linux-kernel - [PATCH] net: bridge: switchdev: Don't drop packets between ports with no hwdom

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Message-ID: <20241020162105.3217305-1-leon@georgemail.de>
Date: Sun, 20 Oct 2024 18:20:14 +0200
From: "Leon M. Busch-George" <leon@...rgemail.de>
To: "Nikolay Aleksandrov" <razor@...ckwall.org>,
	linux-kernel@...r.kernel.org
Cc: bridge@...ts.linux.dev,
	"David S. Miller" <davem@...emloft.net>,
	Felix Fietkau <nbd@....name>
Subject: [PATCH] net: bridge: switchdev: Don't drop packets between ports with no hwdom

From: "Leon M. Busch-George" <leon@...rgemail.eu>

nbp_switchdev_allowed_egress uses hwdom to determine whether or not a
packet has already been forwarded to a hardware domain. For
net_bridge_ports that aren't set up to use forward offloading, hwdom is
set to 0. When both ingress and egress port have no hwdom,
'cb->src_hwdom != p->hwdom' indicates that the packet is already known in
the target domain - which it isn't - and the packet is wrongly dropped.

The error was found on a bridge containing a wifi device and a VLAN
tagging device (e.g. eth0.12). With VLAN filtering, this shouldn't happen.

This patch adds a check for p->hwdom != 0 before comparing hardware
domains to restore forwarding between ports with hwdom = 0.

fwd_hwdoms are only set for ports with offloading enabled, which also
implies a valid hwdom, so the check '!test_bit(p->hwdom, &cb->fwd_hwdoms)'
doesn't fail in this way (yet - fingers crossed..) and it is left in place.

Co-developed-by: Felix Fietkau <nbd@....name>
Signed-off-by: Felix Fietkau <nbd@....name>
Signed-off-by: Leon M. Busch-George <leon@...rgemail.eu>
---
 net/bridge/br_switchdev.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/bridge/br_switchdev.c b/net/bridge/br_switchdev.c
index 7b41ee8740cb..29ff9af99276 100644
--- a/net/bridge/br_switchdev.c
+++ b/net/bridge/br_switchdev.c
@@ -67,7 +67,7 @@ bool nbp_switchdev_allowed_egress(const struct net_bridge_port *p,
 	struct br_input_skb_cb *cb = BR_INPUT_SKB_CB(skb);

 	return !test_bit(p->hwdom, &cb->fwd_hwdoms) &&
-		(!skb->offload_fwd_mark || cb->src_hwdom != p->hwdom);
+		(!skb->offload_fwd_mark || !p->hwdom || cb->src_hwdom != p->hwdom);
 }

 /* Flags that can be offloaded to hardware */
-- 
2.47.0