netfilter: Pass struct net into the netfilter hooks

Pass a network namespace parameter into the netfilter hooks.  At the
call site of the netfilter hooks the path a packet is taking through
the network stack is well known which allows the network namespace to
be easily and reliabily.

This allows the replacement of magic code like
"dev_net(state->in?:state->out)" that appears at the start of most
netfilter hooks with "state->net".

In almost all cases the network namespace passed in is derived
from the first network device passed in, guaranteeing those
paths will not see any changes in practice.

The exceptions are:
xfrm/xfrm_output.c:xfrm_output_resume()         xs_net(skb_dst(skb)->xfrm)
ipvs/ip_vs_xmit.c:ip_vs_nat_send_or_cont()      ip_vs_conn_net(cp)
ipvs/ip_vs_xmit.c:ip_vs_send_or_cont()          ip_vs_conn_net(cp)
ipv4/raw.c:raw_send_hdrinc()                    sock_net(sk)
ipv6/ip6_output.c:ip6_xmit()			sock_net(sk)
ipv6/ndisc.c:ndisc_send_skb()                   dev_net(skb->dev) not dev_net(dst->dev)
ipv6/raw.c:raw6_send_hdrinc()                   sock_net(sk)
br_netfilter_hooks.c:br_nf_pre_routing_finish() dev_net(skb->dev) before skb->dev is set to nf_bridge->physindev

In all cases these exceptions seem to be a better expression for the
network namespace the packet is being processed in then the historic
"dev_net(in?in:out)".  I am documenting them in case something odd
pops up and someone starts trying to track down what happened.

Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 6 insertions, 4 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index 3632e98eb0f9..ae71e9ade5f9 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -632,8 +632,9 @@ static int arp_xmit_finish(struct sock *sk, struct sk_buff *skb)
 void arp_xmit(struct sk_buff *skb)
 {
         /* Send it off, maybe filter it using firewalling first.  */
-        NF_HOOK(NFPROTO_ARP, NF_ARP_OUT, NULL, skb,
-                NULL, skb->dev, arp_xmit_finish);
+        NF_HOOK(NFPROTO_ARP, NF_ARP_OUT,
+                dev_net(skb->dev), NULL, skb, NULL, skb->dev,
+                arp_xmit_finish);
 }
 EXPORT_SYMBOL(arp_xmit);
 
@@ -897,8 +898,9 @@ static int arp_rcv(struct sk_buff *skb, struct net_device *dev,
 
         memset(NEIGH_CB(skb), 0, sizeof(struct neighbour_cb));
 
-        return NF_HOOK(NFPROTO_ARP, NF_ARP_IN, NULL, skb,
-                       dev, NULL, arp_process);
+        return NF_HOOK(NFPROTO_ARP, NF_ARP_IN,
+                       dev_net(dev), NULL, skb, dev, NULL,
+                       arp_process);
 
 consumeskb:
         consume_skb(skb);