From a752c0a4524889cdc0765925258fd1fd72344100 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Linus=20L=C3=BCssing?= Date: Thu, 22 Mar 2018 00:21:32 +0100 Subject: [PATCH] batman-adv: fix packet loss for broadcasted DHCP packets to a server MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit DHCP connectivity issues can currently occur if the following conditions are met: 1) A DHCP packet from a client to a server 2) This packet has a multicast destination 3) This destination has a matching entry in the translation table (FF:FF:FF:FF:FF:FF for IPv4, 33:33:00:01:00:02/33:33:00:01:00:03 for IPv6) 4) The orig-node determined by TT for the multicast destination does not match the orig-node determined by best-gateway-selection In this case the DHCP packet will be dropped. The "gateway-out-of-range" check is supposed to only be applied to unicasted DHCP packets to a specific DHCP server. In that case dropping the the unicasted frame forces the client to retry via a broadcasted one, but now directed to the new best gateway. A DHCP packet with broadcast/multicast destination is already ensured to always be delivered to the best gateway. Dropping a multicasted DHCP packet here will only prevent completing DHCP as there is no other fallback. So far, it seems the unicast check was implicitly performed by expecting the batadv_transtable_search() to return NULL for multicast destinations. However, a multicast address could have always ended up in the translation table and in fact is now common. To fix this potential loss of a DHCP client-to-server packet to a multicast address this patch adds an explicit multicast destination check to reliably bail out of the gateway-out-of-range check for such destinations. The issue and fix were tested in the following three node setup: - Line topology, A-B-C - A: gateway client, DHCP client - B: gateway server, hop-penalty increased: 30->60, DHCP server - C: gateway server, code modifications to announce FF:FF:FF:FF:FF:FF Without this patch, A would never transmit its DHCP Discover packet due to an always "out-of-range" condition. With this patch, a full DHCP handshake between A and B was possible again. Fixes: be7af5cf9cae ("batman-adv: refactoring gateway handling code") Signed-off-by: Linus Lüssing Signed-off-by: Sven Eckelmann Signed-off-by: Simon Wunderlich --- net/batman-adv/gateway_client.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/net/batman-adv/gateway_client.c b/net/batman-adv/gateway_client.c index 37fe9a6..808d2dd 100644 --- a/net/batman-adv/gateway_client.c +++ b/net/batman-adv/gateway_client.c @@ -746,7 +746,7 @@ bool batadv_gw_out_of_range(struct batadv_priv *bat_priv, { struct batadv_neigh_node *neigh_curr = NULL; struct batadv_neigh_node *neigh_old = NULL; - struct batadv_orig_node *orig_dst_node; + struct batadv_orig_node *orig_dst_node = NULL; struct batadv_gw_node *gw_node = NULL; struct batadv_gw_node *curr_gw = NULL; struct batadv_neigh_ifinfo *curr_ifinfo, *old_ifinfo; @@ -757,6 +757,9 @@ bool batadv_gw_out_of_range(struct batadv_priv *bat_priv, vid = batadv_get_vid(skb, 0); + if (is_multicast_ether_addr(ethhdr->h_dest)) + goto out; + orig_dst_node = batadv_transtable_search(bat_priv, ethhdr->h_source, ethhdr->h_dest, vid); if (!orig_dst_node) -- 2.7.4