net: dsa: don't set skb->offload_fwd_mark when not offloading the bridge

DSA has gained the recent ability to deal gracefully with upper
interfaces it cannot offload, such as the bridge, bonding or team
drivers. When such uppers exist, the ports are still in standalone mode
as far as the hardware is concerned.

But when we deliver packets to the software bridge in order for that to
do the forwarding, there is an unpleasant surprise in that the bridge
will refuse to forward them. This is because we unconditionally set
skb->offload_fwd_mark = true, meaning that the bridge thinks the frames
were already forwarded in hardware by us.

Since dp->bridge_dev is populated only when there is hardware offload
for it, but not in the software fallback case, let's introduce a new
helper that can be called from the tagger data path which sets the
skb->offload_fwd_mark accordingly to zero when there is no hardware
offload for bridging. This lets the bridge forward packets back to other
interfaces of our switch, if needed.

Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Tobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 14 insertions, 0 deletions

diff --git a/net/dsa/dsa_priv.h b/net/dsa/dsa_priv.h
index da3ad02d6ceb..e43c5dc04282 100644
--- a/net/dsa/dsa_priv.h
+++ b/net/dsa/dsa_priv.h
@@ -440,6 +440,20 @@ dsa_find_designated_bridge_port_by_vid(struct net_device *master, u16 vid)
 	return NULL;
 }
 
+/* If the ingress port offloads the bridge, we mark the frame as autonomously
+ * forwarded by hardware, so the software bridge doesn't forward in twice, back
+ * to us, because we already did. However, if we're in fallback mode and we do
+ * software bridging, we are not offloading it, therefore the dp->bridge_dev
+ * pointer is not populated, and flooding needs to be done by software (we are
+ * effectively operating in standalone ports mode).
+ */
+static inline void dsa_default_offload_fwd_mark(struct sk_buff *skb)
+{
+	struct dsa_port *dp = dsa_slave_to_port(skb->dev);
+
+	skb->offload_fwd_mark = !!(dp->bridge_dev);
+}
+
 /* switch.c */
 int dsa_switch_register_notifier(struct dsa_switch *ds);
 void dsa_switch_unregister_notifier(struct dsa_switch *ds);