/**
* \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);
}