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netfilter: bridge: detect NAT66 correctly and change MAC address

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IPv4 iptables allows to REDIRECT/DNAT/SNAT any traffic over a bridge.

e.g. REDIRECT
$ sysctl -w net.bridge.bridge-nf-call-iptables=1
$ iptables -t nat -A PREROUTING -p tcp -m tcp --dport 8080 \
  -j REDIRECT --to-ports 81

This does not work with ip6tables on a bridge in NAT66 scenario
because the REDIRECT/DNAT/SNAT is not correctly detected.

The bridge pre-routing (finish) netfilter hook has to check for a possible
redirect and then fix the destination mac address. This allows to use the
ip6tables rules for local REDIRECT/DNAT/SNAT REDIRECT similar to the IPv4
iptables version.

e.g. REDIRECT
$ sysctl -w net.bridge.bridge-nf-call-ip6tables=1
$ ip6tables -t nat -A PREROUTING -p tcp -m tcp --dport 8080 \
  -j REDIRECT --to-ports 81

This patch makes it possible to use IPv6 NAT66 on a bridge. It was tested
on a bridge with two interfaces using SNAT/DNAT NAT66 rules.

Reported-by: Artie Hamilton <artiemhamilton@yahoo.com>
Signed-off-by: Sven Eckelmann <sven@open-mesh.com>
[bernhard.thaler@wvnet.at: rebased, add indirect call to ip6_route_input()]
[bernhard.thaler@wvnet.at: rebased, split into separate patches]
Signed-off-by: Bernhard Thaler <bernhard.thaler@wvnet.at>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
This commit is contained in:
Bernhard Thaler 2015-05-30 15:27:40 +02:00 committed by Pablo Neira Ayuso
parent 8cae308d2b
commit 72b31f7271
4 changed files with 53 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/netfilter_ipv6.h
View File

@ -25,6 +25,7 @@ void ipv6_netfilter_fini(void);
struct nf_ipv6_ops {
int (*chk_addr)(struct net *net, const struct in6_addr *addr,
const struct net_device *dev, int strict);
void (*route_input)(struct sk_buff *skb);
};
extern const struct nf_ipv6_ops __rcu *nf_ipv6_ops;

6
include/linux/skbuff.h
View File

@ -36,6 +36,7 @@
#include <linux/sched.h>
#include <net/flow_dissector.h>
#include <linux/splice.h>
#include <linux/in6.h>
/* A. Checksumming of received packets by device.
*
@ -179,7 +180,10 @@ struct nf_bridge_info {
struct net_device *physoutdev;
char neigh_header[8];
};
__be32 ipv4_daddr;
union {
__be32 ipv4_daddr;
struct in6_addr ipv6_daddr;
};
};
#endif

55
net/bridge/br_netfilter.c
View File

@ -326,30 +326,63 @@ static int br_nf_pre_routing_finish_bridge(struct sock *sk, struct sk_buff *skb)
static bool daddr_was_changed(const struct sk_buff *skb,
const struct nf_bridge_info *nf_bridge)
{
return ip_hdr(skb)->daddr != nf_bridge->ipv4_daddr;
switch (skb->protocol) {
case htons(ETH_P_IP):
return ip_hdr(skb)->daddr != nf_bridge->ipv4_daddr;
case htons(ETH_P_IPV6):
return memcmp(&nf_bridge->ipv6_daddr, &ipv6_hdr(skb)->daddr,
sizeof(ipv6_hdr(skb)->daddr)) != 0;
default:
return false;
}
}
/* PF_BRIDGE/PRE_ROUTING *********************************************/
/* Undo the changes made for ip6tables PREROUTING and continue the
* bridge PRE_ROUTING hook.
/* PF_BRIDGE/PRE_ROUTING: Undo the changes made for ip6tables
* PREROUTING and continue the bridge PRE_ROUTING hook. See comment
* for br_nf_pre_routing_finish(), same logic is used here but
* equivalent IPv6 function ip6_route_input() called indirectly.
*/
static int br_nf_pre_routing_finish_ipv6(struct sock *sk, struct sk_buff *skb)
{
struct nf_bridge_info *nf_bridge = nf_bridge_info_get(skb);
struct rtable *rt;
struct net_device *dev = skb->dev;
const struct nf_ipv6_ops *v6ops = nf_get_ipv6_ops();
if (nf_bridge->pkt_otherhost) {
skb->pkt_type = PACKET_OTHERHOST;
nf_bridge->pkt_otherhost = false;
}
nf_bridge->mask &= ~BRNF_NF_BRIDGE_PREROUTING;
if (daddr_was_changed(skb, nf_bridge)) {
skb_dst_drop(skb);
v6ops->route_input(skb);
rt = bridge_parent_rtable(nf_bridge->physindev);
if (!rt) {
kfree_skb(skb);
return 0;
if (skb_dst(skb)->error) {
kfree_skb(skb);
return 0;
}
if (skb_dst(skb)->dev == dev) {
skb->dev = nf_bridge->physindev;
nf_bridge_update_protocol(skb);
nf_bridge_push_encap_header(skb);
NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING,
sk, skb, skb->dev, NULL,
br_nf_pre_routing_finish_bridge,
1);
return 0;
}
ether_addr_copy(eth_hdr(skb)->h_dest, dev->dev_addr);
skb->pkt_type = PACKET_HOST;
} else {
rt = bridge_parent_rtable(nf_bridge->physindev);
if (!rt) {
kfree_skb(skb);
return 0;
}
skb_dst_set_noref(skb, &rt->dst);
}
skb_dst_set_noref(skb, &rt->dst);
skb->dev = nf_bridge->physindev;
nf_bridge_update_protocol(skb);
@ -579,6 +612,7 @@ static unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
struct sk_buff *skb,
const struct nf_hook_state *state)
{
struct nf_bridge_info *nf_bridge;
const struct ipv6hdr *hdr;
u32 pkt_len;
@ -610,6 +644,9 @@ static unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
if (!setup_pre_routing(skb))
return NF_DROP;
nf_bridge = nf_bridge_info_get(skb);
nf_bridge->ipv6_daddr = ipv6_hdr(skb)->daddr;
skb->protocol = htons(ETH_P_IPV6);
NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, state->sk, skb,
skb->dev, NULL,

1
net/ipv6/netfilter.c
View File

@ -191,6 +191,7 @@ static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
static const struct nf_ipv6_ops ipv6ops = {
.chk_addr = ipv6_chk_addr,
.route_input = ip6_route_input
};
static const struct nf_afinfo nf_ip6_afinfo = {