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From: Martin Willi <martin@strongswan.org>
To: Steffen Klassert <steffen.klassert@secunet.com>,
	Benedict Wong <benedictwong@google.com>,
	Eyal Birger <eyal.birger@gmail.com>
Cc: Herbert Xu <herbert@gondor.apana.org.au>,
	"David S . Miller" <davem@davemloft.net>,
	Eric Dumazet <edumazet@google.com>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	netdev@vger.kernel.org
Subject: [PATCH ipsec v2] xfrm: Preserve xfrm interface secpath for packets forwarded
Date: Wed, 12 Apr 2023 10:56:15 +0200	[thread overview]
Message-ID: <20230412085615.124791-1-martin@strongswan.org> (raw)

The commit referenced below clears the secpath on packets received via
xfrm interfaces to support nested IPsec tunnels. This breaks Netfilter
policy matching using xt_policy in the FORWARD chain, as the secpath
is missing during forwarding. INPUT matching is not affected, as it is
done before secpath reset.

A work-around could use XFRM input interface matching for such rules,
but this does not work if the XFRM interface is part of a VRF; the
Netfilter input interface is replaced by the VRF interface, making a
sufficient match for IPsec-protected packets difficult.

So instead, limit the secpath reset to packets that are not using a
XFRM forward policy. This should allow nested tunnels, but keeps the
secpath intact on packets that are passed to Netfilter chains with
potential IPsec policy matches.

Fixes: b0355dbbf13c ("Fix XFRM-I support for nested ESP tunnels")
Suggested-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: Martin Willi <martin@strongswan.org>
---
v1 -> v2: Use policy dir instead of flowi outif to check for forwarding

 net/xfrm/xfrm_policy.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 5c61ec04b839..669c3c0880a6 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -3745,7 +3745,7 @@ int __xfrm_policy_check(struct sock *sk, int dir, struct sk_buff *skb,
 			goto reject;
 		}
 
-		if (if_id)
+		if (if_id && dir != XFRM_POLICY_FWD)
 			secpath_reset(skb);
 
 		xfrm_pols_put(pols, npols);
-- 
2.34.1


             reply	other threads:[~2023-04-12  8:57 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-04-12  8:56 Martin Willi [this message]
2023-04-13 18:04 ` [PATCH ipsec v2] xfrm: Preserve xfrm interface secpath for packets forwarded Benedict Wong
2023-04-17 22:01   ` Benedict Wong
2023-04-19  6:06     ` Steffen Klassert
2023-04-25  7:45   ` Martin Willi
2023-04-25  7:47     ` Steffen Klassert

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