Re: [B.A.T.M.A.N.] [PATCH 5/5] batman-adv: avoid temporary routing loops by being strict on forwarded OGMs

Simon Wunderlich
2012-03-11T21:50:39Z

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Hey there,

I've tested this patch on my old ring setup which used to create temporary
routing loops, and this patch improved the situation.

Feel free to add:

Tested-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>

On Sun, Mar 11, 2012 at 06:17:53AM +0800, Marek Lindner wrote:
> 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>
> ---
> bat_iv_ogm.c | 61 ++++++++++++++++++++++++++++++---------------------------
> packet.h | 1 +
> 2 files changed, 33 insertions(+), 29 deletions(-)
>
> diff --git a/bat_iv_ogm.c b/bat_iv_ogm.c
> index 1e92e38..85617c4 100644
> --- a/bat_iv_ogm.c
> +++ b/bat_iv_ogm.c
> @@ -507,11 +507,10 @@ static void bat_iv_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->header.ttl <= 1) {
> @@ -519,41 +518,31 @@ static void bat_iv_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->header.ttl;
> tt_num_changes = batman_ogm_packet->tt_num_changes;
>
> batman_ogm_packet->header.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->header.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->header.ttl);
> + "Forwarding packet: tq: %i, ttl: %i\n",
> + batman_ogm_packet->tq, batman_ogm_packet->header.ttl);
>
> batman_ogm_packet->seqno = htonl(batman_ogm_packet->seqno);
> batman_ogm_packet->tt_crc = htons(batman_ogm_packet->tt_crc);
> @@ -949,6 +938,7 @@ static void bat_iv_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;
>
> @@ -1070,6 +1060,13 @@ static void bat_iv_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;
> @@ -1094,6 +1091,10 @@ static void bat_iv_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)) &&
> @@ -1144,7 +1145,8 @@ static void bat_iv_ogm_process(const struct ethhdr *ethhdr,
>
> /* mark direct link on incoming interface */
> bat_iv_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");
> @@ -1167,7 +1169,8 @@ static void bat_iv_ogm_process(const struct ethhdr *ethhdr,
> bat_dbg(DBG_BATMAN, bat_priv,
> "Forwarding packet: rebroadcast originator packet\n");
> bat_iv_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 02b0c87..3c4c533 100644
> --- a/packet.h
> +++ b/packet.h
> @@ -47,6 +47,7 @@ enum bat_subtype {
> #define COMPAT_VERSION 14
>
> enum batman_iv_flags {
> + NOT_BEST_NEXT_HOP = 1 << 3,
> PRIMARIES_FIRST_HOP = 1 << 4,
> VIS_SERVER = 1 << 5,
> DIRECTLINK = 1 << 6
> --
> 1.7.9.1
>
>

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