From 71d8c47fc653711c41bc3282e5b0e605b3727956 Mon Sep 17 00:00:00 2001 From: Pablo Neira Ayuso Date: Sun, 1 May 2016 00:28:40 +0200 Subject: netfilter: conntrack: introduce clash resolution on insertion race This patch introduces nf_ct_resolve_clash() to resolve race condition on conntrack insertions. This is particularly a problem for connection-less protocols such as UDP, with no initial handshake. Two or more packets may race to insert the entry resulting in packet drops. Another problematic scenario are packets enqueued to userspace via NFQUEUE after the raw table, that make it easier to trigger this race. To resolve this, the idea is to reset the conntrack entry to the one that won race. Packet and bytes counters are also merged. The 'insert_failed' stats still accounts for this situation, after this patch, the drop counter is bumped whenever we drop packets, so we can watch for unresolved clashes. Signed-off-by: Pablo Neira Ayuso --- include/net/netfilter/nf_conntrack_l4proto.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/net') diff --git a/include/net/netfilter/nf_conntrack_l4proto.h b/include/net/netfilter/nf_conntrack_l4proto.h index 956d8a6ac069..1a5fb36f165f 100644 --- a/include/net/netfilter/nf_conntrack_l4proto.h +++ b/include/net/netfilter/nf_conntrack_l4proto.h @@ -23,6 +23,9 @@ struct nf_conntrack_l4proto { /* L4 Protocol number. */ u_int8_t l4proto; + /* Resolve clashes on insertion races. */ + bool allow_clash; + /* Try to fill in the third arg: dataoff is offset past network protocol hdr. Return true if possible. */ bool (*pkt_to_tuple)(const struct sk_buff *skb, unsigned int dataoff, -- cgit v1.2.3