[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: Bart De Schuymer <bdschuym@pandora.be> Signed-off-by: Patrick McHardy <kaber@trash.net> Signed-off-by: David S. Miller <davem@davemloft.net>
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@ -34,6 +34,7 @@
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#include <linux/netfilter_ipv6.h>
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#include <linux/netfilter_arp.h>
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#include <linux/in_route.h>
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#include <linux/inetdevice.h>
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#include <net/ip.h>
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#include <net/ipv6.h>
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@ -221,10 +222,14 @@ static void __br_dnat_complain(void)
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*
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* Otherwise, the packet is considered to be routed and we just
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* change the destination MAC address so that the packet will
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* later be passed up to the IP stack to be routed.
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* later be passed up to the IP stack to be routed. For a redirected
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* packet, ip_route_input() will give back the localhost as output device,
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* which differs from the bridge device.
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*
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* Let us now consider the case that ip_route_input() fails:
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*
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* This can be because the destination address is martian, in which case
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* the packet will be dropped.
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* After a "echo '0' > /proc/sys/net/ipv4/ip_forward" ip_route_input()
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* will fail, while __ip_route_output_key() will return success. The source
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* address for __ip_route_output_key() is set to zero, so __ip_route_output_key
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@ -237,7 +242,8 @@ static void __br_dnat_complain(void)
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*
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* --Lennert, 20020411
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* --Bart, 20020416 (updated)
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* --Bart, 20021007 (updated) */
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* --Bart, 20021007 (updated)
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* --Bart, 20062711 (updated) */
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static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
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{
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if (skb->pkt_type == PACKET_OTHERHOST) {
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@ -264,15 +270,15 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb)
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struct net_device *dev = skb->dev;
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struct iphdr *iph = skb->nh.iph;
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struct nf_bridge_info *nf_bridge = skb->nf_bridge;
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int err;
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if (nf_bridge->mask & BRNF_PKT_TYPE) {
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skb->pkt_type = PACKET_OTHERHOST;
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nf_bridge->mask ^= BRNF_PKT_TYPE;
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}
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nf_bridge->mask ^= BRNF_NF_BRIDGE_PREROUTING;
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if (dnat_took_place(skb)) {
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if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev)) {
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if ((err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev))) {
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struct rtable *rt;
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struct flowi fl = {
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.nl_u = {
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@ -283,19 +289,33 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb)
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},
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.proto = 0,
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};
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struct in_device *in_dev = in_dev_get(dev);
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/* If err equals -EHOSTUNREACH the error is due to a
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* martian destination or due to the fact that
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* forwarding is disabled. For most martian packets,
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* ip_route_output_key() will fail. It won't fail for 2 types of
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* martian destinations: loopback destinations and destination
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* 0.0.0.0. In both cases the packet will be dropped because the
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* destination is the loopback device and not the bridge. */
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if (err != -EHOSTUNREACH || !in_dev || IN_DEV_FORWARD(in_dev))
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goto free_skb;
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if (!ip_route_output_key(&rt, &fl)) {
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/* - Bridged-and-DNAT'ed traffic doesn't
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* require ip_forwarding.
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* - Deal with redirected traffic. */
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if (((struct dst_entry *)rt)->dev == dev ||
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rt->rt_type == RTN_LOCAL) {
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* require ip_forwarding. */
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if (((struct dst_entry *)rt)->dev == dev) {
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skb->dst = (struct dst_entry *)rt;
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goto bridged_dnat;
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}
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/* we are sure that forwarding is disabled, so printing
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* this message is no problem. Note that the packet could
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* still have a martian destination address, in which case
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* the packet could be dropped even if forwarding were enabled */
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__br_dnat_complain();
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dst_release((struct dst_entry *)rt);
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}
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free_skb:
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kfree_skb(skb);
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return 0;
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} else {
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