netfilter: nf_conntrack: extend with extra stat counter

I suspect an unfortunatly series of events occuring under a DDoS
attack, in function __nf_conntrack_find() nf_contrack_core.c.

Adding a stats counter to see if the search is restarted too often.

Signed-off-by: Jesper Dangaard Brouer <hawk@comx.dk>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 3 insertions, 1 deletions

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 0c9bbe93cc1..3907efb97a7 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -319,8 +319,10 @@ begin:
          * not the expected one, we must restart lookup.
          * We probably met an item that was moved to another chain.
          */
-        if (get_nulls_value(n) != hash)
+        if (get_nulls_value(n) != hash) {
+                NF_CT_STAT_INC(net, search_restart);
                 goto begin;
+        }
         local_bh_enable();
 
         return NULL;