netdev - [PATCH netfilter] Fix hw flow offload from nftables

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Message-ID: <20231023101347.564898-1-donald.hunter@gmail.com>
Date: Mon, 23 Oct 2023 11:13:47 +0100
From: Donald Hunter <donald.hunter@...il.com>
To: Pablo Neira Ayuso <pablo@...filter.org>,
	Jozsef Kadlecsik <kadlec@...filter.org>,
	Florian Westphal <fw@...len.de>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Paolo Abeni <pabeni@...hat.com>,
	Paul Blakey <paulb@...dia.com>,
	Vlad Buslov <vladbu@...dia.com>,
	netfilter-devel@...r.kernel.org,
	coreteam@...filter.org,
	netdev@...r.kernel.org
Cc: Donald Hunter <donald.hunter@...il.com>
Subject: [PATCH netfilter] Fix hw flow offload from nftables

The NF_FLOW_HW_ESTABLISHED bit was not getting set in any nftables code
paths. It seems that the state was never correctly maintained but there
was no negative side-effect until commit 41f2c7c342d3 ("net/sched:
act_ct: Fix promotion of offloaded unreplied tuple") which uses it as
part of a flow outdated check. The net result is repeated cycles of
FLOW_CLS_REPLACE / FLOW_CLS_DESTROY commands and never getting any
FLOW_CLS_STATS commands for a flow.

This patch sets and clears the NF_FLOW_HW_ESTABLISHED bit for nftables.

Note that I don't have hardware to test this with. I have observed
the behaviour and verified the fix with modified veth code.

Signed-off-by: Donald Hunter <donald.hunter@...il.com>
Fixes: 41f2c7c342d3 ("net/sched: act_ct: Fix promotion of offloaded unreplied tuple")
---
 net/netfilter/nf_flow_table_offload.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/netfilter/nf_flow_table_offload.c b/net/netfilter/nf_flow_table_offload.c
index 1c26f03fc661..1d017191af80 100644
--- a/net/netfilter/nf_flow_table_offload.c
+++ b/net/netfilter/nf_flow_table_offload.c
@@ -918,6 +918,7 @@ static void flow_offload_work_add(struct flow_offload_work *offload)
 		goto out;
 
 	set_bit(IPS_HW_OFFLOAD_BIT, &offload->flow->ct->status);
+	set_bit(NF_FLOW_HW_ESTABLISHED, &offload->flow->flags);
 
 out:
 	nf_flow_offload_destroy(flow_rule);
@@ -925,6 +926,7 @@ static void flow_offload_work_add(struct flow_offload_work *offload)
 
 static void flow_offload_work_del(struct flow_offload_work *offload)
 {
+	clear_bit(NF_FLOW_HW_ESTABLISHED, &offload->flow->flags);
 	clear_bit(IPS_HW_OFFLOAD_BIT, &offload->flow->ct->status);
 	flow_offload_tuple_del(offload, FLOW_OFFLOAD_DIR_ORIGINAL);
 	if (test_bit(NF_FLOW_HW_BIDIRECTIONAL, &offload->flow->flags))
-- 
2.41.0