batman-adv: tvlv - basic infrastructure

The goal is to provide the infrastructure for sending, receiving and
parsing information 'containers' while preserving backward
compatibility. TVLV (based on the commonly known Type Length Value
technique) was chosen as the format for those containers. Even if a
node does not know the tvlv type of a certain container it can simply
skip the current container and proceed with the next. Past experience
has shown features evolve over time, so a 'version' field was added
right from the start to allow differentiating between feature
variants - hence the name: T(ype) V(ersion) L(ength) V(alue).

This patch introduces the basic TVLV infrastructure:
 * register / unregister tvlv containers to be sent with each OGM
   (on primary interfaces only)
 * register / unregister callback handlers to be called upon
   finding the corresponding tvlv type in a tvlv buffer
 * unicast tvlv send / receive API calls

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Spyros Gasteratos <morfeas3000@gmail.com>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

net/batman-adv/bat_iv_ogm.c

@@ -207,12 +207,12 @@ static uint8_t batadv_hop_penalty(uint8_t tq,
 
 /* is there another aggregated packet here? */
 static int batadv_iv_ogm_aggr_packet(int buff_pos, int packet_len,
-				     int tt_num_changes)
+				     __be16 tvlv_len)
 {
 	int next_buff_pos = 0;
 
 	next_buff_pos += buff_pos + BATADV_OGM_HLEN;
-	next_buff_pos += batadv_tt_len(tt_num_changes);
+	next_buff_pos += ntohs(tvlv_len);
 
 	return (next_buff_pos <= packet_len) &&
 	       (next_buff_pos <= BATADV_MAX_AGGREGATION_BYTES);
@@ -240,7 +240,7 @@ static void batadv_iv_ogm_send_to_if(struct batadv_forw_packet *forw_packet,
 
 	/* adjust all flags and log packets */
 	while (batadv_iv_ogm_aggr_packet(buff_pos, forw_packet->packet_len,
-					 batadv_ogm_packet->tt_num_changes)) {
+					 batadv_ogm_packet->tvlv_len)) {
 		/* we might have aggregated direct link packets with an
 		 * ordinary base packet
 		 */
@@ -267,7 +267,7 @@ static void batadv_iv_ogm_send_to_if(struct batadv_forw_packet *forw_packet,
 			   hard_iface->net_dev->dev_addr);
 
 		buff_pos += BATADV_OGM_HLEN;
-		buff_pos += batadv_tt_len(batadv_ogm_packet->tt_num_changes);
+		buff_pos += ntohs(batadv_ogm_packet->tvlv_len);
 		packet_num++;
 		packet_pos = forw_packet->skb->data + buff_pos;
 		batadv_ogm_packet = (struct batadv_ogm_packet *)packet_pos;
@@ -601,7 +601,7 @@ static void batadv_iv_ogm_forward(struct batadv_orig_node *orig_node,
 				  struct batadv_hard_iface *if_incoming)
 {
 	struct batadv_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
-	uint8_t tt_num_changes;
+	uint16_t tvlv_len;
 
 	if (batadv_ogm_packet->header.ttl <= 1) {
 		batadv_dbg(BATADV_DBG_BATMAN, bat_priv, "ttl exceeded\n");
@@ -621,7 +621,7 @@ static void batadv_iv_ogm_forward(struct batadv_orig_node *orig_node,
 			return;
 	}
 
-	tt_num_changes = batadv_ogm_packet->tt_num_changes;
+	tvlv_len = ntohs(batadv_ogm_packet->tvlv_len);
 
 	batadv_ogm_packet->header.ttl--;
 	memcpy(batadv_ogm_packet->prev_sender, ethhdr->h_source, ETH_ALEN);
@@ -642,7 +642,7 @@ static void batadv_iv_ogm_forward(struct batadv_orig_node *orig_node,
 		batadv_ogm_packet->flags &= ~BATADV_DIRECTLINK;
 
 	batadv_iv_ogm_queue_add(bat_priv, (unsigned char *)batadv_ogm_packet,
-				BATADV_OGM_HLEN + batadv_tt_len(tt_num_changes),
+				BATADV_OGM_HLEN + tvlv_len,
 				if_incoming, 0, batadv_iv_ogm_fwd_send_time());
 }
 
@@ -691,16 +691,18 @@ static void batadv_iv_ogm_schedule(struct batadv_hard_iface *hard_iface)
 	int vis_server, tt_num_changes = 0;
 	uint32_t seqno;
 	uint8_t bandwidth;
+	uint16_t tvlv_len = 0;
 
 	vis_server = atomic_read(&bat_priv->vis_mode);
 	primary_if = batadv_primary_if_get_selected(bat_priv);
 
 	if (hard_iface == primary_if)
-		tt_num_changes = batadv_tt_append_diff(bat_priv, ogm_buff,
-						       ogm_buff_len,
-						       BATADV_OGM_HLEN);
+		tvlv_len = batadv_tvlv_container_ogm_append(bat_priv, ogm_buff,
+							    ogm_buff_len,
+							    BATADV_OGM_HLEN);
 
 	batadv_ogm_packet = (struct batadv_ogm_packet *)(*ogm_buff);
+	batadv_ogm_packet->tvlv_len = htons(tvlv_len);
 
 	/* change sequence number to network order */
 	seqno = (uint32_t)atomic_read(&hard_iface->bat_iv.ogm_seqno);
@@ -1254,6 +1256,8 @@ static void batadv_iv_ogm_process(const struct ethhdr *ethhdr,
 		goto out;
 	}
 
+	batadv_tvlv_ogm_receive(bat_priv, batadv_ogm_packet, orig_node);
+
 	/* if sender is a direct neighbor the sender mac equals
 	 * originator mac
 	 */
@@ -1350,9 +1354,9 @@ static int batadv_iv_ogm_receive(struct sk_buff *skb,
 	struct batadv_ogm_packet *batadv_ogm_packet;
 	struct ethhdr *ethhdr;
 	int buff_pos = 0, packet_len;
-	unsigned char *tt_buff, *packet_buff;
-	bool ret;
+	unsigned char *tvlv_buff, *packet_buff;
 	uint8_t *packet_pos;
+	bool ret;
 
 	ret = batadv_check_management_packet(skb, if_incoming, BATADV_OGM_HLEN);
 	if (!ret)
@@ -1375,14 +1379,14 @@ static int batadv_iv_ogm_receive(struct sk_buff *skb,
 
 	/* unpack the aggregated packets and process them one by one */
 	while (batadv_iv_ogm_aggr_packet(buff_pos, packet_len,
-					 batadv_ogm_packet->tt_num_changes)) {
-		tt_buff = packet_buff + buff_pos + BATADV_OGM_HLEN;
+					 batadv_ogm_packet->tvlv_len)) {
+		tvlv_buff = packet_buff + buff_pos + BATADV_OGM_HLEN;
 
-		batadv_iv_ogm_process(ethhdr, batadv_ogm_packet, tt_buff,
-				      if_incoming);
+		batadv_iv_ogm_process(ethhdr, batadv_ogm_packet,
+				      tvlv_buff, if_incoming);
 
 		buff_pos += BATADV_OGM_HLEN;
-		buff_pos += batadv_tt_len(batadv_ogm_packet->tt_num_changes);
+		buff_pos += ntohs(batadv_ogm_packet->tvlv_len);
 
 		packet_pos = packet_buff + buff_pos;
 		batadv_ogm_packet = (struct batadv_ogm_packet *)packet_pos;