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#include "dsa_priv.h"
 15
 16#define DSA_HLEN	4
 17#define EDSA_HLEN	8
 18
 19static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
 20{
 21	struct dsa_slave_priv *p = netdev_priv(dev);
 22	u8 *edsa_header;
 23
 24	/*
 25	 * Convert the outermost 802.1q tag to a DSA tag and prepend
 26	 * a DSA ethertype field is the packet is tagged, or insert
 27	 * a DSA ethertype plus DSA tag between the addresses and the
 28	 * current ethertype field if the packet is untagged.
 29	 */
 30	if (skb->protocol == htons(ETH_P_8021Q)) {
 31		if (skb_cow_head(skb, DSA_HLEN) < 0)
 32			goto out_free;
 33		skb_push(skb, DSA_HLEN);
 34
 35		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
 36
 37		/*
 38		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
 39		 */
 40		edsa_header = skb->data + 2 * ETH_ALEN;
 41		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 42		edsa_header[1] = ETH_P_EDSA & 0xff;
 43		edsa_header[2] = 0x00;
 44		edsa_header[3] = 0x00;
 45		edsa_header[4] = 0x60 | p->parent->index;
 46		edsa_header[5] = p->port << 3;
 47
 48		/*
 49		 * Move CFI field from byte 6 to byte 5.
 50		 */
 51		if (edsa_header[6] & 0x10) {
 52			edsa_header[5] |= 0x01;
 53			edsa_header[6] &= ~0x10;
 54		}
 55	} else {
 56		if (skb_cow_head(skb, EDSA_HLEN) < 0)
 57			goto out_free;
 58		skb_push(skb, EDSA_HLEN);
 59
 60		memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
 61
 62		/*
 63		 * Construct untagged FROM_CPU DSA tag.
 64		 */
 65		edsa_header = skb->data + 2 * ETH_ALEN;
 66		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
 67		edsa_header[1] = ETH_P_EDSA & 0xff;
 68		edsa_header[2] = 0x00;
 69		edsa_header[3] = 0x00;
 70		edsa_header[4] = 0x40 | p->parent->index;
 71		edsa_header[5] = p->port << 3;
 72		edsa_header[6] = 0x00;
 73		edsa_header[7] = 0x00;
 74	}
 75
 76	return skb;
 77
 78out_free:
 79	kfree_skb(skb);
 80	return NULL;
 81}
 82
 83static int edsa_rcv(struct sk_buff *skb, struct net_device *dev,
 84		    struct packet_type *pt, struct net_device *orig_dev)
 85{
 86	struct dsa_switch_tree *dst = dev->dsa_ptr;
 87	struct dsa_switch *ds;
 88	u8 *edsa_header;
 89	int source_device;
 90	int source_port;
 91
 92	if (unlikely(dst == NULL))
 93		goto out_drop;
 94
 95	skb = skb_unshare(skb, GFP_ATOMIC);
 96	if (skb == NULL)
 97		goto out;
 98
 99	if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
100		goto out_drop;
101
102	/*
103	 * Skip the two null bytes after the ethertype.
104	 */
105	edsa_header = skb->data + 2;
106
107	/*
108	 * Check that frame type is either TO_CPU or FORWARD.
109	 */
110	if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
111		goto out_drop;
112
113	/*
114	 * Determine source device and port.
115	 */
116	source_device = edsa_header[0] & 0x1f;
117	source_port = (edsa_header[1] >> 3) & 0x1f;
118
119	/*
120	 * Check that the source device exists and that the source
121	 * port is a registered DSA port.
122	 */
123	if (source_device >= DSA_MAX_SWITCHES)
124		goto out_drop;
125
126	ds = dst->ds[source_device];
127	if (!ds)
128		goto out_drop;
129
130	if (source_port >= DSA_MAX_PORTS || !ds->ports[source_port].netdev)
131		goto out_drop;
132
133	/*
134	 * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
135	 * tag and delete the ethertype part.  If the 'tagged' bit is
136	 * clear, delete the ethertype and the DSA tag parts.
137	 */
138	if (edsa_header[0] & 0x20) {
139		u8 new_header[4];
140
141		/*
142		 * Insert 802.1q ethertype and copy the VLAN-related
143		 * fields, but clear the bit that will hold CFI (since
144		 * DSA uses that bit location for another purpose).
145		 */
146		new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
147		new_header[1] = ETH_P_8021Q & 0xff;
148		new_header[2] = edsa_header[2] & ~0x10;
149		new_header[3] = edsa_header[3];
150
151		/*
152		 * Move CFI bit from its place in the DSA header to
153		 * its 802.1q-designated place.
154		 */
155		if (edsa_header[1] & 0x01)
156			new_header[2] |= 0x10;
157
158		skb_pull_rcsum(skb, DSA_HLEN);
159
160		/*
161		 * Update packet checksum if skb is CHECKSUM_COMPLETE.
162		 */
163		if (skb->ip_summed == CHECKSUM_COMPLETE) {
164			__wsum c = skb->csum;
165			c = csum_add(c, csum_partial(new_header + 2, 2, 0));
166			c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
167			skb->csum = c;
168		}
169
170		memcpy(edsa_header, new_header, DSA_HLEN);
171
172		memmove(skb->data - ETH_HLEN,
173			skb->data - ETH_HLEN - DSA_HLEN,
174			2 * ETH_ALEN);
175	} else {
176		/*
177		 * Remove DSA tag and update checksum.
178		 */
179		skb_pull_rcsum(skb, EDSA_HLEN);
180		memmove(skb->data - ETH_HLEN,
181			skb->data - ETH_HLEN - EDSA_HLEN,
182			2 * ETH_ALEN);
183	}
184
185	skb->dev = ds->ports[source_port].netdev;
186	skb_push(skb, ETH_HLEN);
187	skb->pkt_type = PACKET_HOST;
188	skb->protocol = eth_type_trans(skb, skb->dev);
189
190	skb->dev->stats.rx_packets++;
191	skb->dev->stats.rx_bytes += skb->len;
192
193	netif_receive_skb(skb);
194
195	return 0;
196
197out_drop:
198	kfree_skb(skb);
199out:
200	return 0;
201}
202
203const struct dsa_device_ops edsa_netdev_ops = {
204	.xmit	= edsa_xmit,
205	.rcv	= edsa_rcv,
206};