1 /*
2 * net/dsa/tag_edsa.c - Ethertype DSA tagging
3 * Copyright (c) 2008-2009 Marvell Semiconductor
4 *
5 * This program is free software; you can redistribute it and/or modify
6 * it under the terms of the GNU General Public License as published by
7 * the Free Software Foundation; either version 2 of the License, or
8 * (at your option) any later version.
9 */
10
11 #include <linux/etherdevice.h>
12 #include <linux/list.h>
13 #include <linux/slab.h>
14
15 #include "dsa_priv.h"
16
17 #define DSA_HLEN 4
18 #define EDSA_HLEN 8
19
20 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
21 {
22 struct dsa_port *dp = dsa_slave_to_port(dev);
23 u8 *edsa_header;
24
25 /*
26 * Convert the outermost 802.1q tag to a DSA tag and prepend
27 * a DSA ethertype field is the packet is tagged, or insert
28 * a DSA ethertype plus DSA tag between the addresses and the
29 * current ethertype field if the packet is untagged.
30 */
31 if (skb->protocol == htons(ETH_P_8021Q)) {
32 if (skb_cow_head(skb, DSA_HLEN) < 0)
33 return NULL;
34 skb_push(skb, DSA_HLEN);
35
36 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
37
38 /*
39 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
40 */
41 edsa_header = skb->data + 2 * ETH_ALEN;
42 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
43 edsa_header[1] = ETH_P_EDSA & 0xff;
44 edsa_header[2] = 0x00;
45 edsa_header[3] = 0x00;
46 edsa_header[4] = 0x60 | dp->ds->index;
47 edsa_header[5] = dp->index << 3;
48
49 /*
50 * Move CFI field from byte 6 to byte 5.
51 */
52 if (edsa_header[6] & 0x10) {
53 edsa_header[5] |= 0x01;
54 edsa_header[6] &= ~0x10;
55 }
56 } else {
57 if (skb_cow_head(skb, EDSA_HLEN) < 0)
58 return NULL;
59 skb_push(skb, EDSA_HLEN);
60
61 memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
62
63 /*
64 * Construct untagged FROM_CPU DSA tag.
65 */
66 edsa_header = skb->data + 2 * ETH_ALEN;
67 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
68 edsa_header[1] = ETH_P_EDSA & 0xff;
69 edsa_header[2] = 0x00;
70 edsa_header[3] = 0x00;
71 edsa_header[4] = 0x40 | dp->ds->index;
72 edsa_header[5] = dp->index << 3;
73 edsa_header[6] = 0x00;
74 edsa_header[7] = 0x00;
75 }
76
77 return skb;
78 }
79
80 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
81 struct packet_type *pt)
82 {
83 u8 *edsa_header;
84 int source_device;
85 int source_port;
86
87 if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
88 return NULL;
89
90 /*
91 * Skip the two null bytes after the ethertype.
92 */
93 edsa_header = skb->data + 2;
94
95 /*
96 * Check that frame type is either TO_CPU or FORWARD.
97 */
98 if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
99 return NULL;
100
101 /*
102 * Determine source device and port.
103 */
104 source_device = edsa_header[0] & 0x1f;
105 source_port = (edsa_header[1] >> 3) & 0x1f;
106
107 skb->dev = dsa_master_find_slave(dev, source_device, source_port);
108 if (!skb->dev)
109 return NULL;
110
111 /*
112 * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
113 * tag and delete the ethertype part. If the 'tagged' bit is
114 * clear, delete the ethertype and the DSA tag parts.
115 */
116 if (edsa_header[0] & 0x20) {
117 u8 new_header[4];
118
119 /*
120 * Insert 802.1q ethertype and copy the VLAN-related
121 * fields, but clear the bit that will hold CFI (since
122 * DSA uses that bit location for another purpose).
123 */
124 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
125 new_header[1] = ETH_P_8021Q & 0xff;
126 new_header[2] = edsa_header[2] & ~0x10;
127 new_header[3] = edsa_header[3];
128
129 /*
130 * Move CFI bit from its place in the DSA header to
131 * its 802.1q-designated place.
132 */
133 if (edsa_header[1] & 0x01)
134 new_header[2] |= 0x10;
135
136 skb_pull_rcsum(skb, DSA_HLEN);
137
138 /*
139 * Update packet checksum if skb is CHECKSUM_COMPLETE.
140 */
141 if (skb->ip_summed == CHECKSUM_COMPLETE) {
142 __wsum c = skb->csum;
143 c = csum_add(c, csum_partial(new_header + 2, 2, 0));
144 c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
145 skb->csum = c;
146 }
147
148 memcpy(edsa_header, new_header, DSA_HLEN);
149
150 memmove(skb->data - ETH_HLEN,
151 skb->data - ETH_HLEN - DSA_HLEN,
152 2 * ETH_ALEN);
153 } else {
154 /*
155 * Remove DSA tag and update checksum.
156 */
157 skb_pull_rcsum(skb, EDSA_HLEN);
158 memmove(skb->data - ETH_HLEN,
159 skb->data - ETH_HLEN - EDSA_HLEN,
160 2 * ETH_ALEN);
161 }
162
163 skb->offload_fwd_mark = 1;
164
165 return skb;
166 }
167
168 const struct dsa_device_ops edsa_netdev_ops = {
169 .xmit = edsa_xmit,
170 .rcv = edsa_rcv,
171 };
172
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