Add --pidfile option to vde_vmnet

That way the pidfile will be owned by the user running the daemon,
and we can safely add e.g. `pkill -f /var/run/vde_vmnet.pid` to the
sudoers file.

Signed-off-by: Jan Dubois <[email protected]>

Author: jandubois

cli.c

@@ -47,6 +47,7 @@ static void print_usage(const char *argv0) {
          "specified\n");
   printf("--vmnet-interface-id=UUID           vmnet interface ID (default: "
          "random)\n");
+  printf("-p, --pidfile=PIDFILE               save pid to PIDFILE\n");
   printf("-h, --help                          display this help and exit\n");
   printf("-v, --version                       display version information and "
          "exit\n");
@@ -81,12 +82,13 @@ struct cli_options *cli_options_parse(int argc, char *argv[]) {
       {"vmnet-mask", required_argument, NULL, CLI_OPTIONS_ID_VMNET_MASK},
       {"vmnet-interface-id", required_argument, NULL,
        CLI_OPTIONS_ID_VMNET_INTERFACE_ID},
+      {"pidfile", required_argument, NULL, 'p'},
       {"help", no_argument, NULL, 'h'},
       {"version", no_argument, NULL, 'v'},
       {0, 0, 0, 0},
   };
   int opt = 0;
-  while ((opt = getopt_long(argc, argv, "hv", longopts, NULL)) != -1) {
+  while ((opt = getopt_long(argc, argv, "hvp", longopts, NULL)) != -1) {
     switch (opt) {
     case CLI_OPTIONS_ID_VDE_GROUP:
       res->vde_group = strdup(optarg);
@@ -121,6 +123,9 @@ struct cli_options *cli_options_parse(int argc, char *argv[]) {
         goto error;
       }
       break;
+    case 'p':
+      res->pidfile = strdup(optarg);
+      break;
     case 'h':
       print_usage(argv[0]);
       cli_options_destroy(res);
@@ -233,5 +238,7 @@ void cli_options_destroy(struct cli_options *x) {
     free(x->vmnet_dhcp_end);
   if (x->vmnet_mask != NULL)
     free(x->vmnet_mask);
+  if (x->pidfile != NULL)
+    free(x->pidfile);
   free(x);
 }

cli.h

@@ -20,6 +20,8 @@ struct cli_options {
   char *vmnet_mask;
   // --vmnet-interface-id, corresponds to vmnet_interface_id_key
   uuid_t vmnet_interface_id;
+  // -p, --pidfile; writes pidfile using permissions of vde_vmnet
+  char *pidfile;
   // arg
   char *vde_switch;
 };

main.c

@@ -249,6 +249,14 @@ int main(int argc, char *argv[]) {
     fprintf(stderr, "WARNING: Seems running with SETUID. This is insecure and "
                     "highly discouraged. See README.md .\n");
   }
+  int pid_fd = -1;
+  if (cliopt->pidfile != NULL) {
+    pid_fd = open(cliopt->pidfile, O_WRONLY | O_CREAT | O_EXLOCK | O_TRUNC | O_NONBLOCK, 0644);
+    if (pid_fd == -1) {
+      perror("pidfile_open");
+      goto done;
+    }
+  }
   DEBUGF("Opening VDE \"%s\" (for UNIX group \"%s\")", cliopt->vde_switch,
          cliopt->vde_group);
   struct vde_open_args vdeargs = {
@@ -274,6 +282,14 @@ int main(int argc, char *argv[]) {
     perror("malloc");
     goto done;
   }
+  if (pid_fd != -1 ) {
+    char pid[20];
+    snprintf(pid, sizeof(pid), "%u", getpid());
+    if (write(pid_fd, pid, strlen(pid)) != (ssize_t)strlen(pid)) {
+      perror("pidfile_write");
+      goto done;
+    }
+  }
   for (uint64_t i = 0;; i++) {
     DEBUGF("[VDE-to-VMNET i=%lld] Receiving from VDE", i);
     ssize_t received = vde_recv(vdeconn, buf, buf_len, 0);
@@ -312,6 +328,10 @@ int main(int argc, char *argv[]) {
   if (vdeconn != NULL) {
     vde_close(vdeconn);
   }
+  if (pid_fd != -1) {
+    unlink(cliopt->pidfile);
+    close(pid_fd);
+  }
   if (buf != NULL) {
     free(buf);
   }