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 "dsa_priv.h"
12
trailer_xmit(struct sk_buff * skb,struct net_device * dev)13 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
14 {
15 struct dsa_port *dp = dsa_slave_to_port(dev);
16 struct sk_buff *nskb;
17 int padlen;
18 u8 *trailer;
19
20 /*
21 * We have to make sure that the trailer ends up as the very
22 * last 4 bytes of the packet. This means that we have to pad
23 * the packet to the minimum ethernet frame size, if necessary,
24 * before adding the trailer.
25 */
26 padlen = 0;
27 if (skb->len < 60)
28 padlen = 60 - skb->len;
29
30 nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
31 if (!nskb)
32 return NULL;
33 skb_reserve(nskb, NET_IP_ALIGN);
34
35 skb_reset_mac_header(nskb);
36 skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
37 skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
38 skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
39 consume_skb(skb);
40
41 if (padlen) {
42 skb_put_zero(nskb, padlen);
43 }
44
45 trailer = skb_put(nskb, 4);
46 trailer[0] = 0x80;
47 trailer[1] = 1 << dp->index;
48 trailer[2] = 0x10;
49 trailer[3] = 0x00;
50
51 return nskb;
52 }
53
trailer_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt)54 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev,
55 struct packet_type *pt)
56 {
57 u8 *trailer;
58 int source_port;
59
60 if (skb_linearize(skb))
61 return NULL;
62
63 trailer = skb_tail_pointer(skb) - 4;
64 if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
65 (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
66 return NULL;
67
68 source_port = trailer[1] & 7;
69
70 skb->dev = dsa_master_find_slave(dev, 0, source_port);
71 if (!skb->dev)
72 return NULL;
73
74 if (pskb_trim_rcsum(skb, skb->len - 4))
75 return NULL;
76
77 return skb;
78 }
79
80 static const struct dsa_device_ops trailer_netdev_ops = {
81 .name = "trailer",
82 .proto = DSA_TAG_PROTO_TRAILER,
83 .xmit = trailer_xmit,
84 .rcv = trailer_rcv,
85 .overhead = 4,
86 };
87
88 MODULE_LICENSE("GPL");
89 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER);
90
91 module_dsa_tag_driver(trailer_netdev_ops);
92