[PATCH net v2] netfilter: Use consistent ct id hash calculation

[Dirk Morris <dmorris@metaloft.com>]

Change ct id hash calculation to only use invariants.

Currently the ct id hash calculation is based on some fields that can
change in the lifetime on a conntrack entry in some corner cases. This
results on the ct id change after the conntrack has been confirmed.
This changes the hash to be based on attributes which should never
change. Now the ct id hash is also consistent from initialization to
conntrack confirmation either even though it is unconfirmed.

Signed-off-by: Dirk Morris <dmorris@metaloft.com>
---
  nf_conntrack_core.c |    7 ++++---
  1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index ab73c5f..dad6868 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -318,9 +318,10 @@ u32 nf_ct_get_id(const struct nf_conn *ct)
  	net_get_random_once(&ct_id_seed, sizeof(ct_id_seed));
  
  	a = (unsigned long)ct;
-	b = (unsigned long)ct->master ^ net_hash_mix(nf_ct_net(ct));
-	c = (unsigned long)ct->ext;
-	d = (unsigned long)siphash(&ct->tuplehash, sizeof(ct->tuplehash),
+	b = (unsigned long)ct->master;
+	c = (unsigned long)nf_ct_net(ct);
+	d = (unsigned long)siphash(&ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple,
+				   sizeof(ct->tuplehash[IP_CT_DIR_ORIGINAL].tuple),
  				   &ct_id_seed);
  #ifdef CONFIG_64BIT
  	return siphash_4u64((u64)a, (u64)b, (u64)c, (u64)d, &ct_id_seed);