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Diffstat (limited to 'src/common/procmon.c')
| -rw-r--r-- | src/common/procmon.c | 336 |
1 files changed, 336 insertions, 0 deletions
diff --git a/src/common/procmon.c b/src/common/procmon.c new file mode 100644 index 0000000000..5c10e9a22b --- /dev/null +++ b/src/common/procmon.c @@ -0,0 +1,336 @@ + +/** + * \file procmon.c + * \brief Process-termination monitor functions + **/ + +#include "procmon.h" + +#include "util.h" + +#ifdef HAVE_EVENT2_EVENT_H +#include <event2/event.h> +#else +#include <event.h> +#endif + +#ifdef HAVE_SIGNAL_H +#include <signal.h> +#endif +#ifdef HAVE_ERRNO_H +#include <errno.h> +#endif + +#ifdef MS_WINDOWS +#include <windows.h> + +/* Windows does not define pid_t, but _getpid() returns an int. */ +typedef int pid_t; +#endif + +/* Define to 1 if process-termination monitors on this OS and Libevent + version must poll for process termination themselves. */ +#define PROCMON_POLLS 1 +/* Currently we need to poll in some way on all systems. */ + +#ifdef PROCMON_POLLS +static void tor_process_monitor_poll_cb(evutil_socket_t unused1, short unused2, + void *procmon_); +#endif + +/* This struct may contain pointers into the original process + * specifier string, but it should *never* contain anything which + * needs to be freed. */ +struct parsed_process_specifier_t { + pid_t pid; +}; + +/** Parse the process specifier given in <b>process_spec</b> into + * *<b>ppspec</b>. Return 0 on success; return -1 and store an error + * message into *<b>msg</b> on failure. The caller must not free the + * returned error message. */ +static int +parse_process_specifier(const char *process_spec, + struct parsed_process_specifier_t *ppspec, + const char **msg) +{ + long pid_l; + int pid_ok = 0; + char *pspec_next; + + /* If we're lucky, long will turn out to be large enough to hold a + * PID everywhere that Tor runs. */ + pid_l = tor_parse_long(process_spec, 0, 1, LONG_MAX, &pid_ok, &pspec_next); + + /* Reserve room in the ‘process specifier’ for additional + * (platform-specific) identifying information beyond the PID, to + * make our process-existence checks a bit less racy in a future + * version. */ + if ((*pspec_next != 0) && (*pspec_next != ' ') && (*pspec_next != ':')) { + pid_ok = 0; + } + + ppspec->pid = (pid_t)(pid_l); + if (!pid_ok || (pid_l != (long)(ppspec->pid))) { + *msg = "invalid PID"; + goto err; + } + + return 0; + err: + return -1; +} + +struct tor_process_monitor_t { + /** Log domain for warning messages. */ + log_domain_mask_t log_domain; + + /** All systems: The best we can do in general is poll for the + * process's existence by PID periodically, and hope that the kernel + * doesn't reassign the same PID to another process between our + * polls. */ + pid_t pid; + +#ifdef MS_WINDOWS + /** Windows-only: Should we poll hproc? If false, poll pid + * instead. */ + int poll_hproc; + + /** Windows-only: Get a handle to the process (if possible) and + * periodically check whether the process we have a handle to has + * ended. */ + HANDLE hproc; + /* XXX023 We can and should have Libevent watch hproc for us, + * if/when some version of Libevent 2.x can be told to do so. */ +#endif + + /* XXX023 On Linux, we can and should receive the 22nd + * (space-delimited) field (‘starttime’) of /proc/$PID/stat from the + * owning controller and store it, and poll once in a while to see + * whether it has changed -- if so, the kernel has *definitely* + * reassigned the owning controller's PID and we should exit. On + * FreeBSD, we can do the same trick using either the 8th + * space-delimited field of /proc/$PID/status on the seven FBSD + * systems whose admins have mounted procfs, or the start-time field + * of the process-information structure returned by kvmgetprocs() on + * any system. The latter is ickier. */ + /* XXX023 On FreeBSD (and possibly other kqueue systems), we can and + * should arrange to receive EVFILT_PROC NOTE_EXIT notifications for + * pid, so we don't have to do such a heavyweight poll operation in + * order to avoid the PID-reassignment race condition. (We would + * still need to poll our own kqueue periodically until some version + * of Libevent 2.x learns to receive these events for us.) */ + + /** A Libevent event structure, to either poll for the process's + * existence or receive a notification when the process ends. */ + struct event *e; + + /** A callback to be called when the process ends. */ + tor_procmon_callback_t cb; + void *cb_arg; /**< A user-specified pointer to be passed to cb. */ +}; + +/** Verify that the process specifier given in <b>process_spec</b> is + * syntactically valid. Return 0 on success; return -1 and store an + * error message into *<b>msg</b> on failure. The caller must not + * free the returned error message. */ +int +tor_validate_process_specifier(const char *process_spec, + const char **msg) +{ + struct parsed_process_specifier_t ppspec; + + tor_assert(msg != NULL); + *msg = NULL; + + return parse_process_specifier(process_spec, &ppspec, msg); +} + +#ifdef HAVE_EVENT2_EVENT_H +#define PERIODIC_TIMER_FLAGS EV_PERSIST +#else +#define PERIODIC_TIMER_FLAGS (0) +#endif + +static struct timeval poll_interval_tv = {15, 0}; +/* Note: If you port this file to plain Libevent 2, you can make + * poll_interval_tv const. It has to be non-const here because in + * libevent 1.x, event_add expects a pointer to a non-const struct + * timeval. */ + +/** Create a process-termination monitor for the process specifier + * given in <b>process_spec</b>. Return a newly allocated + * tor_process_monitor_t on success; return NULL and store an error + * message into *<b>msg</b> on failure. The caller must not free + * the returned error message. + * + * When the monitored process terminates, call + * <b>cb</b>(<b>cb_arg</b>). + */ +tor_process_monitor_t * +tor_process_monitor_new(struct event_base *base, + const char *process_spec, + log_domain_mask_t log_domain, + tor_procmon_callback_t cb, void *cb_arg, + const char **msg) +{ + tor_process_monitor_t *procmon = tor_malloc(sizeof(tor_process_monitor_t)); + struct parsed_process_specifier_t ppspec; + + tor_assert(msg != NULL); + *msg = NULL; + + if (procmon == NULL) { + *msg = "out of memory"; + goto err; + } + + procmon->log_domain = log_domain; + + if (parse_process_specifier(process_spec, &ppspec, msg)) + goto err; + + procmon->pid = ppspec.pid; + +#ifdef MS_WINDOWS + procmon->hproc = OpenProcess(PROCESS_QUERY_INFORMATION | SYNCHRONIZE, + FALSE, + procmon->pid); + + if (procmon->hproc != NULL) { + procmon->poll_hproc = 1; + log_info(procmon->log_domain, "Successfully opened handle to process %d; " + "monitoring it.", + (int)(procmon->pid)); + } else { + /* If we couldn't get a handle to the process, we'll try again the + * first time we poll. */ + log_info(procmon->log_domain, "Failed to open handle to process %d; will " + "try again later.", + (int)(procmon->pid)); + } +#endif + + procmon->cb = cb; + procmon->cb_arg = cb_arg; + +#ifdef PROCMON_POLLS + procmon->e = tor_event_new(base, -1 /* no FD */, PERIODIC_TIMER_FLAGS, + tor_process_monitor_poll_cb, procmon); + /* Note: If you port this file to plain Libevent 2, check that + * procmon->e is non-NULL. We don't need to here because + * tor_evtimer_new never returns NULL. */ + + evtimer_add(procmon->e, &poll_interval_tv); +#else +#error OOPS? +#endif + + return procmon; + err: + tor_process_monitor_free(procmon); + return NULL; +} + +#ifdef PROCMON_POLLS +/** Libevent callback to poll for the existence of the process + * monitored by <b>procmon_</b>. */ +static void +tor_process_monitor_poll_cb(evutil_socket_t unused1, short unused2, + void *procmon_) +{ + tor_process_monitor_t *procmon = (tor_process_monitor_t *)(procmon_); + int its_dead_jim; + + (void)unused1; (void)unused2; + + tor_assert(procmon != NULL); + +#ifdef MS_WINDOWS + if (procmon->poll_hproc) { + DWORD exit_code; + if (!GetExitCodeProcess(procmon->hproc, &exit_code)) { + char *errmsg = format_win32_error(GetLastError()); + log_warn(procmon->log_domain, "Error \"%s\" occurred while polling " + "handle for monitored process %d; assuming it's dead.", + errmsg, procmon->pid); + tor_free(errmsg); + its_dead_jim = 1; + } else { + its_dead_jim = (exit_code != STILL_ACTIVE); + } + } else { + /* All we can do is try to open the process, and look at the error + * code if it fails again. */ + procmon->hproc = OpenProcess(PROCESS_QUERY_INFORMATION | SYNCHRONIZE, + FALSE, + procmon->pid); + + if (procmon->hproc != NULL) { + log_info(procmon->log_domain, "Successfully opened handle to monitored " + "process %d.", + procmon->pid); + its_dead_jim = 0; + procmon->poll_hproc = 1; + } else { + DWORD err_code = GetLastError(); + char *errmsg = format_win32_error(err_code); + + /* When I tested OpenProcess's error codes on Windows 7, I + * received error code 5 (ERROR_ACCESS_DENIED) for PIDs of + * existing processes that I could not open and error code 87 + * (ERROR_INVALID_PARAMETER) for PIDs that were not in use. + * Since the nonexistent-process error code is sane, I'm going + * to assume that all errors other than ERROR_INVALID_PARAMETER + * mean that the process we are monitoring is still alive. */ + its_dead_jim = (err_code == ERROR_INVALID_PARAMETER); + + if (!its_dead_jim) + log_info(procmon->log_domain, "Failed to open handle to monitored " + "process %d, and error code %lu (%s) is not 'invalid " + "parameter' -- assuming the process is still alive.", + procmon->pid, + err_code, errmsg); + + tor_free(errmsg); + } + } +#else + /* Unix makes this part easy, if a bit racy. */ + its_dead_jim = kill(procmon->pid, 0); + its_dead_jim = its_dead_jim && (errno == ESRCH); +#endif + + log(its_dead_jim ? LOG_NOTICE : LOG_INFO, + procmon->log_domain, "Monitored process %d is %s.", + (int)procmon->pid, + its_dead_jim ? "dead" : "still alive"); + + if (its_dead_jim) { + procmon->cb(procmon->cb_arg); +#ifndef HAVE_EVENT2_EVENT_H + } else { + evtimer_add(procmon->e, &poll_interval_tv); +#endif + } +} +#endif + +/** Free the process-termination monitor <b>procmon</b>. */ +void +tor_process_monitor_free(tor_process_monitor_t *procmon) +{ + if (procmon == NULL) + return; + +#ifdef MS_WINDOWS + if (procmon->hproc != NULL) + CloseHandle(procmon->hproc); +#endif + + if (procmon->e != NULL) + tor_event_free(procmon->e); + + tor_free(procmon); +} + |