Implement sending of unicast and unscheduled IHUs.

This just implements the sending functions, it doesn't actually do anything
with them yet.

babeld.c

@@ -814,7 +814,7 @@ main(int argc, char **argv)
         send_wildcard_retraction(ifp);
         /* Make sure that we expire quickly from our neighbours'
            association caches. */
-        send_hello_noihu(ifp, 10);
+        send_multicast_hello(ifp, 10, 1);
         flushbuf(&ifp->buf, ifp);
         usleep(roughly(1000));
         gettime(&now);
@@ -824,7 +824,7 @@ main(int argc, char **argv)
             continue;
         /* Make sure they got it. */
         send_wildcard_retraction(ifp);
-        send_hello_noihu(ifp, 1);
+        send_multicast_hello(ifp, 1, 1);
         flushbuf(&ifp->buf, ifp);
         usleep(roughly(10000));
         gettime(&now);

message.c

@@ -1024,45 +1024,86 @@ send_ack(struct neighbour *neigh, unsigned short nonce, unsigned short interval)
     schedule_flush_ms(&neigh->buf, roughly(interval * 6));
 }
 
+static void
+buffer_hello(struct buffered *buf, struct interface *ifp,
+             unsigned short seqno, unsigned interval, int unicast)
+{
+    int timestamp = !!(ifp->flags & IF_TIMESTAMPS);
+    start_message(buf, ifp, MESSAGE_HELLO, timestamp ? 12 : 6);
+    buf->hello = buf->len - 2;
+    accumulate_short(buf, unicast ? 0x8000 : 0);
+    accumulate_short(buf, seqno);
+    accumulate_short(buf, interval > 0xFFFF ? 0xFFFF : interval);
+    if(timestamp) {
+        /* Sub-TLV containing the local time of emission. We use a
+           Pad4 sub-TLV, which we'll fill just before sending. */
+        accumulate_byte(buf, SUBTLV_PADN);
+        accumulate_byte(buf, 4);
+        accumulate_int(buf, 0);
+    }
+    end_message(&ifp->buf, MESSAGE_HELLO, timestamp ? 12 : 6);
+}
+
 void
-send_hello_noihu(struct interface *ifp, unsigned interval)
+send_multicast_hello(struct interface *ifp, unsigned interval, int force)
 {
+    if(!if_up(ifp))
+        return;
+
+    if(interval == 0 && (ifp->flags & IF_RFC6126) != 0)
+        /* Unscheduled hellos are incompatible with RFC 6126. */
+        return;
+
     /* This avoids sending multiple hellos in a single packet, which breaks
        link quality estimation. */
     if(ifp->buf.hello >= 0) {
-        flushupdates(ifp);
-        flushbuf(&ifp->buf, ifp);
+        if(force) {
+            flushupdates(ifp);
+            flushbuf(&ifp->buf, ifp);
+        } else {
+            return;
+        }
     }
 
     ifp->hello_seqno = seqno_plus(ifp->hello_seqno, 1);
-    set_timeout(&ifp->hello_timeout, ifp->hello_interval);
-
-    if(!if_up(ifp))
-        return;
+    if(interval > 0)
+        set_timeout(&ifp->hello_timeout, ifp->hello_interval);
 
     debugf("Sending hello %d (%d) to %s.\n",
            ifp->hello_seqno, interval, ifp->name);
 
-    start_message(&ifp->buf, ifp, MESSAGE_HELLO,
-                  (ifp->flags & IF_TIMESTAMPS) ? 12 : 6);
-    ifp->buf.hello = ifp->buf.len - 2;
-    accumulate_short(&ifp->buf, 0);
-    accumulate_short(&ifp->buf, ifp->hello_seqno);
-    accumulate_short(&ifp->buf, interval > 0xFFFF ? 0xFFFF : interval);
-    if((ifp->flags & IF_TIMESTAMPS) != 0) {
-        /* Sub-TLV containing the local time of emission. We use a
-           Pad4 sub-TLV, which we'll fill just before sending. */
-        accumulate_byte(&ifp->buf, SUBTLV_PADN);
-        accumulate_byte(&ifp->buf, 4);
-        accumulate_int(&ifp->buf, 0);
+    buffer_hello(&ifp->buf, ifp, ifp->hello_seqno, interval, 0);
+}
+
+void
+send_unicast_hello(struct neighbour *neigh, unsigned interval, int force)
+{
+    if(!if_up(neigh->ifp))
+        return;
+
+    if((neigh->ifp->flags & IF_RFC6126) != 0)
+        /* Unicast hellos are incompatible with RFC 6126. */
+        return;
+
+    if(neigh->buf.hello >= 0) {
+        if(force)
+            flushbuf(&neigh->buf, neigh->ifp);
+        else
+            return;
     }
-    end_message(&ifp->buf, MESSAGE_HELLO, (ifp->flags & IF_TIMESTAMPS) ? 12 : 6);
+
+    neigh->hello_seqno = seqno_plus(neigh->hello_seqno, 1);
+
+    debugf("Sending unicast hello %d (%d) on %s.\n",
+           neigh->hello_seqno, interval, neigh->ifp->name);
+
+    buffer_hello(&neigh->buf, neigh->ifp, neigh->hello_seqno, interval, 1);
 }
 
 void
 send_hello(struct interface *ifp)
 {
-    send_hello_noihu(ifp, (ifp->hello_interval + 9) / 10);
+    send_multicast_hello(ifp, (ifp->hello_interval + 9) / 10, 1);
     /* Send full IHU every 3 hellos, and marginal IHU each time */
     if(ifp->hello_seqno % 3 == 0)
         send_ihu(NULL, ifp);

message.h

@@ -55,7 +55,8 @@ void flushbuf(struct buffered *buf, struct interface *ifp);
 void flushupdates(struct interface *ifp);
 void send_ack(struct neighbour *neigh, unsigned short nonce,
               unsigned short interval);
-void send_hello_noihu(struct interface *ifp, unsigned interval);
+void send_multicast_hello(struct interface *ifp, unsigned interval, int force);
+void send_unicast_hello(struct neighbour *neigh, unsigned interval, int force);
 void send_hello(struct interface *ifp);
 void flush_unicast(int dofree);
 void send_update(struct interface *ifp, int urgent,

neighbour.h

@@ -32,8 +32,9 @@ struct neighbour {
     /* This is -1 when unknown, so don't make it unsigned */
     unsigned char address[16];
     struct hello_history hello;
-    struct hello_history uhello; /* for Unicast hellos */
+    struct hello_history uhello; /* for Unicast Hellos */
     unsigned short txcost;
+    unsigned short hello_seqno; /* for Unicast Hellos */
     struct timeval ihu_time;
     unsigned short ihu_interval;   /* in centiseconds */
     /* Used for RTT estimation. */