net: dsa: microchip: add switch offload forwarding support

The flag offload_fwd_mark is set as the switch can forward frames by
itself.

This can be considered a fix to a problem introduced in commit
c2e86691 where the port membership are not set in sync.  The flag
offload_fwd_mark just needs to be set in tag_ksz.c to prevent the software
bridge from forwarding duplicate multicast frames.

Fixes: c2e86691 ("microchip: break KSZ9477 DSA driver into two files")
Signed-off-by: Tristram Ha <Tristram.Ha@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/dsa/microchip/ksz9477.c

@@ -397,6 +397,7 @@ static void ksz9477_port_stp_state_set(struct dsa_switch *ds, int port,
 	struct ksz_port *p = &dev->ports[port];
 	u8 data;
 	int member = -1;
+	int forward = dev->member;
 
 	ksz_pread8(dev, port, P_STP_CTRL, &data);
 	data &= ~(PORT_TX_ENABLE | PORT_RX_ENABLE | PORT_LEARN_DISABLE);
@@ -464,10 +465,10 @@ static void ksz9477_port_stp_state_set(struct dsa_switch *ds, int port,
 	}
 
 	/* When topology has changed the function ksz_update_port_member
-	 * should be called to modify port forwarding behavior.  However
-	 * as the offload_fwd_mark indication cannot be reported here
-	 * the switch forwarding function is not enabled.
+	 * should be called to modify port forwarding behavior.
 	 */
+	if (forward != dev->member)
+		ksz_update_port_member(dev, port);
 }
 
 static void ksz9477_flush_dyn_mac_table(struct ksz_device *dev, int port)

net/dsa/tag_ksz.c

@@ -67,6 +67,8 @@ static struct sk_buff *ksz_common_rcv(struct sk_buff *skb,
 
 	pskb_trim_rcsum(skb, skb->len - len);
 
+	skb->offload_fwd_mark = true;
+
 	return skb;
 }