rpc: Don't rewrite msg->fds on every read dispatch

When we are receiving data in smaller chunks it might happen that
virNetServerClientDispatchRead() will be called multiple times.  And as
that happens, if it is a message that also transfer headers, we decode
the number of them every single time and, unfortunately, also allocate
the memory for them.  That causes a leak, in the best scenario.

Best viewed with '-w'.
Signed-off-by: NMartin Kletzander <mkletzan@redhat.com>

src/rpc/virnetserverclient.c

@@ -1107,7 +1107,8 @@ static void virNetServerClientDispatchRead(virNetServerClientPtr client)
 
         /* Now figure out if we need to read more data to get some
          * file descriptors */
-        if (msg->header.type == VIR_NET_CALL_WITH_FDS &&
+        if (msg->header.type == VIR_NET_CALL_WITH_FDS) {
+            if (msg->nfds == 0 &&
                 virNetMessageDecodeNumFDs(msg) < 0) {
                 virNetMessageQueueServe(&client->rx);
                 virNetMessageFree(msg);
@@ -1138,6 +1139,7 @@ static void virNetServerClientDispatchRead(virNetServerClientPtr client)
                 client->rx->bufferOffset = client->rx->bufferLength;
                 return;
             }
+        }
 
         /* Definitely finished reading, so remove from queue */
         virNetMessageQueueServe(&client->rx);