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
 20static 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
 80static 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
168const struct dsa_device_ops edsa_netdev_ops = {
169	.xmit	= edsa_xmit,
170	.rcv	= edsa_rcv,
171};