Implement last-ditch send moderation.

babel.c

@@ -607,6 +607,8 @@ add_network(char *ifname, int ifindex, int mtu,
     }
     nets[numnets].sendbuf = p;
     nets[numnets].buffered = 0;
+    nets[numnets].bucket_time = now.tv_sec;
+    nets[numnets].bucket = 0;
     numnets++;
     return &nets[numnets - 1];
 }

babel.h

@@ -70,6 +70,8 @@ struct network {
     struct timeval flush_time;
     int bufsize;
     unsigned char *sendbuf;
+    int bucket_time;
+    unsigned int bucket;
     unsigned char hello_seqno;
     unsigned int hello_interval;
     unsigned int self_update_interval;

message.c

@@ -157,6 +157,28 @@ parse_packet(const unsigned char *from, struct network *net,
     return;
 }
 
+/* Under normal circumstances, there are enough moderation mechanisms
+   elsewhere in the protocol to make sure that this last-ditch check
+   should never trigger.  But I'm superstitious. */
+
+static int
+check_bucket(struct network *net)
+{
+    if(net->bucket > 0 && now.tv_sec > net->bucket_time) {
+        net->bucket =
+            MAX(0, net->bucket - 40 * (now.tv_sec - net->bucket_time));
+    }
+
+    net->bucket_time = now.tv_sec;
+
+    if(net->bucket < 400) {
+        net->bucket++;
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
 void
 flushbuf(struct network *net)
 {
@@ -171,6 +193,7 @@ flushbuf(struct network *net)
     if(net->buffered > 0) {
         debugf("  (flushing %d buffered bytes on %s)\n",
                net->buffered, net->ifname);
+        if(check_bucket(net)) {
             memset(&sin6, 0, sizeof(sin6));
             sin6.sin6_family = AF_INET6;
             memcpy(&sin6.sin6_addr, protocol_group, 16);
@@ -182,6 +205,10 @@ flushbuf(struct network *net)
                             (struct sockaddr*)&sin6, sizeof(sin6));
             if(rc < 0)
                 perror("send");
+        } else {
+            fprintf(stderr, "Warning: bucket full, dropping packet to %s.\n",
+                    net->ifname);
+        }
     }
     VALGRIND_MAKE_MEM_UNDEFINED(net->sendbuf, net->bufsize);
     net->buffered = 0;
@@ -273,6 +300,7 @@ send_unicast_packet(struct neighbour *neigh, unsigned char *buf, int buflen)
     struct sockaddr_in6 sin6;
     int rc;
 
+    if(check_bucket(neigh->network)) {
         memset(&sin6, 0, sizeof(sin6));
         sin6.sin6_family = AF_INET6;
         memcpy(&sin6.sin6_addr, neigh->address, 16);
@@ -284,6 +312,10 @@ send_unicast_packet(struct neighbour *neigh, unsigned char *buf, int buflen)
                         (struct sockaddr*)&sin6, sizeof(sin6));
         if(rc < 0)
             perror("send(unicast)");
+    } else {
+        fprintf(stderr, "Warning: bucket full, dropping packet to %s.\n",
+                neigh->network->ifname);
+    }
 }