Implement handling of seqno requests

src/babel.h

@@ -154,6 +154,12 @@ static inline bool gp_babel_node_id_is_unspec(const gp_babel_node_id_t *id) {
 	return gp_babel_node_id_equal(id, &gp_babel_node_id_unspec);
 };
 
+static inline bool gp_babel_less(uint16_t a, uint16_t b) {
+	int16_t diff = a - b;
+
+	return (diff < 0);
+}
+
 static inline bool gp_babel_is_metric_better(gp_babel_metric_seqno_t ms1, gp_babel_metric_seqno_t ms2) {
 	if (ms1.metric == GP_BABEL_INFINITY)
 		return false;

src/send.c

@@ -236,6 +236,7 @@ void gp_babel_send_seqno_request(gmrf_context_t *ctx, gp_babel_neigh_t *neigh, g
 
 	req->seqno = htons(seqno);
 	req->hop_count = hop_count;
+	req->reserved = 0;
 	req->node = announce->node;
 	req->type = htons(announce->type);
 	req->key = htons(announce->key);

src/tlv_types.c

@@ -218,6 +218,55 @@ static void handle_tlv_update(gmrf_context_t *ctx, const gp_babel_tlv_update_t *
 	gp_babel_announce_update_nexthop(ctx, announce, nexthop, ms, ntohs(tlv_update->interval));
 }
 
+static void handle_tlv_seqno_req(gmrf_context_t *ctx, const gp_babel_tlv_seqno_req_t *tlv_seqno_req, size_t len, handle_tlv_arg_t *arg) {
+	if (len < sizeof(gp_babel_tlv_seqno_req_t)) {
+		gmrf_logf(ctx->gmrf, LOG_WARNING, "received short seqno request TLV.");
+		return;
+	}
+
+	gp_babel_announce_t *announce = gp_babel_announce_get(ctx, &tlv_seqno_req->node, ntohs(tlv_seqno_req->type), ntohs(tlv_seqno_req->key));
+	if (!announce || !announce->selected) {
+		gmrf_logf(ctx->gmrf, LOG_DEBUG, "received seqno request for unknown/unreachable announce.");
+		return;
+	}
+
+	gmrf_logf(ctx->gmrf, LOG_DEBUG, "seqno request received for %04x%04x, seqno %04x.",
+		  ntohl(*(uint32_t*)tlv_seqno_req->node.id), ntohl(*(uint32_t*)(tlv_seqno_req->node.id+4)),
+		  ntohs(tlv_seqno_req->seqno));
+
+	gp_babel_neigh_t *neigh = get_tlv_neigh(arg);
+
+	if (!gp_babel_less(announce->metric.seqno, ntohs(tlv_seqno_req->seqno))) {
+		/* local seqno is high enough */
+		gmrf_logf(ctx->gmrf, LOG_DEBUG, "sending update.");
+		gp_babel_send_update(ctx, arg->iface, neigh, announce, false);
+		return;
+	}
+
+	if (!announce->selected->neigh) {
+		/* announce is local, increment seqno */
+		gmrf_logf(ctx->gmrf, LOG_DEBUG, "incrementing seqno.");
+		announce->selected->metric_seqno.seqno++;
+
+		gp_babel_send_update(ctx, arg->iface, neigh, announce, false);
+		return;
+	}
+
+	if (tlv_seqno_req->hop_count < 2) {
+		gmrf_logf(ctx->gmrf, LOG_DEBUG, "hopcount too low, discarding.");
+		return;
+	}
+
+	if (announce->selected->neigh == neigh) {
+		gmrf_logf(ctx->gmrf, LOG_DEBUG, "not forwarding backwards.");
+		return;
+	}
+
+	/* forward request */
+	gmrf_logf(ctx->gmrf, LOG_DEBUG, "forwarding request.");
+	gp_babel_send_seqno_request(ctx, announce->selected->neigh, announce, ntohs(tlv_seqno_req->seqno), tlv_seqno_req->hop_count-1);
+}
+
 static void handle_tlv(gmrf_context_t *ctx, gp_babel_tlv_type_t type, const void *data, size_t len, void *arg) {
 	handle_tlv_arg_t *tlv_arg = arg;
 
@@ -246,6 +295,10 @@ static void handle_tlv(gmrf_context_t *ctx, gp_babel_tlv_type_t type, const void
 		handle_tlv_update(ctx, data, len, tlv_arg);
 		return;
 
+	case TLV_SEQNO_REQ:
+		handle_tlv_seqno_req(ctx, data, len, tlv_arg);
+		return;
+
 	default:
 		gmrf_logf(ctx->gmrf, LOG_DEBUG, "received unknown TLV %u on %s.", type, gmrf_iface_get_name(ctx->gmrf, tlv_arg->iface->gmrf_iface));
 		return;