rconn: Speed up in-band control connections, by caching the remote address.

In-band control needs to know the IP and port of the controller, so that
it can set up the correct flows to talk to that controller.  Until now,
the rconn code has only made this available when a connection was actually
in progress.  This means that, say, ARP packets will not be allowed through
when the rconn backs off.  The same is true of packets sent by switches
that access the controller through this one.

This commit makes the rconn cache the remote IP and port and local IP
across connection attempts, improving the situation.  In particular, it
reduces the overall amount of time that it takes to connect in my own
simple test case from over 10 seconds to about 2 seconds.

diff --git a/lib/rconn.c b/lib/rconn.c
index 09c0e9ddae1d17eb4750110aab87bad662cbe86f..be030d4a49d5b68c6d32794b0fde2270067a29dd 100644 (file)
--- a/lib/rconn.c
+++ b/lib/rconn.c
@@ -111,6 +111,18 @@ struct rconn {
      * a response. */
     int probe_interval;         /* Secs of inactivity before sending probe. */
 
+    /* When we create a vconn we obtain these values, to save them past the end
+     * of the vconn's lifetime.  Otherwise, in-band control will only allow
+     * traffic when a vconn is actually open, but it is nice to allow ARP to
+     * complete even between connection attempts, and it is also polite to
+     * allow traffic from other switches to go through to the controller
+     * whether or not we are connected.
+     *
+     * We don't cache the local port, because that changes from one connection
+     * attempt to the next. */
+    uint32_t local_ip, remote_ip;
+    uint16_t remote_port;
+
     /* Messages sent or received are copied to the monitor connections. */
 #define MAX_MONITORS 8
     struct vconn *monitors[8];
@@ -121,6 +133,7 @@ static unsigned int elapsed_in_this_state(const struct rconn *);
 static unsigned int timeout(const struct rconn *);
 static bool timed_out(const struct rconn *);
 static void state_transition(struct rconn *, enum state);
+static void set_vconn_name(struct rconn *, const char *name);
 static int try_send(struct rconn *);
 static int reconnect(struct rconn *);
 static void disconnect(struct rconn *, int error);
@@ -236,8 +249,7 @@ int
 rconn_connect(struct rconn *rc, const char *name)
 {
     rconn_disconnect(rc);
-    free(rc->name);
-    rc->name = xstrdup(name);
+    set_vconn_name(rc, name);
     rc->reliable = true;
     return reconnect(rc);
 }
@@ -248,8 +260,7 @@ rconn_connect_unreliably(struct rconn *rc,
 {
     assert(vconn != NULL);
     rconn_disconnect(rc);
-    free(rc->name);
-    rc->name = xstrdup(name);
+    set_vconn_name(rc, name);
     rc->reliable = false;
     rc->vconn = vconn;
     rc->last_connected = time_now();
@@ -273,8 +284,7 @@ rconn_disconnect(struct rconn *rc)
             vconn_close(rc->vconn);
             rc->vconn = NULL;
         }
-        free(rc->name);
-        rc->name = xstrdup("void");
+        set_vconn_name(rc, "void");
         rc->reliable = false;
 
         rc->backoff = 0;
@@ -323,6 +333,9 @@ reconnect(struct rconn *rc)
     rc->n_attempted_connections++;
     retval = vconn_open(rc->name, OFP_VERSION, &rc->vconn);
     if (!retval) {
+        rc->remote_ip = vconn_get_remote_ip(rc->vconn);
+        rc->local_ip = vconn_get_local_ip(rc->vconn);
+        rc->remote_port = vconn_get_remote_port(rc->vconn);
         rc->backoff_deadline = time_now() + rc->backoff;
         state_transition(rc, S_CONNECTING);
     } else {
@@ -635,20 +648,20 @@ rconn_failure_duration(const struct rconn *rconn)
     return rconn_is_connected(rconn) ? 0 : time_now() - rconn->last_admitted;
 }
 
-/* Returns the IP address of the peer, or 0 if the peer is not connected over
- * an IP-based protocol or if its IP address is not known. */
+/* Returns the IP address of the peer, or 0 if the peer's IP address is not
+ * known. */
 uint32_t
 rconn_get_remote_ip(const struct rconn *rconn) 
 {
-    return rconn->vconn ? vconn_get_remote_ip(rconn->vconn) : 0;
+    return rconn->remote_ip;
 }
 
-/* Returns the transport port of the peer, or 0 if the peer does not 
- * contain a port or if the port is not known. */
+/* Returns the transport port of the peer, or 0 if the peer's port is not
+ * known. */
 uint16_t
 rconn_get_remote_port(const struct rconn *rconn) 
 {
-    return rconn->vconn ? vconn_get_remote_port(rconn->vconn) : 0;
+    return rconn->remote_port;
 }
 
 /* Returns the IP address used to connect to the peer, or 0 if the
@@ -657,7 +670,7 @@ rconn_get_remote_port(const struct rconn *rconn)
 uint32_t
 rconn_get_local_ip(const struct rconn *rconn) 
 {
-    return rconn->vconn ? vconn_get_local_ip(rconn->vconn) : 0;
+    return rconn->local_ip;
 }
 
 /* Returns the transport port used to connect to the peer, or 0 if the
@@ -805,6 +818,19 @@ rconn_packet_counter_dec(struct rconn_packet_counter *c)
     }
 }
 \f
+/* Set the name of the remote vconn to 'name' and clear out the cached IP
+ * address and port information, since changing the name also likely changes
+ * these values. */
+static void
+set_vconn_name(struct rconn *rc, const char *name)
+{
+    free(rc->name);
+    rc->name = xstrdup(name);
+    rc->local_ip = 0;
+    rc->remote_ip = 0;
+    rc->remote_port = 0;
+}
+
 /* Tries to send a packet from 'rc''s send buffer.  Returns 0 if successful,
  * otherwise a positive errno value. */
 static int