Re: [PATCH 1/1] bridge: Fix NAT66ed IPv6 packets not being bridged correctly

From: David Miller
Date: Mon Sep 15 2014 - 17:40:21 EST

From: Bernhard Thaler <bernhard.thaler@xxxxxxxx>
Date: Mon, 15 Sep 2014 23:27:28 +0200

CC:'ing netfilter-devel and the netfilter maintainer, which is
probably the primary place this patch should have been submitted.

> Ethernet frames are not bridged to correct interface when packets have
> been NAT66ed; compared to IPv4 logic in code, IPv6 code does not store
> original address (before NAT) on transmit to determine if packet was
> NAT66ed on receive to swap addresses back.
>
> Changes added in br_netfilter.c to store original address, compare
> against it and determine correct output interface. Changes needed in
> netfilter_bridge.h to store IPv6 address in pre-existing union.
> Export of ip6_route_input needed to use it in br_netfilter.c.
>
> Problem may only affect systems doing NAT66 and ethernet bridging at
> the same time. Tested in NAT66 setup on base of an ethernet bridge.
>
> Signed-off-by: Bernhard Thaler <bernhard.thaler@xxxxxxxx>
> ---
> include/linux/netfilter_bridge.h | 2 +
> net/bridge/br_netfilter.c | 136 ++++++++++++++++++++++++++++----------
> net/ipv6/route.c | 1 +
> 3 files changed, 105 insertions(+), 34 deletions(-)
>
> diff --git a/include/linux/netfilter_bridge.h b/include/linux/netfilter_bridge.h
> index 8ab1c27..3a9cdcd 100644
> --- a/include/linux/netfilter_bridge.h
> +++ b/include/linux/netfilter_bridge.h
> @@ -2,6 +2,7 @@
> #define __LINUX_BRIDGE_NETFILTER_H
>
> #include <uapi/linux/netfilter_bridge.h>
> +#include <uapi/linux/in6.h>
>
>
> enum nf_br_hook_priorities {
> @@ -79,6 +80,7 @@ static inline unsigned int nf_bridge_pad(const struct sk_buff *skb)
> struct bridge_skb_cb {
> union {
> __be32 ipv4;
> + struct in6_addr ipv6;
> } daddr;
> };
>
> diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
> index a615264..2ae3888 100644
> --- a/net/bridge/br_netfilter.c
> +++ b/net/bridge/br_netfilter.c
> @@ -35,6 +35,9 @@
> #include <net/ip.h>
> #include <net/ipv6.h>
> #include <net/route.h>
> +#include <net/ip6_route.h>
> +#include <net/flow.h>
> +#include <net/dst.h>
>
> #include <asm/uaccess.h>
> #include "br_private.h"
> @@ -42,10 +45,18 @@
> #include <linux/sysctl.h>
> #endif
>
> -#define skb_origaddr(skb) (((struct bridge_skb_cb *) \
> - (skb->nf_bridge->data))->daddr.ipv4)
> -#define store_orig_dstaddr(skb) (skb_origaddr(skb) = ip_hdr(skb)->daddr)
> -#define dnat_took_place(skb) (skb_origaddr(skb) != ip_hdr(skb)->daddr)
> +#define skb_origaddr(skb) (((struct bridge_skb_cb *)\
> + (skb->nf_bridge->data))->daddr.ipv4)
> +#define skb_origaddr_ipv6(skb) (((struct bridge_skb_cb *)\
> + (skb->nf_bridge->data))->daddr.ipv6)
> +#define store_orig_dstaddr(skb) (skb_origaddr(skb) = ip_hdr(skb)->daddr)
> +#define store_orig_dstaddr_ipv6(skb) (skb_origaddr_ipv6(skb) = \
> + ipv6_hdr(skb)->daddr)
> +#define dnat_took_place(skb) (skb_origaddr(skb) != \
> + ip_hdr(skb)->daddr)
> +#define dnat_took_place_ipv6(skb) (memcmp(&skb_origaddr_ipv6(skb), \
> + &(ipv6_hdr(skb)->daddr), \
> + sizeof(struct in6_addr)) != 0)
>
> #ifdef CONFIG_SYSCTL
> static struct ctl_table_header *brnf_sysctl_header;
> @@ -340,36 +351,6 @@ int nf_bridge_copy_header(struct sk_buff *skb)
> return 0;
> }
>
> -/* PF_BRIDGE/PRE_ROUTING *********************************************/
> -/* Undo the changes made for ip6tables PREROUTING and continue the
> - * bridge PRE_ROUTING hook. */
> -static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
> -{
> - struct nf_bridge_info *nf_bridge = skb->nf_bridge;
> - struct rtable *rt;
> -
> - 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;
> -
> - rt = bridge_parent_rtable(nf_bridge->physindev);
> - if (!rt) {
> - kfree_skb(skb);
> - return 0;
> - }
> - skb_dst_set_noref(skb, &rt->dst);
> -
> - 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, skb, skb->dev, NULL,
> - br_handle_frame_finish, 1);
> -
> - return 0;
> -}
> -
> /* Obtain the correct destination MAC address, while preserving the original
> * source MAC address. If we already know this address, we just copy it. If we
> * don't, we use the neighbour framework to find out. In both cases, we make
> @@ -527,6 +508,92 @@ bridged_dnat:
> return 0;
> }
>
> +/* PF_BRIDGE/PRE_ROUTING *********************************************
> + * Undo the changes made for ip6tables PREROUTING and continue the
> + * bridge PRE_ROUTING hook.
> + */
> +static int br_nf_pre_routing_finish_ipv6(struct sk_buff *skb)
> +{
> + struct net_device *dev = skb->dev;
> + struct ipv6hdr *iph = ipv6_hdr(skb);
> + struct nf_bridge_info *nf_bridge = skb->nf_bridge;
> + struct rtable *rt;
> + struct dst_entry *dst;
> + struct flowi6 fl6 = {
> + .flowi6_iif = skb->dev->ifindex,
> + .daddr = iph->daddr,
> + .saddr = iph->saddr,
> + .flowlabel = ip6_flowinfo(iph),
> + .flowi6_mark = skb->mark,
> + .flowi6_proto = iph->nexthdr,
> + };
> +
> + 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_ipv6(skb)) {
> + ip6_route_input(skb);
> + /* ip6_route_input is void function,
> + * no int returned as in ip4_route_input
> + * changes value of skb->_skb_refdst) on success
> + */
> + if (skb->_skb_refdst == 0) {
> + struct in_device *in_dev = __in_dev_get_rcu(dev);
> +
> + if (!in_dev || IN_DEV_FORWARD(in_dev))
> + goto free_skb;
> +
> + dst = ip6_route_output(dev_net(dev), skb->sk, &fl6);
> + if (!IS_ERR(dst)) {
> + /* - Bridged-and-DNAT'ed traffic doesn't
> + * require ip_forwarding.
> + */
> + if (dst->dev == dev) {
> + skb_dst_set(skb, dst);
> + goto bridged_dnat;
> + }
> + dst_release(dst);
> + }
> +free_skb:
> + kfree_skb(skb);
> + return 0;
> + } else {
> + if (skb_dst(skb)->dev == dev) {
> +bridged_dnat:
> + 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,
> + skb, skb->dev, NULL,
> + br_nf_pre_routing_finish_bridge,
> + 1);
> + return 0;
> + }
> + memcpy(eth_hdr(skb)->h_dest, dev->dev_addr, ETH_ALEN);
> + 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->dev = nf_bridge->physindev;
> + nf_bridge_update_protocol(skb);
> + nf_bridge_push_encap_header(skb);
> + NF_HOOK_THRESH(NFPROTO_BRIDGE, NF_BR_PRE_ROUTING, skb, skb->dev, NULL,
> + br_handle_frame_finish, 1);
> +
> + return 0;
> +}
> +
> static struct net_device *brnf_get_logical_dev(struct sk_buff *skb, const struct net_device *dev)
> {
> struct net_device *vlan, *br;
> @@ -658,6 +725,7 @@ static unsigned int br_nf_pre_routing_ipv6(const struct nf_hook_ops *ops,
> if (!setup_pre_routing(skb))
> return NF_DROP;
>
> + store_orig_dstaddr_ipv6(skb);
> skb->protocol = htons(ETH_P_IPV6);
> NF_HOOK(NFPROTO_IPV6, NF_INET_PRE_ROUTING, skb, skb->dev, NULL,
> br_nf_pre_routing_finish_ipv6);
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index f23fbd2..e328905 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1017,6 +1017,7 @@ void ip6_route_input(struct sk_buff *skb)
>
> skb_dst_set(skb, ip6_route_input_lookup(net, skb->dev, &fl6, flags));
> }
> +EXPORT_SYMBOL(ip6_route_input);
>
> static struct rt6_info *ip6_pol_route_output(struct net *net, struct fib6_table *table,
> struct flowi6 *fl6, int flags)
> --
> 1.7.10.4
>
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