diff options
Diffstat (limited to 'src/lib/pubsub')
| -rw-r--r-- | src/lib/pubsub/.may_include | 10 | ||||
| -rw-r--r-- | src/lib/pubsub/include.am | 28 | ||||
| -rw-r--r-- | src/lib/pubsub/lib_pubsub.md | 14 | ||||
| -rw-r--r-- | src/lib/pubsub/pub_binding_st.h | 38 | ||||
| -rw-r--r-- | src/lib/pubsub/publish_subscribe.md | 144 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub.h | 89 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_build.c | 307 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_build.h | 97 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_builder_st.h | 161 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_check.c | 414 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_connect.h | 54 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_flags.h | 32 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_macros.h | 373 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_publish.c | 72 | ||||
| -rw-r--r-- | src/lib/pubsub/pubsub_publish.h | 20 |
15 files changed, 1853 insertions, 0 deletions
diff --git a/src/lib/pubsub/.may_include b/src/lib/pubsub/.may_include new file mode 100644 index 0000000000..5623492f00 --- /dev/null +++ b/src/lib/pubsub/.may_include @@ -0,0 +1,10 @@ +orconfig.h + +lib/cc/*.h +lib/container/*.h +lib/dispatch/*.h +lib/intmath/*.h +lib/log/*.h +lib/malloc/*.h +lib/pubsub/*.h +lib/string/*.h diff --git a/src/lib/pubsub/include.am b/src/lib/pubsub/include.am new file mode 100644 index 0000000000..e2abebcd40 --- /dev/null +++ b/src/lib/pubsub/include.am @@ -0,0 +1,28 @@ + +noinst_LIBRARIES += src/lib/libtor-pubsub.a + +if UNITTESTS_ENABLED +noinst_LIBRARIES += src/lib/libtor-pubsub-testing.a +endif + +# ADD_C_FILE: INSERT SOURCES HERE. +src_lib_libtor_pubsub_a_SOURCES = \ + src/lib/pubsub/pubsub_build.c \ + src/lib/pubsub/pubsub_check.c \ + src/lib/pubsub/pubsub_publish.c + +src_lib_libtor_pubsub_testing_a_SOURCES = \ + $(src_lib_libtor_pubsub_a_SOURCES) +src_lib_libtor_pubsub_testing_a_CPPFLAGS = $(AM_CPPFLAGS) $(TEST_CPPFLAGS) +src_lib_libtor_pubsub_testing_a_CFLAGS = $(AM_CFLAGS) $(TEST_CFLAGS) + +# ADD_C_FILE: INSERT HEADERS HERE. +noinst_HEADERS += \ + src/lib/pubsub/pub_binding_st.h \ + src/lib/pubsub/pubsub.h \ + src/lib/pubsub/pubsub_build.h \ + src/lib/pubsub/pubsub_builder_st.h \ + src/lib/pubsub/pubsub_connect.h \ + src/lib/pubsub/pubsub_flags.h \ + src/lib/pubsub/pubsub_macros.h \ + src/lib/pubsub/pubsub_publish.h diff --git a/src/lib/pubsub/lib_pubsub.md b/src/lib/pubsub/lib_pubsub.md new file mode 100644 index 0000000000..3f4c473436 --- /dev/null +++ b/src/lib/pubsub/lib_pubsub.md @@ -0,0 +1,14 @@ +@dir /lib/pubsub +@brief lib/pubsub: Publish-subscribe message passing. + +This module wraps the \refdir{lib/dispatch} module, to provide a more +ergonomic and type-safe approach to message passing. + +In general, we favor this mechanism for cases where higher-level modules +need to be notified when something happens in lower-level modules. (The +alternative would be calling up from the lower-level modules, which +would be error-prone; or maintaining lists of function-pointers, which +would be clumsy and tend to complicate the call graph.) + +See pubsub.c for more information. + diff --git a/src/lib/pubsub/pub_binding_st.h b/src/lib/pubsub/pub_binding_st.h new file mode 100644 index 0000000000..d7c562fc35 --- /dev/null +++ b/src/lib/pubsub/pub_binding_st.h @@ -0,0 +1,38 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pub_binding_st.h + * @brief Declaration of pub_binding_t. + * + * This is an internal type for the pubsub implementation. + */ + +#ifndef TOR_PUB_BINDING_ST_H +#define TOR_PUB_BINDING_ST_H + +#include "lib/dispatch/msgtypes.h" +struct dispatch_t; + +/** + * A pub_binding_t is an opaque object that subsystems use to publish + * messages. The DISPATCH_ADD_PUB*() macros set it up. + **/ +typedef struct pub_binding_t { + /** + * A pointer to a configured dispatch_t object. This is filled in + * when the dispatch_t is finally constructed. + **/ + struct dispatch_t *dispatch_ptr; + /** + * A template for the msg_t fields that are filled in for this message. + * This is copied into outgoing messages, ensuring that their fields are set + * corretly. + **/ + msg_t msg_template; +} pub_binding_t; + +#endif /* !defined(TOR_PUB_BINDING_ST_H) */ diff --git a/src/lib/pubsub/publish_subscribe.md b/src/lib/pubsub/publish_subscribe.md new file mode 100644 index 0000000000..bb05b100b1 --- /dev/null +++ b/src/lib/pubsub/publish_subscribe.md @@ -0,0 +1,144 @@ + +@page publish_subscribe Publish-subscribe message passing in Tor + +@tableofcontents + +## Introduction + +Tor has introduced a generic publish-subscribe mechanism for delivering +messages internally. It is meant to help us improve the modularity of +our code, by avoiding direct coupling between modules that don't +actually need to invoke one another. + +This publish-subscribe mechanism is *not* meant for handing +multithreading or multiprocess issues, thought we hope that eventually +it might be extended and adapted for that purpose. Instead, we use +publish-subscribe today to decouple modules that shouldn't be calling +each other directly. + +For example, there are numerous parts of our code that might need to +take action when a circuit is completed: a controller might need to be +informed, an onion service negotiation might need to be attached, a +guard might need to be marked as working, or a client connection might +need to be attached. But many of those actions occur at a higher layer +than circuit completion: calling them directly is a layering violation, +and makes our code harder to understand and analyze. + +But with message-passing, we can invert this layering violation: circuit +completion can become a "message" that the circuit code publishes, and +to which higher-level layers subscribe. This means that circuit +handling can be decoupled from higher-level modules, and stay nice and +simple. (@ref pubsub_notyet "1") + +> @anchor pubsub_notyet 1. Unfortunately, like most of our code, circuit +> handling is _not_ yet refactored to use publish-subscribe throughout. +> Instead, layer violations of the type described here are pretty common +> in Tor today. To see a small part of what happens when a circuit is +> completed today, have a look at circuit_build_no_more_hops() and its +> associated code. + +## Channels and delivery policies + +To work with messages, especially when refactoring existing code, you'll +need to understand "channels" and "delivery policies". + +Every message is delivered on a "message channel". Each channel +(conceptually) a queue-like structure that can support an arbitrarily +number of message types. Where channels vary is their delivery +mechanisms, and their guarantees about when messages are processed. + +Currently, three delivery policies are possible: + + - `DELIV_PROMPT` -- causes messages to be processed via a callback in + Tor's event loop. This is generally the best choice, since it + avoids unexpected growth of the stack. + + - `DELIV_IMMEDIATE` -- causes messages to be processed immediately + on the call stack when they are published. This choice grows the + stack, and can lead to unexpected complexity in the call graph. + We should only use it when necessary. + + - `DELIV_NEVER` -- causes messages not to be delivered by the message + dispatch system at all. Instead, some other part of the code must + call dispatch_flush() to get the messages delivered. + +See mainloop_pubsub.c and mainloop_pubsub.h for more information and +implementation details. + +## Layers: Dispatch vs publish-subsubscribe vs mainloop. + +At the lowest level, messages are sent via the "dispatcher" module in +@refdir{lib/dispatch}. For performance, this dispatcher works with a +untyped messages. Publishers, subscribers, channels, and messages are +distinguished by short integers. Associated data is handled as +dynamically-typed data pointers, and its types are also stored as short +integers. + +Naturally, this results in a type-unsafe C API, so most other modules +shouldn't invoke @refdir{lib/dispatch} directly. At a higher level, +@refdir{lib/pubsub} defines a set of functions and macros that make +messages named and type-safe. This is the one that other modules should +use when they want to send or receive a message. + +The two modules above do not handle message delivery. Instead, the +dispatch module takes a callback that it can invoke when a channel +becomes nonempty, and defines a dispatch_flush() function to deliver all +the messages queued in a channel. The work of actually making sure that +dispatch_flush() is called when appropriate falls to the main loop, +which needs to integrate the message dispatcher with the rest of our +events and callbacks. This work happens in mainloop_pubsub.c. + + +## How to publish and subscribe + +This section gives an overview of how to make new messages and how to +use them. For full details, see pubsub_macros.h. + +Before anybody can publish or subscribe to a message, the message must +be declared, typically in a header. This uses DECLARE_MESSAGE() or +DECLARE_MESSAGE_INT(). + +Only subsystems can publish or subscribe messages. For more information +about the subsystems architecture, see @ref initialization. + +To publish a message, you must: + - Include the header that declares the message. + - Declare a set of helper functions via DECLARE_PUBLISH(). These + must be visible wherever you call PUBLISH(). + - Call PUBLISH() to actually send a message. + - Connect your subsystem to the dispatcher by calling + DISPATCH_ADD_PUB() from your subsystem's subsys_fns_t.add_pubsub + callback. + +To subscribe to a message, you must: + - Include the header that declares the message. + - Declare a callback function to be invoked when the message is delivered. + - Use DISPATCH_SUBSCRIBE at file scope to define a set of wrapper + functions to call your callback function with the appropriate type. + - Connect your subsystem to the dispatcher by calling + DISPATCH_ADD_SUB() from your subsystem's subsys_fns_t.add_pubsub + callback. + +Again, the file-level documentation for pubsub_macros.h describes how to +declare a message, how to publish it, and how to subscribe to it. + +## Designing good messages + +**Frequency**: +The publish-subscribe system uses a few function calls +and allocations for each message sent. This makes it unsuitable for +very-high-bandwidth events, like "receiving a single data cell" or "a +socket has become writable." It's fine, however, for events that +ordinarily happen a bit less frequently than that, like a circuit +getting finished, a new connection getting opened, or so on. + +**Semantics**: +A message should declare that something has happened or is happening, +not that something in particular should be done. + +For example, suppose you want to set up a message so that onion services +clean up their replay caches whenever we're low on memory. The event +should be something like `memory_low`, not `clean_up_replay_caches`. +The latter name would imply that the publisher knew who was subscribing +to the message and what they intended to do about it, which would be a +layering violation. diff --git a/src/lib/pubsub/pubsub.h b/src/lib/pubsub/pubsub.h new file mode 100644 index 0000000000..d0a4d317f3 --- /dev/null +++ b/src/lib/pubsub/pubsub.h @@ -0,0 +1,89 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub.h + * @brief Header for OO publish-subscribe functionality. + * + * This module provides a wrapper around the "dispatch" module, + * ensuring type-safety and allowing us to do static analysis on + * publication and subscriptions. + * + * With this module, we enforce: + * <ul> + * <li>that every message has (potential) publishers and subscribers; + * <li>that every message is published and subscribed from the correct + * channels, with the correct type ID, every time it is published. + * <li>that type IDs correspond to a single C type, and that the C types are + * used correctly. + * <li>that when a message is published or subscribed, it is done with + * a correct subsystem identifier + * </ul> + * + * We do this by making "publication requests" and "subscription requests" + * into objects, and doing some computation on them before we create + * a dispatch_t with them. + * + * Rather than using the dispatch module directly, a publishing module + * receives a "binding" object that it uses to send messages with the right + * settings. + * + * Most users of this module will want to use this header, and the + * pubsub_macros.h header for convenience. + */ + +/* + * + * Overview: Messages are sent over channels. Before sending a message on a + * channel, or receiving a message on a channel, a subsystem needs to register + * that it publishes, or subscribes, to that message, on that channel. + * + * Messages, channels, and subsystems are represented internally as short + * integers, though they are associated with human-readable strings for + * initialization and debugging. + * + * When registering for a message, a subsystem must say whether it is an + * exclusive publisher/subscriber to that message type, or whether other + * subsystems may also publish/subscribe to it. + * + * All messages and their publishers/subscribers must be registered early in + * the initialization process. + * + * By default, it is an error for a message type to have publishers and no + * subscribers on a channel, or subscribers and no publishers on a channel. + * + * A subsystem may register for a message with a note that delivery or + * production is disabled -- for example, because the subsystem is + * disabled at compile-time. It is not an error for a message type to + * have all of its publishers or subscribers disabled. + * + * After a message is sent, it is delivered to every recipient. This + * delivery happens from the top level of the event loop; it may be + * interleaved with network events, timers, etc. + * + * Messages may have associated data. This data is typed, and is owned + * by the message. Strings, byte-arrays, and integers have built-in + * support. Other types may be added. If objects are to be sent, + * they should be identified by handle. If an object requires cleanup, + * it should be declared with an associated free function. + * + * Semantically, if two subsystems communicate only by this kind of + * message passing, neither is considered to depend on the other, though + * both are considered to have a dependency on the message and on any + * types it contains. + * + * (Or generational index?) + */ +#ifndef TOR_PUBSUB_PUBSUB_H +#define TOR_PUBSUB_PUBSUB_H + +#include "lib/pubsub/pub_binding_st.h" +#include "lib/pubsub/pubsub_connect.h" +#include "lib/pubsub/pubsub_flags.h" +#include "lib/pubsub/pubsub_macros.h" +#include "lib/pubsub/pubsub_publish.h" + +#endif /* !defined(TOR_PUBSUB_PUBSUB_H) */ diff --git a/src/lib/pubsub/pubsub_build.c b/src/lib/pubsub/pubsub_build.c new file mode 100644 index 0000000000..3c134f015c --- /dev/null +++ b/src/lib/pubsub/pubsub_build.c @@ -0,0 +1,307 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_build.c + * @brief Construct a dispatch_t in safer, more OO way. + **/ + +#define PUBSUB_PRIVATE + +#include "lib/dispatch/dispatch.h" +#include "lib/dispatch/dispatch_cfg.h" +#include "lib/dispatch/dispatch_naming.h" +#include "lib/dispatch/msgtypes.h" +#include "lib/pubsub/pubsub_flags.h" +#include "lib/pubsub/pub_binding_st.h" +#include "lib/pubsub/pubsub_build.h" +#include "lib/pubsub/pubsub_builder_st.h" +#include "lib/pubsub/pubsub_connect.h" + +#include "lib/container/smartlist.h" +#include "lib/log/util_bug.h" +#include "lib/malloc/malloc.h" + + #include <string.h> + +/** Construct and return a new empty pubsub_items_t. */ +static pubsub_items_t * +pubsub_items_new(void) +{ + pubsub_items_t *cfg = tor_malloc_zero(sizeof(*cfg)); + cfg->items = smartlist_new(); + cfg->type_items = smartlist_new(); + return cfg; +} + +/** Release all storage held in a pubsub_items_t. */ +void +pubsub_items_free_(pubsub_items_t *cfg) +{ + if (! cfg) + return; + SMARTLIST_FOREACH(cfg->items, pubsub_cfg_t *, item, tor_free(item)); + SMARTLIST_FOREACH(cfg->type_items, + pubsub_type_cfg_t *, item, tor_free(item)); + smartlist_free(cfg->items); + smartlist_free(cfg->type_items); + tor_free(cfg); +} + +/** Construct and return a new pubsub_builder_t. */ +pubsub_builder_t * +pubsub_builder_new(void) +{ + dispatch_naming_init(); + + pubsub_builder_t *pb = tor_malloc_zero(sizeof(*pb)); + pb->cfg = dcfg_new(); + pb->items = pubsub_items_new(); + return pb; +} + +/** + * Release all storage held by a pubsub_builder_t. + * + * You'll (mostly) only want to call this function on an error case: if you're + * constructing a dispatch_t instead, you should call + * pubsub_builder_finalize() to consume the pubsub_builder_t. + */ +void +pubsub_builder_free_(pubsub_builder_t *pb) +{ + if (pb == NULL) + return; + pubsub_items_free(pb->items); + dcfg_free(pb->cfg); + tor_free(pb); +} + +/** + * Create and return a pubsub_connector_t for the subsystem with ID + * <b>subsys</b> to use in adding publications, subscriptions, and types to + * <b>builder</b>. + **/ +pubsub_connector_t * +pubsub_connector_for_subsystem(pubsub_builder_t *builder, + subsys_id_t subsys) +{ + tor_assert(builder); + ++builder->n_connectors; + + pubsub_connector_t *con = tor_malloc_zero(sizeof(*con)); + + con->builder = builder; + con->subsys_id = subsys; + + return con; +} + +/** + * Release all storage held by a pubsub_connector_t. + **/ +void +pubsub_connector_free_(pubsub_connector_t *con) +{ + if (!con) + return; + + if (con->builder) { + --con->builder->n_connectors; + tor_assert(con->builder->n_connectors >= 0); + } + tor_free(con); +} + +/** + * Use <b>con</b> to add a request for being able to publish messages of type + * <b>msg</b> with auxiliary data of <b>type</b> on <b>channel</b>. + **/ +int +pubsub_add_pub_(pubsub_connector_t *con, + pub_binding_t *out, + channel_id_t channel, + message_id_t msg, + msg_type_id_t type, + unsigned flags, + const char *file, + unsigned line) +{ + pubsub_cfg_t *cfg = tor_malloc_zero(sizeof(*cfg)); + + memset(out, 0, sizeof(*out)); + cfg->is_publish = true; + + out->msg_template.sender = cfg->subsys = con->subsys_id; + out->msg_template.channel = cfg->channel = channel; + out->msg_template.msg = cfg->msg = msg; + out->msg_template.type = cfg->type = type; + + cfg->flags = flags; + cfg->added_by_file = file; + cfg->added_by_line = line; + + /* We're grabbing a pointer to the pub_binding_t so we can tell it about + * the dispatcher later on. + */ + cfg->pub_binding = out; + + smartlist_add(con->builder->items->items, cfg); + + if (dcfg_msg_set_type(con->builder->cfg, msg, type) < 0) + goto err; + if (dcfg_msg_set_chan(con->builder->cfg, msg, channel) < 0) + goto err; + + return 0; + err: + ++con->builder->n_errors; + return -1; +} + +/** + * Use <b>con</b> to add a request for being able to publish messages of type + * <b>msg</b> with auxiliary data of <b>type</b> on <b>channel</b>, + * passing them to the callback in <b>recv_fn</b>. + **/ +int +pubsub_add_sub_(pubsub_connector_t *con, + recv_fn_t recv_fn, + channel_id_t channel, + message_id_t msg, + msg_type_id_t type, + unsigned flags, + const char *file, + unsigned line) +{ + pubsub_cfg_t *cfg = tor_malloc_zero(sizeof(*cfg)); + + cfg->is_publish = false; + cfg->subsys = con->subsys_id; + cfg->channel = channel; + cfg->msg = msg; + cfg->type = type; + cfg->flags = flags; + cfg->added_by_file = file; + cfg->added_by_line = line; + + cfg->recv_fn = recv_fn; + + smartlist_add(con->builder->items->items, cfg); + + if (dcfg_msg_set_type(con->builder->cfg, msg, type) < 0) + goto err; + if (dcfg_msg_set_chan(con->builder->cfg, msg, channel) < 0) + goto err; + if (! (flags & DISP_FLAG_STUB)) { + if (dcfg_add_recv(con->builder->cfg, msg, cfg->subsys, recv_fn) < 0) + goto err; + } + + return 0; + err: + ++con->builder->n_errors; + return -1; +} + +/** + * Use <b>con</b> to define the functions to use for manipulating the type + * <b>type</b>. Any function pointers left as NULL will be implemented as + * no-ops. + **/ +int +pubsub_connector_register_type_(pubsub_connector_t *con, + msg_type_id_t type, + dispatch_typefns_t *fns, + const char *file, + unsigned line) +{ + pubsub_type_cfg_t *cfg = tor_malloc_zero(sizeof(*cfg)); + cfg->type = type; + memcpy(&cfg->fns, fns, sizeof(*fns)); + cfg->subsys = con->subsys_id; + cfg->added_by_file = file; + cfg->added_by_line = line; + + smartlist_add(con->builder->items->type_items, cfg); + + if (dcfg_type_set_fns(con->builder->cfg, type, fns) < 0) + goto err; + + return 0; + err: + ++con->builder->n_errors; + return -1; +} + +/** + * Initialize the dispatch_ptr field in every relevant publish binding + * for <b>d</b>. + */ +static void +pubsub_items_install_bindings(pubsub_items_t *items, + dispatch_t *d) +{ + SMARTLIST_FOREACH_BEGIN(items->items, pubsub_cfg_t *, cfg) { + if (cfg->pub_binding) { + // XXXX we could skip this for STUB publishers, and for any publishers + // XXXX where all subscribers are STUB. + cfg->pub_binding->dispatch_ptr = d; + } + } SMARTLIST_FOREACH_END(cfg); +} + +/** + * Remove the dispatch_ptr fields for all the relevant publish bindings + * in <b>items</b>. The prevents subsequent dispatch_pub_() calls from + * sending messages to a dispatcher that has been freed. + **/ +void +pubsub_items_clear_bindings(pubsub_items_t *items) +{ + SMARTLIST_FOREACH_BEGIN(items->items, pubsub_cfg_t *, cfg) { + if (cfg->pub_binding) { + cfg->pub_binding->dispatch_ptr = NULL; + } + } SMARTLIST_FOREACH_END(cfg); +} + +/** + * Create a new dispatcher as configured in a pubsub_builder_t. + * + * Consumes and frees its input. + **/ +dispatch_t * +pubsub_builder_finalize(pubsub_builder_t *builder, + pubsub_items_t **items_out) +{ + dispatch_t *dispatcher = NULL; + tor_assert_nonfatal(builder->n_connectors == 0); + + if (pubsub_builder_check(builder) < 0) + goto err; + + if (builder->n_errors) { + log_warn(LD_GENERAL, "At least one error occurred previously when " + "configuring the dispatcher."); + goto err; + } + + dispatcher = dispatch_new(builder->cfg); + + if (!dispatcher) + goto err; + + pubsub_items_install_bindings(builder->items, dispatcher); + if (items_out) { + *items_out = builder->items; + builder->items = NULL; /* Prevent free */ + } + + err: + pubsub_builder_free(builder); + return dispatcher; +} diff --git a/src/lib/pubsub/pubsub_build.h b/src/lib/pubsub/pubsub_build.h new file mode 100644 index 0000000000..2781b8251a --- /dev/null +++ b/src/lib/pubsub/pubsub_build.h @@ -0,0 +1,97 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_build.h + * @brief Header used for constructing the OO publish-subscribe facility. + * + * (See pubsub.h for more general information on this API.) + **/ + +#ifndef TOR_PUBSUB_BUILD_H +#define TOR_PUBSUB_BUILD_H + +#include "lib/dispatch/msgtypes.h" + +struct dispatch_t; +struct pubsub_connector_t; + +/** + * A "dispatch builder" is an incomplete dispatcher, used when + * registering messages. It does not have the same integrity guarantees + * as a dispatcher. It cannot actually handle messages itself: once all + * subsystems have registered, it is converted into a dispatch_t. + **/ +typedef struct pubsub_builder_t pubsub_builder_t; + +/** + * A "pubsub items" holds the configuration items used to configure a + * pubsub_builder. After the builder is finalized, this field is extracted, + * and used later to tear down pointers that enable publishing. + **/ +typedef struct pubsub_items_t pubsub_items_t; + +/** + * Create a new pubsub_builder. This should only happen in the + * main-init code. + */ +pubsub_builder_t *pubsub_builder_new(void); + +/** DOCDOC */ +int pubsub_builder_check(pubsub_builder_t *); + +/** + * Free a pubsub builder. This should only happen on error paths, where + * we have decided not to construct a dispatcher for some reason. + */ +#define pubsub_builder_free(db) \ + FREE_AND_NULL(pubsub_builder_t, pubsub_builder_free_, (db)) + +/** Internal implementation of pubsub_builder_free(). */ +void pubsub_builder_free_(pubsub_builder_t *); + +/** + * Create a pubsub connector that a single subsystem will use to + * register its messages. The main-init code does this during susbsystem + * initialization. + */ +struct pubsub_connector_t *pubsub_connector_for_subsystem(pubsub_builder_t *, + subsys_id_t); + +/** + * The main-init code does this after subsystem initialization. + */ +#define pubsub_connector_free(c) \ + FREE_AND_NULL(struct pubsub_connector_t, pubsub_connector_free_, (c)) + +void pubsub_connector_free_(struct pubsub_connector_t *); + +/** + * Constructs a dispatcher from a dispatch_builder, after checking that the + * invariances on the messages, channels, and connections have been + * respected. + * + * This should happen after every subsystem has initialized, and before + * entering the mainloop. + */ +struct dispatch_t *pubsub_builder_finalize(pubsub_builder_t *, + pubsub_items_t **items_out); + +/** + * Clear all pub_binding_t backpointers in <b>items</b>. + **/ +void pubsub_items_clear_bindings(pubsub_items_t *items); + +/** + * @copydoc pubsub_items_free_ + * + * Additionally, set the pointer <b>cfg</b> to NULL. + **/ +#define pubsub_items_free(cfg) \ + FREE_AND_NULL(pubsub_items_t, pubsub_items_free_, (cfg)) +void pubsub_items_free_(pubsub_items_t *cfg); + +#endif /* !defined(TOR_PUBSUB_BUILD_H) */ diff --git a/src/lib/pubsub/pubsub_builder_st.h b/src/lib/pubsub/pubsub_builder_st.h new file mode 100644 index 0000000000..57de1240ee --- /dev/null +++ b/src/lib/pubsub/pubsub_builder_st.h @@ -0,0 +1,161 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_builder_st.h + * + * @brief private structures used for configuring dispatchers and messages. + */ + +#ifndef TOR_PUBSUB_BUILDER_ST_H +#define TOR_PUBSUB_BUILDER_ST_H + +#ifdef PUBSUB_PRIVATE + +#include <stdbool.h> +#include <stddef.h> + +struct dispatch_cfg_t; +struct smartlist_t; +struct pub_binding_t; + +/** + * Configuration for a single publication or subscription request. + * + * These can be stored while the dispatcher is in use, but are only used for + * setup, teardown, and debugging. + * + * There are various fields in this request describing the message; all of + * them must match other descriptions of the message, or a bug has occurred. + **/ +typedef struct pubsub_cfg_t { + /** True if this is a publishing request; false for a subscribing request. */ + bool is_publish; + /** The system making this request. */ + subsys_id_t subsys; + /** The channel on which the message is to be sent. */ + channel_id_t channel; + /** The message ID to be sent or received. */ + message_id_t msg; + /** The C type associated with the message. */ + msg_type_id_t type; + /** One or more DISP_FLAGS_* items, combined with bitwise OR. */ + unsigned flags; + + /** + * Publishing only: a pub_binding object that will receive the binding for + * this request. We will finish filling this in when the dispatcher is + * constructed, so that the subsystem can publish then and not before. + */ + struct pub_binding_t *pub_binding; + + /** + * Subscribing only: a function to receive message objects for this request. + */ + recv_fn_t recv_fn; + + /** The file from which this message was configured */ + const char *added_by_file; + /** The line at which this message was configured */ + unsigned added_by_line; +} pubsub_cfg_t; + +/** + * Configuration request for a single C type. + * + * These are stored while the dispatcher is in use, but are only used for + * setup, teardown, and debugging. + **/ +typedef struct pubsub_type_cfg_t { + /** + * The identifier for this type. + */ + msg_type_id_t type; + /** + * Functions to use when manipulating the type. + */ + dispatch_typefns_t fns; + + /** The subsystem that configured this type. */ + subsys_id_t subsys; + /** The file from which this type was configured */ + const char *added_by_file; + /** The line at which this type was configured */ + unsigned added_by_line; +} pubsub_type_cfg_t; + +/** + * The set of configuration requests for a dispatcher, as made by various + * subsystems. + **/ +struct pubsub_items_t { + /** List of pubsub_cfg_t. */ + struct smartlist_t *items; + /** List of pubsub_type_cfg_t. */ + struct smartlist_t *type_items; +}; + +/** + * Type used to construct a dispatcher. We use this type to build up the + * configuration for a dispatcher, and then pass ownership of that + * configuration to the newly constructed dispatcher. + **/ +struct pubsub_builder_t { + /** Number of outstanding pubsub_connector_t objects pointing to this + * pubsub_builder_t. */ + int n_connectors; + /** Number of errors encountered while constructing this object so far. */ + int n_errors; + /** In-progress configuration that we're constructing, as a list of the + * requests that have been made. */ + struct pubsub_items_t *items; + /** In-progress configuration that we're constructing, in a form that can + * be converted to a dispatch_t. */ + struct dispatch_cfg_t *cfg; +}; + +/** + * Type given to a subsystem when adding connections to a pubsub_builder_t. + * We use this type to force each subsystem to get blamed for the + * publications, subscriptions, and types that it adds. + **/ +struct pubsub_connector_t { + /** The pubsub_builder that this connector refers to. */ + struct pubsub_builder_t *builder; + /** The subsystem that has been given this connector. */ + subsys_id_t subsys_id; +}; + +/** + * Helper structure used when constructing a dispatcher that sorts the + * pubsub_cfg_t objects in various ways. + **/ +typedef struct pubsub_adjmap_t { + /* XXXX The next three fields are currently constructed but not yet + * XXXX used. I believe we'll want them in the future, though. -nickm + */ + /** Number of subsystems; length of the *_by_subsys arrays. */ + size_t n_subsystems; + /** Array of lists of publisher pubsub_cfg_t objects, indexed by + * subsystem. */ + struct smartlist_t **pub_by_subsys; + /** Array of lists of subscriber pubsub_cfg_t objects, indexed by + * subsystem. */ + struct smartlist_t **sub_by_subsys; + + /** Number of message IDs; length of the *_by_msg arrays. */ + size_t n_msgs; + /** Array of lists of publisher pubsub_cfg_t objects, indexed by + * message ID. */ + struct smartlist_t **pub_by_msg; + /** Array of lists of subscriber pubsub_cfg_t objects, indexed by + * message ID. */ + struct smartlist_t **sub_by_msg; +} pubsub_adjmap_t; + +#endif /* defined(PUBSUB_PRIVATE) */ + +#endif /* !defined(TOR_PUBSUB_BUILDER_ST_H) */ diff --git a/src/lib/pubsub/pubsub_check.c b/src/lib/pubsub/pubsub_check.c new file mode 100644 index 0000000000..dbcbb14746 --- /dev/null +++ b/src/lib/pubsub/pubsub_check.c @@ -0,0 +1,414 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_check.c + * @brief Enforce various requirements on a pubsub_builder. + **/ + +/** @{ */ +#define PUBSUB_PRIVATE +/** @} */ + +#include "lib/dispatch/dispatch_naming.h" +#include "lib/dispatch/msgtypes.h" +#include "lib/pubsub/pubsub_flags.h" +#include "lib/pubsub/pubsub_builder_st.h" +#include "lib/pubsub/pubsub_build.h" + +#include "lib/container/bitarray.h" +#include "lib/container/smartlist.h" +#include "lib/log/util_bug.h" +#include "lib/malloc/malloc.h" +#include "lib/string/compat_string.h" + +#include <string.h> + +static void pubsub_adjmap_add(pubsub_adjmap_t *map, + const pubsub_cfg_t *item); + +/** + * Helper: contruct and return a new pubsub_adjacency_map from <b>cfg</b>. + * Return NULL on error. + **/ +static pubsub_adjmap_t * +pubsub_build_adjacency_map(const pubsub_items_t *cfg) +{ + pubsub_adjmap_t *map = tor_malloc_zero(sizeof(*map)); + const size_t n_subsystems = get_num_subsys_ids(); + const size_t n_msgs = get_num_message_ids(); + + map->n_subsystems = n_subsystems; + map->n_msgs = n_msgs; + + map->pub_by_subsys = tor_calloc(n_subsystems, sizeof(smartlist_t*)); + map->sub_by_subsys = tor_calloc(n_subsystems, sizeof(smartlist_t*)); + map->pub_by_msg = tor_calloc(n_msgs, sizeof(smartlist_t*)); + map->sub_by_msg = tor_calloc(n_msgs, sizeof(smartlist_t*)); + + SMARTLIST_FOREACH_BEGIN(cfg->items, const pubsub_cfg_t *, item) { + pubsub_adjmap_add(map, item); + } SMARTLIST_FOREACH_END(item); + + return map; +} + +/** + * Helper: add a single pubsub_cfg_t to an adjacency map. + **/ +static void +pubsub_adjmap_add(pubsub_adjmap_t *map, + const pubsub_cfg_t *item) +{ + smartlist_t **by_subsys; + smartlist_t **by_msg; + + tor_assert(item->subsys < map->n_subsystems); + tor_assert(item->msg < map->n_msgs); + + if (item->is_publish) { + by_subsys = &map->pub_by_subsys[item->subsys]; + by_msg = &map->pub_by_msg[item->msg]; + } else { + by_subsys = &map->sub_by_subsys[item->subsys]; + by_msg = &map->sub_by_msg[item->msg]; + } + + if (! *by_subsys) + *by_subsys = smartlist_new(); + if (! *by_msg) + *by_msg = smartlist_new(); + smartlist_add(*by_subsys, (void*) item); + smartlist_add(*by_msg, (void *) item); +} + +/** + * Release all storage held by m and set m to NULL. + **/ +#define pubsub_adjmap_free(m) \ + FREE_AND_NULL(pubsub_adjmap_t, pubsub_adjmap_free_, m) + +/** + * Free every element of an <b>n</b>-element array of smartlists, then + * free the array itself. + **/ +static void +pubsub_adjmap_free_helper(smartlist_t **lsts, size_t n) +{ + if (!lsts) + return; + + for (unsigned i = 0; i < n; ++i) { + smartlist_free(lsts[i]); + } + tor_free(lsts); +} + +/** + * Release all storage held by <b>map</b>. + **/ +static void +pubsub_adjmap_free_(pubsub_adjmap_t *map) +{ + if (!map) + return; + pubsub_adjmap_free_helper(map->pub_by_subsys, map->n_subsystems); + pubsub_adjmap_free_helper(map->sub_by_subsys, map->n_subsystems); + pubsub_adjmap_free_helper(map->pub_by_msg, map->n_msgs); + pubsub_adjmap_free_helper(map->sub_by_msg, map->n_msgs); + tor_free(map); +} + +/** + * Helper: return the length of <b>sl</b>, or 0 if sl is NULL. + **/ +static int +smartlist_len_opt(const smartlist_t *sl) +{ + if (sl) + return smartlist_len(sl); + else + return 0; +} + +/** Return a pointer to a statically allocated string encoding the + * dispatcher flags in <b>flags</b>. */ +static const char * +format_flags(unsigned flags) +{ + static char buf[32]; + buf[0] = 0; + if (flags & DISP_FLAG_EXCL) { + strlcat(buf, " EXCL", sizeof(buf)); + } + if (flags & DISP_FLAG_STUB) { + strlcat(buf, " STUB", sizeof(buf)); + } + return buf[0] ? buf+1 : buf; +} + +/** + * Log a message containing a description of <b>cfg</b> at severity, prefixed + * by the string <b>prefix</b>. + */ +static void +pubsub_cfg_dump(const pubsub_cfg_t *cfg, int severity, const char *prefix) +{ + tor_assert(prefix); + + tor_log(severity, LD_MESG, + "%s%s %s: %s{%s} on %s (%s) <%u %u %u %u %x> [%s:%d]", + prefix, + get_subsys_id_name(cfg->subsys), + cfg->is_publish ? "PUB" : "SUB", + get_message_id_name(cfg->msg), + get_msg_type_id_name(cfg->type), + get_channel_id_name(cfg->channel), + format_flags(cfg->flags), + cfg->subsys, cfg->msg, cfg->type, cfg->channel, cfg->flags, + cfg->added_by_file, cfg->added_by_line); +} + +/** + * Helper: fill a bitarray <b>out</b> with entries corresponding to the + * subsystems listed in <b>items</b>. + **/ +static void +get_message_bitarray(const pubsub_adjmap_t *map, + const smartlist_t *items, + bitarray_t **out) +{ + *out = bitarray_init_zero((unsigned)map->n_subsystems); + if (! items) + return; + + SMARTLIST_FOREACH_BEGIN(items, const pubsub_cfg_t *, cfg) { + bitarray_set(*out, cfg->subsys); + } SMARTLIST_FOREACH_END(cfg); +} + +/** + * Helper for lint_message: check that all the pubsub_cfg_t items in the two + * respective smartlists obey our local graph topology rules. + * + * (Right now this is just a matter of "each subsystem only + * publishes/subscribes once; no subsystem is a publisher and subscriber for + * the same message.") + * + * Return 0 on success, -1 on failure. + **/ +static int +lint_message_graph(const pubsub_adjmap_t *map, + message_id_t msg, + const smartlist_t *pub, + const smartlist_t *sub) +{ + bitarray_t *published_by = NULL; + bitarray_t *subscribed_by = NULL; + bool ok = true; + + get_message_bitarray(map, pub, &published_by); + get_message_bitarray(map, sub, &subscribed_by); + + /* Check whether any subsystem is publishing and subscribing the same + * message. [??] + */ + for (unsigned i = 0; i < map->n_subsystems; ++i) { + if (bitarray_is_set(published_by, i) && + bitarray_is_set(subscribed_by, i)) { + log_warn(LD_MESG|LD_BUG, + "Message \"%s\" is published and subscribed by the same " + "subsystem \"%s\".", + get_message_id_name(msg), + get_subsys_id_name(i)); + ok = false; + } + } + + bitarray_free(published_by); + bitarray_free(subscribed_by); + + return ok ? 0 : -1; +} + +/** + * Helper for lint_message: check that all the pubsub_cfg_t items in the two + * respective smartlists have compatible flags, channels, and types. + **/ +static int +lint_message_consistency(message_id_t msg, + const smartlist_t *pub, + const smartlist_t *sub) +{ + if (!smartlist_len_opt(pub) && !smartlist_len_opt(sub)) + return 0; // LCOV_EXCL_LINE -- this was already checked. + + /* The 'all' list has the publishers and the subscribers. */ + smartlist_t *all = smartlist_new(); + if (pub) + smartlist_add_all(all, pub); + if (sub) + smartlist_add_all(all, sub); + + const pubsub_cfg_t *item0 = smartlist_get(all, 0); + + /* Indicates which subsystems we've found publishing/subscribing here. */ + bool pub_excl = false, sub_excl = false, chan_same = true, type_same = true; + + /* Simple message consistency properties across messages. + */ + SMARTLIST_FOREACH_BEGIN(all, const pubsub_cfg_t *, cfg) { + chan_same &= (cfg->channel == item0->channel); + type_same &= (cfg->type == item0->type); + if (cfg->is_publish) + pub_excl |= (cfg->flags & DISP_FLAG_EXCL) != 0; + else + sub_excl |= (cfg->flags & DISP_FLAG_EXCL) != 0; + } SMARTLIST_FOREACH_END(cfg); + + bool ok = true; + + if (! chan_same) { + log_warn(LD_MESG|LD_BUG, + "Message \"%s\" is associated with multiple inconsistent " + "channels.", + get_message_id_name(msg)); + ok = false; + } + if (! type_same) { + log_warn(LD_MESG|LD_BUG, + "Message \"%s\" is associated with multiple inconsistent " + "message types.", + get_message_id_name(msg)); + ok = false; + } + + /* Enforce exclusive-ness for publishers and subscribers that have asked for + * it. + */ + if (pub_excl && smartlist_len_opt(pub) > 1) { + log_warn(LD_MESG|LD_BUG, + "Message \"%s\" has multiple publishers, but at least one is " + "marked as exclusive.", + get_message_id_name(msg)); + ok = false; + } + if (sub_excl && smartlist_len_opt(sub) > 1) { + log_warn(LD_MESG|LD_BUG, + "Message \"%s\" has multiple subscribers, but at least one is " + "marked as exclusive.", + get_message_id_name(msg)); + ok = false; + } + + smartlist_free(all); + + return ok ? 0 : -1; +} + +/** + * Check whether there are any errors or inconsistencies for the message + * described by <b>msg</b> in <b>map</b>. If there are problems, log about + * them, and return -1. Otherwise return 0. + **/ +static int +lint_message(const pubsub_adjmap_t *map, message_id_t msg) +{ + /* NOTE: Some of the checks in this function are maybe over-zealous, and we + * might not want to have them forever. I've marked them with [?] below. + */ + if (BUG(msg >= map->n_msgs)) + return 0; // LCOV_EXCL_LINE + + const smartlist_t *pub = map->pub_by_msg[msg]; + const smartlist_t *sub = map->sub_by_msg[msg]; + + const size_t n_pub = smartlist_len_opt(pub); + const size_t n_sub = smartlist_len_opt(sub); + + if (n_pub == 0 && n_sub == 0) { + log_info(LD_MESG, "Nobody is publishing or subscribing to message " + "\"%s\".", + get_message_id_name(msg)); + return 0; // No publishers or subscribers: nothing to do. + } + /* We'll set this to false if there are any problems. */ + bool ok = true; + + /* First make sure that if there are publishers, there are subscribers. */ + if (n_pub == 0) { + log_warn(LD_MESG|LD_BUG, + "Message \"%s\" has subscribers, but no publishers.", + get_message_id_name(msg)); + ok = false; + } else if (n_sub == 0) { + log_warn(LD_MESG|LD_BUG, + "Message \"%s\" has publishers, but no subscribers.", + get_message_id_name(msg)); + ok = false; + } + + /* Check the message graph topology. */ + if (lint_message_graph(map, msg, pub, sub) < 0) + ok = false; + + /* Check whether the messages have the same fields set on them. */ + if (lint_message_consistency(msg, pub, sub) < 0) + ok = false; + + if (!ok) { + /* There was a problem -- let's log all the publishers and subscribers on + * this message */ + if (pub) { + SMARTLIST_FOREACH(pub, pubsub_cfg_t *, cfg, + pubsub_cfg_dump(cfg, LOG_WARN, " ")); + } + if (sub) { + SMARTLIST_FOREACH(sub, pubsub_cfg_t *, cfg, + pubsub_cfg_dump(cfg, LOG_WARN, " ")); + } + } + + return ok ? 0 : -1; +} + +/** + * Check all the messages in <b>map</b> for consistency. Return 0 on success, + * -1 on problems. + **/ +static int +pubsub_adjmap_check(const pubsub_adjmap_t *map) +{ + bool all_ok = true; + for (unsigned i = 0; i < map->n_msgs; ++i) { + if (lint_message(map, i) < 0) { + all_ok = false; + } + } + return all_ok ? 0 : -1; +} + +/** + * Check builder for consistency and various constraints. Return 0 on success, + * -1 on failure. + **/ +int +pubsub_builder_check(pubsub_builder_t *builder) +{ + pubsub_adjmap_t *map = pubsub_build_adjacency_map(builder->items); + int rv = -1; + + if (!map) + goto err; // should be impossible + + if (pubsub_adjmap_check(map) < 0) + goto err; + + rv = 0; + err: + pubsub_adjmap_free(map); + return rv; +} diff --git a/src/lib/pubsub/pubsub_connect.h b/src/lib/pubsub/pubsub_connect.h new file mode 100644 index 0000000000..b0d6ae7e92 --- /dev/null +++ b/src/lib/pubsub/pubsub_connect.h @@ -0,0 +1,54 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_connect.h + * @brief Header for functions that add relationships to a pubsub builder. + * + * These functions are used by modules that need to add publication and + * subscription requests. Most users will want to call these functions + * indirectly, via the macros in pubsub_macros.h. + **/ + +#ifndef TOR_PUBSUB_CONNECT_H +#define TOR_PUBSUB_CONNECT_H + +#include "lib/dispatch/msgtypes.h" + +struct pub_binding_t; +/** + * A "dispatch connector" is a view of the dispatcher that a subsystem + * uses while initializing itself. It is specific to the subsystem, and + * ensures that each subsystem doesn't need to identify itself + * repeatedly while registering its messages. + **/ +typedef struct pubsub_connector_t pubsub_connector_t; + +int pubsub_add_pub_(struct pubsub_connector_t *con, + struct pub_binding_t *out, + channel_id_t channel, + message_id_t msg, + msg_type_id_t type, + unsigned flags, + const char *file, + unsigned line); + +int pubsub_add_sub_(struct pubsub_connector_t *con, + recv_fn_t recv_fn, + channel_id_t channel, + message_id_t msg, + msg_type_id_t type, + unsigned flags, + const char *file, + unsigned line); + +int pubsub_connector_register_type_(struct pubsub_connector_t *, + msg_type_id_t, + dispatch_typefns_t *, + const char *file, + unsigned line); + +#endif /* !defined(TOR_PUBSUB_CONNECT_H) */ diff --git a/src/lib/pubsub/pubsub_flags.h b/src/lib/pubsub/pubsub_flags.h new file mode 100644 index 0000000000..9912c1ae89 --- /dev/null +++ b/src/lib/pubsub/pubsub_flags.h @@ -0,0 +1,32 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_flags.h + * @brief Flags that can be set on publish/subscribe messages. + **/ + +#ifndef TOR_PUBSUB_FLAGS_H +#define TOR_PUBSUB_FLAGS_H + +/** + * Flag for registering a message: declare that no other module is allowed to + * publish this message if we are publishing it, or subscribe to it if we are + * subscribing to it. + */ +#define DISP_FLAG_EXCL (1u<<0) + +/** + * Flag for registering a message: declare that this message is a stub, and we + * will not actually publish/subscribe it, but that the dispatcher should + * treat us as if we did when typechecking. + * + * We use this so that messages aren't treated as "dangling" if they are + * potentially used by some other build of Tor. + */ +#define DISP_FLAG_STUB (1u<<1) + +#endif /* !defined(TOR_PUBSUB_FLAGS_H) */ diff --git a/src/lib/pubsub/pubsub_macros.h b/src/lib/pubsub/pubsub_macros.h new file mode 100644 index 0000000000..e5ffbe501a --- /dev/null +++ b/src/lib/pubsub/pubsub_macros.h @@ -0,0 +1,373 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file pubsub_macros.h + * \brief Macros to help with the publish/subscribe dispatch API. + * + * The dispatch API allows different subsystems of Tor to communicate with + * another asynchronously via a shared "message" system. Some subsystems + * declare that they publish a given message, and others declare that they + * subscribe to it. Both subsystems depend on the message, but not upon one + * another. + * + * To declare a message, use DECLARE_MESSAGE() (for messages that take their + * data as a pointer) or DECLARE_MESSAGE_INT() (for messages that take their + * data as an integer. For example, you might say + * + * DECLARE_MESSAGE(new_circuit, circ, circuit_handle_t *); + * or + * DECLARE_MESSAGE_INT(shutdown_requested, boolean, bool); + * + * Every message has a unique name, a "type name" that the dispatch system + * uses to manage associated data, and a C type name. You'll want to put + * these declarations in a header, to be included by all publishers and all + * subscribers. + * + * When a subsystem wants to publish a message, it uses DECLARE_PUBLISH() at + * file scope to create necessary static functions. Then, in its subsystem + * initialization (in the "bind to dispatcher" callback) (TODO: name this + * properly!), it calls DISPATCH_ADD_PUB() to tell the dispatcher about its + * intent to publish. When it actually wants to publish, it uses the + * PUBLISH() macro. For example: + * + * // At file scope + * DECLARE_PUBLISH(shutdown_requested); + * + * static void bind_to_dispatcher(pubsub_connector_t *con) + * { + * DISPATCH_ADD_PUB(con, mainchannel, shutdown_requested); + * } + * + * // somewhere in a function + * { + * PUBLISH(shutdown_requested, true); + * } + * + * When a subsystem wants to subscribe to a message, it uses + * DECLARE_SUBSCRIBE() at file scope to declare static functions. It must + * declare a hook function that receives the message type. Then, in its "bind + * to dispatcher" function, it calls DISPATCHER_ADD_SUB() to tell the + * dispatcher about its intent to subscribe. When another module publishes + * the message, the dispatcher will call the provided hook function. + * + * // At file scope. The first argument is the message that you're + * // subscribing to; the second argument is the hook function to declare. + * DECLARE_SUBSCRIBE(shutdown_requested, on_shutdown_req_cb); + * + * // You need to declare this function. + * static void on_shutdown_req_cb(const msg_t *msg, + * bool value) + * { + * // (do something here.) + * } + * + * static void bind_to_dispatcher(pubsub_connector_t *con) + * { + * DISPATCH_ADD_SUB(con, mainchannel, shutdown_requested); + * } + * + * Where did these types come from? Somewhere in the code, you need to call + * DISPATCH_REGISTER_TYPE() to make sure that the dispatcher can manage the + * message auxiliary data. It associates a vtbl-like structure with the + * type name, so that the dispatcher knows how to manipulate the type you're + * giving it. + * + * For example, the "boolean" type we're using above could be defined as: + * + * static char *boolean_fmt(msg_aux_data_t d) + * { + * // This is used for debugging and dumping messages. + * if (d.u64) + * return tor_strdup("true"); + * else + * return tor_strdup("false"); + * } + * + * static void boolean_free(msg_aux_data_t d) + * { + * // We don't actually need to do anything to free a boolean. + * // We could use "NULL" instead of this function, but I'm including + * // it as an example. + * } + * + * static void bind_to_dispatcher(pubsub_connector_t *con) + * { + * dispatch_typefns_t boolean_fns = { + * .fmt_fn = boolean_fmt, + * .free_fn = boolean_free, + * }; + * DISPATCH_REGISTER_TYPE(con, boolean, &boolean_fns); + * } + * + * + * + * So, how does this all work? (You can stop reading here, unless you're + * debugging something.) + * + * When you declare a message in a header with DECLARE_MESSAGE() or + * DECLARE_MESSAGE_INT(), it creates five things: + * + * * two typedefs for the message argument (constant and non-constant + * variants). + * * a constant string to hold the declared message type name + * * two inline functions, to coerce the message argument type to and from + * a "msg_aux_data_t" union. + * + * All of these declarations have names based on the message name. + * + * Later, when you say DECLARE_PUBLISH() or DECLARE_SUBSCRIBE(), we use the + * elements defined by DECLARE_MESSAGE() to make sure that the publish + * function takes the correct argument type, and that the subscription hook is + * declared with the right argument type. + **/ + +#ifndef TOR_DISPATCH_MSG_H +#define TOR_DISPATCH_MSG_H + +#include "lib/cc/compat_compiler.h" +#include "lib/dispatch/dispatch_naming.h" +#include "lib/pubsub/pub_binding_st.h" +#include "lib/pubsub/pubsub_connect.h" +#include "lib/pubsub/pubsub_flags.h" +#include "lib/pubsub/pubsub_publish.h" + +/* Implemenation notes: + * + * For a messagename "foo", the DECLARE_MESSAGE*() macros must declare: + * + * msg_arg_type__foo -- a typedef for the argument type of the foo message. + * msg_arg_consttype__foo -- a typedef for the const argument type of the + * foo message. + * msg_arg_name__foo[] -- a static string constant holding the unique + * identifier for the type of the foo message. + * msg_arg_get__foo() -- an inline function taking a msg_aux_data_t and + * returning the C data type. + * msg_arg_set__foo() -- an inline function taking a msg_aux_data_t and + * the C type, setting the msg_aux_data_t to hold the C type. + * + * For a messagename "foo", the DECLARE_PUBLISH() macro must declare: + * + * pub_binding__foo -- A static pub_binding_t object used to send messages + * from this module. + * publish_fn__foo -- A function taking an argument of the appropriate + * C type, to be invoked by PUBLISH(). + * + * For a messagename "foo", the DECLARE_SUBSCRIBE() macro must declare: + * + * hookfn -- A user-provided function name, with the correct signature. + * recv_fn__foo -- A wrapper callback that takes a msg_t *, and calls + * hookfn with the appropriate arguments. + */ + +/** Macro to declare common elements shared by DECLARE_MESSAGE and + * DECLARE_MESSAGE_INT. Don't call this directly. + * + * Note that the "msg_arg_name" string constant is defined in each + * translation unit. This might be undesirable; we can tweak it in the + * future if need be. + */ +#define DECLARE_MESSAGE_COMMON__(messagename, typename, c_type) \ + typedef c_type msg_arg_type__ ##messagename; \ + typedef const c_type msg_arg_consttype__ ##messagename; \ + ATTR_UNUSED static const char msg_arg_name__ ##messagename[] = # typename; + +/** + * Use this macro in a header to declare the existence of a given message, + * taking a pointer as auxiliary data. + * + * "messagename" is a unique identifier for the message; it must be a valid + * C identifier. + * + * "typename" is a unique identifier for the type of the auxiliary data. + * It needs to be defined somewhere in Tor, using + * "DISPATCH_REGISTER_TYPE." + * + * "c_ptr_type" is a C pointer type (like "char *" or "struct foo *"). + * The "*" needs to be included. + */ +#define DECLARE_MESSAGE(messagename, typename, c_ptr_type) \ + DECLARE_MESSAGE_COMMON__(messagename, typename, c_ptr_type) \ + ATTR_UNUSED static inline c_ptr_type \ + msg_arg_get__ ##messagename(msg_aux_data_t m) \ + { \ + return m.ptr; \ + } \ + ATTR_UNUSED static inline void \ + msg_arg_set__ ##messagename(msg_aux_data_t *m, c_ptr_type v) \ + { \ + m->ptr = v; \ + } \ + EAT_SEMICOLON + +/** + * Use this macro in a header to declare the existence of a given message, + * taking an integer as auxiliary data. + * + * "messagename" is a unique identifier for the message; it must be a valid + * C identifier. + * + * "typename" is a unique identifier for the type of the auxiliary data. It + * needs to be defined somewhere in Tor, using "DISPATCH_REGISTER_TYPE." + * + * "c_type" is a C integer type, like "int" or "bool". It needs to fit inside + * a uint64_t. + */ +#define DECLARE_MESSAGE_INT(messagename, typename, c_type) \ + DECLARE_MESSAGE_COMMON__(messagename, typename, c_type) \ + ATTR_UNUSED static inline c_type \ + msg_arg_get__ ##messagename(msg_aux_data_t m) \ + { \ + return (c_type)m.u64; \ + } \ + ATTR_UNUSED static inline void \ + msg_arg_set__ ##messagename(msg_aux_data_t *m, c_type v) \ + { \ + m->u64 = (uint64_t)v; \ + } \ + EAT_SEMICOLON + +/** + * Use this macro inside a C module declare that we'll be publishing a given + * message type from within this module. + * + * It creates necessary functions and wrappers to publish a message whose + * unique identifier is "messagename". + * + * Before you use this, you need to include the header where DECLARE_MESSAGE*() + * was used for this message. + * + * You can only use this once per message in each subsystem. + */ +#define DECLARE_PUBLISH(messagename) \ + static pub_binding_t pub_binding__ ##messagename; \ + static void \ + publish_fn__ ##messagename(msg_arg_type__ ##messagename arg) \ + { \ + msg_aux_data_t data; \ + msg_arg_set__ ##messagename(&data, arg); \ + pubsub_pub_(&pub_binding__ ##messagename, data); \ + } \ + EAT_SEMICOLON + +/** + * Use this macro inside a C file to declare that we're subscribing to a + * given message and associating it with a given "hook function". It + * declares the hook function static, and helps with strong typing. + * + * Before you use this, you need to include the header where + * DECLARE_MESSAGE*() was used for the message whose unique identifier is + * "messagename". + * + * You will need to define a function with the name that you provide for + * "hookfn". The type of this function will be: + * static void hookfn(const msg_t *, const c_type) + * where c_type is the c type that you declared in the header. + * + * You can only use this once per message in each subsystem. + */ +#define DECLARE_SUBSCRIBE(messagename, hookfn) \ + static void hookfn(const msg_t *, \ + const msg_arg_consttype__ ##messagename); \ + static void recv_fn__ ## messagename(const msg_t *m) \ + { \ + msg_arg_type__ ## messagename arg; \ + arg = msg_arg_get__ ##messagename(m->aux_data__); \ + hookfn(m, arg); \ + } \ + EAT_SEMICOLON + +/** + * Add a fake use of the publish function for 'messagename', so that + * the compiler does not call it unused. + */ +#define DISPATCH__FAKE_USE_OF_PUBFN_(messagename) \ + ( 0 ? (publish_fn__ ##messagename((msg_arg_type__##messagename)0), 1) \ + : 1) + +/** + * This macro is for internal use. It backs DISPATCH_ADD_PUB*() + */ +#define DISPATCH_ADD_PUB_(connector, channel, messagename, flags) \ + ( \ + DISPATCH__FAKE_USE_OF_PUBFN_(messagename), \ + pubsub_add_pub_((connector), \ + &pub_binding__ ##messagename, \ + get_channel_id(# channel), \ + get_message_id(# messagename), \ + get_msg_type_id(msg_arg_name__ ## messagename), \ + (flags), \ + __FILE__, \ + __LINE__) \ + ) + +/** + * Use a given connector and channel name to declare that this subsystem will + * publish a given message type. + * + * Call this macro from within the add_subscriptions() function of a module. + */ +#define DISPATCH_ADD_PUB(connector, channel, messagename) \ + DISPATCH_ADD_PUB_(connector, channel, messagename, 0) + +/** + * Use a given connector and channel name to declare that this subsystem will + * publish a given message type, and that no other subsystem is allowed to. + * + * Call this macro from within the add_subscriptions() function of a module. + */ +#define DISPATCH_ADD_PUB_EXCL(connector, channel, messagename) \ + DISPATCH_ADD_PUB_(connector, channel, messagename, DISP_FLAG_EXCL) + +/** + * This macro is for internal use. It backs DISPATCH_ADD_SUB*() + */ +#define DISPATCH_ADD_SUB_(connector, channel, messagename, flags) \ + pubsub_add_sub_((connector), \ + recv_fn__ ##messagename, \ + get_channel_id(#channel), \ + get_message_id(# messagename), \ + get_msg_type_id(msg_arg_name__ ##messagename), \ + (flags), \ + __FILE__, \ + __LINE__) +/** + * Use a given connector and channel name to declare that this subsystem will + * receive a given message type. + * + * Call this macro from within the add_subscriptions() function of a module. + */ +#define DISPATCH_ADD_SUB(connector, channel, messagename) \ + DISPATCH_ADD_SUB_(connector, channel, messagename, 0) +/** + * Use a given connector and channel name to declare that this subsystem will + * receive a given message type, and that no other subsystem is allowed to do + * so. + * + * Call this macro from within the add_subscriptions() function of a module. + */ +#define DISPATCH_ADD_SUB_EXCL(connector, channel, messagename) \ + DISPATCH_ADD_SUB_(connector, channel, messagename, DISP_FLAG_EXCL) + +/** + * Publish a given message with a given argument. (Takes ownership of the + * argument if it is a pointer.) + */ +#define PUBLISH(messagename, arg) \ + publish_fn__ ##messagename(arg) + +/** + * Use a given connector to declare that the functions to be used to manipuate + * a certain C type. + **/ +#define DISPATCH_REGISTER_TYPE(con, type, fns) \ + pubsub_connector_register_type_((con), \ + get_msg_type_id(#type), \ + (fns), \ + __FILE__, \ + __LINE__) + +#endif /* !defined(TOR_DISPATCH_MSG_H) */ diff --git a/src/lib/pubsub/pubsub_publish.c b/src/lib/pubsub/pubsub_publish.c new file mode 100644 index 0000000000..84c7dae02c --- /dev/null +++ b/src/lib/pubsub/pubsub_publish.c @@ -0,0 +1,72 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_publish.c + * @brief Header for functions to publish using a pub_binding_t. + **/ + +#define PUBSUB_PRIVATE +#define DISPATCH_PRIVATE +#include "orconfig.h" + +#include "lib/dispatch/dispatch.h" +#include "lib/dispatch/dispatch_st.h" + +#include "lib/pubsub/pub_binding_st.h" +#include "lib/pubsub/pubsub_publish.h" + +#include "lib/malloc/malloc.h" +#include "lib/log/util_bug.h" + +#include <string.h> + +/** + * Publish a message from the publication binding <b>pub</b> using the + * auxiliary data <b>auxdata</b>. + * + * Return 0 on success, -1 on failure. + **/ +int +pubsub_pub_(const pub_binding_t *pub, msg_aux_data_t auxdata) +{ + dispatch_t *d = pub->dispatch_ptr; + if (BUG(! d)) { + /* Tried to publish a message before the dispatcher was configured. */ + /* (Without a dispatcher, we don't know how to free auxdata.) */ + return -1; + } + + if (BUG(pub->msg_template.type >= d->n_types)) { + /* The type associated with this message is not known to the dispatcher. */ + /* (Without a correct type, we don't know how to free auxdata.) */ + return -1; + } + + if (BUG(pub->msg_template.msg >= d->n_msgs) || + BUG(pub->msg_template.channel >= d->n_queues)) { + /* The message ID or channel ID was out of bounds. */ + // LCOV_EXCL_START + d->typefns[pub->msg_template.type].free_fn(auxdata); + return -1; + // LCOV_EXCL_STOP + } + + if (! d->table[pub->msg_template.msg]) { + /* Fast path: nobody wants this data. */ + + // XXXX Faster path: we could store this in the pub_binding_t. + d->typefns[pub->msg_template.type].free_fn(auxdata); + return 0; + } + + /* Construct the message object */ + msg_t *m = tor_malloc(sizeof(msg_t)); + memcpy(m, &pub->msg_template, sizeof(msg_t)); + m->aux_data__ = auxdata; + + return dispatch_send_msg_unchecked(d, m); +} diff --git a/src/lib/pubsub/pubsub_publish.h b/src/lib/pubsub/pubsub_publish.h new file mode 100644 index 0000000000..d9d6fa9ba5 --- /dev/null +++ b/src/lib/pubsub/pubsub_publish.h @@ -0,0 +1,20 @@ +/* Copyright (c) 2001, Matej Pfajfar. + * Copyright (c) 2001-2004, Roger Dingledine. + * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. + * Copyright (c) 2007-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * @file pubsub_publish.h + * @brief Header for pubsub_publish.c + **/ + +#ifndef TOR_PUBSUB_PUBLISH_H +#define TOR_PUBSUB_PUBLISH_H + +#include "lib/dispatch/msgtypes.h" +struct pub_binding_t; + +int pubsub_pub_(const struct pub_binding_t *pub, msg_aux_data_t auxdata); + +#endif /* !defined(TOR_PUBSUB_PUBLISH_H) */ |