1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3 * net/dsa/tag_edsa.c - 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 #define EDSA_HLEN 8
15
16 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
17 {
18 struct dsa_port *dp = dsa_slave_to_port(dev);
19 u8 *edsa_header;
20
21 /*
22 * Convert the outermost 802.1q tag to a DSA tag and prepend
23 * a DSA ethertype field is the packet is tagged, or insert
24 * a DSA ethertype plus DSA tag between the addresses and the
25 * current ethertype field if the packet is untagged.
26 */
27 if (skb->protocol == htons(ETH_P_8021Q)) {
28 if (skb_cow_head(skb, DSA_HLEN) < 0)
29 return NULL;
30 skb_push(skb, DSA_HLEN);
31
32 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
33
34 /*
35 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
36 */
37 edsa_header = skb->data + 2 * ETH_ALEN;
38 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
39 edsa_header[1] = ETH_P_EDSA & 0xff;
40 edsa_header[2] = 0x00;
41 edsa_header[3] = 0x00;
42 edsa_header[4] = 0x60 | dp->ds->index;
43 edsa_header[5] = dp->index << 3;
44
45 /*
46 * Move CFI field from byte 6 to byte 5.
47 */
48 if (edsa_header[6] & 0x10) {
49 edsa_header[5] |= 0x01;
50 edsa_header[6] &= ~0x10;
51 }
52 } else {
53 if (skb_cow_head(skb, EDSA_HLEN) < 0)
54 return NULL;
55 skb_push(skb, EDSA_HLEN);
56
57 memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
58
59 /*
60 * Construct untagged FROM_CPU DSA tag.
61 */
62 edsa_header = skb->data + 2 * ETH_ALEN;
63 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
64 edsa_header[1] = ETH_P_EDSA & 0xff;
65 edsa_header[2] = 0x00;
66 edsa_header[3] = 0x00;
67 edsa_header[4] = 0x40 | dp->ds->index;
68 edsa_header[5] = dp->index << 3;
69 edsa_header[6] = 0x00;
70 edsa_header[7] = 0x00;
71 }
72
73 return skb;
74 }
75
76 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
77 struct packet_type *pt)
78 {
79 u8 *edsa_header;
80 int source_device;
81 int source_port;
82
83 if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
84 return NULL;
85
86 /*
87 * Skip the two null bytes after the ethertype.
88 */
89 edsa_header = skb->data + 2;
90
91 /*
92 * Check that frame type is either TO_CPU or FORWARD.
93 */
94 if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
95 return NULL;
96
97 /*
98 * Determine source device and port.
99 */
100 source_device = edsa_header[0] & 0x1f;
101 source_port = (edsa_header[1] >> 3) & 0x1f;
102
103 skb->dev = dsa_master_find_slave(dev, source_device, source_port);
104 if (!skb->dev)
105 return NULL;
106
107 /*
108 * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
109 * tag and delete the ethertype part. If the 'tagged' bit is
110 * clear, delete the ethertype and the DSA tag parts.
111 */
112 if (edsa_header[0] & 0x20) {
113 u8 new_header[4];
114
115 /*
116 * Insert 802.1q ethertype and copy the VLAN-related
117 * fields, but clear the bit that will hold CFI (since
118 * DSA uses that bit location for another purpose).
119 */
120 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
121 new_header[1] = ETH_P_8021Q & 0xff;
122 new_header[2] = edsa_header[2] & ~0x10;
123 new_header[3] = edsa_header[3];
124
125 /*
126 * Move CFI bit from its place in the DSA header to
127 * its 802.1q-designated place.
128 */
129 if (edsa_header[1] & 0x01)
130 new_header[2] |= 0x10;
131
132 skb_pull_rcsum(skb, DSA_HLEN);
133
134 /*
135 * Update packet checksum if skb is CHECKSUM_COMPLETE.
136 */
137 if (skb->ip_summed == CHECKSUM_COMPLETE) {
138 __wsum c = skb->csum;
139 c = csum_add(c, csum_partial(new_header + 2, 2, 0));
140 c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
141 skb->csum = c;
142 }
143
144 memcpy(edsa_header, new_header, DSA_HLEN);
145
146 memmove(skb->data - ETH_HLEN,
147 skb->data - ETH_HLEN - DSA_HLEN,
148 2 * ETH_ALEN);
149 } else {
150 /*
151 * Remove DSA tag and update checksum.
152 */
153 skb_pull_rcsum(skb, EDSA_HLEN);
154 memmove(skb->data - ETH_HLEN,
155 skb->data - ETH_HLEN - EDSA_HLEN,
156 2 * ETH_ALEN);
157 }
158
159 skb->offload_fwd_mark = 1;
160
161 return skb;
162 }
163
164 static int edsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
165 int *offset)
166 {
167 *offset = 8;
168 *proto = ((__be16 *)skb->data)[3];
169 return 0;
170 }
171
172 static const struct dsa_device_ops edsa_netdev_ops = {
173 .name = "edsa",
174 .proto = DSA_TAG_PROTO_EDSA,
175 .xmit = edsa_xmit,
176 .rcv = edsa_rcv,
177 .flow_dissect = edsa_tag_flow_dissect,
178 .overhead = EDSA_HLEN,
179 };
180
181 MODULE_LICENSE("GPL");
182 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_EDSA);
183
184 module_dsa_tag_driver(edsa_netdev_ops);
185
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