From mboxrd@z Thu Jan 1 00:00:00 1970 From: Patrick McHardy Subject: [NETFILTER 05/05]: bridge netfilter: deal with martians correctly Date: Mon, 4 Dec 2006 11:56:03 +0100 (MET) Message-ID: <20061204105913.6456.38138.sendpatchset@localhost.localdomain> References: <20061204105906.6456.62345.sendpatchset@localhost.localdomain> Cc: netfilter-devel@lists.netfilter.org, Patrick McHardy Return-path: To: davem@davemloft.net In-Reply-To: <20061204105906.6456.62345.sendpatchset@localhost.localdomain> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: netfilter-devel-bounces@lists.netfilter.org Errors-To: netfilter-devel-bounces@lists.netfilter.org List-Id: netfilter-devel.vger.kernel.org [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 --- commit a2c49af72d2edaa200fed12d840e9b2a37e266f5 tree dab62da592c8991515a487687aebf5da0696b48d parent b7c3fd1079bf21b37b3135466418a2576d7d5fa1 author Bart De Schuymer Mon, 04 Dec 2006 11:42:25 +0100 committer Patrick McHardy Mon, 04 Dec 2006 11:42:25 +0100 net/bridge/br_netfilter.c | 36 ++++++++++++++++++++++++++++-------- 1 files changed, 28 insertions(+), 8 deletions(-) diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c index ac47ba2..bd221ad 100644 --- a/net/bridge/br_netfilter.c +++ b/net/bridge/br_netfilter.c @@ -34,6 +34,7 @@ #include #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(stru 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(stru }, .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 {