From f216f082b2b37c4943f1e7c393e2786648d48f6f Mon Sep 17 00:00:00 2001 From: Bart De Schuymer Date: Tue, 5 Dec 2006 13:45:21 -0800 Subject: [PATCH] [NETFILTER]: bridge netfilter: deal with martians correctly The attached patch resolves an issue where a IP DNATed packet with a martian source is forwarded while it's better to drop it. It also resolves messages complaining about ip forwarding being disabled while it's actually enabled. Thanks to lepton for reporting this problem. This is probably a candidate for the -stable release. Signed-off-by: Bart De Schuymer Signed-off-by: Patrick McHardy Signed-off-by: David S. Miller --- net/bridge/br_netfilter.c | 36 ++++++++++++++++++++++++++++-------- 1 file changed, 28 insertions(+), 8 deletions(-) diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c index ac47ba2ba028..bd221ad52eaf 100644 --- a/net/bridge/br_netfilter.c +++ b/net/bridge/br_netfilter.c @@ -34,6 +34,7 @@ #include #include #include +#include #include #include @@ -221,10 +222,14 @@ static void __br_dnat_complain(void) * * Otherwise, the packet is considered to be routed and we just * change the destination MAC address so that the packet will - * later be passed up to the IP stack to be routed. + * later be passed up to the IP stack to be routed. For a redirected + * packet, ip_route_input() will give back the localhost as output device, + * which differs from the bridge device. * * Let us now consider the case that ip_route_input() fails: * + * This can be because the destination address is martian, in which case + * the packet will be dropped. * After a "echo '0' > /proc/sys/net/ipv4/ip_forward" ip_route_input() * will fail, while __ip_route_output_key() will return success. The source * address for __ip_route_output_key() is set to zero, so __ip_route_output_key @@ -237,7 +242,8 @@ static void __br_dnat_complain(void) * * --Lennert, 20020411 * --Bart, 20020416 (updated) - * --Bart, 20021007 (updated) */ + * --Bart, 20021007 (updated) + * --Bart, 20062711 (updated) */ static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb) { if (skb->pkt_type == PACKET_OTHERHOST) { @@ -264,15 +270,15 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb) struct net_device *dev = skb->dev; struct iphdr *iph = skb->nh.iph; struct nf_bridge_info *nf_bridge = skb->nf_bridge; + int err; if (nf_bridge->mask & BRNF_PKT_TYPE) { skb->pkt_type = PACKET_OTHERHOST; nf_bridge->mask ^= BRNF_PKT_TYPE; } nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING; - if (dnat_took_place(skb)) { - if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev)) { + if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) { struct rtable *rt; struct flowi fl = { .nl_u = { @@ -283,19 +289,33 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb) }, .proto = 0, }; + struct in_device *in_dev = in_dev_get(dev); + + /* If err equals -EHOSTUNREACH the error is due to a + * martian destination or due to the fact that + * forwarding is disabled. For most martian packets, + * ip_route_output_key() will fail. It won't fail for 2 types of + * martian destinations: loopback destinations and destination + * 0.0.0.0. In both cases the packet will be dropped because the + * destination is the loopback device and not the bridge. */ + if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev)) + goto free_skb; if (!ip_route_output_key(&rt, &fl)) { /* - Bridged-and-DNAT'ed traffic doesn't - * require ip_forwarding. - * - Deal with redirected traffic. */ - if (((struct dst_entry *)rt)->dev == dev || - rt->rt_type == RTN_LOCAL) { + * require ip_forwarding. */ + if (((struct dst_entry *)rt)->dev == dev) { skb->dst = (struct dst_entry *)rt; goto bridged_dnat; } + /* we are sure that forwarding is disabled, so printing + * this message is no problem. Note that the packet could + * still have a martian destination address, in which case + * the packet could be dropped even if forwarding were enabled */ __br_dnat_complain(); dst_release((struct dst_entry *)rt); } +free_skb: kfree_skb(skb); return 0; } else { -- 2.20.1