358 lines
11 KiB
C
358 lines
11 KiB
C
/* Copyright (c) 2011-2013, The Tor Project, Inc. */
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/* See LICENSE for licensing information */
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/**
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* \file procmon.c
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* \brief Process-termination monitor functions
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**/
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#include "procmon.h"
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#include "util.h"
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#ifdef HAVE_EVENT2_EVENT_H
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#include <event2/event.h>
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#else
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#include <event.h>
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#endif
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#ifdef HAVE_SIGNAL_H
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#include <signal.h>
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#endif
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#ifdef HAVE_ERRNO_H
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#include <errno.h>
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#endif
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#ifdef _WIN32
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#include <windows.h>
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#endif
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#if (0 == SIZEOF_PID_T) && defined(_WIN32)
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/* Windows does not define pid_t sometimes, but _getpid() returns an int.
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* Everybody else needs to have a pid_t. */
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typedef int pid_t;
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#define PID_T_FORMAT "%d"
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#elif (SIZEOF_PID_T == SIZEOF_INT) || (SIZEOF_PID_T == SIZEOF_SHORT)
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#define PID_T_FORMAT "%d"
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#elif (SIZEOF_PID_T == SIZEOF_LONG)
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#define PID_T_FORMAT "%ld"
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#elif (SIZEOF_PID_T == SIZEOF_INT64_T)
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#define PID_T_FORMAT I64_FORMAT
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#else
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#error Unknown: SIZEOF_PID_T
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#endif
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/* Define to 1 if process-termination monitors on this OS and Libevent
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version must poll for process termination themselves. */
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#define PROCMON_POLLS 1
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/* Currently we need to poll in some way on all systems. */
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#ifdef PROCMON_POLLS
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static void tor_process_monitor_poll_cb(evutil_socket_t unused1, short unused2,
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void *procmon_);
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#endif
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/* This struct may contain pointers into the original process
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* specifier string, but it should *never* contain anything which
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* needs to be freed. */
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/* DOCDOC parsed_process_specifier_t */
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struct parsed_process_specifier_t {
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pid_t pid;
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};
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/** Parse the process specifier given in <b>process_spec</b> into
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* *<b>ppspec</b>. Return 0 on success; return -1 and store an error
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* message into *<b>msg</b> on failure. The caller must not free the
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* returned error message. */
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static int
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parse_process_specifier(const char *process_spec,
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struct parsed_process_specifier_t *ppspec,
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const char **msg)
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{
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long pid_l;
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int pid_ok = 0;
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char *pspec_next;
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/* If we're lucky, long will turn out to be large enough to hold a
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* PID everywhere that Tor runs. */
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pid_l = tor_parse_long(process_spec, 0, 1, LONG_MAX, &pid_ok, &pspec_next);
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/* Reserve room in the ‘process specifier’ for additional
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* (platform-specific) identifying information beyond the PID, to
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* make our process-existence checks a bit less racy in a future
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* version. */
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if ((*pspec_next != 0) && (*pspec_next != ' ') && (*pspec_next != ':')) {
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pid_ok = 0;
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}
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ppspec->pid = (pid_t)(pid_l);
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if (!pid_ok || (pid_l != (long)(ppspec->pid))) {
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*msg = "invalid PID";
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goto err;
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}
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return 0;
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err:
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return -1;
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}
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/* DOCDOC tor_process_monitor_t */
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struct tor_process_monitor_t {
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/** Log domain for warning messages. */
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log_domain_mask_t log_domain;
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/** All systems: The best we can do in general is poll for the
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* process's existence by PID periodically, and hope that the kernel
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* doesn't reassign the same PID to another process between our
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* polls. */
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pid_t pid;
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#ifdef _WIN32
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/** Windows-only: Should we poll hproc? If false, poll pid
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* instead. */
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int poll_hproc;
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/** Windows-only: Get a handle to the process (if possible) and
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* periodically check whether the process we have a handle to has
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* ended. */
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HANDLE hproc;
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/* XXX023 We can and should have Libevent watch hproc for us,
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* if/when some version of Libevent 2.x can be told to do so. */
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#endif
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/* XXX023 On Linux, we can and should receive the 22nd
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* (space-delimited) field (‘starttime’) of /proc/$PID/stat from the
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* owning controller and store it, and poll once in a while to see
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* whether it has changed -- if so, the kernel has *definitely*
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* reassigned the owning controller's PID and we should exit. On
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* FreeBSD, we can do the same trick using either the 8th
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* space-delimited field of /proc/$PID/status on the seven FBSD
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* systems whose admins have mounted procfs, or the start-time field
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* of the process-information structure returned by kvmgetprocs() on
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* any system. The latter is ickier. */
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/* XXX023 On FreeBSD (and possibly other kqueue systems), we can and
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* should arrange to receive EVFILT_PROC NOTE_EXIT notifications for
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* pid, so we don't have to do such a heavyweight poll operation in
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* order to avoid the PID-reassignment race condition. (We would
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* still need to poll our own kqueue periodically until some version
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* of Libevent 2.x learns to receive these events for us.) */
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/** A Libevent event structure, to either poll for the process's
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* existence or receive a notification when the process ends. */
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struct event *e;
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/** A callback to be called when the process ends. */
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tor_procmon_callback_t cb;
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void *cb_arg; /**< A user-specified pointer to be passed to cb. */
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};
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/** Verify that the process specifier given in <b>process_spec</b> is
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* syntactically valid. Return 0 on success; return -1 and store an
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* error message into *<b>msg</b> on failure. The caller must not
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* free the returned error message. */
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int
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tor_validate_process_specifier(const char *process_spec,
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const char **msg)
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{
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struct parsed_process_specifier_t ppspec;
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tor_assert(msg != NULL);
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*msg = NULL;
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return parse_process_specifier(process_spec, &ppspec, msg);
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}
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/* XXXX we should use periodic_timer_new() for this stuff */
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#ifdef HAVE_EVENT2_EVENT_H
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#define PERIODIC_TIMER_FLAGS EV_PERSIST
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#else
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#define PERIODIC_TIMER_FLAGS (0)
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#endif
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/* DOCDOC poll_interval_tv */
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static struct timeval poll_interval_tv = {15, 0};
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/* Note: If you port this file to plain Libevent 2, you can make
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* poll_interval_tv const. It has to be non-const here because in
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* libevent 1.x, event_add expects a pointer to a non-const struct
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* timeval. */
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/** Create a process-termination monitor for the process specifier
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* given in <b>process_spec</b>. Return a newly allocated
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* tor_process_monitor_t on success; return NULL and store an error
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* message into *<b>msg</b> on failure. The caller must not free
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* the returned error message.
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*
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* When the monitored process terminates, call
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* <b>cb</b>(<b>cb_arg</b>).
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*/
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tor_process_monitor_t *
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tor_process_monitor_new(struct event_base *base,
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const char *process_spec,
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log_domain_mask_t log_domain,
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tor_procmon_callback_t cb, void *cb_arg,
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const char **msg)
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{
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tor_process_monitor_t *procmon = tor_malloc(sizeof(tor_process_monitor_t));
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struct parsed_process_specifier_t ppspec;
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tor_assert(msg != NULL);
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*msg = NULL;
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if (procmon == NULL) {
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*msg = "out of memory";
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goto err;
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}
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procmon->log_domain = log_domain;
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if (parse_process_specifier(process_spec, &ppspec, msg))
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goto err;
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procmon->pid = ppspec.pid;
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#ifdef _WIN32
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procmon->hproc = OpenProcess(PROCESS_QUERY_INFORMATION | SYNCHRONIZE,
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FALSE,
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procmon->pid);
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if (procmon->hproc != NULL) {
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procmon->poll_hproc = 1;
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log_info(procmon->log_domain, "Successfully opened handle to process "
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PID_T_FORMAT"; "
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"monitoring it.",
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procmon->pid);
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} else {
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/* If we couldn't get a handle to the process, we'll try again the
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* first time we poll. */
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log_info(procmon->log_domain, "Failed to open handle to process "
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PID_T_FORMAT"; will "
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"try again later.",
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procmon->pid);
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}
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#endif
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procmon->cb = cb;
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procmon->cb_arg = cb_arg;
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#ifdef PROCMON_POLLS
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procmon->e = tor_event_new(base, -1 /* no FD */, PERIODIC_TIMER_FLAGS,
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tor_process_monitor_poll_cb, procmon);
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/* Note: If you port this file to plain Libevent 2, check that
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* procmon->e is non-NULL. We don't need to here because
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* tor_evtimer_new never returns NULL. */
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evtimer_add(procmon->e, &poll_interval_tv);
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#else
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#error OOPS?
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#endif
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return procmon;
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err:
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tor_process_monitor_free(procmon);
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return NULL;
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}
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#ifdef PROCMON_POLLS
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/** Libevent callback to poll for the existence of the process
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* monitored by <b>procmon_</b>. */
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static void
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tor_process_monitor_poll_cb(evutil_socket_t unused1, short unused2,
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void *procmon_)
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{
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tor_process_monitor_t *procmon = (tor_process_monitor_t *)(procmon_);
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int its_dead_jim;
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(void)unused1; (void)unused2;
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tor_assert(procmon != NULL);
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#ifdef _WIN32
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if (procmon->poll_hproc) {
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DWORD exit_code;
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if (!GetExitCodeProcess(procmon->hproc, &exit_code)) {
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char *errmsg = format_win32_error(GetLastError());
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log_warn(procmon->log_domain, "Error \"%s\" occurred while polling "
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"handle for monitored process "PID_T_FORMAT"; assuming "
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"it's dead.",
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errmsg, procmon->pid);
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tor_free(errmsg);
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its_dead_jim = 1;
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} else {
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its_dead_jim = (exit_code != STILL_ACTIVE);
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}
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} else {
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/* All we can do is try to open the process, and look at the error
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* code if it fails again. */
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procmon->hproc = OpenProcess(PROCESS_QUERY_INFORMATION | SYNCHRONIZE,
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FALSE,
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procmon->pid);
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if (procmon->hproc != NULL) {
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log_info(procmon->log_domain, "Successfully opened handle to monitored "
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"process "PID_T_FORMAT".",
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procmon->pid);
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its_dead_jim = 0;
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procmon->poll_hproc = 1;
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} else {
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DWORD err_code = GetLastError();
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char *errmsg = format_win32_error(err_code);
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/* When I tested OpenProcess's error codes on Windows 7, I
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* received error code 5 (ERROR_ACCESS_DENIED) for PIDs of
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* existing processes that I could not open and error code 87
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* (ERROR_INVALID_PARAMETER) for PIDs that were not in use.
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* Since the nonexistent-process error code is sane, I'm going
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* to assume that all errors other than ERROR_INVALID_PARAMETER
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* mean that the process we are monitoring is still alive. */
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its_dead_jim = (err_code == ERROR_INVALID_PARAMETER);
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if (!its_dead_jim)
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log_info(procmon->log_domain, "Failed to open handle to monitored "
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"process "PID_T_FORMAT", and error code %lu (%s) is not "
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"'invalid parameter' -- assuming the process is still alive.",
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procmon->pid,
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err_code, errmsg);
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tor_free(errmsg);
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}
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}
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#else
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/* Unix makes this part easy, if a bit racy. */
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its_dead_jim = kill(procmon->pid, 0);
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its_dead_jim = its_dead_jim && (errno == ESRCH);
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#endif
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tor_log(its_dead_jim ? LOG_NOTICE : LOG_INFO,
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procmon->log_domain, "Monitored process "PID_T_FORMAT" is %s.",
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procmon->pid,
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its_dead_jim ? "dead" : "still alive");
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if (its_dead_jim) {
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procmon->cb(procmon->cb_arg);
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#ifndef HAVE_EVENT2_EVENT_H
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} else {
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evtimer_add(procmon->e, &poll_interval_tv);
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#endif
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}
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}
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#endif
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/** Free the process-termination monitor <b>procmon</b>. */
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void
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tor_process_monitor_free(tor_process_monitor_t *procmon)
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{
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if (procmon == NULL)
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return;
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#ifdef _WIN32
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if (procmon->hproc != NULL)
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CloseHandle(procmon->hproc);
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#endif
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if (procmon->e != NULL)
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tor_event_free(procmon->e);
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tor_free(procmon);
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}
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