Option to forward BPDU (Ethernet control class) frames

Currently, a NORMAL action bridge drops reserved-multicast-mac addresses;
01-80-c2-00-00-[f0:ff]. A node that does not implement STP should have an
option to forward such frames.

This commit proposes to have a configuration option to allow forwarding of
BPDU class frames.  To ensure backward compatibility, this option is
disabled by default.

This config can be set using bridge's other-config column, for e.g
ovs-vsctl set bridge br0 other-config:forward-bpdu=true

Changing this option can revalidate all flows in a software-OVS
implementation (ofproto-dpif)

--------
unit tests:

------------
make config changes, test runtime behavior

-- test runtime behavior --
continuously send packets to br0 with dest-mac=01:80:c2:00:00:00

ovs-dpctl dump-flows br0
ovs-vsctl set bridge br0 other-config:forward-bpdu=true
ovs-dpctl dump-flows br0
ovs-vsctl set bridge br0 other-config:forward-bpdu=false
ovs-dpctl dump-flows br0
ovs-vsctl set bridge br0 other-config:forward-bpdu=true
ovs-dpctl dump-flows br0
ovs-vsctl remove bridge br0 other-config forward-bpdu=true
ovs-dpctl dump-flows br0

--result--
 ovs-dpctl dump-flows br0
 in_port(1),eth(src=00:0c:29:d1:39:42,dst=01:80:c2:00:00:00), packets:29550, bytes:1773000, used:0.004s, actions:drop
 ovs-vsctl set bridge br0 other-config:forward-bpdu=true

 ovs-dpctl dump-flows br0
in_port(1),eth(src=00:0c:29:d1:39:42,dst=01:80:c2:00:00:00), packets:8209, bytes:492540, used:0.000s, actions:2,0

 ovs-vsctl set bridge br0 other-config:forward-bpdu=false
 ovs-dpctl dump-flows br0
in_port(1),eth(src=00:0c:29:d1:39:42,dst=01:80:c2:00:00:00), packets:19, bytes:1140, used:0.000s, actions:drop

 ovs-vsctl set bridge br0 other-config:forward-bpdu=true
 ovs-dpctl dump-flows br0
in_port(1),eth(src=00:0c:29:d1:39:42,dst=01:80:c2:00:00:00), packets:29, bytes:1740, used:0.000s, actions:2,0

 ovs-vsctl remove bridge br0 other-config forward-bpdu=true
 ovs-dpctl dump-flows br0
in_port(1),eth(src=00:0c:29:d1:39:42,dst=01:80:c2:00:00:00), packets:0, bytes:0, used:never, actions:drop

Bug #6624
Reported-by: Niklas Andersson <nandersson@nicira.com>

4 files changed, 36 insertions, 2 deletions

diff --git a/ofproto/ofproto-dpif.c b/ofproto/ofproto-dpif.c
index 8b65becfc..f53cc430a 100644
--- a/ofproto/ofproto-dpif.c
+++ b/ofproto/ofproto-dpif.c
@@ -1395,6 +1395,14 @@ is_mirror_output_bundle(struct ofproto *ofproto_, void *aux)
     struct ofbundle *bundle = bundle_lookup(ofproto, aux);
     return bundle && bundle->mirror_out != 0;
 }
+
+static void
+forward_bpdu_changed(struct ofproto *ofproto_) 
+{
+    struct ofproto_dpif *ofproto = ofproto_dpif_cast(ofproto_);
+    /* Revalidate cached flows whenever forward_bpdu option changes. */
+    ofproto->need_revalidate = true;
+}
 
 /* Ports. */
 
@@ -3769,8 +3777,10 @@ is_admissible(struct ofproto_dpif *ofproto, const struct flow *flow,
         return false;
     }
 
-    /* Drop frames for reserved multicast addresses. */
-    if (eth_addr_is_reserved(flow->dl_dst)) {
+    /* Drop frames for reserved multicast addresses 
+     * only if forward_bpdu option is absent. */
+    if (eth_addr_is_reserved(flow->dl_dst) && 
+        !ofproto->up.forward_bpdu) {
         return false;
     }
 
@@ -4203,4 +4213,5 @@ const struct ofproto_class ofproto_dpif_class = {
     mirror_set,
     set_flood_vlans,
     is_mirror_output_bundle,
+    forward_bpdu_changed,
 };
diff --git a/ofproto/ofproto-provider.h b/ofproto/ofproto-provider.h
index 8c32e4fc3..037dbae5b 100644
--- a/ofproto/ofproto-provider.h
+++ b/ofproto/ofproto-provider.h
@@ -41,6 +41,8 @@ struct ofproto {
     unsigned flow_eviction_threshold; /* Threshold at which to begin flow
                                        * table eviction. Only affects the
                                        * ofproto-dpif implementation */
+    bool forward_bpdu;          /* Option to allow forwarding of BPDU frames
+                                 * when NORMAL action is invoked. */
     char *mfr_desc;             /* Manufacturer. */
     char *hw_desc;              /* Hardware. */
     char *sw_desc;              /* Software version. */
@@ -926,6 +928,10 @@ struct ofproto_class {
     /* Returns true if 'aux' is a registered bundle that is currently in use as
      * the output for a mirror. */
     bool (*is_mirror_output_bundle)(struct ofproto *ofproto, void *aux);
+
+    /* When the configuration option of forward_bpdu changes, this function
+     * will be invoked. */
+    void (*forward_bpdu_changed)(struct ofproto *ofproto);
 };
 
 extern const struct ofproto_class ofproto_dpif_class;
diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
index 2dd3c9f71..c94549faf 100644
--- a/ofproto/ofproto.c
+++ b/ofproto/ofproto.c
@@ -324,6 +324,7 @@ ofproto_create(const char *datapath_name, const char *datapath_type,
     ofproto->datapath_id = 0;
     ofproto_set_flow_eviction_threshold(ofproto,
                                         OFPROTO_FLOW_EVICTON_THRESHOLD_DEFAULT);
+    ofproto->forward_bpdu = false;
     ofproto->fallback_dpid = pick_fallback_dpid();
     ofproto->mfr_desc = xstrdup(DEFAULT_MFR_DESC);
     ofproto->hw_desc = xstrdup(DEFAULT_HW_DESC);
@@ -429,6 +430,21 @@ ofproto_set_flow_eviction_threshold(struct ofproto *ofproto, unsigned threshold)
     }
 }
 
+/* If forward_bpdu is true, the NORMAL action will forward frames with 
+ * reserved (e.g. STP) destination Ethernet addresses. if forward_bpdu is false,
+ * the NORMAL action will drop these frames. */
+void
+ofproto_set_forward_bpdu(struct ofproto *ofproto, bool forward_bpdu)
+{
+    bool old_val = ofproto->forward_bpdu;
+    ofproto->forward_bpdu = forward_bpdu;
+    if (old_val != ofproto->forward_bpdu) {
+        if (ofproto->ofproto_class->forward_bpdu_changed) {
+            ofproto->ofproto_class->forward_bpdu_changed(ofproto);
+        }
+    }   
+}
+
 void
 ofproto_set_desc(struct ofproto *p,
                  const char *mfr_desc, const char *hw_desc,
diff --git a/ofproto/ofproto.h b/ofproto/ofproto.h
index 4975a8d3b..e0c99eac8 100644
--- a/ofproto/ofproto.h
+++ b/ofproto/ofproto.h
@@ -160,6 +160,7 @@ void ofproto_set_extra_in_band_remotes(struct ofproto *,
                                        const struct sockaddr_in *, size_t n);
 void ofproto_set_in_band_queue(struct ofproto *, int queue_id);
 void ofproto_set_flow_eviction_threshold(struct ofproto *, unsigned threshold);
+void ofproto_set_forward_bpdu(struct ofproto *, bool forward_bpdu);
 void ofproto_set_desc(struct ofproto *,
                       const char *mfr_desc, const char *hw_desc,
                       const char *sw_desc, const char *serial_desc,