+/* A veth may be created using the 'command' "+<name>,<peer>". A veth may
+ * be destroyed by using the 'command' "-<name>", where <name> can be
+ * either side of the device.
+ */
+static int
+modify_veth(const char *format, ...)
+{
+ FILE *veth_file;
+ va_list args;
+ int retval;
+
+ veth_file = fopen("/sys/class/net/veth_pairs", "w");
+ if (!veth_file) {
+ VLOG_WARN_RL(&rl, "could not open veth device. Are you running a "
+ "supported XenServer with the kernel module loaded?");
+ return ENODEV;
+ }
+ setvbuf(veth_file, NULL, _IONBF, 0);
+
+ va_start(args, format);
+ retval = vfprintf(veth_file, format, args);
+ va_end(args);
+
+ fclose(veth_file);
+ if (retval < 0) {
+ VLOG_WARN_RL(&rl, "could not destroy patch: %s", strerror(errno));
+ return errno;
+ }
+
+ return 0;
+}
+
+static int
+create_patch(const char *name, const char *peer)
+{
+ int retval;
+ struct netdev_dev *peer_nd;
+
+
+ /* Only create the veth if the peer didn't already do it. */
+ peer_nd = netdev_dev_from_name(peer);
+ if (peer_nd) {
+ if (!strcmp("patch", netdev_dev_get_type(peer_nd))) {
+ struct netdev_dev_linux *ndl = netdev_dev_linux_cast(peer_nd);
+ if (!strcmp(name, ndl->state.patch.peer)) {
+ return 0;
+ } else {
+ VLOG_WARN_RL(&rl, "peer '%s' already paired with '%s'",
+ peer, ndl->state.patch.peer);
+ return EINVAL;
+ }
+ } else {
+ VLOG_WARN_RL(&rl, "peer '%s' exists and is not a patch", peer);
+ return EINVAL;
+ }
+ }
+
+ retval = modify_veth("+%s,%s", name, peer);
+ if (retval) {
+ return retval;
+ }
+
+ retval = if_up(name);
+ if (retval) {
+ return retval;
+ }
+
+ retval = if_up(peer);
+ if (retval) {
+ return retval;
+ }
+
+ return 0;
+}
+
+static int
+setup_patch(const char *name, const struct shash *args, char **peer_)
+{
+ const char *peer;
+
+ peer = shash_find_data(args, "peer");
+ if (!peer) {
+ VLOG_WARN("patch type requires valid 'peer' argument");
+ return EINVAL;
+ }
+
+ if (shash_count(args) > 1) {
+ VLOG_WARN("patch type takes only a 'peer' argument");
+ return EINVAL;
+ }
+
+ if (strlen(peer) >= IFNAMSIZ) {
+ VLOG_WARN_RL(&rl, "patch 'peer' arg too long");
+ return EINVAL;
+ }
+
+ *peer_ = xstrdup(peer);
+ return create_patch(name, peer);
+}
+