1// SPDX-License-Identifier: GPL-2.0+
2/*
3 * net/dsa/tag_trailer.c - Trailer tag format handling
4 * Copyright (c) 2008-2009 Marvell Semiconductor
5 */
6
7#include <linux/etherdevice.h>
8#include <linux/list.h>
9#include <linux/slab.h>
10
11#include "tag.h"
12
13#define TRAILER_NAME "trailer"
14
15static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
16{
17	struct dsa_port *dp = dsa_user_to_port(dev);
18	u8 *trailer;
19
20	trailer = skb_put(skb, 4);
21	trailer[0] = 0x80;
22	trailer[1] = 1 << dp->index;
23	trailer[2] = 0x10;
24	trailer[3] = 0x00;
25
26	return skb;
27}
28
29static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev)
30{
31	u8 *trailer;
32	int source_port;
33
34	if (skb_linearize(skb))
35		return NULL;
36
37	trailer = skb_tail_pointer(skb) - 4;
38	if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
39	    (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
40		return NULL;
41
42	source_port = trailer[1] & 7;
43
44	skb->dev = dsa_conduit_find_user(dev, 0, source_port);
45	if (!skb->dev)
46		return NULL;
47
48	if (pskb_trim_rcsum(skb, skb->len - 4))
49		return NULL;
50
51	return skb;
52}
53
54static const struct dsa_device_ops trailer_netdev_ops = {
55	.name	= TRAILER_NAME,
56	.proto	= DSA_TAG_PROTO_TRAILER,
57	.xmit	= trailer_xmit,
58	.rcv	= trailer_rcv,
59	.needed_tailroom = 4,
60};
61
62MODULE_DESCRIPTION("DSA tag driver for switches using a trailer tag");
63MODULE_LICENSE("GPL");
64MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER, TRAILER_NAME);
65
66module_dsa_tag_driver(trailer_netdev_ops);
67