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 if (skb_cow_head(skb, 0) < 0)
27 return NULL;
28
29 /*
30 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
31 */
32 dsa_header = skb->data + 2 * ETH_ALEN;
33 dsa_header[0] = 0x60 | dp->ds->index;
34 dsa_header[1] = dp->index << 3;
35
36 /*
37 * Move CFI field from byte 2 to byte 1.
38 */
39 if (dsa_header[2] & 0x10) {
40 dsa_header[1] |= 0x01;
41 dsa_header[2] &= ~0x10;
42 }
43 } else {
44 if (skb_cow_head(skb, DSA_HLEN) < 0)
45 return NULL;
46 skb_push(skb, DSA_HLEN);
47
48 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
49
50 /*
51 * Construct untagged FROM_CPU DSA tag.
52 */
53 dsa_header = skb->data + 2 * ETH_ALEN;
54 dsa_header[0] = 0x40 | dp->ds->index;
55 dsa_header[1] = dp->index << 3;
56 dsa_header[2] = 0x00;
57 dsa_header[3] = 0x00;
58 }
59
60 return skb;
61 }
62
dsa_rcv(struct sk_buff * skb,struct net_device * dev,struct packet_type * pt)63 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
64 struct packet_type *pt)
65 {
66 u8 *dsa_header;
67 int source_device;
68 int source_port;
69
70 if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
71 return NULL;
72
73 /*
74 * The ethertype field is part of the DSA header.
75 */
76 dsa_header = skb->data - 2;
77
78 /*
79 * Check that frame type is either TO_CPU or FORWARD.
80 */
81 if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
82 return NULL;
83
84 /*
85 * Determine source device and port.
86 */
87 source_device = dsa_header[0] & 0x1f;
88 source_port = (dsa_header[1] >> 3) & 0x1f;
89
90 skb->dev = dsa_master_find_slave(dev, source_device, source_port);
91 if (!skb->dev)
92 return NULL;
93
94 /*
95 * Convert the DSA header to an 802.1q header if the 'tagged'
96 * bit in the DSA header is set. If the 'tagged' bit is clear,
97 * delete the DSA header entirely.
98 */
99 if (dsa_header[0] & 0x20) {
100 u8 new_header[4];
101
102 /*
103 * Insert 802.1q ethertype and copy the VLAN-related
104 * fields, but clear the bit that will hold CFI (since
105 * DSA uses that bit location for another purpose).
106 */
107 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
108 new_header[1] = ETH_P_8021Q & 0xff;
109 new_header[2] = dsa_header[2] & ~0x10;
110 new_header[3] = dsa_header[3];
111
112 /*
113 * Move CFI bit from its place in the DSA header to
114 * its 802.1q-designated place.
115 */
116 if (dsa_header[1] & 0x01)
117 new_header[2] |= 0x10;
118
119 /*
120 * Update packet checksum if skb is CHECKSUM_COMPLETE.
121 */
122 if (skb->ip_summed == CHECKSUM_COMPLETE) {
123 __wsum c = skb->csum;
124 c = csum_add(c, csum_partial(new_header + 2, 2, 0));
125 c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
126 skb->csum = c;
127 }
128
129 memcpy(dsa_header, new_header, DSA_HLEN);
130 } else {
131 /*
132 * Remove DSA tag and update checksum.
133 */
134 skb_pull_rcsum(skb, DSA_HLEN);
135 memmove(skb->data - ETH_HLEN,
136 skb->data - ETH_HLEN - DSA_HLEN,
137 2 * ETH_ALEN);
138 }
139
140 skb->offload_fwd_mark = 1;
141
142 return skb;
143 }
144
dsa_tag_flow_dissect(const struct sk_buff * skb,__be16 * proto,int * offset)145 static int dsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
146 int *offset)
147 {
148 *offset = 4;
149 *proto = ((__be16 *)skb->data)[1];
150 return 0;
151 }
152
153 static const struct dsa_device_ops dsa_netdev_ops = {
154 .name = "dsa",
155 .proto = DSA_TAG_PROTO_DSA,
156 .xmit = dsa_xmit,
157 .rcv = dsa_rcv,
158 .flow_dissect = dsa_tag_flow_dissect,
159 .overhead = DSA_HLEN,
160 };
161
162 MODULE_LICENSE("GPL");
163 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
164
165 module_dsa_tag_driver(dsa_netdev_ops);
166
