diff options
Diffstat (limited to 'src/common/compat_libevent.c')
| -rw-r--r-- | src/common/compat_libevent.c | 323 |
1 files changed, 287 insertions, 36 deletions
diff --git a/src/common/compat_libevent.c b/src/common/compat_libevent.c index 4a3b1af922..e60eb148d8 100644 --- a/src/common/compat_libevent.c +++ b/src/common/compat_libevent.c @@ -1,4 +1,4 @@ -/* Copyright (c) 2009-2016, The Tor Project, Inc. */ +/* Copyright (c) 2009-2017, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** @@ -11,7 +11,7 @@ #define COMPAT_LIBEVENT_PRIVATE #include "compat_libevent.h" -#include "crypto.h" +#include "crypto_rand.h" #include "util.h" #include "torlog.h" @@ -69,7 +69,7 @@ suppress_libevent_log_msg(const char *msg) /* Wrapper for event_free() that tolerates tor_event_free(NULL) */ void -tor_event_free(struct event *ev) +tor_event_free_(struct event *ev) { if (ev == NULL) return; @@ -79,6 +79,43 @@ tor_event_free(struct event *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). */ @@ -88,8 +125,8 @@ static struct event_base *the_event_base = NULL; (__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1040) #else #define MACOSX_KQUEUE_IS_BROKEN 0 -#endif -#endif +#endif /* defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) */ +#endif /* defined(__APPLE__) */ /** Initialize the Libevent library and set up the event base. */ void @@ -126,7 +163,16 @@ tor_libevent_initialize(tor_libevent_cfg *torcfg) if (!the_event_base) { /* LCOV_EXCL_START */ log_err(LD_GENERAL, "Unable to initialize Libevent: cannot continue."); - exit(1); + 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 */ } @@ -207,13 +253,42 @@ periodic_timer_new(struct event_base *base, } timer->cb = cb; timer->data = data; - event_add(timer->ev, (struct timeval *)tv); /*drop const for old libevent*/ + 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) +periodic_timer_free_(periodic_timer_t *timer) { if (!timer) return; @@ -221,6 +296,173 @@ periodic_timer_free(periodic_timer_t *timer) 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) { @@ -237,49 +479,58 @@ tor_init_libevent_rng(void) return rv; } -#if defined(LIBEVENT_VERSION_NUMBER) && LIBEVENT_VERSION_NUMBER >= V(2,1,1) \ - && !defined(TOR_UNIT_TESTS) +/** + * Un-initialize libevent in preparation for an exit + */ void -tor_gettimeofday_cached(struct timeval *tv) +tor_libevent_free_all(void) { - event_base_gettimeofday_cached(the_event_base, tv); + tor_event_free(rescan_mainloop_ev); + if (the_event_base) + event_base_free(the_event_base); + the_event_base = NULL; } -void -tor_gettimeofday_cache_clear(void) + +/** + * 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) { - event_base_update_cache_time(the_event_base); + const int flags = once ? EVLOOP_ONCE : 0; + return event_base_loop(base, flags); } -#else -/** Cache the current hi-res time; the cache gets reset when libevent - * calls us. */ -static struct timeval cached_time_hires = {0, 0}; -/** Return a fairly recent view of the current time. */ +/** 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_gettimeofday_cached(struct timeval *tv) +tor_libevent_exit_loop_after_delay(struct event_base *base, + const struct timeval *delay) { - if (cached_time_hires.tv_sec == 0) { - tor_gettimeofday(&cached_time_hires); - } - *tv = cached_time_hires; + event_base_loopexit(base, delay); } -/** Reset the cached view of the current time, so that the next time we try - * to learn it, we will get an up-to-date value. */ +/** Tell the event loop to exit after running whichever callback is currently + * active. */ void -tor_gettimeofday_cache_clear(void) +tor_libevent_exit_loop_after_callback(struct event_base *base) { - cached_time_hires.tv_sec = 0; + event_base_loopbreak(base); } -#ifdef TOR_UNIT_TESTS -/** For testing: force-update the cached time to a given value. */ +#if defined(TOR_UNIT_TESTS) +/** For testing: called post-fork to make libevent reinitialize + * kernel structures. */ void -tor_gettimeofday_cache_set(const struct timeval *tv) +tor_libevent_postfork(void) { - tor_assert(tv); - memcpy(&cached_time_hires, tv, sizeof(*tv)); + int r = event_reinit(tor_libevent_get_base()); + tor_assert(r == 0); } -#endif -#endif +#endif /* defined(TOR_UNIT_TESTS) */ |