dsa: add support for original DSA tagging format

Most of the DSA switches currently in the field do not support the
Ethertype DSA tagging format that one of the previous patches added
support for, but only the original DSA tagging format.

The original DSA tagging format carries the same information as the
Ethertype DSA tagging format, but with the difference that it does not
have an ethertype field.  In other words, when receiving a packet that
is tagged with an original DSA tag, there is no way of telling in
eth_type_trans() that this packet is in fact a DSA-tagged packet.

This patch adds a hook into eth_type_trans() which is only compiled in
if support for a switch chip that doesn't support Ethertype DSA is
selected, and which checks whether there is a DSA switch driver
instance attached to this network device which uses the old tag format.
If so, it sets the protocol field to ETH_P_DSA without looking at the
packet, so that the packet ends up in the right place.

Signed-off-by: Lennert Buytenhek <buytenh@marvell.com>
Tested-by: Nicolas Pitre <nico@marvell.com>
Tested-by: Peter van Valderen <linux@ddcrew.com>
Tested-by: Dirk Teurlings <dirk@upexia.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 16 insertions, 0 deletions

diff --git a/net/dsa/dsa.c b/net/dsa/dsa.c
index 6cc5be2ec7f1..f8c549281c30 100644
--- a/net/dsa/dsa.c
+++ b/net/dsa/dsa.c
@@ -202,6 +202,22 @@ static void dsa_switch_destroy(struct dsa_switch *ds)
 }
 
 
+/* hooks for ethertype-less tagging formats *********************************/
+/*
+ * The original DSA tag format and some other tag formats have no
+ * ethertype, which means that we need to add a little hack to the
+ * networking receive path to make sure that received frames get
+ * the right ->protocol assigned to them when one of those tag
+ * formats is in use.
+ */
+bool dsa_uses_dsa_tags(void *dsa_ptr)
+{
+	struct dsa_switch *ds = dsa_ptr;
+
+	return !!(ds->tag_protocol == htons(ETH_P_DSA));
+}
+
+
 /* link polling *************************************************************/
 static void dsa_link_poll_work(struct work_struct *ugly)
 {