netfilter: reset netfilter state when duplicating packet

We should also toss nf_bridge_info, if any -- packet is leaving via
ip_local_out, also, this skb isn't bridged -- it is a locally generated
copy.  Also this avoids the need to touch this later when skb->nfct is
replaced with 'unsigned long _nfct' in followup patch.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/ipv4/netfilter/nf_dup_ipv4.c

@@ -68,7 +68,7 @@ void nf_dup_ipv4(struct net *net, struct sk_buff *skb, unsigned int hooknum,
 
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
 	/* Avoid counting cloned packets towards the original connection. */
-	nf_conntrack_put(skb->nfct);
+	nf_reset(skb);
 	skb->nfct     = &nf_ct_untracked_get()->ct_general;
 	skb->nfctinfo = IP_CT_NEW;
 	nf_conntrack_get(skb->nfct);

net/ipv6/netfilter/nf_dup_ipv6.c

@@ -57,7 +57,7 @@ void nf_dup_ipv6(struct net *net, struct sk_buff *skb, unsigned int hooknum,
 		return;
 
 #if IS_ENABLED(CONFIG_NF_CONNTRACK)
-	nf_conntrack_put(skb->nfct);
+	nf_reset(skb);
 	skb->nfct     = &nf_ct_untracked_get()->ct_general;
 	skb->nfctinfo = IP_CT_NEW;
 	nf_conntrack_get(skb->nfct);