* calling action_xlate_ctx_init(). */
     void (*resubmit_hook)(struct action_xlate_ctx *, const struct rule *);
 
+    /* If true, the speciality of 'flow' should be checked before executing
+     * its actions.  If special_cb returns false on 'flow' rendered
+     * uninstallable and no actions will be executed. */
+    bool check_special;
+
 /* xlate_actions() initializes and uses these members.  The client might want
  * to look at them after it returns. */
 
     struct ofpbuf *odp_actions;
 
     action_xlate_ctx_init(&ctx, p, flow, packet);
+    /* Always xlate packets originated in this function. */
+    ctx.check_special = false;
     odp_actions = xlate_actions(&ctx, actions, n_actions);
 
     /* XXX Should we translate the dpif_execute() errno value into an OpenFlow
     ctx->flow = *flow;
     ctx->packet = packet;
     ctx->resubmit_hook = NULL;
+    ctx->check_special = true;
 }
 
 static struct ofpbuf *
     ctx->nf_output_iface = NF_OUT_DROP;
     ctx->recurse = 0;
     ctx->last_pop_priority = -1;
-    do_xlate_actions(in, n_in, ctx);
+
+    if (!ctx->check_special
+        || (ctx->ofproto->ofhooks->special_cb
+            && ctx->ofproto->ofhooks->special_cb(&ctx->flow, ctx->packet,
+                                                 ctx->ofproto->aux))) {
+        do_xlate_actions(in, n_in, ctx);
+    } else {
+        ctx->may_set_up_flow = false;
+    }
+
     remove_pop_action(ctx);
 
     /* Check with in-band control to see if we're allowed to set up this
     /* Set header pointers in 'flow'. */
     flow_extract(upcall->packet, flow.tun_id, flow.in_port, &flow);
 
+    if (p->ofhooks->special_cb
+        && !p->ofhooks->special_cb(&flow, upcall->packet, p->aux)) {
+        ofpbuf_delete(upcall->packet);
+        return;
+    }
+
     /* Check with in-band control to see if this packet should be sent
      * to the local port regardless of the flow table. */
     if (in_band_msg_in_hook(p->in_band, &flow, upcall->packet)) {
 static const struct ofhooks default_ofhooks = {
     default_normal_ofhook_cb,
     NULL,
+    NULL,
     NULL
 };
 
     bool (*normal_cb)(const struct flow *, const struct ofpbuf *packet,
                       struct ofpbuf *odp_actions, tag_type *,
                       uint16_t *nf_output_iface, void *aux);
+    bool (*special_cb)(const struct flow *flow, const struct ofpbuf *packet,
+                       void *aux);
     void (*account_flow_cb)(const struct flow *, tag_type tags,
                             const struct nlattr *odp_actions,
                             size_t actions_len,
 
 
 COVERAGE_DEFINE(bridge_flush);
 COVERAGE_DEFINE(bridge_process_flow);
+COVERAGE_DEFINE(bridge_process_cfm);
+COVERAGE_DEFINE(bridge_process_lacp);
 COVERAGE_DEFINE(bridge_reconfigure);
 COVERAGE_DEFINE(bridge_lacp_update);
 
                         struct ofpbuf *actions, tag_type *tags,
                         uint16_t *nf_output_iface, void *br_)
 {
-    struct iface *iface;
     struct bridge *br = br_;
 
     COVERAGE_INC(bridge_process_flow);
+    return process_flow(br, flow, packet, actions, tags, nf_output_iface);
+}
+
+static bool
+bridge_special_ofhook_cb(const struct flow *flow,
+                         const struct ofpbuf *packet, void *br_)
+{
+    struct iface *iface;
+    struct bridge *br = br_;
 
     iface = iface_from_dp_ifidx(br, flow->in_port);
 
     if (cfm_should_process_flow(flow)) {
-        if (packet && iface->cfm) {
+
+        if (iface && packet && iface->cfm) {
+            COVERAGE_INC(bridge_process_cfm);
             cfm_process_heartbeat(iface->cfm, packet);
         }
         return false;
     } else if (flow->dl_type == htons(ETH_TYPE_LACP)) {
-        if (packet) {
+
+        if (iface && packet) {
+            COVERAGE_INC(bridge_process_lacp);
             lacp_process_packet(packet, iface);
         }
         return false;
     }
 
-    return process_flow(br, flow, packet, actions, tags, nf_output_iface);
+    return true;
 }
 
 static void
 
 static struct ofhooks bridge_ofhooks = {
     bridge_normal_ofhook_cb,
+    bridge_special_ofhook_cb,
     bridge_account_flow_ofhook_cb,
     bridge_account_checkpoint_ofhook_cb,
 };