ipv6: Pass struct net into nf_ct_frag6_gather

The function nf_ct_frag6_gather is called on both the input and the
output paths of the networking stack.  In particular ipv6_defrag which
calls nf_ct_frag6_gather is called from both the the PRE_ROUTING chain
on input and the LOCAL_OUT chain on output.

The addition of a net parameter makes it explicit which network
namespace the packets are being reassembled in, and removes the need
for nf_ct_frag6_gather to guess.
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/netfilter/ipv6/nf_defrag_ipv6.h

@@ -5,7 +5,7 @@ void nf_defrag_ipv6_enable(void);
 
 int nf_ct_frag6_init(void);
 void nf_ct_frag6_cleanup(void);
-struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user);
+struct sk_buff *nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user);
 void nf_ct_frag6_consume_orig(struct sk_buff *skb);
 
 struct inet_frags_ctl;

net/ipv6/netfilter/nf_conntrack_reasm.c

@@ -563,12 +563,10 @@ find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
 	return 0;
 }
 
-struct sk_buff *nf_ct_frag6_gather(struct sk_buff *skb, u32 user)
+struct sk_buff *nf_ct_frag6_gather(struct net *net, struct sk_buff *skb, u32 user)
 {
 	struct sk_buff *clone;
 	struct net_device *dev = skb->dev;
-	struct net *net = skb_dst(skb) ? dev_net(skb_dst(skb)->dev)
-				       : dev_net(skb->dev);
 	struct frag_hdr *fhdr;
 	struct frag_queue *fq;
 	struct ipv6hdr *hdr;

net/ipv6/netfilter/nf_defrag_ipv6_hooks.c

@@ -63,7 +63,8 @@ static unsigned int ipv6_defrag(void *priv,
 		return NF_ACCEPT;
 #endif
 
-	reasm = nf_ct_frag6_gather(skb, nf_ct6_defrag_user(state->hook, skb));
+	reasm = nf_ct_frag6_gather(state->net, skb,
+				   nf_ct6_defrag_user(state->hook, skb));
 	/* queued */
 	if (reasm == NULL)
 		return NF_STOLEN;

net/openvswitch/conntrack.c

@@ -315,7 +315,7 @@ static int handle_fragments(struct net *net, struct sw_flow_key *key,
 		struct sk_buff *reasm;
 
 		memset(IP6CB(skb), 0, sizeof(struct inet6_skb_parm));
-		reasm = nf_ct_frag6_gather(skb, user);
+		reasm = nf_ct_frag6_gather(net, skb, user);
 		if (!reasm)
 			return -EINPROGRESS;