netdev - [PATCH net 1/1] Revert "netfilter: flowtable: teardown flow if cached mtu is stale"

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Message-Id: <20250213100502.3983-2-pablo@netfilter.org>
Date: Thu, 13 Feb 2025 11:05:02 +0100
From: Pablo Neira Ayuso <pablo@...filter.org>
To: netfilter-devel@...r.kernel.org
Cc: davem@...emloft.net,
	netdev@...r.kernel.org,
	kuba@...nel.org,
	pabeni@...hat.com,
	edumazet@...gle.com,
	fw@...len.de,
	horms@...nel.org
Subject: [PATCH net 1/1] Revert "netfilter: flowtable: teardown flow if cached mtu is stale"

This reverts commit b8baac3b9c5cc4b261454ff87d75ae8306016ffd.

IPv4 packets with no DF flag set on result in frequent flow entry
teardown cycles, this is visible in the network topology that is used in
the nft_flowtable.sh test.

nft_flowtable.sh test ocassionally fails reporting that the dscp_fwd
test sees no packets going through the flowtable path.

Fixes: b8baac3b9c5c ("netfilter: flowtable: teardown flow if cached mtu is stale")
Reported-by: Jakub Kicinski <kuba@...nel.org>
Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 net/netfilter/nf_flow_table_ip.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/net/netfilter/nf_flow_table_ip.c b/net/netfilter/nf_flow_table_ip.c
index 97c6eb8847a0..8cd4cf7ae211 100644
--- a/net/netfilter/nf_flow_table_ip.c
+++ b/net/netfilter/nf_flow_table_ip.c
@@ -381,10 +381,8 @@ static int nf_flow_offload_forward(struct nf_flowtable_ctx *ctx,
 	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 
 	mtu = flow->tuplehash[dir].tuple.mtu + ctx->offset;
-	if (unlikely(nf_flow_exceeds_mtu(skb, mtu))) {
-		flow_offload_teardown(flow);
+	if (unlikely(nf_flow_exceeds_mtu(skb, mtu)))
 		return 0;
-	}
 
 	iph = (struct iphdr *)(skb_network_header(skb) + ctx->offset);
 	thoff = (iph->ihl * 4) + ctx->offset;
@@ -662,10 +660,8 @@ static int nf_flow_offload_ipv6_forward(struct nf_flowtable_ctx *ctx,
 	flow = container_of(tuplehash, struct flow_offload, tuplehash[dir]);
 
 	mtu = flow->tuplehash[dir].tuple.mtu + ctx->offset;
-	if (unlikely(nf_flow_exceeds_mtu(skb, mtu))) {
-		flow_offload_teardown(flow);
+	if (unlikely(nf_flow_exceeds_mtu(skb, mtu)))
 		return 0;
-	}
 
 	ip6h = (struct ipv6hdr *)(skb_network_header(skb) + ctx->offset);
 	thoff = sizeof(*ip6h) + ctx->offset;
-- 
2.30.2