lm: Make relay label manager async

To avoid blocking zebra when it's acting as a proxy for an external
label manager.

Besides:

Fix get chunk reconnection. Socket was still being destroyed on failure,
so next attempt would never work.

Filter out unwanted messages in lm sync sock.
Until LDE client sends ZEBRA_LABEL_MANAGER_CONNECT message, zserv
doesn't know which kind of client it is, so it might enqueue unwanted
messages like interface add, interface up, etc. Changes in this commit
discard those messages in the client side in case they arrive before the
expected response.

Change function name for zclient_connect in label manager to avoid
confusion with zclient one.

Signed-off-by: ßingen <bingen@voltanet.io>

3 files changed, 97 insertions, 43 deletions

diff --git a/zebra/label_manager.c b/zebra/label_manager.c
index 7dbb36edb..08f3c3cfe 100644
--- a/zebra/label_manager.c
+++ b/zebra/label_manager.c
@@ -56,6 +56,80 @@ static void delete_label_chunk(void *val)
 	XFREE(MTYPE_LM_CHUNK, val);
 }
 
+static int relay_response_back(struct zserv *zserv)
+{
+	int ret = 0;
+	struct stream *src, *dst;
+	u_int16_t size = 0;
+	u_char marker;
+	u_char version;
+	vrf_id_t vrf_id;
+	u_int16_t resp_cmd;
+
+	src = zclient->ibuf;
+	dst = zserv->obuf;
+
+	stream_reset(src);
+
+	ret = zclient_read_header(src, zclient->sock, &size, &marker, &version,
+							  &vrf_id, &resp_cmd);
+	if (ret < 0 && errno != EAGAIN) {
+		zlog_err("%s: Error reading Label Manager response: %s", __func__,
+				 strerror(errno));
+		return -1;
+	}
+	zlog_debug("%s: Label Manager response received, %d bytes", __func__,
+			   size);
+	if (size == 0)
+		return -1;
+
+	/* send response back */
+	stream_copy(dst, src);
+	ret = writen(zserv->sock, dst->data, stream_get_endp(dst));
+	if (ret <= 0) {
+		zlog_err("%s: Error sending Label Manager response back: %s",
+				 __func__, strerror(errno));
+		return -1;
+	}
+	zlog_debug("%s: Label Manager response (%d bytes) sent back", __func__,
+			   ret);
+
+	return 0;
+}
+
+static int lm_zclient_read(struct thread *t)
+{
+	struct zserv *zserv;
+	int ret;
+
+	/* Get socket to zebra. */
+	zserv = THREAD_ARG(t);
+	zclient->t_read = NULL;
+
+	/* read response and send it back */
+	ret = relay_response_back(zserv);
+
+	return ret;
+}
+
+static int reply_error (int cmd, struct zserv *zserv, vrf_id_t vrf_id)
+{
+	struct stream *s;
+
+	s = zserv->obuf;
+	stream_reset (s);
+
+	zserv_create_header (s, cmd, vrf_id);
+
+	/* result */
+	stream_putc (s, 1);
+
+	/* Write packet size. */
+	stream_putw_at (s, 0, stream_get_endp (s));
+
+	return writen (zserv->sock, s->data, stream_get_endp (s));
+
+}
 /**
  * Receive a request to get or release a label chunk and forward it to external
  * label manager.
@@ -64,19 +138,25 @@ static void delete_label_chunk(void *val)
  * proxy.
  *
  * @param cmd Type of request (connect, get or release)
- * @param src Input buffer from zserv
+ * @param zserv
  * @return 0 on success, -1 otherwise
  */
-int zread_relay_label_manager_request(int cmd, struct zserv *zserv)
+int zread_relay_label_manager_request(int cmd, struct zserv *zserv, vrf_id_t vrf_id)
 {
 	struct stream *src, *dst;
-	int ret;
+	int ret = 0;
 
 	if (zclient->sock < 0) {
 		zlog_err("%s: Error relaying label chunk request: no zclient socket",
 				 __func__);
+		reply_error (cmd, zserv, vrf_id);
 		return -1;
 	}
+
+	/* in case there's any incoming message enqueued, read and forward it */
+	while (ret == 0)
+		ret = relay_response_back(zserv);
+
 	/* Send request to external label manager */
 	src = zserv->ibuf;
 	dst = zclient->obuf;
@@ -87,6 +167,7 @@ int zread_relay_label_manager_request(int cmd, struct zserv *zserv)
 	if (ret <= 0) {
 		zlog_err("%s: Error relaying label chunk request: %s", __func__,
 			 strerror(errno));
+		reply_error (cmd, zserv, vrf_id);
 		return -1;
 	}
 	zlog_debug("%s: Label chunk request relayed. %d bytes sent", __func__,
@@ -96,43 +177,15 @@ int zread_relay_label_manager_request(int cmd, struct zserv *zserv)
 	if (cmd == ZEBRA_RELEASE_LABEL_CHUNK)
 		return 0;
 
-	/* read response */
-	src = zclient->ibuf;
-	dst = zserv->obuf;
-
-	stream_reset(src);
-
-	u_int16_t size;
-	u_char marker;
-	u_char version;
-	vrf_id_t vrf_id;
-	u_int16_t resp_cmd;
-	ret = zclient_read_header(src, zclient->sock, &size, &marker, &version,
-				  &vrf_id, &resp_cmd);
-	if (ret < 0) {
-		zlog_err("%s: Error reading label chunk response: %s", __func__,
-			 strerror(errno));
-		return -1;
-	}
-	zlog_debug("%s: Label chunk response received, %d bytes", __func__,
-		   size);
-
-	/* send response back */
-	stream_copy(dst, src);
-	stream_copy(zserv->obuf, zclient->ibuf);
-	ret = writen(zserv->sock, dst->data, stream_get_endp(dst));
-	if (ret <= 0) {
-		zlog_err("%s: Error sending label chunk response back: %s",
-			 __func__, strerror(errno));
-		return -1;
-	}
-	zlog_debug("%s: Label chunk response (%d bytes) sent back", __func__,
-		   ret);
+	/* make sure we listen to the response */
+	if (!zclient->t_read)
+		zclient->t_read =
+			thread_add_read(zclient->master, lm_zclient_read, zserv, zclient->sock);
 
 	return 0;
 }
 
-static int zclient_connect(struct thread *t)
+static int lm_zclient_connect(struct thread *t)
 {
 	zclient->t_connect = NULL;
 
@@ -142,11 +195,15 @@ static int zclient_connect(struct thread *t)
 	if (zclient_socket_connect(zclient) < 0) {
 		zlog_err("Error connecting synchronous zclient!");
 		THREAD_TIMER_ON(zebrad.master, zclient->t_connect,
-						zclient_connect,
+						lm_zclient_connect,
 						zclient, CONNECTION_DELAY);
 		return -1;
 	}
 
+	/* make socket non-blocking */
+	if (set_nonblocking(zclient->sock) < 0)
+		zlog_warn("%s: set_nonblocking(%d) failed", __func__, zclient->sock);
+
 	return 0;
 }
 
@@ -165,7 +222,7 @@ static void lm_zclient_init(char *lm_zserv_path)
 	zclient = zclient_new(zebrad.master);
 	zclient->sock = -1;
 	zclient->t_connect = NULL;
-	zclient_connect (NULL);
+	lm_zclient_connect(NULL);
 }
 
 /**
diff --git a/zebra/label_manager.h b/zebra/label_manager.h
index 0c6a5ebc7..fd0b3b549 100644
--- a/zebra/label_manager.h
+++ b/zebra/label_manager.h
@@ -62,7 +62,7 @@ struct label_manager {
 
 bool lm_is_external;
 
-int zread_relay_label_manager_request(int cmd, struct zserv *zserv);
+int zread_relay_label_manager_request(int cmd, struct zserv *zserv, vrf_id_t vrf_id);
 void label_manager_init(char *lm_zserv_path);
 struct label_manager_chunk *assign_label_chunk(u_char proto, u_short instance,
 					       u_char keep, uint32_t size);
diff --git a/zebra/zserv.c b/zebra/zserv.c
index 3477dc36d..533678f16 100644
--- a/zebra/zserv.c
+++ b/zebra/zserv.c
@@ -1911,10 +1911,7 @@ zread_label_manager_request (int cmd, struct zserv *client, vrf_id_t vrf_id)
 
   /* external label manager */
   if (lm_is_external)
-    {
-      if (zread_relay_label_manager_request (cmd, client) != 0)
-        zsend_label_manager_connect_response (client, vrf_id, 1);
-    }
+    zread_relay_label_manager_request (cmd, client, vrf_id);
   /* this is a label manager */
   else
     {