netfilter: flowtable: reload ip{v6}h in nf_flow_tuple_ip{v6}

Since pskb_may_pull may change skb->data, so we need to reload ip{v6}h at
the right place.

Fixes: a908fdec ("netfilter: nf_flow_table: move ipv6 offload hook code to nf_flow_table")
Fixes: 7d208687 ("netfilter: nf_flow_table: move ipv4 offload hook code to nf_flow_table")
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_flow_table_ip.c

@@ -191,6 +191,7 @@ static int nf_flow_tuple_ip(struct sk_buff *skb, const struct net_device *dev,
 	if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
 		return -1;
 
+	iph = ip_hdr(skb);
 	ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 
 	tuple->src_v4.s_addr	= iph->saddr;
@@ -463,6 +464,7 @@ static int nf_flow_tuple_ipv6(struct sk_buff *skb, const struct net_device *dev,
 	if (!pskb_may_pull(skb, thoff + sizeof(*ports)))
 		return -1;
 
+	ip6h = ipv6_hdr(skb);
 	ports = (struct flow_ports *)(skb_network_header(skb) + thoff);
 
 	tuple->src_v6		= ip6h->saddr;