Commit 812fa71f authored by Ido Schimmel's avatar Ido Schimmel Committed by Pablo Neira Ayuso
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netfilter: Dissect flow after packet mangling 



Netfilter tries to reroute mangled packets as a different route might
need to be used following the mangling. When this happens, netfilter
does not populate the IP protocol, the source port and the destination
port in the flow key. Therefore, FIB rules that match on these fields
are ignored and packets can be misrouted.

Solve this by dissecting the outer flow and populating the flow key
before rerouting the packet. Note that flow dissection only happens when
FIB rules that match on these fields are installed, so in the common
case there should not be a penalty.

Reported-by: default avatarMichal Soltys <msoltyspl@yandex.pl>
Signed-off-by: default avatarIdo Schimmel <idosch@nvidia.com>
Signed-off-by: default avatarPablo Neira Ayuso <pablo@netfilter.org>
parent 783003f3

net/ipv4/netfilter.c

+2 −0
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, un 
	__be32 saddr = iph->saddr;

	__u8 flags;

	struct net_device *dev = skb_dst(skb)->dev;

	struct flow_keys flkeys;

	unsigned int hh_len;



	sk = sk_to_full_sk(sk);
@@ -48,6 +49,7 @@ int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, un 
		fl4.flowi4_oif = l3mdev_master_ifindex(dev);

	fl4.flowi4_mark = skb->mark;

	fl4.flowi4_flags = flags;

	fib4_rules_early_flow_dissect(net, skb, &fl4, &flkeys);

	rt = ip_route_output_key(net, &fl4);

	if (IS_ERR(rt))

		return PTR_ERR(rt);

net/ipv6/netfilter.c

+2 −0
Original line number Diff line number Diff line
@@ -24,6 +24,7 @@ int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff 
{

	const struct ipv6hdr *iph = ipv6_hdr(skb);

	struct sock *sk = sk_to_full_sk(sk_partial);

	struct flow_keys flkeys;

	unsigned int hh_len;

	struct dst_entry *dst;

	int strict = (ipv6_addr_type(&iph->daddr) &
@@ -38,6 +39,7 @@ int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff 
	};

	int err;



	fib6_rules_early_flow_dissect(net, skb, &fl6, &flkeys);

	dst = ip6_route_output(net, sk, &fl6);

	err = dst->error;

	if (err) {