[PATCH 6.18 251/752] netfilter: nf_conntrack: Add allow_clash to generic protocol handler

Sasha Levin
2026-02-28T17:51:39Z

From: Yuto Hamaguchi <Hamaguchi.Yuto@da.MitsubishiElectric.co.jp>

[ Upstream commit 8a49fc8d8a3e83dc51ec05bcd4007bdea3c56eec ]

The upstream commit, 71d8c47fc653711c41bc3282e5b0e605b3727956
("netfilter: conntrack: introduce clash resolution on insertion race"),
sets allow_clash=true in the UDP/UDPLITE protocol handler
but does not set it in the generic protocol handler.

As a result, packets composed of connectionless protocols at each layer,
such as UDP over IP-in-IP, still drop packets due to conflicts during conntrack insertion.

To resolve this, this patch sets allow_clash in the nf_conntrack_l4proto_generic.

Signed-off-by: Yuto Hamaguchi <Hamaguchi.Yuto@da.MitsubishiElectric.co.jp>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/netfilter/nf_conntrack_proto_generic.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/net/netfilter/nf_conntrack_proto_generic.c b/net/netfilter/nf_conntrack_proto_generic.c
index e831637bc8ca8..cb260eb3d012c 100644
--- a/net/netfilter/nf_conntrack_proto_generic.c
+++ b/net/netfilter/nf_conntrack_proto_generic.c
@@ -67,6 +67,7 @@ void nf_conntrack_generic_init_net(struct net *net)
const struct nf_conntrack_l4proto nf_conntrack_l4proto_generic =
{
.l4proto = 255,
+ .allow_clash = true,
#ifdef CONFIG_NF_CONNTRACK_TIMEOUT
.ctnl_timeout = {
.nlattr_to_obj = generic_timeout_nlattr_to_obj,
--
2.51.0