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

Since nf_flow_snat_port and nf_flow_snat_ip{v6} call pskb_may_pull()
which 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

@@ -146,11 +146,13 @@ static int nf_flow_nat_ip(const struct flow_offload *flow, struct sk_buff *skb,
 
 	if (test_bit(NF_FLOW_SNAT, &flow->flags) &&
 	    (nf_flow_snat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
-	     nf_flow_snat_ip(flow, skb, iph, thoff, dir) < 0))
+	     nf_flow_snat_ip(flow, skb, ip_hdr(skb), thoff, dir) < 0))
 		return -1;
+
+	iph = ip_hdr(skb);
 	if (test_bit(NF_FLOW_DNAT, &flow->flags) &&
 	    (nf_flow_dnat_port(flow, skb, thoff, iph->protocol, dir) < 0 ||
-	     nf_flow_dnat_ip(flow, skb, iph, thoff, dir) < 0))
+	     nf_flow_dnat_ip(flow, skb, ip_hdr(skb), thoff, dir) < 0))
 		return -1;
 
 	return 0;
@@ -426,11 +428,13 @@ static int nf_flow_nat_ipv6(const struct flow_offload *flow,
 
 	if (test_bit(NF_FLOW_SNAT, &flow->flags) &&
 	    (nf_flow_snat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
-	     nf_flow_snat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
+	     nf_flow_snat_ipv6(flow, skb, ipv6_hdr(skb), thoff, dir) < 0))
 		return -1;
+
+	ip6h = ipv6_hdr(skb);
 	if (test_bit(NF_FLOW_DNAT, &flow->flags) &&
 	    (nf_flow_dnat_port(flow, skb, thoff, ip6h->nexthdr, dir) < 0 ||
-	     nf_flow_dnat_ipv6(flow, skb, ip6h, thoff, dir) < 0))
+	     nf_flow_dnat_ipv6(flow, skb, ipv6_hdr(skb), thoff, dir) < 0))
 		return -1;
 
 	return 0;