1/*
2 * net/dsa/tag_dsa.c - (Non-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#include "dsa_priv.h"
15
16#define DSA_HLEN	4
17
18static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
19{
20	struct dsa_slave_priv *p = netdev_priv(dev);
21	u8 *dsa_header;
22
23	/*
24	 * Convert the outermost 802.1q tag to a DSA tag for tagged
25	 * packets, or insert a DSA tag between the addresses and
26	 * the ethertype field for untagged packets.
27	 */
28	if (skb->protocol == htons(ETH_P_8021Q)) {
29		if (skb_cow_head(skb, 0) < 0)
30			goto out_free;
31
32		/*
33		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
34		 */
35		dsa_header = skb->data + 2 * ETH_ALEN;
36		dsa_header[0] = 0x60 | p->parent->index;
37		dsa_header[1] = p->port << 3;
38
39		/*
40		 * Move CFI field from byte 2 to byte 1.
41		 */
42		if (dsa_header[2] & 0x10) {
43			dsa_header[1] |= 0x01;
44			dsa_header[2] &= ~0x10;
45		}
46	} else {
47		if (skb_cow_head(skb, DSA_HLEN) < 0)
48			goto out_free;
49		skb_push(skb, DSA_HLEN);
50
51		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
52
53		/*
54		 * Construct untagged FROM_CPU DSA tag.
55		 */
56		dsa_header = skb->data + 2 * ETH_ALEN;
57		dsa_header[0] = 0x40 | p->parent->index;
58		dsa_header[1] = p->port << 3;
59		dsa_header[2] = 0x00;
60		dsa_header[3] = 0x00;
61	}
62
63	return skb;
64
65out_free:
66	kfree_skb(skb);
67	return NULL;
68}
69
70static int dsa_rcv(struct sk_buff *skb, struct net_device *dev,
71		   struct packet_type *pt, struct net_device *orig_dev)
72{
73	struct dsa_switch_tree *dst = dev->dsa_ptr;
74	struct dsa_switch *ds;
75	u8 *dsa_header;
76	int source_device;
77	int source_port;
78
79	if (unlikely(dst == NULL))
80		goto out_drop;
81
82	skb = skb_unshare(skb, GFP_ATOMIC);
83	if (skb == NULL)
84		goto out;
85
86	if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
87		goto out_drop;
88
89	/*
90	 * The ethertype field is part of the DSA header.
91	 */
92	dsa_header = skb->data - 2;
93
94	/*
95	 * Check that frame type is either TO_CPU or FORWARD.
96	 */
97	if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
98		goto out_drop;
99
100	/*
101	 * Determine source device and port.
102	 */
103	source_device = dsa_header[0] & 0x1f;
104	source_port = (dsa_header[1] >> 3) & 0x1f;
105
106	/*
107	 * Check that the source device exists and that the source
108	 * port is a registered DSA port.
109	 */
110	if (source_device >= dst->pd->nr_chips)
111		goto out_drop;
112	ds = dst->ds[source_device];
113	if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
114		goto out_drop;
115
116	/*
117	 * Convert the DSA header to an 802.1q header if the 'tagged'
118	 * bit in the DSA header is set.  If the 'tagged' bit is clear,
119	 * delete the DSA header entirely.
120	 */
121	if (dsa_header[0] & 0x20) {
122		u8 new_header[4];
123
124		/*
125		 * Insert 802.1q ethertype and copy the VLAN-related
126		 * fields, but clear the bit that will hold CFI (since
127		 * DSA uses that bit location for another purpose).
128		 */
129		new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
130		new_header[1] = ETH_P_8021Q & 0xff;
131		new_header[2] = dsa_header[2] & ~0x10;
132		new_header[3] = dsa_header[3];
133
134		/*
135		 * Move CFI bit from its place in the DSA header to
136		 * its 802.1q-designated place.
137		 */
138		if (dsa_header[1] & 0x01)
139			new_header[2] |= 0x10;
140
141		/*
142		 * Update packet checksum if skb is CHECKSUM_COMPLETE.
143		 */
144		if (skb->ip_summed == CHECKSUM_COMPLETE) {
145			__wsum c = skb->csum;
146			c = csum_add(c, csum_partial(new_header + 2, 2, 0));
147			c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
148			skb->csum = c;
149		}
150
151		memcpy(dsa_header, new_header, DSA_HLEN);
152	} else {
153		/*
154		 * Remove DSA tag and update checksum.
155		 */
156		skb_pull_rcsum(skb, DSA_HLEN);
157		memmove(skb->data - ETH_HLEN,
158			skb->data - ETH_HLEN - DSA_HLEN,
159			2 * ETH_ALEN);
160	}
161
162	skb->dev = ds->ports[source_port];
163	skb_push(skb, ETH_HLEN);
164	skb->pkt_type = PACKET_HOST;
165	skb->protocol = eth_type_trans(skb, skb->dev);
166
167	skb->dev->stats.rx_packets++;
168	skb->dev->stats.rx_bytes += skb->len;
169
170	netif_receive_skb(skb);
171
172	return 0;
173
174out_drop:
175	kfree_skb(skb);
176out:
177	return 0;
178}
179
180const struct dsa_device_ops dsa_netdev_ops = {
181	.xmit	= dsa_xmit,
182	.rcv	= dsa_rcv,
183};
184