From 2cc1e9eb153d0c2d64cb0fb0747063ba63472925 Mon Sep 17 00:00:00 2001 From: Andreas Pape apape@phoenixcontact.com Date: Fri, 12 Feb 2016 13:19:25 +0100 Subject: [PATCH 3/4] batman-adv: prevent duplication of ARP replies in BLA setups when DAT does address resolution

This patch covers the case of a bla setup with enabled dat if none of the common gateways of the same backbone has already knowledge of the searched ip address and therefore has to ask via DAT some of the other mesh nodes. A broadcast arp request is coming from the backbone and each backbone gateway starts an address resolution via other DAT mesh nodes. In this case it should be prevented, that multiple answers from DAT enabled mesh nodes reach the backbone gateways leading to multiple replies in a common backbone again.

Signed-off-by: Andreas Pape apape@phoenixcontact.com --- net/batman-adv/distributed-arp-table.c | 56 +++++++++++++++++++++++++++++++- 1 files changed, 55 insertions(+), 1 deletions(-)

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c index 4e64e6c..22976fb 100644 --- a/net/batman-adv/distributed-arp-table.c +++ b/net/batman-adv/distributed-arp-table.c @@ -1080,6 +1080,8 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv, u8 *hw_src; struct sk_buff *skb_new; struct batadv_dat_entry *dat_entry = NULL; + struct batadv_unicast_4addr_packet *unicast_4addr_packet; + struct batadv_orig_node *orig_node = NULL; bool ret = false; unsigned short vid; int err; @@ -1103,8 +1105,31 @@ bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv, batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid);

dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst, vid); - if (!dat_entry) + if (!dat_entry) { + /* Check if this is a 4addr unicast DAT_DHT_GET frame from + * another backbone gw of the same backbone. If yes, drop + * it as this leads to multiplication of arp requests in bla setups + * as long as there is no dat_entry fo this answer. In this + * case better drop the DHT_GET. Normal bla code doesn't take care of + * these packets as they are tunneled via unicast. + */ + unicast_4addr_packet = (struct batadv_unicast_4addr_packet *)skb->data; + orig_node = batadv_orig_hash_find(bat_priv, unicast_4addr_packet->src); + if (orig_node) { + if ((unicast_4addr_packet->u.packet_type == BATADV_UNICAST_4ADDR) && + (unicast_4addr_packet->subtype == BATADV_P_DAT_DHT_GET) && + (batadv_bla_is_backbone_gw(skb, orig_node, hdr_size))) { + batadv_dbg(BATADV_DBG_DAT, bat_priv, "Doubled ARP request removed: " + "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]; originator: %pM\n", + hw_src, &ip_src, batadv_arp_hw_dst(skb, hdr_size), &ip_dst, + unicast_4addr_packet->src); + ret = true; + } + batadv_orig_node_put(orig_node); + } + goto out; + }

skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src, bat_priv->soft_iface, ip_dst, hw_src, @@ -1203,6 +1228,7 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv, __be32 ip_src, ip_dst; u8 *hw_src, *hw_dst; bool dropped = false; + struct batadv_dat_entry *dat_entry = NULL; unsigned short vid;

if (!atomic_read(&bat_priv->distributed_arp_table)) @@ -1222,12 +1248,38 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv, hw_dst = batadv_arp_hw_dst(skb, hdr_size); ip_dst = batadv_arp_ip_dst(skb, hdr_size);

+ /* If ip_dst is already in cache and has the right mac address, + * drop this frame if this ARP reply is destined for us. We have + * most probably received already a reply from someone else. Delivering + * this frame would lead to doubled receive of an ARP reply. + */ + dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_src, vid); + if ((dat_entry) && (batadv_compare_eth(hw_src, dat_entry->mac_addr))) { + batadv_dbg(BATADV_DBG_DAT, bat_priv, "Doubled ARP reply removed: " + "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]; dat_entry: %pM-%pI4\n", + hw_src, &ip_src, hw_dst, &ip_dst, dat_entry->mac_addr, &dat_entry->ip); + dropped = true; + goto out; + } + /* Update our internal cache with both the IP addresses the node got * within the ARP reply */ batadv_dat_entry_add(bat_priv, ip_src, hw_src, vid); batadv_dat_entry_add(bat_priv, ip_dst, hw_dst, vid);

+ /* If BLA is enabled, only forward ARP replies if we have claimed the source of + * the ARP reply or if no one else of the same backbone has already claimed + * that client. This prevents that different gateways to the same backbone all + * forward the ARP reply leading to multiple replies in the backbone. + */ + if (!batadv_bla_check_local_claim(bat_priv, hw_src, vid)) { + batadv_dbg(BATADV_DBG_DAT, bat_priv, "Device %pM claimed by another backbone" + " gw. Drop ARP reply.\n", hw_src); + dropped = true; + goto out; + } + /* if this REPLY is directed to a client of mine, let's deliver the * packet to the interface */ @@ -1240,6 +1292,8 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv, out: if (dropped) kfree_skb(skb); + if (dat_entry) + batadv_dat_entry_put(dat_entry); /* if dropped == false -> deliver to the interface */ return dropped; } -- 1.7.0.4

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