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Diffstat (limited to 'src/lib/evloop/compat_libevent.c')
| -rw-r--r-- | src/lib/evloop/compat_libevent.c | 535 |
1 files changed, 535 insertions, 0 deletions
diff --git a/src/lib/evloop/compat_libevent.c b/src/lib/evloop/compat_libevent.c new file mode 100644 index 0000000000..9d21cf20bd --- /dev/null +++ b/src/lib/evloop/compat_libevent.c @@ -0,0 +1,535 @@ +/* Copyright (c) 2009-2018, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file compat_libevent.c + * \brief Wrappers and utility functions for Libevent. + */ + +#include "orconfig.h" +#define COMPAT_LIBEVENT_PRIVATE +#include "common/compat_libevent.h" + +#include "lib/crypt_ops/crypto_rand.h" +#include "lib/log/torlog.h" +#include "lib/log/util_bug.h" +#include "lib/string/compat_string.h" + +#include <event2/event.h> +#include <event2/thread.h> +#include <string.h> + +/** 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_debug(LD_NOCB|LD_NET, "Message from libevent: %s", buf); + break; + case _EVENT_LOG_MSG: + log_info(LD_NOCB|LD_NET, "Message from libevent: %s", buf); + break; + case _EVENT_LOG_WARN: + log_warn(LD_NOCB|LD_GENERAL, "Warning from libevent: %s", buf); + break; + case _EVENT_LOG_ERR: + log_err(LD_NOCB|LD_GENERAL, "Error from libevent: %s", buf); + break; + default: + log_warn(LD_NOCB|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; +} + +/* Wrapper for event_free() that tolerates tor_event_free(NULL) */ +void +tor_event_free_(struct event *ev) +{ + if (ev == NULL) + return; + event_free(ev); +} + +/** Global event base for use by the main thread. */ +static struct event_base *the_event_base = NULL; + +/** + * @defgroup postloop post-loop event helpers + * + * If we're not careful, Libevent can susceptible to infinite event chains: + * one event can activate another, whose callback activates another, whose + * callback activates another, ad infinitum. While this is happening, + * Libevent won't be checking timeouts, socket-based events, signals, and so + * on. + * + * We solve this problem by marking some events as "post-loop". A post-loop + * event behaves like any ordinary event, but any events that _it_ activates + * cannot run until Libevent has checked for other events at least once. + * + * @{ */ + +/** + * An event that stops Libevent from running any more events on the current + * iteration of its loop, until it has re-checked for socket events, signal + * events, timeouts, etc. + */ +static struct event *rescan_mainloop_ev = NULL; + +/** + * Callback to implement rescan_mainloop_ev: it simply exits the mainloop, + * and relies on Tor to re-enter the mainloop since no error has occurred. + */ +static void +rescan_mainloop_cb(evutil_socket_t fd, short events, void *arg) +{ + (void)fd; + (void)events; + struct event_base *the_base = arg; + event_base_loopbreak(the_base); +} + +/** @} */ + +/* 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 /* defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) */ +#endif /* defined(__APPLE__) */ + +/** Initialize the Libevent library and set up the event base. */ +void +tor_libevent_initialize(tor_libevent_cfg *torcfg) +{ + tor_assert(the_event_base == NULL); + /* some paths below don't use torcfg, so avoid unused variable warnings */ + (void)torcfg; + + { + int attempts = 0; + struct event_config *cfg; + + ++attempts; + cfg = event_config_new(); + tor_assert(cfg); + + /* Telling Libevent not to try to turn locking on can avoid a needless + * socketpair() attempt. */ + event_config_set_flag(cfg, EVENT_BASE_FLAG_NOLOCK); + + if (torcfg->num_cpus > 0) + event_config_set_num_cpus_hint(cfg, torcfg->num_cpus); + + /* We can enable changelist support with epoll, since we don't give + * Libevent any dup'd fds. This lets us avoid some syscalls. */ + event_config_set_flag(cfg, EVENT_BASE_FLAG_EPOLL_USE_CHANGELIST); + + the_event_base = event_base_new_with_config(cfg); + + event_config_free(cfg); + } + + if (!the_event_base) { + /* LCOV_EXCL_START */ + log_err(LD_GENERAL, "Unable to initialize Libevent: cannot continue."); + exit(1); // exit ok: libevent is broken. + /* LCOV_EXCL_STOP */ + } + + rescan_mainloop_ev = event_new(the_event_base, -1, 0, + rescan_mainloop_cb, the_event_base); + if (!rescan_mainloop_ev) { + /* LCOV_EXCL_START */ + log_err(LD_GENERAL, "Unable to create rescan event: cannot continue."); + exit(1); // exit ok: libevent is broken. + /* LCOV_EXCL_STOP */ + } + + log_info(LD_GENERAL, + "Initialized libevent version %s using method %s. Good.", + event_get_version(), tor_libevent_get_method()); +} + +/** Return the current Libevent event base that we're set up to use. */ +MOCK_IMPL(struct event_base *, +tor_libevent_get_base, (void)) +{ + tor_assert(the_event_base != NULL); + return the_event_base; +} + +/** Return the name of the Libevent backend we're using. */ +const char * +tor_libevent_get_method(void) +{ + return event_base_get_method(the_event_base); +} + +/** Return a string representation of the version of the currently running + * version of Libevent. */ +const char * +tor_libevent_get_version_str(void) +{ + return event_get_version(); +} + +/** Return a string representation of the version of Libevent that was used +* at compilation time. */ +const char * +tor_libevent_get_header_version_str(void) +{ + return LIBEVENT_VERSION; +} + +/** Represents a timer that's run every N microseconds by Libevent. */ +struct periodic_timer_t { + /** Underlying event used to implement this periodic event. */ + struct event *ev; + /** The callback we'll be invoking whenever the event triggers */ + void (*cb)(struct periodic_timer_t *, void *); + /** User-supplied data for the callback */ + void *data; +}; + +/** Libevent callback to implement a periodic event. */ +static void +periodic_timer_cb(evutil_socket_t fd, short what, void *arg) +{ + periodic_timer_t *timer = arg; + (void) what; + (void) fd; + timer->cb(timer, timer->data); +} + +/** Create and schedule a new timer that will run every <b>tv</b> in + * the event loop of <b>base</b>. When the timer fires, it will + * run the timer in <b>cb</b> with the user-supplied data in <b>data</b>. */ +periodic_timer_t * +periodic_timer_new(struct event_base *base, + const struct timeval *tv, + void (*cb)(periodic_timer_t *timer, void *data), + void *data) +{ + periodic_timer_t *timer; + tor_assert(base); + tor_assert(tv); + tor_assert(cb); + timer = tor_malloc_zero(sizeof(periodic_timer_t)); + if (!(timer->ev = tor_event_new(base, -1, EV_PERSIST, + periodic_timer_cb, timer))) { + tor_free(timer); + return NULL; + } + timer->cb = cb; + timer->data = data; + periodic_timer_launch(timer, tv); + return timer; +} + +/** + * Launch the timer <b>timer</b> to run at <b>tv</b> from now, and every + * <b>tv</b> thereafter. + * + * If the timer is already enabled, this function does nothing. + */ +void +periodic_timer_launch(periodic_timer_t *timer, const struct timeval *tv) +{ + tor_assert(timer); + if (event_pending(timer->ev, EV_TIMEOUT, NULL)) + return; + event_add(timer->ev, tv); +} + +/** + * Disable the provided <b>timer</b>, but do not free it. + * + * You can reenable the same timer later with periodic_timer_launch. + * + * If the timer is already disabled, this function does nothing. + */ +void +periodic_timer_disable(periodic_timer_t *timer) +{ + tor_assert(timer); + (void) event_del(timer->ev); +} + +/** Stop and free a periodic timer */ +void +periodic_timer_free_(periodic_timer_t *timer) +{ + if (!timer) + return; + tor_event_free(timer->ev); + tor_free(timer); +} + +/** + * Type used to represent events that run directly from the main loop, + * either because they are activated from elsewhere in the code, or + * because they have a simple timeout. + * + * We use this type to avoid exposing Libevent's API throughout the rest + * of the codebase. + * + * This type can't be used for all events: it doesn't handle events that + * are triggered by signals or by sockets. + */ +struct mainloop_event_t { + struct event *ev; + void (*cb)(mainloop_event_t *, void *); + void *userdata; +}; + +/** + * Internal: Implements mainloop event using a libevent event. + */ +static void +mainloop_event_cb(evutil_socket_t fd, short what, void *arg) +{ + (void)fd; + (void)what; + mainloop_event_t *mev = arg; + mev->cb(mev, mev->userdata); +} + +/** + * As mainloop_event_cb, but implements a post-loop event. + */ +static void +mainloop_event_postloop_cb(evutil_socket_t fd, short what, void *arg) +{ + (void)fd; + (void)what; + + /* Note that if rescan_mainloop_ev is already activated, + * event_active() will do nothing: only the first post-loop event that + * happens each time through the event loop will cause it to be + * activated. + * + * Because event_active() puts events on a FIFO queue, every event + * that is made active _after_ rescan_mainloop_ev will get its + * callback run after rescan_mainloop_cb is called -- that is, on the + * next iteration of the loop. + */ + event_active(rescan_mainloop_ev, EV_READ, 1); + + mainloop_event_t *mev = arg; + mev->cb(mev, mev->userdata); +} + +/** + * Helper for mainloop_event_new() and mainloop_event_postloop_new(). + */ +static mainloop_event_t * +mainloop_event_new_impl(int postloop, + void (*cb)(mainloop_event_t *, void *), + void *userdata) +{ + tor_assert(cb); + + struct event_base *base = tor_libevent_get_base(); + mainloop_event_t *mev = tor_malloc_zero(sizeof(mainloop_event_t)); + mev->ev = tor_event_new(base, -1, 0, + postloop ? mainloop_event_postloop_cb : mainloop_event_cb, + mev); + tor_assert(mev->ev); + mev->cb = cb; + mev->userdata = userdata; + return mev; +} + +/** + * Create and return a new mainloop_event_t to run the function <b>cb</b>. + * + * When run, the callback function will be passed the mainloop_event_t + * and <b>userdata</b> as its arguments. The <b>userdata</b> pointer + * must remain valid for as long as the mainloop_event_t event exists: + * it is your responsibility to free it. + * + * The event is not scheduled by default: Use mainloop_event_activate() + * or mainloop_event_schedule() to make it run. + */ +mainloop_event_t * +mainloop_event_new(void (*cb)(mainloop_event_t *, void *), + void *userdata) +{ + return mainloop_event_new_impl(0, cb, userdata); +} + +/** + * As mainloop_event_new(), but create a post-loop event. + * + * A post-loop event behaves like any ordinary event, but any events + * that _it_ activates cannot run until Libevent has checked for other + * events at least once. + */ +mainloop_event_t * +mainloop_event_postloop_new(void (*cb)(mainloop_event_t *, void *), + void *userdata) +{ + return mainloop_event_new_impl(1, cb, userdata); +} + +/** + * Schedule <b>event</b> to run in the main loop, immediately. If it is + * not scheduled, it will run anyway. If it is already scheduled to run + * later, it will run now instead. This function will have no effect if + * the event is already scheduled to run. + * + * This function may only be called from the main thread. + */ +void +mainloop_event_activate(mainloop_event_t *event) +{ + tor_assert(event); + event_active(event->ev, EV_READ, 1); +} + +/** Schedule <b>event</b> to run in the main loop, after a delay of <b>tv</b>. + * + * If the event is scheduled for a different time, cancel it and run + * after this delay instead. If the event is currently pending to run + * <em>now</b>, has no effect. + * + * Do not call this function with <b>tv</b> == NULL -- use + * mainloop_event_activate() instead. + * + * This function may only be called from the main thread. + */ +int +mainloop_event_schedule(mainloop_event_t *event, const struct timeval *tv) +{ + tor_assert(event); + if (BUG(tv == NULL)) { + // LCOV_EXCL_START + mainloop_event_activate(event); + return 0; + // LCOV_EXCL_STOP + } + return event_add(event->ev, tv); +} + +/** Cancel <b>event</b> if it is currently active or pending. (Do nothing if + * the event is not currently active or pending.) */ +void +mainloop_event_cancel(mainloop_event_t *event) +{ + if (!event) + return; + (void) event_del(event->ev); +} + +/** Cancel <b>event</b> and release all storage associated with it. */ +void +mainloop_event_free_(mainloop_event_t *event) +{ + if (!event) + return; + tor_event_free(event->ev); + memset(event, 0xb8, sizeof(*event)); + tor_free(event); +} + +int +tor_init_libevent_rng(void) +{ + int rv = 0; + char buf[256]; + if (evutil_secure_rng_init() < 0) { + rv = -1; + } + crypto_rand(buf, 32); +#ifdef HAVE_EVUTIL_SECURE_RNG_ADD_BYTES + evutil_secure_rng_add_bytes(buf, 32); +#endif + evutil_secure_rng_get_bytes(buf, sizeof(buf)); + return rv; +} + +/** + * Un-initialize libevent in preparation for an exit + */ +void +tor_libevent_free_all(void) +{ + tor_event_free(rescan_mainloop_ev); + if (the_event_base) + event_base_free(the_event_base); + the_event_base = NULL; +} + +/** + * Run the event loop for the provided event_base, handling events until + * something stops it. If <b>once</b> is set, then just poll-and-run + * once, then exit. Return 0 on success, -1 if an error occurred, or 1 + * if we exited because no events were pending or active. + * + * This isn't reentrant or multithreaded. + */ +int +tor_libevent_run_event_loop(struct event_base *base, int once) +{ + const int flags = once ? EVLOOP_ONCE : 0; + return event_base_loop(base, flags); +} + +/** Tell the event loop to exit after <b>delay</b>. If <b>delay</b> is NULL, + * instead exit after we're done running the currently active events. */ +void +tor_libevent_exit_loop_after_delay(struct event_base *base, + const struct timeval *delay) +{ + event_base_loopexit(base, delay); +} + +/** Tell the event loop to exit after running whichever callback is currently + * active. */ +void +tor_libevent_exit_loop_after_callback(struct event_base *base) +{ + event_base_loopbreak(base); +} + +#if defined(TOR_UNIT_TESTS) +/** For testing: called post-fork to make libevent reinitialize + * kernel structures. */ +void +tor_libevent_postfork(void) +{ + int r = event_reinit(tor_libevent_get_base()); + tor_assert(r == 0); +} +#endif /* defined(TOR_UNIT_TESTS) */ |