Re: [B.A.T.M.A.N.] routing loops on interconnected routers / adhoc + ethernet

[Marek Lindner <lindner_marek@yahoo.de>]

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On Sunday, March 18, 2012 07:31:57 Nicolás Echániz wrote:
> I've finally had the time to look into this again.
> 
> The routers have been updated to current OpenWRT trunk and batman-adv
> version has changed, would it be too much inconvenience for you to send
> me your patches for 2012.0.0?

Here you go.

Regards,
Marek

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From b37e92a7211aa605c2532af4c41c7082bf7a5d10 Mon Sep 17 00:00:00 2001
From: Marek Lindner <lindner_marek@yahoo.de>
Date: Thu, 1 Mar 2012 15:35:16 +0800
Subject: [PATCH 1/2] batman-adv: introduce is_single_hop_neigh variable to
 increase readability

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Acked-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
---
 bat_iv_ogm.c |   21 ++++++++++++---------
 1 files changed, 12 insertions(+), 9 deletions(-)

diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
index 3512e25..2b14828 100644
--- a/bat_iv_ogm.c
+++ b/bat_iv_ogm.c
@@ -462,9 +462,10 @@ static void bat_ogm_queue_add(struct bat_priv *bat_priv,
 }
 
 static void bat_ogm_forward(struct orig_node *orig_node,
-			    const struct ethhdr *ethhdr,
-			    struct batman_ogm_packet *batman_ogm_packet,
-			    int directlink, struct hard_iface *if_incoming)
+			       const struct ethhdr *ethhdr,
+			       struct batman_ogm_packet *batman_ogm_packet,
+			       bool is_single_hop_neigh,
+			       struct hard_iface *if_incoming)
 {
 	struct bat_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
 	struct neigh_node *router;
@@ -517,7 +518,7 @@ static void bat_ogm_forward(struct orig_node *orig_node,
 
 	/* switch of primaries first hop flag when forwarding */
 	batman_ogm_packet->flags &= ~PRIMARIES_FIRST_HOP;
-	if (directlink)
+	if (is_single_hop_neigh)
 		batman_ogm_packet->flags |= DIRECTLINK;
 	else
 		batman_ogm_packet->flags &= ~DIRECTLINK;
@@ -902,7 +903,8 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 	struct neigh_node *orig_neigh_router = NULL;
 	int has_directlink_flag;
 	int is_my_addr = 0, is_my_orig = 0, is_my_oldorig = 0;
-	int is_broadcast = 0, is_bidirectional, is_single_hop_neigh;
+	int is_broadcast = 0, is_bidirectional;
+	bool is_single_hop_neigh = false;
 	int is_duplicate;
 	uint32_t if_incoming_seqno;
 
@@ -926,8 +928,8 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 
 	has_directlink_flag = (batman_ogm_packet->flags & DIRECTLINK ? 1 : 0);
 
-	is_single_hop_neigh = (compare_eth(ethhdr->h_source,
-					   batman_ogm_packet->orig) ? 1 : 0);
+	if (compare_eth(ethhdr->h_source, batman_ogm_packet->orig))
+		is_single_hop_neigh = true;
 
 	bat_dbg(DBG_BATMAN, bat_priv,
 		"Received BATMAN packet via NB: %pM, IF: %s [%pM] "
@@ -1101,7 +1103,7 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 
 		/* mark direct link on incoming interface */
 		bat_ogm_forward(orig_node, ethhdr, batman_ogm_packet,
-				1, if_incoming);
+				is_single_hop_neigh, if_incoming);
 
 		bat_dbg(DBG_BATMAN, bat_priv, "Forwarding packet: "
 			"rebroadcast neighbor packet with direct link flag\n");
@@ -1123,7 +1125,8 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 
 	bat_dbg(DBG_BATMAN, bat_priv,
 		"Forwarding packet: rebroadcast originator packet\n");
-	bat_ogm_forward(orig_node, ethhdr, batman_ogm_packet, 0, if_incoming);
+	bat_ogm_forward(orig_node, ethhdr, batman_ogm_packet,
+			is_single_hop_neigh, if_incoming);
 
 out_neigh:
 	if ((orig_neigh_node) && (!is_single_hop_neigh))
-- 
1.7.9.1


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From dcda7aca8c2adb7d35e55ef66479941fd82c6b4e Mon Sep 17 00:00:00 2001
From: Marek Lindner <lindner_marek@yahoo.de>
Date: Sun, 11 Mar 2012 06:17:53 +0800
Subject: [PATCH 2/2] batman-adv: avoid temporary routing loops by being
 strict on forwarded OGMs

batman-adv would forward OGMs from non-besthops while replacing the the TQ
and TTL values with the values from the best hop. In certain corner cases
this leads to a temporary routing loop.
This patch changes this behavior: Only packets from best next hops are
forwarded - TQ and TTL values won't be replaced anymore. However, the protocol
needs to rebroadcast OGMs from single hop neighbors regardless of whether or
not they are the best hop. To handle this case a new flag is introduced to
alert neighboring nodes about the forwarded OGM that is not from my best
next hop. It is to be discarded by all nodes except for the one originating
the OGM.

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Acked-by: Daniele Furlan <daniele.furlan@gmail.com>
Tested-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
---
 bat_iv_ogm.c |   62 ++++++++++++++++++++++++++++++---------------------------
 packet.h     |    1 +
 2 files changed, 34 insertions(+), 29 deletions(-)

diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
index 2b14828..9143271 100644
--- a/bat_iv_ogm.c
+++ b/bat_iv_ogm.c
@@ -465,11 +465,10 @@ static void bat_ogm_forward(struct orig_node *orig_node,
 			       const struct ethhdr *ethhdr,
 			       struct batman_ogm_packet *batman_ogm_packet,
 			       bool is_single_hop_neigh,
+			       bool is_from_best_next_hop,
 			       struct hard_iface *if_incoming)
 {
 	struct bat_priv *bat_priv = netdev_priv(if_incoming->soft_iface);
-	struct neigh_node *router;
-	uint8_t in_tq, in_ttl, tq_avg = 0;
 	uint8_t tt_num_changes;
 
 	if (batman_ogm_packet->ttl <= 1) {
@@ -477,41 +476,31 @@ static void bat_ogm_forward(struct orig_node *orig_node,
 		return;
 	}
 
-	router = orig_node_get_router(orig_node);
+	if (!is_from_best_next_hop) {
+		/**
+		* Mark the forwarded packet when it is not coming from our best
+		* next hop. We still need to forward the packet for our neighbor
+		* link quality detection to work in case the packet originated
+		* from a single hop neighbor. Otherwise we can simply drop the
+		* ogm.
+		*/
+		if (is_single_hop_neigh)
+			batman_ogm_packet->flags |= NOT_BEST_NEXT_HOP;
+		else
+			return;
+	}
 
-	in_tq = batman_ogm_packet->tq;
-	in_ttl = batman_ogm_packet->ttl;
 	tt_num_changes = batman_ogm_packet->tt_num_changes;
 
 	batman_ogm_packet->ttl--;
 	memcpy(batman_ogm_packet->prev_sender, ethhdr->h_source, ETH_ALEN);
 
-	/* rebroadcast tq of our best ranking neighbor to ensure the rebroadcast
-	 * of our best tq value */
-	if (router && router->tq_avg != 0) {
-
-		/* rebroadcast ogm of best ranking neighbor as is */
-		if (!compare_eth(router->addr, ethhdr->h_source)) {
-			batman_ogm_packet->tq = router->tq_avg;
-
-			if (router->last_ttl)
-				batman_ogm_packet->ttl = router->last_ttl - 1;
-		}
-
-		tq_avg = router->tq_avg;
-	}
-
-	if (router)
-		neigh_node_free_ref(router);
-
 	/* apply hop penalty */
 	batman_ogm_packet->tq = hop_penalty(batman_ogm_packet->tq, bat_priv);
 
 	bat_dbg(DBG_BATMAN, bat_priv,
-		"Forwarding packet: tq_orig: %i, tq_avg: %i, "
-		"tq_forw: %i, ttl_orig: %i, ttl_forw: %i\n",
-		in_tq, tq_avg, batman_ogm_packet->tq, in_ttl - 1,
-		batman_ogm_packet->ttl);
+		"Forwarding packet: tq: %i, ttl: %i\n",
+		batman_ogm_packet->tq, batman_ogm_packet->ttl);
 
 	batman_ogm_packet->seqno = htonl(batman_ogm_packet->seqno);
 	batman_ogm_packet->tt_crc = htons(batman_ogm_packet->tt_crc);
@@ -905,6 +894,7 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 	int is_my_addr = 0, is_my_orig = 0, is_my_oldorig = 0;
 	int is_broadcast = 0, is_bidirectional;
 	bool is_single_hop_neigh = false;
+	bool is_from_best_next_hop = false;
 	int is_duplicate;
 	uint32_t if_incoming_seqno;
 
@@ -1029,6 +1019,13 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 		return;
 	}
 
+	if (batman_ogm_packet->flags & NOT_BEST_NEXT_HOP) {
+		bat_dbg(DBG_BATMAN, bat_priv,
+			"Drop packet: ignoring all packets not forwarded from "
+			"the best next hop (sender: %pM)\n", ethhdr->h_source);
+		return;
+	}
+
 	orig_node = get_orig_node(bat_priv, batman_ogm_packet->orig);
 	if (!orig_node)
 		return;
@@ -1053,6 +1050,10 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 	if (router)
 		router_router = orig_node_get_router(router->orig_node);
 
+	if ((router && router->tq_avg != 0) &&
+	    (compare_eth(router->addr, ethhdr->h_source)))
+		is_from_best_next_hop = true;
+
 	/* avoid temporary routing loops */
 	if (router && router_router &&
 	    (compare_eth(router->addr, batman_ogm_packet->prev_sender)) &&
@@ -1103,7 +1104,8 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 
 		/* mark direct link on incoming interface */
 		bat_ogm_forward(orig_node, ethhdr, batman_ogm_packet,
-				is_single_hop_neigh, if_incoming);
+				is_single_hop_neigh, is_from_best_next_hop,
+				if_incoming);
 
 		bat_dbg(DBG_BATMAN, bat_priv, "Forwarding packet: "
 			"rebroadcast neighbor packet with direct link flag\n");
@@ -1125,8 +1127,10 @@ static void bat_ogm_process(const struct ethhdr *ethhdr,
 
 	bat_dbg(DBG_BATMAN, bat_priv,
 		"Forwarding packet: rebroadcast originator packet\n");
+
 	bat_ogm_forward(orig_node, ethhdr, batman_ogm_packet,
-			is_single_hop_neigh, if_incoming);
+			is_single_hop_neigh, is_from_best_next_hop,
+			if_incoming);
 
 out_neigh:
 	if ((orig_neigh_node) && (!is_single_hop_neigh))
diff --git a/packet.h b/packet.h
index 4d9e54c..667ed75 100644
--- a/packet.h
+++ b/packet.h
@@ -39,6 +39,7 @@ enum bat_packettype {
 #define COMPAT_VERSION 14
 
 enum batman_flags {
+	NOT_BEST_NEXT_HOP   = 1 << 3,
 	PRIMARIES_FIRST_HOP = 1 << 4,
 	VIS_SERVER	    = 1 << 5,
 	DIRECTLINK	    = 1 << 6
-- 
1.7.9.1