netfilter: nf_flow_table: clear skb tstamp before xmit

If 'fq' qdisc is used and a program has requested timestamps,
skb->tstamp needs to be cleared, else fq will treat these as
'transmit time'.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_flow_table_ip.c

@@ -228,7 +228,6 @@ static unsigned int nf_flow_xmit_xfrm(struct sk_buff *skb,
 {
 	skb_orphan(skb);
 	skb_dst_set_noref(skb, dst);
-	skb->tstamp = 0;
 	dst_output(state->net, state->sk, skb);
 	return NF_STOLEN;
 }
@@ -284,6 +283,7 @@ nf_flow_offload_ip_hook(void *priv, struct sk_buff *skb,
 	flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
 	iph = ip_hdr(skb);
 	ip_decrease_ttl(iph);
+	skb->tstamp = 0;
 
 	if (unlikely(dst_xfrm(&rt->dst))) {
 		memset(skb->cb, 0, sizeof(struct inet_skb_parm));
@@ -512,6 +512,7 @@ nf_flow_offload_ipv6_hook(void *priv, struct sk_buff *skb,
 	flow->timeout = (u32)jiffies + NF_FLOW_TIMEOUT;
 	ip6h = ipv6_hdr(skb);
 	ip6h->hop_limit--;
+	skb->tstamp = 0;
 
 	if (unlikely(dst_xfrm(&rt->dst))) {
 		memset(skb->cb, 0, sizeof(struct inet6_skb_parm));