[patch 14/32] NETFILTER: bridge netfilter: deal with martians correctly

Chris Wright
2006-12-09T00:09:00Z

[-- Attachment #1: netfilter-bridge-netfilter-deal-with-martians-correctly.patch --]
[-- Type: text/plain, Size: 4594 bytes --]

-stable review patch. If anyone has any objections, please let us know.
------------------

From: Bart De Schuymer <bdschuym@pandora.be>

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: Bart De Schuymer <bdschuym@pandora.be>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
---
commit bb01f827bae980efdecc33fbcdc1b90f1c355b3e
tree 432a8f2843b47ccac094efea35da6f19731ed834
parent 14f5487cb9bd34cd59360d2cac7dccac9b27e8ce
author Bart De Schuymer <bdschuym@pandora.be> Mon, 04 Dec 2006 12:19:46 +0100
committer Patrick McHardy <kaber@trash.net> Mon, 04 Dec 2006 12:19:46 +0100

net/bridge/br_netfilter.c | 36 ++++++++++++++++++++++++++++--------
1 file changed, 28 insertions(+), 8 deletions(-)

--- linux-2.6.19.orig/net/bridge/br_netfilter.c
+++ linux-2.6.19/net/bridge/br_netfilter.c
@@ -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>
@@ -222,10 +223,14 @@ 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
@@ -238,7 +243,8 @@ 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) {
@@ -265,15 +271,15 @@ 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 = {
@@ -284,19 +290,33 @@ 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 {

--