[patch net-next 2/3] netfilter: ip6_tables: use reasm skb for matching

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Currently, when ipv6 fragment goes through the netfilter, match
functions are called on them directly. This might cause match function
to fail. So benefit from the fact that nf_defrag_ipv6 constructs
reassembled skb for us and use this reassembled skb for matching.

This patch fixes for example following situation:
On HOSTA do:
ip6tables -I INPUT -p icmpv6 -j DROP
ip6tables -I INPUT -p icmpv6 -m icmp6 --icmpv6-type 128 -j ACCEPT

and on HOSTB you do:
ping6 HOSTA -s2000    (MTU is 1500)

Incoming echo requests will be filtered out on HOSTA. This issue does
not occur with smaller packets than MTU (where fragmentation does not happen).

Signed-off-by: Jiri Pirko <jiri@xxxxxxxxxxx>
---
 net/ipv6/netfilter/ip6_tables.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/netfilter/ip6_tables.c b/net/ipv6/netfilter/ip6_tables.c
index 710238f..ec9cb1a 100644
--- a/net/ipv6/netfilter/ip6_tables.c
+++ b/net/ipv6/netfilter/ip6_tables.c
@@ -328,6 +328,10 @@ ip6t_do_table(struct sk_buff *skb,
 	const struct xt_table_info *private;
 	struct xt_action_param acpar;
 	unsigned int addend;
+	struct sk_buff *reasm = skb_nfct_reasm(skb);
+
+	if (!reasm)
+		reasm = skb;
 
 	/* Initialization */
 	indev = in ? in->name : nulldevname;
@@ -368,7 +372,7 @@ ip6t_do_table(struct sk_buff *skb,
 
 		IP_NF_ASSERT(e);
 		acpar.thoff = 0;
-		if (!ip6_packet_match(skb, indev, outdev, &e->ipv6,
+		if (!ip6_packet_match(reasm, indev, outdev, &e->ipv6,
 		    &acpar.thoff, &acpar.fragoff, &acpar.hotdrop)) {
  no_match:
 			e = ip6t_next_entry(e);
@@ -378,7 +382,7 @@ ip6t_do_table(struct sk_buff *skb,
 		xt_ematch_foreach(ematch, e) {
 			acpar.match     = ematch->u.kernel.match;
 			acpar.matchinfo = ematch->data;
-			if (!acpar.match->match(skb, &acpar))
+			if (!acpar.match->match(reasm, &acpar))
 				goto no_match;
 		}
 
-- 
1.8.3.1

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