Merge branch 'feature3049-v2' into maint-0.2.2

Conflicts:
	src/common/Makefile.am

1 files changed, 332 insertions, 0 deletions

diff --git a/src/common/procmon.c b/src/common/procmon.c
new file mode 100644
index 000000000..bd25bc10e
--- /dev/null
+++ b/src/common/procmon.c
@@ -0,0 +1,332 @@
+
+/**
+ * \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 const struct timeval poll_interval_tv = {15, 0};
+
+/** 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 %d (%s) is not 'invalid "
+                 "parameter' -- assuming the process is still alive.",
+                 procmon->pid,
+                 err_code, err_msg);
+
+      tor_free(err_msg);
+    }
+  }
+#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);
+}
+