Commit 86dd9868 authored by Linus Walleij's avatar Linus Walleij Committed by David S. Miller
Browse files

net: dsa: tag_rtl4_a: Support also egress tags 



Support also transmitting frames using the custom "8899 A"
4 byte tag.

Qingfang came up with the solution: we need to pad the
ethernet frame to 60 bytes using eth_skb_pad(), then the
switch will happily accept frames with custom tags.

Cc: Mauri Sandberg <sandberg@mailfence.com>
Reported-by: default avatarDENG Qingfang <dqfext@gmail.com>
Fixes: efd7fe68 ("net: dsa: tag_rtl4_a: Implement Realtek 4 byte A tag")
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c544fcb4

net/dsa/tag_rtl4_a.c

+29 −14
Original line number Diff line number Diff line
@@ -12,9 +12,7 @@ 
 *

 * The 2 bytes tag form a 16 bit big endian word. The exact

 * meaning has been guessed from packet dumps from ingress

 * frames, as no working egress traffic has been available

 * we do not know the format of the egress tags or if they

 * are even supported.

 * frames.

 */



#include <linux/etherdevice.h>
@@ -36,17 +34,34 @@ 
static struct sk_buff *rtl4a_tag_xmit(struct sk_buff *skb,

				      struct net_device *dev)

{

	/*

	 * Just let it pass thru, we don't know if it is possible

	 * to tag a frame with the 0x8899 ethertype and direct it

	 * to a specific port, all attempts at reverse-engineering have

	 * ended up with the frames getting dropped.

	 *

	 * The VLAN set-up needs to restrict the frames to the right port.

	 *

	 * If you have documentation on the tagging format for RTL8366RB

	 * (tag type A) then please contribute.

	 */

	struct dsa_port *dp = dsa_slave_to_port(dev);

	u8 *tag;

	u16 *p;

	u16 out;



	/* Pad out to at least 60 bytes */

	if (unlikely(eth_skb_pad(skb)))

		return NULL;

	if (skb_cow_head(skb, RTL4_A_HDR_LEN) < 0)

		return NULL;



	netdev_dbg(dev, "add realtek tag to package to port %d\n",

		   dp->index);

	skb_push(skb, RTL4_A_HDR_LEN);



	memmove(skb->data, skb->data + RTL4_A_HDR_LEN, 2 * ETH_ALEN);

	tag = skb->data + 2 * ETH_ALEN;



	/* Set Ethertype */

	p = (u16 *)tag;

	*p = htons(RTL4_A_ETHERTYPE);



	out = (RTL4_A_PROTOCOL_RTL8366RB << 12) | (2 << 8);

	/* The lower bits is the port numer */

	out |= (u8)dp->index;

	p = (u16 *)(tag + 2);

	*p = htons(out);



	return skb;

}