1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * net/dsa/tag_dsa.c - (Non-ethertype) DSA tagging
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
13 #define DSA_HLEN 4
14
dsa_xmit(struct sk_buff * skb,struct net_device * dev)15 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
16 {
17 struct dsa_port *dp = dsa_slave_to_port(dev);
18 u8 *dsa_header;
19
20 /*
21 * Convert the outermost 802.1q tag to a DSA tag for tagged
22 * packets, or insert a DSA tag between the addresses and
23 * the ethertype field for untagged packets.
24 */
25 if (skb->protocol == htons(ETH_P_8021Q)) {
26 /*
27 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
28 */
29 dsa_header = skb->data + 2 * ETH_ALEN;
30 dsa_header[0] = 0x60 | dp->ds->index;
31 dsa_header[1] = dp->index << 3;
32
33 /*
34 * Move CFI field from byte 2 to byte 1.
35 */
36 if (dsa_header[2] & 0x10) {
37 dsa_header[1] |= 0x01;
38 dsa_header[2] &= ~0x10;
39 }
40 } else {
41 skb_push(skb, DSA_HLEN);
42
43 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
44
45 /*
46 * Construct untagged FROM_CPU DSA tag.
47 */
48 dsa_header = skb->data + 2 * ETH_ALEN;
49 dsa_header[0] = 0x40 | dp->ds->index;
50 dsa_header[1] = dp->index << 3;
51 dsa_header[2] = 0x00;
52 dsa_header[3] = 0x00;
53 }
54
55 return skb;
56 }
57
dsa_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt)58 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
59 struct packet_type *pt)
60 {
61 u8 *dsa_header;
62 int source_device;
63 int source_port;
64
65 if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
66 return NULL;
67
68 /*
69 * The ethertype field is part of the DSA header.
70 */
71 dsa_header = skb->data - 2;
72
73 /*
74 * Check that frame type is either TO_CPU or FORWARD.
75 */
76 if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
77 return NULL;
78
79 /*
80 * Determine source device and port.
81 */
82 source_device = dsa_header[0] & 0x1f;
83 source_port = (dsa_header[1] >> 3) & 0x1f;
84
85 skb->dev = dsa_master_find_slave(dev, source_device, source_port);
86 if (!skb->dev)
87 return NULL;
88
89 /*
90 * Convert the DSA header to an 802.1q header if the 'tagged'
91 * bit in the DSA header is set. If the 'tagged' bit is clear,
92 * delete the DSA header entirely.
93 */
94 if (dsa_header[0] & 0x20) {
95 u8 new_header[4];
96
97 /*
98 * Insert 802.1q ethertype and copy the VLAN-related
99 * fields, but clear the bit that will hold CFI (since
100 * DSA uses that bit location for another purpose).
101 */
102 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
103 new_header[1] = ETH_P_8021Q & 0xff;
104 new_header[2] = dsa_header[2] & ~0x10;
105 new_header[3] = dsa_header[3];
106
107 /*
108 * Move CFI bit from its place in the DSA header to
109 * its 802.1q-designated place.
110 */
111 if (dsa_header[1] & 0x01)
112 new_header[2] |= 0x10;
113
114 /*
115 * Update packet checksum if skb is CHECKSUM_COMPLETE.
116 */
117 if (skb->ip_summed == CHECKSUM_COMPLETE) {
118 __wsum c = skb->csum;
119 c = csum_add(c, csum_partial(new_header + 2, 2, 0));
120 c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
121 skb->csum = c;
122 }
123
124 memcpy(dsa_header, new_header, DSA_HLEN);
125 } else {
126 /*
127 * Remove DSA tag and update checksum.
128 */
129 skb_pull_rcsum(skb, DSA_HLEN);
130 memmove(skb->data - ETH_HLEN,
131 skb->data - ETH_HLEN - DSA_HLEN,
132 2 * ETH_ALEN);
133 }
134
135 skb->offload_fwd_mark = 1;
136
137 return skb;
138 }
139
140 static const struct dsa_device_ops dsa_netdev_ops = {
141 .name = "dsa",
142 .proto = DSA_TAG_PROTO_DSA,
143 .xmit = dsa_xmit,
144 .rcv = dsa_rcv,
145 .overhead = DSA_HLEN,
146 };
147
148 MODULE_LICENSE("GPL");
149 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
150
151 module_dsa_tag_driver(dsa_netdev_ops);
152