Resend last ACK if it is explicitly NACKed

overlay_packet.h

@@ -33,6 +33,8 @@ struct overlay_frame {
   unsigned char ttl;
   unsigned char queue;
   char resend;
+  void *send_context;
+  int (*send_hook)(struct overlay_frame *, int seq, void *context);
   
   /* Mark which interfaces the frame has been sent on,
    so that we can ensure that broadcast frames get sent

overlay_packetformats.c

@@ -253,7 +253,7 @@ int parseEnvelopeHeader(struct decode_context *context, struct overlay_interface
     sender_interface = ob_get(buffer);
   
   if (packet_flags & PACKET_SEQ)
-    sender_seq = ob_get(buffer);
+    sender_seq = ob_get(buffer)&0xFF;
   
   if (context->sender){
     // ignore packets that have been reflected back to me

overlay_queue.c

@@ -469,10 +469,21 @@ overlay_stuff_packet(struct outgoing_packet *packet, overlay_txqueue *queue, tim
       }
     }
     
+    if (frame->send_hook){
+      // last minute check if we really want to send this frame, or track when we sent it
+      if (frame->send_hook(frame, packet->seq, frame->send_context)){
+        // drop packet
+        frame = overlay_queue_remove(queue, frame);
+        continue;
+      }
+    }
+
     if (overlay_frame_append_payload(&packet->context, packet->interface, frame, packet->buffer)){
       // payload was not queued
       goto skip;
     }
+    if (frame->sent_seq!=-1 && config.debug.overlayframes)
+      DEBUGF("Retransmitted frame from seq %d in seq %d", frame->sent_seq, packet->seq);
     frame->sent_seq = packet->seq;
     
   sent:

route_link.c

@@ -87,6 +87,7 @@ struct neighbour{
   // next link update
   time_ms_t next_neighbour_update;
   time_ms_t last_update;
+  int last_update_seq;
   time_ms_t rtt;
   int ack_counter;
 
@@ -157,6 +158,7 @@ static struct neighbour *get_neighbour(struct subscriber *subscriber, char creat
     n = emalloc_zero(sizeof(struct neighbour));
     n->subscriber = subscriber;
     n->_next = neighbours;
+    n->last_update_seq = -1;
     // TODO measure min/max rtt
     n->rtt = 120;
     neighbours = n;
@@ -565,7 +567,18 @@ static int neighbour_find_best_link(struct neighbour *n)
   return 0;
 }
 
-static int send_neighbour_link(struct neighbour *n){
+static int neighbour_link_sent(struct overlay_frame *frame, int sequence, void *context)
+{
+  struct subscriber *subscriber = context;
+  struct neighbour *neighbour = get_neighbour(subscriber, 1);
+  neighbour->last_update_seq = sequence;
+  if (config.debug.linkstate && config.debug.verbose)
+    DEBUGF("LINK STATE; ack sent to neighbour %s in seq %d", alloca_tohex_sid(subscriber->sid), sequence);
+  return 0;
+}
+
+static int send_neighbour_link(struct neighbour *n)
+{
   IN();
   if (!n->best_link)
     RETURN(-1);
@@ -582,6 +595,9 @@ static int send_neighbour_link(struct neighbour *n){
     frame->ttl=1;
     frame->queue=OQ_MESH_MANAGEMENT;
     frame->payload = ob_new();
+    frame->send_hook = neighbour_link_sent;
+    frame->send_context = n->subscriber;
+
     if (n->subscriber->reachable & REACHABLE_DIRECT && (!(n->subscriber->reachable&REACHABLE_ASSUMED))){
       frame->destination_resolved = 1;
       frame->interface = n->subscriber->interface;
@@ -907,8 +923,24 @@ int link_receive(overlay_mdp_frame *mdp)
 	version++;
 
       // process acks / nacks
+      if (ack_seq!=-1){
         overlay_queue_ack(sender, interface, ack_mask, ack_seq);
 
+        // did they miss our last ack?
+        if (neighbour->last_update_seq!=-1){
+	  int seq_delta = (ack_seq - neighbour->last_update_seq)&0xFF;
+	  if (seq_delta <= 32 && (seq_delta==0 || ack_mask&(1<<(seq_delta-1)))){
+	    neighbour->last_update_seq = -1;
+	  }else if(seq_delta < 128){
+	    // send another ack asap
+	    if (config.debug.linkstate && config.debug.verbose)
+	      DEBUGF("LINK STATE; neighbour %s missed ack %d, queue another", alloca_tohex_sid(sender->sid), neighbour->last_update_seq);
+	    neighbour->next_neighbour_update=now;
+	    update_alarm(neighbour->next_neighbour_update);
+	  }
+        }
+      }
+
       link->last_ack_seq = ack_seq;
     }
 

tests/routing

@@ -363,7 +363,7 @@ test_multi_interface() {
    wait_until multi_has_link $SIDA
 }
 
-doc_ping_unreliable="Ping over an unreliable link"
+doc_ping_unreliable="Ping over a 1-hop unreliable link"
 setup_ping_unreliable() {
   setup_servald
   assert_no_servald_processes
@@ -380,7 +380,7 @@ test_ping_unreliable() {
    wait_until path_exists +A +B
    wait_until path_exists +B +A
    set_instance +A
-   executeOk_servald mdp ping $SIDB 40
+   executeOk_servald mdp ping --interval=0.020 --timeout=1 $SIDB 500
    tfw_cat --stdout --stderr
 }