netmon: Network interface monitor

Monitor a network interface. If the IP address disappears, reconfigure
the interface.

3 files changed, 276 insertions, 0 deletions

diff --git a/jobmon/Makefile b/jobmon/Makefile
new file mode 100644
index 0000000..9fa9050
--- /dev/null
+++ b/jobmon/Makefile
@@ -0,0 +1,11 @@
+# Use EXTRA_FLAGS on the command line for additional options (-g, -static, etc.)
+all: netmon
+netmon: netmon.c
+	$(CC) -Wall $(CFLAGS) $(EXTRA_FLAGS) -o $@ $<
+install-netmon: netmon
+	install -m 0555 netmon    /usr/sbin/netmon
+	install -m 0555 netmon.rc /etc/rc.d/netmon
+	@echo "-> Enable netmon service manually with rcctl(8)"
+install: install-netmon
+clean:
+	rm -f netmon
diff --git a/jobmon/netmon.c b/jobmon/netmon.c
new file mode 100644
index 0000000..6c2b13b
--- /dev/null
+++ b/jobmon/netmon.c
@@ -0,0 +1,256 @@
+/*
+ * netmon --
+ *    Monitor a network interface.  If the IP address disappears, run "ifconfig <interface> inet autoconf"
+ */
+
+#include <arpa/inet.h>
+#include <errno.h>
+#include <getopt.h>
+#include <ifaddrs.h>
+#include <netinet/in.h>
+#include <signal.h>
+#include <stdarg.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/wait.h>
+#include <syslog.h>
+#include <unistd.h>
+
+#define DEFAULT_INTERVAL 10
+#define MAX_INTERVAL 3600
+
+bool foreground;
+bool use_syslog;
+#define PID_DIR "/var/run"
+#define PID_FILE "netmon.pid"
+const char *pid_file = PID_DIR"/"PID_FILE;
+
+void
+do_log (int priority, const char *msg, va_list ap) {
+   if (use_syslog) {
+      vsyslog (priority, msg, ap);
+   } else {
+      FILE *out = (priority == LOG_NOTICE ||
+                   priority == LOG_INFO ||
+                   priority == LOG_DEBUG) ? stdout : stderr;
+      vfprintf (out, msg, ap);
+      fputc ('\n', out);
+   }
+}
+
+void
+debug (const char *msg, ...) {
+   if (foreground) {
+      va_list ap;
+      va_start (ap, msg);
+      do_log (LOG_DEBUG, msg, ap);
+      va_end (ap);
+   }
+}
+
+void
+info (const char *msg, ...) {
+   va_list ap;
+   va_start (ap, msg);
+   do_log (LOG_INFO, msg, ap);
+   va_end (ap);
+}
+
+void
+error (const char *msg, ...) {
+   va_list ap;
+   va_start (ap, msg);
+   do_log (LOG_ERR, msg, ap);
+   va_end (ap);
+}
+
+void
+die (const char *msg, ...) {
+   va_list ap;
+   va_start (ap, msg);
+   do_log (LOG_ERR, msg, ap);
+   va_end (ap);
+   unlink (pid_file);
+   exit (EXIT_FAILURE);
+}
+
+
+void
+sigexit (int sig) {
+   unlink (pid_file);
+   exit (EXIT_SUCCESS);
+}
+
+
+bool
+is_up (int af, char *interface) {
+   struct ifaddrs *ifap, *ifa = NULL;
+   bool found = false;
+
+   if (getifaddrs (&ifa) == -1) die ("getifaddrs: %s", strerror (errno));
+
+   for (ifap = ifa; ifap != NULL; ifap = ifap->ifa_next) {
+      struct sockaddr *sa = ifap->ifa_addr;
+
+      if (sa->sa_family == af && ! strcmp (interface, ifap->ifa_name)) {
+         if (foreground) {
+            if (sa->sa_family == AF_INET) {
+               char addr[INET_ADDRSTRLEN] = {0};
+               debug ("%s up: %s", ifap->ifa_name, inet_ntop (AF_INET, &(((struct sockaddr_in *)sa)->sin_addr), addr, sizeof (addr)));
+            } else if (sa->sa_family == AF_INET6) {
+               char addr[INET6_ADDRSTRLEN] = {0};
+               debug ("%s up: %s", ifap->ifa_name, inet_ntop (AF_INET6, &(((struct sockaddr_in6 *)sa)->sin6_addr), addr, sizeof (addr)));
+            }
+         }
+
+         found = true;
+         goto out;
+      }
+   }
+
+  out:
+   freeifaddrs (ifa);
+
+   return found;
+}
+
+void
+configure (int af, char *interface) {
+   pid_t p, wp;
+   int status;
+   unsigned int iters = 0;
+#define MAX_ITERS 30
+
+   info ("reconfiguring %s", interface);
+
+   if ((p = fork ()) == -1) die ("fork failure: %s", strerror (errno));
+
+   if (p == 0) {
+      execl ("/sbin/ifconfig", "ifconfig", (af == AF_INET) ? "inet" : "inet6", "autoconf", NULL);
+      die ("exec failure: %s", strerror (errno));
+   }
+
+   while (1) {
+      wp = waitpid (p, &status, WNOHANG);
+
+      if (wp == -1) {
+         if (errno == ECHILD) { break; }
+         die ("waitpid failure: %s", strerror (errno));
+      } else if (wp == 0) {
+         if (iters++ > MAX_ITERS) {
+            error ("child overdue, killing and bailing");
+            kill (p, SIGTERM);
+            sleep (1);
+            kill (p, SIGKILL);
+            unlink (pid_file);
+            exit (EXIT_FAILURE);
+         }
+      } else {
+         if (WIFEXITED (status)) {
+            debug ("child exited with exit code %d", WEXITSTATUS (status));
+         } else if (WIFSIGNALED (status)) {
+            debug ("child exited with signal %d", WTERMSIG (status));
+         } else {
+            debug ("child exited with status %d", status);
+         }
+      }
+
+      sleep (1);
+   }
+}
+
+void
+help (int ec) {
+   printf ("netmon [--interval|-i <seconds>] [-4|-6] <interface>\n"
+           "\n"
+           "    Monitor a network interface and reconfigure it if it goes down\n"
+           "\n"
+           "Options:\n"
+           "    --debug|-d      run in the foreground and send output to the console\n"
+           "    --interval|-i   how frequently to check in seconds (default %u)\n"
+           "    --ipv4|-4       check for configured IPv4 address (default)\n"
+           "    --ipv6|-6       check for a configured IPv6 address instead of IPv4\n",
+           DEFAULT_INTERVAL);
+   exit (ec);
+}
+
+int
+main (int argc, char *argv[]) {
+   struct option options[] = {
+      { "interval", required_argument, NULL, 'i' },
+      { "debug",          no_argument, NULL, 'd' },
+      { "ipv4",           no_argument, NULL, '4' },
+      { "ipv6",           no_argument, NULL, '6' },
+      { "help",           no_argument, NULL, 'h' },
+      { 0, 0, 0, 0 }
+   };
+   int opt;
+   int af = AF_INET;
+   unsigned long interval = DEFAULT_INTERVAL;
+   char *interface = NULL;
+
+   while ((opt = getopt_long (argc, argv, "i:46dh", options, NULL)) != -1) {
+      switch (opt) {
+      case 'i':
+         errno = 0;
+         interval = strtoul (optarg, NULL, 10);
+         if (interval < 1 || interval > MAX_INTERVAL || errno) {
+            die ("invalid interval '%s', must be in the range [1,%u]", optarg, MAX_INTERVAL);
+         }
+         break;
+      case '4':
+         af = AF_INET;
+         break;
+      case '6':
+         af = AF_INET6;
+         break;
+      case 'd':
+         foreground = true;
+         break;
+      case 'h':
+         help (EXIT_SUCCESS);
+         break;
+      default:
+         help (EXIT_FAILURE);
+      }
+   }
+
+   if (optind >= argc) {
+      help (EXIT_FAILURE);
+   }
+
+   interface = argv[optind];
+
+   if (! foreground) {
+      if (access (PID_DIR, W_OK) == -1) die ("unable to write pid file '%s'", pid_file);
+
+      use_syslog = true;
+      if (daemon (0, 0) == -1) die ("daemon failed: %s", strerror (errno));
+
+      FILE *fp = fopen (pid_file, "w");
+      if (fp == NULL) die ("error writing pid file '%s': %s", pid_file, strerror (errno));
+      fprintf (fp, "%d\n", getpid ());
+      fclose (fp);
+
+      if (pledge ("cpath exec inet proc stdio unveil", NULL) == -1) die ("pledge: %s", strerror (errno));
+
+      if (unveil (pid_file, "c") == -1) die ("unveil %s: %s", pid_file, strerror (errno));
+      if (unveil ("/sbin", "rx") == -1) die ("unveil /sbin: %s", strerror (errno));
+      if (unveil (NULL, NULL) == -1) die ("unveil: %s", strerror (errno));
+   }
+
+   signal (SIGINT, sigexit);
+   signal (SIGTERM, sigexit);
+   signal (SIGQUIT, sigexit);
+
+   while (1) {
+      if (! is_up (af, interface)) configure (af, interface);
+      sleep ((unsigned int)interval);
+   }
+
+   return 0;
+}
diff --git a/jobmon/netmon.rc b/jobmon/netmon.rc
new file mode 100644
index 0000000..77a2ee7
--- /dev/null
+++ b/jobmon/netmon.rc
@@ -0,0 +1,9 @@
+#!/bin/ksh
+
+daemon="/usr/sbin/netmon"
+
+rc_reload=NO
+
+. /etc/rc.d/rc.subr
+
+rc_cmd $1