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

David Miller davem at davemloft.net
Mon Sep 15 21:40:09 UTC 2014


From: Bernhard Thaler <bernhard.thaler at wvnet.at>
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 at wvnet.at>
> ---
>  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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