netfilter: conntrack: fix dropping packet after l4proto->packet()

We currently use the negative value in the conntrack code to encode
the packet verdict in the error. As NF_DROP is equal to 0, inverting
NF_DROP makes no sense and, as a result, no packets are ever dropped.

Signed-off-by: Christoph Paasch <christoph.paasch@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

2 files changed, 3 insertions, 3 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 90ce9ddb9451..f4935e344b61 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -726,7 +726,7 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
         NF_CT_ASSERT(skb->nfct);
 
         ret = l4proto->packet(ct, skb, dataoff, ctinfo, pf, hooknum);
-        if (ret < 0) {
+        if (ret <= 0) {
                 /* Invalid: inverse of the return code tells
                  * the netfilter core what to do */
                 pr_debug("nf_conntrack_in: Can't track with proto module\n");
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index a1edb9c1adee..f3fd154d1ddd 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -859,7 +859,7 @@ static int tcp_packet(struct nf_conn *ct,
                          */
                         if (nf_ct_kill(ct))
                                 return -NF_REPEAT;
-                        return -NF_DROP;
+                        return NF_DROP;
                 }
                 /* Fall through */
         case TCP_CONNTRACK_IGNORE:
@@ -892,7 +892,7 @@ static int tcp_packet(struct nf_conn *ct,
                                 nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
                                           "nf_ct_tcp: killing out of sync session ");
                         nf_ct_kill(ct);
-                        return -NF_DROP;
+                        return NF_DROP;
                 }
                 ct->proto.tcp.last_index = index;
                 ct->proto.tcp.last_dir = dir;