[RFC,7/7] batman-adv: add bonding again

diff --git a/routing.c b/routing.c
index c1b6d85..87591b6 100644
--- a/routing.c
+++ b/routing.c
@@ -403,9 +403,15 @@  static int batadv_check_unicast_packet(struct batadv_priv *bat_priv,
 struct batadv_neigh_node *
 batadv_find_router(struct batadv_priv *bat_priv,
 		   struct batadv_orig_node *orig_node,
-		   const struct batadv_hard_iface *recv_if)
+		   struct batadv_hard_iface *recv_if)
 {
-	struct batadv_neigh_node *router;
+	struct batadv_neigh_node *router, *cand_router,
+				 *first_candidate_router = NULL,
+				 *next_candidate_router;
+	struct batadv_neigh_node_ifinfo *router_ifinfo, *cand_ifinfo;
+	struct batadv_orig_node_ifinfo *cand, *first_candidate = NULL,
+				       *next_candidate = NULL;
+	bool last_candidate_found = false;
 
 	if (!orig_node)
 		return NULL;
@@ -414,7 +420,99 @@  batadv_find_router(struct batadv_priv *bat_priv,
 	if (!router)
 		return NULL;
 
-	/* TODO: fill this later with new bonding mechanism */
+	/* only consider bonding for recv_if == NULL (first hop) and if
+	 * activated.
+	 */
+	if (recv_if || !atomic_read(&bat_priv->bonding))
+		return router;
+
+	/* bonding: loop through the list of possible routers found
+	 * for the various outgoing interfaces and find a candidate after
+	 * the last chosen bonding candidate (next_candidate). If no such
+	 * router is found, use the first candidate found (the last chosen
+	 * bonding candidate might have been the last one in the list).
+	 * If this can't be found either, return the previously choosen
+	 * router - obviously there are no other candidates.
+	 */
+	rcu_read_lock();
+	router_ifinfo = batadv_neigh_node_get_ifinfo(router, recv_if);
+	hlist_for_each_entry_rcu(cand, &orig_node->ifinfo_list,
+				 list) {
+		cand_router = rcu_dereference(cand->router);
+		if (!cand_router)
+			continue;
+
+		if (!atomic_inc_not_zero(&cand_router->refcount))
+			continue;
+
+		cand_ifinfo = batadv_neigh_node_get_ifinfo(cand_router,
+							   cand->if_outgoing);
+		if (!cand_ifinfo)
+			goto next;
+
+		/* alternative candidate should be good enough to be
+		 * considered
+		 */
+		if (cand_ifinfo->tq_avg <
+		    (router_ifinfo->tq_avg - BATADV_BONDING_TQ_THRESHOLD))
+			goto next;
+
+		/* don't use the same router twice */
+		if (orig_node->last_bonding_candidate &&
+		    (orig_node->last_bonding_candidate->router ==
+		     cand_router))
+				goto next;
+
+		/* mark the first possible candidate */
+		if (!first_candidate) {
+			atomic_inc(&cand_router->refcount);
+			first_candidate = cand;
+			first_candidate_router = cand_router;
+		}
+
+		/* check if already passed the next candidate ... this function
+		 * should get the next candidate AFTER the last used bonding
+		 * candidate.
+		 */
+		if (orig_node->last_bonding_candidate) {
+			if (orig_node->last_bonding_candidate == cand) {
+				last_candidate_found = true;
+				goto next;
+			}
+
+			if (!last_candidate_found)
+				goto next;
+		}
+
+		next_candidate = cand;
+		next_candidate_router = cand_router;
+		break;
+next:
+		batadv_neigh_node_free_ref(cand_router);
+	}
+
+	if (next_candidate) {
+		/* found a possible candidate after the last chosen bonding
+		 * candidate, return it.
+		 */
+		batadv_neigh_node_free_ref(router);
+		if (first_candidate)
+			batadv_neigh_node_free_ref(first_candidate_router);
+		router = next_candidate_router;
+		orig_node->last_bonding_candidate = next_candidate;
+	} else if (first_candidate) {
+		/* found no possible candidate after the last candidate, return
+		 * the first candidate if available, or the already selected
+		 * router otherwise.
+		 */
+		batadv_neigh_node_free_ref(router);
+		router = first_candidate_router;
+		orig_node->last_bonding_candidate = first_candidate;
+	} else {
+		orig_node->last_bonding_candidate = NULL;
+	}
+
+	rcu_read_unlock();
 
 	return router;
 }
diff --git a/routing.h b/routing.h
index 7a7c6e9..2c80b6a 100644
--- a/routing.h
+++ b/routing.h
@@ -46,7 +46,7 @@  int batadv_recv_unhandled_unicast_packet(struct sk_buff *skb,
 struct batadv_neigh_node *
 batadv_find_router(struct batadv_priv *bat_priv,
 		   struct batadv_orig_node *orig_node,
-		   const struct batadv_hard_iface *recv_if);
+		   struct batadv_hard_iface *recv_if);
 int batadv_window_protected(struct batadv_priv *bat_priv, int32_t seq_num_diff,
 			    unsigned long *last_reset);
 
diff --git a/types.h b/types.h
index 37bf7db..f043125 100644
--- a/types.h
+++ b/types.h
@@ -135,6 +135,7 @@  struct batadv_frag_list_entry {
  * @orig: originator ethernet address
  * @primary_addr: hosts primary interface address
  * @ifinfo_list: list for routers per outgoing interface
+ * @last_bonding_candidate: pointer to last ifinfo of last used router
  * @batadv_dat_addr_t:  address of the orig node in the distributed hash
  * @bcast_own: bitfield containing the number of our OGMs this orig_node
  *  rebroadcasted "back" to us (relative to last_real_seqno)
@@ -175,6 +176,7 @@  struct batadv_orig_node {
 	uint8_t orig[ETH_ALEN];
 	uint8_t primary_addr[ETH_ALEN];
 	struct hlist_head ifinfo_list;
+	struct batadv_orig_node_ifinfo *last_bonding_candidate;
 #ifdef CONFIG_BATMAN_ADV_DAT
 	batadv_dat_addr_t dat_addr;
 #endif