirroring.
                "EXIT"  ; Carrying traffic between the tor network and an
                          external destination.

     BytesRead = 1*DIGIT
     BytesWritten = 1*DIGIT

  Controllers MUST tolerate unrecognized connection types.

  BytesWritten and BytesRead are the number of bytes written and read
  by Tor since the last CONN_BW event on this connection.

  These events are generated about once per second per connection; no
  events are generated for connections that have not read or written.
  These events are only generated if TestingTorNetwork is set.

  [First added in 0.2.5.2-alpha]

4.1.22. Bandwidth used by all streams attached to a circuit

  The syntax is:

     "650" SP "CIRC_BW" SP "ID=" CircuitID SP "READ=" BytesRead SP
              "WRITTEN=" BytesWritten SP "TIME=" Time SP
              "DELIVERED_READ=" DeliveredBytesRead SP
              "OVERHEAD_READ=" OverheadBytesRead SP
              "DELIVERED_WRITTEN=" DeliveredBytesWritten SP
              "OVERHEAD_WRITTEN=" OverheadBytesWritten SP
              "SS=" SlowStartState SP
              "CWND=" CWNDCells SP
              "RTT=" RTTMilliseconds SP
              "MIN_RTT=" RTTMilliseconds CRLF
     BytesRead = 1*DIGIT
     BytesWritten = 1*DIGIT
     OverheadBytesRead = 1*DIGIT
     OverheadBytesWritten = 1*DIGIT
     DeliveredBytesRead = 1*DIGIT
     DeliveredBytesWritten = 1*DIGIT
     SlowStartState = 0 or 1
     CWNDCells = 1*DIGIT
     RTTMilliseconds= 1*DIGIT
     Time = ISOTime2Frac

  BytesRead and BytesWritten are the number of bytes read and written
  on this circuit since the last CIRC_BW event. These bytes have not
  necessarily been validated by Tor, and can include invalid cells,
  dropped cells, and ignored cells (such as padding cells). These
  values include the relay headers, but not circuit headers.

  Circuit data that has been validated and processed by Tor is further
  broken down into two categories: delivered payloads and overhead.
  DeliveredBytesRead and DeliveredBytesWritten are the total relay cell
  payloads transmitted since the last CIRC_BW event, not counting relay
  cell headers or circuit headers. OverheadBytesRead and
  OverheadBytesWritten are the extra unused bytes at the end of each
  cell in order for it to be the fixed CELL_LEN bytes long.

  The sum of DeliveredBytesRead and OverheadBytesRead MUST be less than
  BytesRead, and the same is true for their written counterparts. This
  sum represents the total relay cell bytes on the circuit that
  have been validated by Tor, not counting relay headers and cell headers.
  Subtracting this sum (plus relay cell headers) from the BytesRead
  (or BytesWritten) value gives the byte count that Tor has decided to
  reject due to protocol errors, or has otherwise decided to ignore.

  The Time field is provided only in versions 0.3.2.1-alpha and later. It
  records when Tor created the bandwidth event.

  The SS, CWND, RTT, and MIN_RTT fields are present only if the circuit
  has negotiated congestion control to an onion service or Exit hop (any
  intermediate leaky pipe congestion control hops are not examined here).
  SS provides an indication if the circuit is in slow start (1), or not (0).
  CWND is the size of the congestion window in terms of number of cells.
  RTT is the N_EWMA smoothed current RTT value, and MIN_RTT is the minimum
  RTT value of the circuit. The SS and CWND fields apply only to the
  upstream direction of the circuit. The slow start state and CWND values
  of the other endpoint may be different.

  These events are generated about once per second per circuit; no events
  are generated for circuits that had no attached stream writing or
  reading.

  [First added in 0.2.5.2-alpha]

  [DELIVERED_READ, OVERHEAD_READ, DELIVERED_WRITTEN, and OVERHEAD_WRITTEN
  were added in Tor 0.3.4.0-alpha]

  [SS, CWND, RTT, and MIN_RTT were added in Tor 0.4.7.5-alpha]

4.1.23. Per-circuit cell stats

  The syntax is:

     "650" SP "CELL_STATS"
              [ SP "ID=" CircuitID ]
              [ SP "InboundQueue=" QueueID SP "InboundConn=" ConnID ]
              [ SP "InboundAdded=" CellsByType ]
              [ SP "InboundRemoved=" CellsByType SP
                   "InboundTime=" MsecByType ]
              [ SP "OutboundQueue=" QueueID SP "OutboundConn=" ConnID ]
              [ SP "OutboundAdded=" CellsByType ]
              [ SP "OutboundRemoved=" CellsByType SP
                   "OutboundTime=" MsecByType ] CRLF
     CellsByType, MsecByType = CellType ":" 1*DIGIT
                               0*( "," CellType ":" 1*DIGIT )
     CellType = 1*( "a" - "z" / "0" - "9" / "_" )

  Examples are:

     650 CELL_STATS ID=14 OutboundQueue=19403 OutboundConn=15
         OutboundAdded=create_fast:1,relay_early:2
         OutboundRemoved=create_fast:1,relay_early:2
         OutboundTime=create_fast:0,relay_early:0
     650 CELL_STATS InboundQueue=19403 InboundConn=32
         InboundAdded=relay:1,created_fast:1
         InboundRemoved=relay:1,created_fast:1
         InboundTime=relay:0,created_fast:0
         OutboundQueue=6710 OutboundConn=18
         OutboundAdded=create:1,relay_early:1
         OutboundRemoved=create:1,relay_early:1
         OutboundTime=create:0,relay_early:0

  ID is the locally unique circuit identifier that is only included if the
  circuit originates at this node.

  Inbound and outbound refer to the direction of cell flow through the
  circuit which is either to origin (inbound) or from origin (outbound).

  InboundQueue and OutboundQueue are identifiers of the inbound and
  outbound circuit queues of this circuit.  These identifiers are only
  unique per OR connection.  OutboundQueue is chosen by this node and
  matches InboundQueue of the next node in the circuit.

  InboundConn and OutboundConn are locally unique IDs of inbound and
  outbound OR connection.  OutboundConn does not necessarily match
  InboundConn of the next node in the circuit.

  InboundQueue and InboundConn are not present if the circuit originates
  at this node.  OutboundQueue and OutboundConn are not present if the
  circuit (currently) ends at this node.

  InboundAdded and OutboundAdded are total number of cells by cell type
  added to inbound and outbound queues.  Only present if at least one cell
  was added to a queue.

  InboundRemoved and OutboundRemoved are total number of cells by
  cell type processed from inbound and outbound queues.  InboundTime and
  OutboundTime are total waiting times in milliseconds of all processed
  cells by cell type.  Only present if at least one cell was removed from
  a queue.

  These events are generated about once per second per circuit; no
  events are generated for circuits that have not added or processed any
  cell.  These events are only generated if TestingTorNetwork is set.

  [First added in 0.2.5.2-alpha]

4.1.24. Token buckets refilled

  The syntax is:

     "650" SP "TB_EMPTY" SP BucketName [ SP "ID=" ConnID ] SP
              "READ=" ReadBucketEmpty SP "WRITTEN=" WriteBucketEmpty SP
              "LAST=" LastRefill CRLF

     BucketName = "GLOBAL" / "RELAY" / "ORCONN"
     ReadBucketEmpty = 1*DIGIT
     WriteBucketEmpty = 1*DIGIT
     LastRefill = 1*DIGIT

  Examples are:

     650 TB_EMPTY ORCONN ID=16 READ=0 WRITTEN=0 LAST=100
     650 TB_EMPTY GLOBAL READ=93 WRITTEN=93 LAST=100
     650 TB_EMPTY RELAY READ=93 WRITTEN=93 LAST=100

  This event is generated when refilling a previously empty token
  bucket.  BucketNames "GLOBAL" and "RELAY" keywords are used for the
  global or relay token buckets, BucketName "ORCONN" is used for the
  token buckets of an OR connection.  Controllers MUST tolerate
  unrecognized bucket names.

  ConnID is only included if the BucketName is "ORCONN".

  If both global and relay buckets and/or the buckets of one or more OR
  connections run out of tokens at the same time, multiple separate
  events are generated.

  ReadBucketEmpty (WriteBucketEmpty) is the time in millis that the read
  (write) bucket was empty since the last refill.  LastRefill is the
  time in millis since the last refill.

  If a bucket went negative and if refilling tokens didn't make it go
  positive again, there will be multiple consecutive TB_EMPTY events for
  each refill interval during which the bucket contained zero tokens or
  less.  In such a case, ReadBucketEmpty or WriteBucketEmpty are capped
  at LastRefill in order not to report empty times more than once.

  These events are only generated if TestingTorNetwork is set.

  [First added in 0.2.5.2-alpha]

4.1.25. HiddenService descriptors

  The syntax is:

    "650" SP "HS_DESC" SP Action SP HSAddress SP AuthType SP HsDir
             [SP DescriptorID] [SP "REASON=" Reason] [SP "REPLICA=" Replica]
             [SP "HSDIR_INDEX=" HSDirIndex]

    Action =  "REQUESTED" / "UPLOAD" / "RECEIVED" / "UPLOADED" / "IGNORE" /
              "FAILED" / "CREATED"
    HSAddress = 16*Base32Character / 56*Base32Character / "UNKNOWN"
    AuthType = "NO_AUTH" / "BASIC_AUTH" / "STEALTH_AUTH" / "UNKNOWN"
    HsDir = LongName / Fingerprint / "UNKNOWN"
    DescriptorID = 32*Base32Character / 43*Base64Character
    Reason = "BAD_DESC" / "QUERY_REJECTED" / "UPLOAD_REJECTED" / "NOT_FOUND" /
             "UNEXPECTED" / "QUERY_NO_HSDIR" / "QUERY_RATE_LIMITED"
    Replica = 1*DIGIT
    HSDirIndex = 64*HEXDIG

    These events will be triggered when required HiddenService descriptor is
    not found in the cache and a fetch or upload with the network is performed.

    If the fetch was triggered with only a DescriptorID (using the HSFETCH
    command for instance), the HSAddress only appears in the Action=RECEIVED
    since there is no way to know the HSAddress from the DescriptorID thus
    the value will be "UNKNOWN".

    If we already had the v0 descriptor, the newly fetched v2 descriptor
    will be ignored and a "HS_DESC" event with "IGNORE" action will be
    generated.

    For HsDir, LongName is always preferred. If HsDir cannot be found in node
    list at the time event is sent, Fingerprint will be used instead.

    If Action is "FAILED", Tor SHOULD send Reason field as well. Possible
    values of Reason are:
       - "BAD_DESC" - descriptor was retrieved, but found to be unparsable.
       - "QUERY_REJECTED" - query was rejected by HS directory.
       - "UPLOAD_REJECTED" - descriptor was rejected by HS directory.
       - "NOT_FOUND" - HS descriptor with given identifier was not found.
       - "UNEXPECTED" - nature of failure is unknown.
       - "QUERY_NO_HSDIR" - No suitable HSDir were found for the query.
       - "QUERY_RATE_LIMITED" - query for this service is rate-limited

    For "QUERY_NO_HSDIR" or "QUERY_RATE_LIMITED", the HsDir will be set to
    "UNKNOWN" which was introduced in tor 0.3.1.0-alpha and 0.4.1.0-alpha
    respectively.

    If Action is "CREATED", Tor SHOULD send Replica field as well. The Replica
    field contains the replica number of the generated descriptor. The Replica
    number is specified in rend-spec.txt section 1.3 and determines the
    descriptor ID of the descriptor.

    For hidden service v3, the following applies:

       The "HSDIR_INDEX=" is an optional field that is only for version 3
       which contains the computed index of the HsDir the descriptor was
       uploaded to or fetched from.

       The "DescriptorID" key is the descriptor blinded key used for the index
       value at the "HsDir".

       The "REPLICA=" field is not used for the "CREATED" event because v3
       doesn't use the replica number in the descriptor ID computation.

       Because client authentication is not yet implemented, the "AuthType"
       field is always "NO_AUTH".

   [HS v3 support added 0.3.3.1-alpha]

4.1.26. HiddenService descriptors content

  The syntax is:

    "650" "+" "HS_DESC_CONTENT" SP HSAddress SP DescId SP HsDir CRLF
               Descriptor CRLF "." CRLF "650" SP "OK" CRLF

    HSAddress = 16*Base32Character / 56*Base32Character / "UNKNOWN"
    DescId = 32*Base32Character / 32*Base64Character
    HsDir = LongName / "UNKNOWN"
    Descriptor = The text of the descriptor formatted as specified in
                 rend-spec.txt section 1.3 (v2) or rend-spec-v3.txt
                 section 2.4 (v3) or empty string on failure.

  This event is triggered when a successfully fetched HS descriptor is
  received. The text of that descriptor is then replied. If the HS_DESC
  event is enabled, it is replied just after the RECEIVED action.

  If a fetch fails, the Descriptor is an empty string and HSAddress is set
  to "UNKNOWN". The HS_DESC event should be used to get more information on
  the failed request.

  If the fetch fails for the QUERY_NO_HSDIR or QUERY_RATE_LIMITED reason from
  the HS_DESC event, the HsDir is set to "UNKNOWN". This was introduced in
  0.3.1.0-alpha and 0.4.1.0-alpha respectively.

  It's expected to receive a reply relatively fast as in it's the time it
  takes to fetch something over the Tor network. This can be between a
  couple of seconds up to 60 seconds (not a hard limit). But, in any cases,
  this event will reply either the descriptor's content or an empty one.

  [HS_DESC_CONTENT was added in Tor 0.2.7.1-alpha]
  [HS v3 support added 0.3.3.1-alpha]

4.1.27. Network liveness has changed

  Syntax:

     "650" SP "NETWORK_LIVENESS" SP Status CRLF
     Status = "UP" /  ; The network now seems to be reachable.
              "DOWN" /  ; The network now seems to be unreachable.

  Controllers MUST tolerate unrecognized status types.

  [NETWORK_LIVENESS was added in Tor 0.2.7.2-alpha]

4.1.28. Pluggable Transport Logs

   Syntax:

      "650" SP "PT_LOG" SP PT=Program SP Message

      Program = The program path as defined in the *TransportPlugin
                configuration option. Tor accepts relative and full path.
      Message = The log message that the PT sends back to the tor parent
                process minus the "LOG" string prefix. Formatted as
                specified in pt-spec.txt section "3.3.4. Pluggable
                Transport Log Message".

   This event is triggered when tor receives a log message from the PT.

   Example:

      PT (obfs4): LOG SEVERITY=debug MESSAGE="Connected to bridge A"

    the resulting control port event would be:

      Tor: 650 PT_LOG PT=/usr/bin/obs4proxy SEVERITY=debug MESSAGE="Connected to bridge A"

   [PT_LOG was added in Tor 0.4.0.1-alpha]

4.1.29. Pluggable Transport Status

   Syntax:

      "650" SP "PT_STATUS" SP PT=Program SP TRANSPORT=Transport SP Message

      Program = The program path as defined in the *TransportPlugin
                configuration option. Tor accepts relative and full path.
      Transport = This value indicates a hint on what the PT is such as the
                  name or the protocol used for instance.
      Message = The status message that the PT sends back to the tor parent
                process minus the "STATUS" string prefix. Formatted as
                specified in pt-spec.txt section "3.3.5 Pluggable
                Transport Status Message".

   This event is triggered when tor receives a log message from the PT.

   Example:

      PT (obfs4): STATUS TRANSPORT=obfs4 CONNECT=Success

   the resulting control port event would be:

      Tor: 650 PT_STATUS PT=/usr/bin/obs4proxy TRANSPORT=obfs4 CONNECT=Success

   [PT_STATUS was added in Tor 0.4.0.1-alpha]

5. Implementation notes

5.1. Authentication

  If the control port is open and no authentication operation is enabled, Tor
  trusts any local user that connects to the control port.  This is generally
  a poor idea.

  If the 'CookieAuthentication' option is true, Tor writes a "magic
  cookie" file named "control_auth_cookie" into its data directory (or
  to another file specified in the 'CookieAuthFile' option).  To
  authenticate, the controller must demonstrate that it can read the
  contents of the cookie file:

  * Current versions of Tor support cookie authentication

    using the "COOKIE" authentication method: the controller sends the
    contents of the cookie file, encoded in hexadecimal.  This
    authentication method exposes the user running a controller to an
    unintended information disclosure attack whenever the controller
    has greater filesystem read access than the process that it has
    connected to.  (Note that a controller may connect to a process
    other than Tor.)  It is almost never safe to use, even if the
    controller's user has explicitly specified which filename to read
    an authentication cookie from.  For this reason, the COOKIE
    authentication method has been deprecated and will be removed from
    Tor before some future version of Tor.

  * 0.2.2.x versions of Tor starting with 0.2.2.36, and all versions of

    Tor after 0.2.3.12-alpha, support cookie authentication using the
    "SAFECOOKIE" authentication method, which discloses much less
    information about the contents of the cookie file.

  If the 'HashedControlPassword' option is set, it must contain the salted
  hash of a secret password.  The salted hash is computed according to the
  S2K algorithm in RFC 2440 (OpenPGP), and prefixed with the s2k specifier.
  This is then encoded in hexadecimal, prefixed by the indicator sequence
  "16:".  Thus, for example, the password 'foo' could encode to:

     16:660537E3E1CD49996044A3BF558097A981F539FEA2F9DA662B4626C1C2
        ++++++++++++++++**^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
           salt                       hashed value
                       indicator

  You can generate the salt of a password by calling

           'tor --hash-password <password>'

  or by using the example code in the Python and Java controller libraries.
  To authenticate under this scheme, the controller sends Tor the original
  secret that was used to generate the password, either as a quoted string
  or encoded in hexadecimal.

5.2. Don't let the buffer get too big.

  With old versions of Tor (before 0.2.0.16-alpha), if you ask for
  lots of events, and 16MB of them queue up on the buffer, the Tor
  process will close the socket.

  Newer Tor versions do not have this 16 MB buffer limit. However,
  if you leave huge numbers of events unread, Tor may still run out
  of memory, so you should still be careful about buffer size.

5.3. Backward compatibility with v0 control protocol.

  The 'version 0' control protocol was replaced in Tor 0.1.1.x. Support
  was removed in Tor 0.2.0.x. Every non-obsolete version of Tor now
  supports the version 1 control protocol.

  For backward compatibility with the "version 0" control protocol,
  Tor used to check whether the third octet of the first command is zero.
  (If it was, Tor assumed that version 0 is in use.)

  This compatibility was removed in Tor 0.1.2.16 and 0.2.0.4-alpha.

5.4. Tor config options for use by controllers

  Tor provides a few special configuration options for use by controllers.
  These options are not saved to disk by SAVECONF.  Most can be set and
  examined by the SETCONF and GETCONF commands, but some (noted below) can
  only be given in a torrc file or on the command line.

  Generally, these options make Tor unusable by disabling a portion of Tor's
  normal operations.  Unless a controller provides replacement functionality
  to fill this gap, Tor will not correctly handle user requests.

  __AllDirActionsPrivate

    If true, Tor will try to launch all directory operations through
    anonymous connections.  (Ordinarily, Tor only tries to anonymize
    requests related to hidden services.)  This option will slow down
    directory access, and may stop Tor from working entirely if it does not
    yet have enough directory information to build circuits.

    (Boolean. Default: "0".)

  __DisablePredictedCircuits

    If true, Tor will not launch preemptive "general-purpose" circuits for
    streams to attach to.  (It will still launch circuits for testing and
    for hidden services.)

    (Boolean. Default: "0".)

  __LeaveStreamsUnattached

    If true, Tor will not automatically attach new streams to circuits;
    instead, the controller must attach them with ATTACHSTREAM.  If the
    controller does not attach the streams, their data will never be routed.

    (Boolean. Default: "0".)

  __HashedControlSessionPassword

    As HashedControlPassword, but is not saved to the torrc file by
    SAVECONF.  Added in Tor 0.2.0.20-rc.

  __ReloadTorrcOnSIGHUP

    If this option is true (the default), we reload the torrc from disk
    every time we get a SIGHUP (from the controller or via a signal).
    Otherwise, we don't.  This option exists so that controllers can keep
    their options from getting overwritten when a user sends Tor a HUP for
    some other reason (for example, to rotate the logs).

    (Boolean.  Default: "1")

  __OwningControllerProcess

    If this option is set to a process ID, Tor will periodically check
    whether a process with the specified PID exists, and exit if one
    does not.  Added in Tor 0.2.2.28-beta.  This option's intended use
    is documented in section 3.23 with the related TAKEOWNERSHIP
    command.

    Note that this option can only specify a single process ID, unlike
    the TAKEOWNERSHIP command which can be sent along multiple control
    connections.

    (String.  Default: unset.)

  __OwningControllerFD

    If this option is a valid socket, Tor will start with an open control
    connection on this socket.  Added in Tor 0.3.3.1-alpha.

    This socket will be an owning controller, as if it had already called
    TAKEOWNERSHIP.  It will be automatically authenticated.  This option
    should only be used by other programs that are starting Tor.

    This option cannot be changed via SETCONF; it must be set in a torrc or
    via the command line.

    (Integer. Default: -1.)

  __DisableSignalHandlers

    If this option is set to true during startup, then Tor will not install
    any signal handlers to watch for POSIX signals.  The SIGNAL controller
    command will still work.

    This option is meant for embedding Tor inside another process, when
    the controlling process would rather handle signals on its own.

    This option cannot be changed via SETCONF; it must be set in a torrc or
    via the command line.

    (Boolean. Default: 0.)

5.5. Phases from the Bootstrap status event.

 [For the bootstrap phases reported by Tor prior to 0.4.0.x, see
  Section 5.6.]

  This section describes the various bootstrap phases currently reported
  by Tor. Controllers should not assume that the percentages and tags
  listed here will continue to match up, or even that the tags will stay
  in the same order. Some phases might also be skipped (not reported)
  if the associated bootstrap step is already complete, or if the phase
  no longer is necessary. Only "starting" and "done" are guaranteed to
  exist in all future versions.

  Current Tor versions enter these phases in order, monotonically.
  Future Tors MAY revisit earlier phases, for example, if the network
  fails.

5.5.1. Overview of Bootstrap reporting.

  Bootstrap phases can be viewed as belonging to one of three stages:

  1. Initial connection to a Tor relay or bridge
  2. Obtaining directory information
  3. Building an application circuit

  Tor doesn't specifically enter Stage 1; that is a side effect of
  other actions that Tor is taking. Tor could be making a connection
  to a fallback directory server, or it could be making a connection
  to a guard candidate. Either one counts as Stage 1 for the purposes
  of bootstrap reporting.

  Stage 2 might involve Tor contacting directory servers, or it might
  involve reading cached directory information from a previous
  session. Large parts of Stage 2 might be skipped if there is already
  enough cached directory information to build circuits. Tor will
  defer reporting progress in Stage 2 until Stage 1 is complete.

  Tor defers this reporting because Tor can already have enough
  directory information to build circuits, yet not be able to connect
  to a relay. Without that deferral, a user might misleadingly see Tor
  stuck at a large amount of progress when something as fundamental as
  making a TCP connection to any relay is failing.

  Tor also doesn't specifically enter Stage 3; that is a side effect
  of Tor building circuits for some purpose or other. In a typical
  client, Tor builds predicted circuits to provide lower latency for
  application connection requests. In Stage 3, Tor might make new
  connections to relays or bridges that it did not connect to in Stage
  1.

5.5.2. Phases in Bootstrap Stage 1.

  Phase 0:
  tag=starting summary="Starting"

  Tor starts out in this phase.

  Phase 1:
  tag=conn_pt summary="Connecting to pluggable transport"
 [This phase is new in 0.4.0.x]

  Tor is making a TCP connection to the transport plugin for a
  pluggable transport. Tor will use this pluggable transport to make
  its first connection to a bridge.

  Phase 2:
  tag=conn_done_pt summary="Connected to pluggable transport"
 [New in 0.4.0.x]

  Tor has completed its TCP connection to the transport plugin for the
  pluggable transport.

  Phase 3:
  tag=conn_proxy summary="Connecting to proxy"
 [New in 0.4.0.x]

  Tor is making a TCP connection to a proxy to make its first
  connection to a relay or bridge.

  Phase 4:
  tag=conn_done_proxy summary="Connected to proxy"
 [New in 0.4.0.x]

  Tor has completed its TCP connection to a proxy to make its first
  connection to a relay or bridge.

  Phase 5:
  tag=conn summary="Connecting to a relay"
 [New in 0.4.0.x; prior versions of Tor had a "conn_dir" phase that
  sometimes but not always corresponded to connecting to a directory server]

  Tor is making its first connection to a relay. This might be through
  a pluggable transport or proxy connection that Tor has already
  established.

  Phase 10:
  tag=conn_done summary="Connected to a relay"
 [New in 0.4.0.x]

  Tor has completed its first connection to a relay.

  Phase 14:
  tag=handshake summary="Handshaking with a relay"
 [New in 0.4.0.x; prior versions of Tor had a "handshake_dir" phase]

  Tor is in the process of doing a TLS handshake with a relay.

  Phase 15:
  tag=handshake_done summary="Handshake with a relay done"
 [New in 0.4.0.x]

  Tor has completed its TLS handshake with a relay.

5.5.3. Phases in Bootstrap Stage 2.

  Phase 20:
  tag=onehop_create summary="Establishing an encrypted directory connection"
 [prior to 0.4.0.x, this was numbered 15]

  Once TLS is finished with a relay, Tor will send a CREATE_FAST cell
  to establish a one-hop circuit for retrieving directory information.
  It will remain in this phase until it receives the CREATED_FAST cell
  back, indicating that the circuit is ready.

  Phase 25:
  tag=requesting_status summary="Asking for networkstatus consensus"
 [prior to 0.4.0.x, this was numbered 20]

  Once we've finished our one-hop circuit, we will start a new stream
  for fetching the networkstatus consensus. We'll stay in this phase
  until we get the 'connected' relay cell back, indicating that we've
  established a directory connection.

  Phase 30:
  tag=loading_status summary="Loading networkstatus consensus"
 [prior to 0.4.0.x, this was numbered 25]

  Once we've established a directory connection, we will start fetching
  the networkstatus consensus document. This could take a while; this
  phase is a good opportunity for using the "progress" keyword to indicate
  partial progress.

  This phase could stall if the directory server we picked doesn't
  have a copy of the networkstatus consensus so we have to ask another,
  or it does give us a copy but we don't find it valid.

  Phase 40:
  tag=loading_keys summary="Loading authority key certs"

  Sometimes when we've finished loading the networkstatus consensus,
  we find that we don't have all the authority key certificates for the
  keys that signed the consensus. At that point we put the consensus we
  fetched on hold and fetch the keys so we can verify the signatures.

  Phase 45
  tag=requesting_descriptors summary="Asking for relay descriptors"

  Once we have a valid networkstatus consensus and we've checked all
  its signatures, we start asking for relay descriptors. We stay in this
  phase until we have received a 'connected' relay cell in response to
  a request for descriptors.

 [Some versions of Tor (starting with 0.2.6.2-alpha but before
  0.4.0.x): Tor could report having internal paths only; see Section
  5.6]

  Phase 50:
  tag=loading_descriptors summary="Loading relay descriptors"

  We will ask for relay descriptors from several different locations,
  so this step will probably make up the bulk of the bootstrapping,
  especially for users with slow connections. We stay in this phase until
  we have descriptors for a significant fraction of the usable relays
  listed in the networkstatus consensus (this can be between 25% and 95%
  depending on Tor's configuration and network consensus parameters).
  This phase is also a good opportunity to use the "progress" keyword to
  indicate partial steps.

 [Some versions of Tor (starting with 0.2.6.2-alpha but before
  0.4.0.x): Tor could report having internal paths only; see Section
  5.6]

  Phase 75:
  tag=enough_dirinfo summary="Loaded enough directory info to build
  circuits"
 [New in 0.4.0.x; previously, Tor would misleadingly report the
  "conn_or" tag once it had enough directory info.]

5.5.4. Phases in Bootstrap Stage 3.

  Phase 76:
  tag=ap_conn_pt summary="Connecting to pluggable transport to build
  circuits"
 [New in 0.4.0.x]

  This is similar to conn_pt, except for making connections to
  additional relays or bridges that Tor needs to use to build
  application circuits.

  Phase 77:
  tag=ap_conn_done_pt summary="Connected to pluggable transport to build circuits"
 [New in 0.4.0.x]

  This is similar to conn_done_pt, except for making connections to
  additional relays or bridges that Tor needs to use to build
  application circuits.

  Phase 78:
  tag=ap_conn_proxy summary="Connecting to proxy to build circuits"
 [New in 0.4.0.x]

  This is similar to conn_proxy, except for making connections to
  additional relays or bridges that Tor needs to use to build
  application circuits.

  Phase 79:
  tag=ap_conn_done_proxy summary="Connected to proxy to build circuits"
 [New in 0.4.0.x]

  This is similar to conn_done_proxy, except for making connections to
  additional relays or bridges that Tor needs to use to build
  application circuits.

  Phase 80:
  tag=ap_conn summary="Connecting to a relay to build circuits"
 [New in 0.4.0.x]

  This is similar to conn, except for making connections to additional
  relays or bridges that Tor needs to use to build application
  circuits.

  Phase 85:
  tag=ap_conn_done summary="Connected to a relay to build circuits"
 [New in 0.4.0.x]

  This is similar to conn_done, except for making connections to
  additional relays or bridges that Tor needs to use to build
  application circuits.

  Phase 89:
  tag=ap_handshake summary="Finishing handshake with a relay to build circuits"
 [New in 0.4.0.x]

  This is similar to handshake, except for making connections to
  additional relays or bridges that Tor needs to use to build
  application circuits.

  Phase 90:
  tag=ap_handshake_done summary="Handshake finished with a relay to build circuits"
 [New in 0.4.0.x]

  This is similar to handshake_done, except for making connections to
  additional relays or bridges that Tor needs to use to build
  application circuits.

  Phase 95:
  tag=circuit_create summary="Establishing a[n internal] Tor circuit"
 [prior to 0.4.0.x, this was numbered 90]

  Once we've finished our TLS handshake with the first hop of a circuit,
  we will set about trying to make some 3-hop circuits in case we need them
  soon.

 [Some versions of Tor (starting with 0.2.6.2-alpha but before
  0.4.0.x): Tor could report having internal paths only; see Section
  5.6]

  Phase 100:
  tag=done summary="Done"

  A full 3-hop circuit has been established. Tor is ready to handle
  application connections now.

 [Some versions of Tor (starting with 0.2.6.2-alpha but before
  0.4.0.x): Tor could report having internal paths only; see Section
  5.6]

5.6. Bootstrap phases reported by older versions of Tor

  These phases were reported by Tor older than 0.4.0.x.  For newer
  versions of Tor, see Section 5.5.

 [Newer versions of Tor (0.2.6.2-alpha and later):
  If the consensus contains Exits (the typical case), Tor will build both
  exit and internal circuits. When bootstrap completes, Tor will be ready
  to handle an application requesting an exit circuit to services like the
  World Wide Web.

  If the consensus does not contain Exits, Tor will only build internal
  circuits. In this case, earlier statuses will have included "internal"
  as indicated above. When bootstrap completes, Tor will be ready to handle
  an application requesting an internal circuit to hidden services at
  ".onion" addresses.

  If a future consensus contains Exits, exit circuits may become available.]

  Phase 0:
  tag=starting summary="Starting"

  Tor starts out in this phase.

  Phase 5:
  tag=conn_dir summary="Connecting to directory server"

  Tor sends this event as soon as Tor has chosen a directory server --
  e.g. one of the authorities if bootstrapping for the first time or
  after a long downtime, or one of the relays listed in its cached
  directory information otherwise.

  Tor will stay at this phase until it has successfully established
  a TCP connection with some directory server. Problems in this phase
  generally happen because Tor doesn't have a network connection, or
  because the local firewall is dropping SYN packets.

  Phase 10:
  tag=handshake_dir summary="Finishing handshake with directory server"

  This event occurs when Tor establishes a TCP connection with a relay or
  authority used as a directory server (or its https proxy if it's using
  one). Tor remains in this phase until the TLS handshake with the relay
  or authority is finished.

  Problems in this phase generally happen because Tor's firewall is
  doing more sophisticated MITM attacks on it, or doing packet-level
  keyword recognition of Tor's handshake.

  Phase 15:
  tag=onehop_create summary="Establishing an encrypted directory connection"

  Once TLS is finished with a relay, Tor will send a CREATE_FAST cell
  to establish a one-hop circuit for retrieving directory information.
  It will remain in this phase until it receives the CREATED_FAST cell
  back, indicating that the circuit is ready.

  Phase 20:
  tag=requesting_status summary="Asking for networkstatus consensus"

  Once we've finished our one-hop circuit, we will start a new stream
  for fetching the networkstatus consensus. We'll stay in this phase
  until we get the 'connected' relay cell back, indicating that we've
  established a directory connection.

  Phase 25:
  tag=loading_status summary="Loading networkstatus consensus"

  Once we've established a directory connection, we will start fetching
  the networkstatus consensus document. This could take a while; this
  phase is a good opportunity for using the "progress" keyword to indicate
  partial progress.

  This phase could stall if the directory server we picked doesn't
  have a copy of the networkstatus consensus so we have to ask another,
  or it does give us a copy but we don't find it valid.

  Phase 40:
  tag=loading_keys summary="Loading authority key certs"

  Sometimes when we've finished loading the networkstatus consensus,
  we find that we don't have all the authority key certificates for the
  keys that signed the consensus. At that point we put the consensus we
  fetched on hold and fetch the keys so we can verify the signatures.

  Phase 45
  tag=requesting_descriptors summary="Asking for relay descriptors
                                      [ for internal paths]"

  Once we have a valid networkstatus consensus and we've checked all
  its signatures, we start asking for relay descriptors. We stay in this
  phase until we have received a 'connected' relay cell in response to
  a request for descriptors.

 [Newer versions of Tor (0.2.6.2-alpha and later):
  If the consensus contains Exits (the typical case), Tor will ask for
  descriptors for both exit and internal paths. If not, Tor will only ask
  for descriptors for internal paths. In this case, this status will
  include "internal" as indicated above.]

  Phase 50:
  tag=loading_descriptors summary="Loading relay descriptors[ for internal
                                   paths]"

  We will ask for relay descriptors from several different locations,
  so this step will probably make up the bulk of the bootstrapping,
  especially for users with slow connections. We stay in this phase until
  we have descriptors for a significant fraction of the usable relays
  listed in the networkstatus consensus (this can be between 25% and 95%
  depending on Tor's configuration and network consensus parameters).
  This phase is also a good opportunity to use the "progress" keyword to
  indicate partial steps.

 [Newer versions of Tor (0.2.6.2-alpha and later):
  If the consensus contains Exits (the typical case), Tor will download
  descriptors for both exit and internal paths. If not, Tor will only
  download descriptors for internal paths. In this case, this status will
  include "internal" as indicated above.]

  Phase 80:
  tag=conn_or summary="Connecting to the Tor network[ internally]"

  Once we have a valid consensus and enough relay descriptors, we choose
  entry guard(s) and start trying to build some circuits. This step
  is similar to the "conn_dir" phase above; the only difference is
  the context.

  If a Tor starts with enough recent cached directory information,
  its first bootstrap status event will be for the conn_or phase.

 [Newer versions of Tor (0.2.6.2-alpha and later):
  If the consensus contains Exits (the typical case), Tor will build both
  exit and internal circuits. If not, Tor will only build internal circuits.
  In this case, this status will include "internal(ly)" as indicated above.]

  Phase 85:
  tag=handshake_or summary="Finishing handshake with first hop[ of internal
                            circuit]"

  This phase is similar to the "handshake_dir" phase, but it gets reached
  if we finish a TCP connection to a Tor relay and we have already reached
  the "conn_or" phase. We'll stay in this phase until we complete a TLS
  handshake with a Tor relay.

 [Newer versions of Tor (0.2.6.2-alpha and later):
  If the consensus contains Exits (the typical case), Tor may be finishing
  a handshake with the first hop if either an exit or internal circuit. In
  this case, it won't specify which type. If the consensus contains no Exits,
  Tor will only build internal circuits. In this case, this status will
  include "internal" as indicated above.]

  Phase 90:
  tag=circuit_create summary="Establishing a[n internal] Tor circuit"

  Once we've finished our TLS handshake with the first hop of a circuit,
  we will set about trying to make some 3-hop circuits in case we need them
  soon.

 [Newer versions of Tor (0.2.6.2-alpha and later):
  If the consensus contains Exits (the typical case), Tor will build both
  exit and internal circuits. If not, Tor will only build internal circuits.
  In this case, this status will include "internal" as indicated above.]

  Phase 100:
  tag=done summary="Done"

  A full 3-hop circuit has been established. Tor is ready to handle
  application connections now.

 [Newer versions of Tor (0.2.6.2-alpha and later):
  If the consensus contains Exits (the typical case), Tor will build both
  exit and internal circuits. At this stage, Tor will be ready to handle
  an application requesting an exit circuit to services like the World
  Wide Web.

  If the consensus does not contain Exits, Tor will only build internal
  circuits. In this case, earlier statuses will have included "internal"
  as indicated above. At this stage, Tor will be ready to handle an
  application requesting an internal circuit to hidden services at ".onion"
  addresses.

  If a future consensus contains Exits, exit circuits may become available.]