rconn: Discard messages received on monitor connections.

Otherwise, if a monitor connection happens to be talking to a (misguided?)
peer that sends it messages, such as replies to what the peer perceives as
echo requests meant for it, then the peer will eventually hang trying to
send data because the monitor connection never sinks it.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Acked-by: Ethan Jackson <ethan@nicira.com>

1 files changed, 15 insertions, 1 deletions

diff --git a/lib/rconn.c b/lib/rconn.c
index d7bb0be21..4922a5c65 100644
--- a/lib/rconn.c
+++ b/lib/rconn.c
@@ -513,8 +513,21 @@ rconn_run(struct rconn *rc)
     if (rc->vconn) {
         vconn_run(rc->vconn);
     }
-    for (i = 0; i < rc->n_monitors; i++) {
+    for (i = 0; i < rc->n_monitors; ) {
+        struct ofpbuf *msg;
+        int retval;
+
         vconn_run(rc->monitors[i]);
+
+        /* Drain any stray message that came in on the monitor connection. */
+        retval = vconn_recv(rc->monitors[i], &msg);
+        if (!retval) {
+            ofpbuf_delete(msg);
+        } else if (retval != EAGAIN) {
+            close_monitor(rc, i, retval);
+            continue;
+        }
+        i++;
     }
 
     do {
@@ -545,6 +558,7 @@ rconn_run_wait(struct rconn *rc)
     }
     for (i = 0; i < rc->n_monitors; i++) {
         vconn_run_wait(rc->monitors[i]);
+        vconn_recv_wait(rc->monitors[i]);
     }
 
     timeo = timeout(rc);