netdev - [PATCH net] net/ipv6: Increment OUTxxx counters after netfilter hook

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Date:   Thu,  5 Apr 2018 21:29:47 +0000
From:   Jeff Barnhill <0xeffeff@...il.com>
To:     netdev@...r.kernel.org
Cc:     dsahern@...il.com, Jeff Barnhill <0xeffeff@...il.com>
Subject: [PATCH net] net/ipv6: Increment OUTxxx counters after netfilter hook

At the end of ip6_forward(), IPSTATS_MIB_OUTFORWDATAGRAMS and
IPSTATS_MIB_OUTOCTETS are incremented immediately before the NF_HOOK call
for NFPROTO_IPV6 / NF_INET_FORWARD.  As a result, these counters get
incremented regardless of whether or not the netfilter hook allows the
packet to continue being processed.  This change increments the counters
in ip6_forward_finish() so that it will not happen if the netfilter hook
chooses to terminate the packet, which is similar to how IPv4 works.

Signed-off-by: Jeff Barnhill <0xeffeff@...il.com>
---
 net/ipv6/ip6_output.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index b8ee50e94af3..2e891d2c30ef 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -375,6 +375,11 @@ static int ip6_forward_proxy_check(struct sk_buff *skb)
 static inline int ip6_forward_finish(struct net *net, struct sock *sk,
 				     struct sk_buff *skb)
 {
+	struct dst_entry *dst = skb_dst(skb);
+
+	__IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTFORWDATAGRAMS);
+	__IP6_ADD_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTOCTETS, skb->len);
+
 	return dst_output(net, sk, skb);
 }
 
@@ -569,8 +574,6 @@ int ip6_forward(struct sk_buff *skb)
 
 	hdr->hop_limit--;
 
-	__IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTFORWDATAGRAMS);
-	__IP6_ADD_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTOCTETS, skb->len);
 	return NF_HOOK(NFPROTO_IPV6, NF_INET_FORWARD,
 		       net, NULL, skb, skb->dev, dst->dev,
 		       ip6_forward_finish);
-- 
2.14.1