netfilter: conntrack: destroy functions need to free queued packets

queued skbs might be using conntrack extensions that are being removed,
such as timeout.  This happens for skbs that have a skb->nfct in
unconfirmed state (i.e., not in hash table yet).

This is destructive, but there are only two use cases:
 - module removal (rare)
 - netns cleanup (most likely no conntracks exist, and if they do,
   they are removed anyway later on).
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_core.c

@@ -56,6 +56,8 @@
 #include <net/netfilter/nf_nat_helper.h>
 #include <net/netns/hash.h>
 
+#include "nf_internals.h"
+
 #define NF_CONNTRACK_VERSION	"0.5.0"
 
 int (*nfnetlink_parse_nat_setup_hook)(struct nf_conn *ct,
@@ -1692,6 +1694,7 @@ void nf_ct_unconfirmed_destroy(struct net *net)
 
 	if (atomic_read(&net->ct.count) > 0) {
 		__nf_ct_unconfirmed_destroy(net);
+		nf_queue_nf_hook_drop(net);
 		synchronize_net();
 	}
 }
@@ -1737,6 +1740,7 @@ nf_ct_iterate_destroy(int (*iter)(struct nf_conn *i, void *data), void *data)
 		if (atomic_read(&net->ct.count) == 0)
 			continue;
 		__nf_ct_unconfirmed_destroy(net);
+		nf_queue_nf_hook_drop(net);
 	}
 	rtnl_unlock();
 

net/netfilter/nf_queue.c

@@ -109,6 +109,7 @@ unsigned int nf_queue_nf_hook_drop(struct net *net)
 
 	return count;
 }
+EXPORT_SYMBOL_GPL(nf_queue_nf_hook_drop);
 
 static int __nf_queue(struct sk_buff *skb, const struct nf_hook_state *state,
 		      struct nf_hook_entry *hook_entry, unsigned int queuenum)