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Commit f216f082 authored by Bart De Schuymer's avatar Bart De Schuymer Committed by David S. Miller
Browse files

[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 <ytht.net@gmail.com> for
reporting this problem.

This is probably a candidate for the -stable release.

Signed-off-by: default avatarBart De Schuymer <bdschuym@pandora.be>
Signed-off-by: default avatarPatrick McHardy <kaber@trash.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ece00641

net/bridge/br_netfilter.c

+28 −8
Original line number Diff line number Diff line
@@ -34,6 +34,7 @@ 
#include <linux/netfilter_ipv6.h>

#include <linux/netfilter_arp.h>

#include <linux/in_route.h>

#include <linux/inetdevice.h>



#include <net/ip.h>

#include <net/ipv6.h>
@@ -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 {