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Diffstat (limited to 'src/common/compat_libevent.c')
| -rw-r--r-- | src/common/compat_libevent.c | 471 |
1 files changed, 471 insertions, 0 deletions
diff --git a/src/common/compat_libevent.c b/src/common/compat_libevent.c new file mode 100644 index 0000000000..dcf51cbbd3 --- /dev/null +++ b/src/common/compat_libevent.c @@ -0,0 +1,471 @@ +/* Copyright (c) 2009, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file compat_libevent.c + * \brief Wrappers to handle porting between different versions of libevent. + * + * In an ideal world, we'd just use Libevent 2.0 from now on. But as of June + * 2009, Libevent 2.0 is still in alpha, and we will have old versions of + * Libevent for the forseeable future. + **/ + +#include "orconfig.h" +#include "compat_libevent.h" + +#include "compat.h" +#include "util.h" +#include "log.h" + +#ifdef HAVE_EVENT2_EVENT_H +#include <event2/event.h> +#else +#include <event.h> +#endif + +/** A number representing a version of Libevent. + + This is a 4-byte number, with the first three bytes representing the + major, minor, and patchlevel respectively of the library. The fourth + byte is unused. + + This is equivalent to the format of LIBEVENT_VERSION_NUMBER on Libevent + 2.0.1 or later. For versions of Libevent before 1.4.0, which followed the + format of "1.0, 1.0a, 1.0b", we define 1.0 to be equivalent to 1.0.0, 1.0a + to be equivalent to 1.0.1, and so on. +*/ +typedef uint32_t le_version_t; + +/* Macros: returns the number of a libevent version. */ +#define V(major, minor, patch) \ + (((major) << 24) | ((minor) << 16) | ((patch) << 8)) +#define V_OLD(major, minor, patch) \ + V((major), (minor), (patch)-'a'+1) + +#define LE_OLD V(0,0,0) +#define LE_OTHER V(0,0,99) + +static le_version_t tor_get_libevent_version(const char **v_out); + +#ifdef HAVE_EVENT_SET_LOG_CALLBACK +/** A string which, if it appears in a libevent log, should be ignored. */ +static const char *suppress_msg = NULL; +/** Callback function passed to event_set_log() so we can intercept + * log messages from libevent. */ +static void +libevent_logging_callback(int severity, const char *msg) +{ + char buf[1024]; + size_t n; + if (suppress_msg && strstr(msg, suppress_msg)) + return; + n = strlcpy(buf, msg, sizeof(buf)); + if (n && n < sizeof(buf) && buf[n-1] == '\n') { + buf[n-1] = '\0'; + } + switch (severity) { + case _EVENT_LOG_DEBUG: + log(LOG_DEBUG, LD_NET, "Message from libevent: %s", buf); + break; + case _EVENT_LOG_MSG: + log(LOG_INFO, LD_NET, "Message from libevent: %s", buf); + break; + case _EVENT_LOG_WARN: + log(LOG_WARN, LD_GENERAL, "Warning from libevent: %s", buf); + break; + case _EVENT_LOG_ERR: + log(LOG_ERR, LD_GENERAL, "Error from libevent: %s", buf); + break; + default: + log(LOG_WARN, LD_GENERAL, "Message [%d] from libevent: %s", + severity, buf); + break; + } +} +/** Set hook to intercept log messages from libevent. */ +void +configure_libevent_logging(void) +{ + event_set_log_callback(libevent_logging_callback); +} +/** Ignore any libevent log message that contains <b>msg</b>. */ +void +suppress_libevent_log_msg(const char *msg) +{ + suppress_msg = msg; +} +#else +void +configure_libevent_logging(void) +{ +} +void +suppress_libevent_log_msg(const char *msg) +{ + (void)msg; +} +#endif + +#ifndef HAVE_EVENT2_EVENT_H +/** Work-alike replacement for event_new() on pre-Libevent-2.0 systems. */ +struct event * +tor_event_new(struct event_base *base, int sock, short what, + void (*cb)(int, short, void *), void *arg) +{ + struct event *e = tor_malloc_zero(sizeof(struct event)); + event_set(e, sock, what, cb, arg); + if (! base) + base = tor_libevent_get_base(); + event_base_set(base, e); + return e; +} +/** Work-alike replacement for evtimer_new() on pre-Libevent-2.0 systems. */ +struct event * +tor_evtimer_new(struct event_base *base, + void (*cb)(int, short, void *), void *arg) +{ + return tor_event_new(base, -1, 0, cb, arg); +} +/** Work-alike replacement for evsignal_new() on pre-Libevent-2.0 systems. */ +struct event * +tor_evsignal_new(struct event_base * base, int sig, + void (*cb)(int, short, void *), void *arg) +{ + return tor_event_new(base, sig, EV_SIGNAL|EV_PERSIST, cb, arg); +} +/** Work-alike replacement for event_free() on pre-Libevent-2.0 systems. */ +void +tor_event_free(struct event *ev) +{ + event_del(ev); + tor_free(ev); +} +#endif + +/** Global event base for use by the main thread. */ +struct event_base *the_event_base = NULL; + +/* This is what passes for version detection on OSX. We set + * MACOSX_KQUEUE_IS_BROKEN to true iff we're on a version of OSX before + * 10.4.0 (aka 1040). */ +#ifdef __APPLE__ +#ifdef __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ +#define MACOSX_KQUEUE_IS_BROKEN \ + (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1040) +#else +#define MACOSX_KQUEUE_IS_BROKEN 0 +#endif +#endif + +/** Initialize the Libevent library and set up the event base. */ +void +tor_libevent_initialize(void) +{ + tor_assert(the_event_base == NULL); + +#ifdef __APPLE__ + if (MACOSX_KQUEUE_IS_BROKEN || + tor_get_libevent_version(NULL) < V_OLD(1,1,'b')) { + setenv("EVENT_NOKQUEUE","1",1); + } +#endif + +#ifdef HAVE_EVENT2_EVENT_H + the_event_base = event_base_new(); +#else + the_event_base = event_init(); +#endif + +#if defined(HAVE_EVENT_GET_VERSION) && defined(HAVE_EVENT_GET_METHOD) + /* Making this a NOTICE for now so we can link bugs to a libevent versions + * or methods better. */ + log(LOG_NOTICE, LD_GENERAL, + "Initialized libevent version %s using method %s. Good.", + event_get_version(), tor_libevent_get_method()); +#else + log(LOG_NOTICE, LD_GENERAL, + "Initialized old libevent (version 1.0b or earlier)."); + log(LOG_WARN, LD_GENERAL, + "You have a *VERY* old version of libevent. It is likely to be buggy; " + "please build Tor with a more recent version."); +#endif +} + +/** Return the current Libevent event base that we're set up to use. */ +struct event_base * +tor_libevent_get_base(void) +{ + return the_event_base; +} + +#ifndef HAVE_EVENT_BASE_LOOPEXIT +/* Replacement for event_base_loopexit on some very old versions of Libevent + that we are not yet brave enough to deprecate. */ +int +tor_event_base_loopexit(struct event_base *base, struct timeval *tv) +{ + tor_assert(base == the_event_base); + return event_loopexit(tv); +} +#endif + +/** Return the name of the Libevent backend we're using. */ +const char * +tor_libevent_get_method(void) +{ +#ifdef HAVE_EVENT2_EVENT_H + return event_base_get_method(the_event_base); +#elif defined(HAVE_EVENT_GET_METHOD) + return event_get_method(); +#else + return "<unknown>"; +#endif +} + +/** Return the le_version_t for the current version of libevent. If the + * version is very new, return LE_OTHER. If the version is so old that it + * doesn't support event_get_version(), return LE_OLD. DOCDOC */ +static le_version_t +tor_decode_libevent_version(const char *v) +{ + unsigned major, minor, patchlevel; + char c, extra; + int fields; + + /* Try the new preferred "1.4.11-stable" format. */ + fields = sscanf(v, "%u.%u.%u%c", &major, &minor, &patchlevel, &c); + if (fields == 3 || + (fields == 4 && (c == '-' || c == '_'))) { + return V(major,minor,patchlevel); + } + + /* Try the old "1.3e" format. */ + fields = sscanf(v, "%u.%u%c%c", &major, &minor, &c, &extra); + if (fields == 3 && TOR_ISALPHA(c)) { + return V_OLD(major, minor, c); + } else if (fields == 2) { + return V(major, minor, 0); + } + + return LE_OTHER; +} + +/** Return an integer representing the binary interface of a Libevent library. + * Two different versions with different numbers are sure not to be binary + * compatible. Two different versions with the same numbers have a decent + * chance of binary compatibility.*/ +static int +le_versions_compatibility(le_version_t v) +{ + if (v == LE_OTHER) + return 0; + if (v < V_OLD(1,0,'c')) + return 1; + else if (v < V(1,4,0)) + return 2; + else if (v < V(1,4,99)) + return 3; + else if (v < V(2,0,1)) + return 4; + else /* Everything 2.0 and later should be compatible. */ + return 5; +} + +/** Return the version number of the currently running version of Libevent. + See le_version_t for info on the format. + */ +static le_version_t +tor_get_libevent_version(const char **v_out) +{ + const char *v; + le_version_t r; +#if defined(HAVE_EVENT_GET_VERSION_NUMBER) + v = event_get_version(); + r = event_get_version_number(); +#elif defined (HAVE_EVENT_GET_VERSION) + v = event_get_version(); + r = tor_decode_libevent_version(v); +#else + v = "pre-1.0c"; + r = LE_OLD; +#endif + if (v_out) + *v_out = v; + return r; +} + +/** Return a string representation of the version of the currently running + * version of Libevent. */ +const char * +tor_libevent_get_version_str(void) +{ +#ifdef HAVE_EVENT_GET_VERSION + return event_get_version(); +#else + return "pre-1.0c"; +#endif +} + +/** + * Compare the current Libevent method and version to a list of versions + * which are known not to work. Warn the user as appropriate. + */ +void +tor_check_libevent_version(const char *m, int server, + const char **badness_out) +{ + int buggy = 0, iffy = 0, slow = 0, thread_unsafe = 0; + le_version_t version; + const char *v = NULL; + const char *badness = NULL; + const char *sad_os = ""; + + version = tor_get_libevent_version(&v); + + /* XXX Would it be worthwhile disabling the methods that we know + * are buggy, rather than just warning about them and then proceeding + * to use them? If so, we should probably not wrap this whole thing + * in HAVE_EVENT_GET_VERSION and HAVE_EVENT_GET_METHOD. -RD */ + /* XXXX The problem is that it's not trivial to get libevent to change it's + * method once it's initialized, and it's not trivial to tell what method it + * will use without initializing it. I guess we could preemptively disable + * buggy libevent modes based on the version _before_ initializing it, + * though, but then there's no good way (afaict) to warn "I would have used + * kqueue, but instead I'm using select." -NM */ + /* XXXX022 revist the above; it is fixable now. */ + if (!strcmp(m, "kqueue")) { + if (version < V_OLD(1,1,'b')) + buggy = 1; + } else if (!strcmp(m, "epoll")) { + if (version < V(1,1,0)) + iffy = 1; + } else if (!strcmp(m, "poll")) { + if (version < V_OLD(1,0,'e')) + buggy = 1; + if (version < V(1,1,0)) + slow = 1; + } else if (!strcmp(m, "select")) { + if (version < V(1,1,0)) + slow = 1; + } else if (!strcmp(m, "win32")) { + if (version < V_OLD(1,1,'b')) + buggy = 1; + } + + /* Libevent versions before 1.3b do very badly on operating systems with + * user-space threading implementations. */ +#if defined(__OpenBSD__) || defined(__FreeBSD__) || defined(__NetBSD__) + if (server && version < V_OLD(1,3,'b')) { + thread_unsafe = 1; + sad_os = "BSD variants"; + } +#elif defined(__APPLE__) || defined(__darwin__) + if (server && version < V_OLD(1,3,'b')) { + thread_unsafe = 1; + sad_os = "Mac OS X"; + } +#endif + + if (thread_unsafe) { + log(LOG_WARN, LD_GENERAL, + "Libevent version %s often crashes when running a Tor server with %s. " + "Please use the latest version of libevent (1.3b or later)",v,sad_os); + badness = "BROKEN"; + } else if (buggy) { + log(LOG_WARN, LD_GENERAL, + "There are serious bugs in using %s with libevent %s. " + "Please use the latest version of libevent.", m, v); + badness = "BROKEN"; + } else if (iffy) { + log(LOG_WARN, LD_GENERAL, + "There are minor bugs in using %s with libevent %s. " + "You may want to use the latest version of libevent.", m, v); + badness = "BUGGY"; + } else if (slow && server) { + log(LOG_WARN, LD_GENERAL, + "libevent %s can be very slow with %s. " + "When running a server, please use the latest version of libevent.", + v,m); + badness = "SLOW"; + } + + *badness_out = badness; +} + +#if defined(LIBEVENT_VERSION) +#define HEADER_VERSION LIBEVENT_VERSION +#elif defined(_EVENT_VERSION) +#define HEADER_VERSION _EVENT_VERSION +#endif + +/** See whether the headers we were built against differ from the library we + * linked against so much that we're likely to crash. If so, warn the + * user. */ +void +tor_check_libevent_header_compatibility(void) +{ + (void) le_versions_compatibility; + (void) tor_decode_libevent_version; + + /* In libevent versions before 2.0, it's hard to keep binary compatibility + * between upgrades, and unpleasant to detect when the version we compiled + * against is unlike the version we have linked against. Here's how. */ +#if defined(HEADER_VERSION) && defined(HAVE_EVENT_GET_VERSION) + /* We have a header-file version and a function-call version. Easy. */ + if (strcmp(HEADER_VERSION, event_get_version())) { + le_version_t v1, v2; + int compat1 = -1, compat2 = -1; + int verybad; + v1 = tor_decode_libevent_version(HEADER_VERSION); + v2 = tor_decode_libevent_version(event_get_version()); + compat1 = le_versions_compatibility(v1); + compat2 = le_versions_compatibility(v2); + + verybad = compat1 != compat2; + + log(verybad ? LOG_WARN : LOG_NOTICE, + LD_GENERAL, "We were compiled with headers from version %s " + "of Libevent, but we're using a Libevent library that says it's " + "version %s.", HEADER_VERSION, event_get_version()); + if (verybad) + log_warn(LD_GENERAL, "This will almost certainly make Tor crash."); + else + log_info(LD_GENERAL, "I think these versions are binary-compatible."); + } +#elif defined(HAVE_EVENT_GET_VERSION) + /* event_get_version but no _EVENT_VERSION. We might be in 1.4.0-beta or + earlier, where that's normal. To see whether we were compiled with an + earlier version, let's see whether the struct event defines MIN_HEAP_IDX. + */ +#ifdef HAVE_STRUCT_EVENT_MIN_HEAP_IDX + /* The header files are 1.4.0-beta or later. If the version is not + * 1.4.0-beta, we are incompatible. */ + { + if (strcmp(event_get_version(), "1.4.0-beta")) { + log_warn(LD_GENERAL, "It's a little hard to tell, but you seem to have " + "Libevent 1.4.0-beta header files, whereas you have linked " + "against Libevent %s. This will probably make Tor crash.", + event_get_version()); + } + } +#else + /* Our headers are 1.3e or earlier. If the library version is not 1.4.x or + later, we're probably fine. */ + { + const char *v = event_get_version(); + if ((v[0] == '1' && v[2] == '.' && v[3] > '3') || v[0] > '1') { + log_warn(LD_GENERAL, "It's a little hard to tell, but you seem to have " + "Libevent header file from 1.3e or earlier, whereas you have " + "linked against Libevent %s. This will probably make Tor " + "crash.", event_get_version()); + } + } +#endif + +#elif defined(HEADER_VERSION) +#warn "_EVENT_VERSION is defined but not get_event_version(): Libevent is odd." +#else + /* Your libevent is ancient. */ +#endif +} + |