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
trailer_xmit(struct sk_buff * skb,struct net_device * dev)15 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
16 {
17 struct dsa_port *dp = dsa_slave_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
trailer_rcv(struct sk_buff * skb,struct net_device * dev)29 static 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_master_find_slave(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
54 static 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
62 MODULE_LICENSE("GPL");
63 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER, TRAILER_NAME);
64
65 module_dsa_tag_driver(trailer_netdev_ops);
66