net: dsa: reduce number of protocol hooks

DSA is currently registering one packet_type function per EtherType it
needs to intercept in the receive path of a DSA-enabled Ethernet device.
Right now we have three of them: trailer, DSA and eDSA, and there might
be more in the future, this will not scale to the addition of new
protocols.

This patch proceeds with adding a new layer of abstraction and two new
functions:

dsa_switch_rcv() which will dispatch into the tag-protocol specific
receive function implemented by net/dsa/tag_*.c

dsa_slave_xmit() which will dispatch into the tag-protocol specific
transmit function implemented by net/dsa/tag_*.c

When we do create the per-port slave network devices, we iterate over
the switch protocol to assign the DSA-specific receive and transmit
operations.

A new fake ethertype value is used: ETH_P_XDSA to illustrate the fact
that this is no longer going to look like ETH_P_DSA or ETH_P_TRAILER
like it used to be.

This allows us to greatly simplify the check in eth_type_trans() and
always override the skb->protocol with ETH_P_XDSA for Ethernet switches
tagged protocol, while also reducing the number repetitive slave
netdevice_ops assignments.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 5 deletions

diff --git a/net/ethernet/eth.c b/net/ethernet/eth.c
index f405e0592407..5cebca134585 100644
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -181,11 +181,8 @@ __be16 eth_type_trans(struct sk_buff *skb, struct net_device *dev)
 	 * variants has been configured on the receiving interface,
 	 * and if so, set skb->protocol without looking at the packet.
 	 */
-	if (unlikely(netdev_uses_dsa_tags(dev)))
-		return htons(ETH_P_DSA);
-
-	if (unlikely(netdev_uses_trailer_tags(dev)))
-		return htons(ETH_P_TRAILER);
+	if (unlikely(netdev_uses_dsa(dev)))
+		return htons(ETH_P_XDSA);
 
 	if (likely(ntohs(eth->h_proto) >= ETH_P_802_3_MIN))
 		return eth->h_proto;