netdev - [PATCH nf] netfilter: nf_conntrack: Add allow

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Message-Id: <20251219115351.5662-1-Hamaguchi.Yuto@da.MitsubishiElectric.co.jp>
Date: Fri, 19 Dec 2025 20:53:51 +0900
From: Yuto Hamaguchi <Hamaguchi.Yuto@...MitsubishiElectric.co.jp>
To: pablo@...filter.org,
	kadlec@...filter.org,
	netfilter-devel@...r.kernel.org
Cc: coreteam@...filter.org,
	netdev@...r.kernel.org,
	Hamaguchi.Yuto@...MitsubishiElectric.co.jp
Subject: [PATCH nf] netfilter: nf_conntrack: Add allow_clash to generic protocol handler

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@...MitsubishiElectric.co.jp>
---
 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 e831637bc8ca..cb260eb3d012 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,
-- 
2.36.1