netfilter: nf_conntrack: log packets dropped by helpers

Log packets dropped by helpers using the netfilter logging API. This
is useful in combination with nfnetlink_log to analyze those packets
in userspace for debugging.

Signed-off-by: Patrick McHardy <kaber@trash.net>

2 files changed, 10 insertions, 2 deletions

diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
index 9ac2fdc36ecc..aa95bb82ee6c 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -26,6 +26,7 @@
 #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
 #include <net/netfilter/nf_nat_helper.h>
 #include <net/netfilter/ipv4/nf_defrag_ipv4.h>
+#include <net/netfilter/nf_log.h>
 
 int (*nf_nat_seq_adjust_hook)(struct sk_buff *skb,
                               struct nf_conn *ct,
@@ -113,8 +114,11 @@ static unsigned int ipv4_confirm(unsigned int hooknum,
 
         ret = helper->help(skb, skb_network_offset(skb) + ip_hdrlen(skb),
                            ct, ctinfo);
-        if (ret != NF_ACCEPT)
+        if (ret != NF_ACCEPT) {
+                nf_log_packet(NFPROTO_IPV4, hooknum, skb, in, out, NULL,
+                              "nf_ct_%s: dropping packet", helper->name);
                 return ret;
+        }
 
         if (test_bit(IPS_SEQ_ADJUST_BIT, &ct->status)) {
                 typeof(nf_nat_seq_adjust_hook) seq_adjust;
diff --git a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
index a7f4cd607356..5f2ec208a8c3 100644
--- a/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
+++ b/net/ipv6/netfilter/nf_conntrack_l3proto_ipv6.c
@@ -27,6 +27,7 @@
 #include <net/netfilter/nf_conntrack_l3proto.h>
 #include <net/netfilter/nf_conntrack_core.h>
 #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
+#include <net/netfilter/nf_log.h>
 
 static bool ipv6_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
                               struct nf_conntrack_tuple *tuple)
@@ -176,8 +177,11 @@ static unsigned int ipv6_confirm(unsigned int hooknum,
         }
 
         ret = helper->help(skb, protoff, ct, ctinfo);
-        if (ret != NF_ACCEPT)
+        if (ret != NF_ACCEPT) {
+                nf_log_packet(NFPROTO_IPV6, hooknum, skb, in, out, NULL,
+                              "nf_ct_%s: dropping packet", helper->name);
                 return ret;
+        }
 out:
         /* We've seen it coming out the other side: confirm it */
         return nf_conntrack_confirm(skb);