Minimal fix for in-band control loop with hub.

When a hub has two switches and the controller on three of its ports,
control traffic from the controller to switch 1 is seen by switch 2 as
data traffic, and switch 2 sends it up over its OpenFlow connection.  That
control traffic is in turn seen by the switch 1 as data traffic, and so
switch 1 sends it up over its OpenFlow connection.  And so on: this is a
loop.

This commit fixes the situation by not sending up over the OpenFlow
connection traffic to the controller that arrived on the controller's
port, as well as traffic from the controller.

diff --git a/secchan/secchan.c b/secchan/secchan.c
index 25cf2d3..d45c5ea 100644 (file)
--- a/secchan/secchan.c
+++ b/secchan/secchan.c
@@ -625,18 +625,30 @@ in_band_packet_cb(struct relay *r, int half, void *in_band_)
                && is_controller_mac(flow.dl_src, in_band)) {
         /* ARP sent by controller. */
         out_port = OFPP_FLOOD;
-    } else if (is_controller_mac(flow.dl_dst, in_band)
-               && in_port == mac_learning_lookup(in_band->ml,
-                                                 controller_mac)) {
-        /* Drop controller traffic that arrives on the controller port. */
-        queue_tx(rc, in_band, make_add_flow(&flow, ntohl(opi->buffer_id),
-                                            in_band->s->max_idle, 0));
-        return true;
+    } else if (is_controller_mac(flow.dl_dst, in_band)) {
+        if (mac_learning_learn(in_band->ml, flow.dl_src, in_port)) {
+            VLOG_DBG_RL(&vrl, "learned that "ETH_ADDR_FMT" is on port %"PRIu16,
+                        ETH_ADDR_ARGS(flow.dl_src), in_port);
+        }
+
+        out_port = mac_learning_lookup(in_band->ml, controller_mac);
+        if (in_port != out_port) {
+            return false;
+        }
+
+        /* This is controller traffic that arrived on the controller port.
+         * It will get dropped below. */
+    } else if (is_controller_mac(flow.dl_src, in_band)) {
+        out_port = mac_learning_lookup(in_band->ml, flow.dl_dst);
     } else {
         return false;
     }
 
-    if (out_port != OFPP_FLOOD) {
+    if (in_port == out_port) {
+        /* The input and output port match.  Set up a flow to drop packets. */
+        queue_tx(rc, in_band, make_add_flow(&flow, ntohl(opi->buffer_id),
+                                          in_band->s->max_idle, 0));
+    } else if (out_port != OFPP_FLOOD) {
         /* The output port is known, so add a new flow. */
         queue_tx(rc, in_band,
                  make_add_simple_flow(&flow, ntohl(opi->buffer_id),