/*
   * net/dsa/tag_edsa.c - Ethertype DSA tagging

   * Copyright (c) 2008-2009 Marvell Semiconductor

   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License as published by
   * the Free Software Foundation; either version 2 of the License, or
   * (at your option) any later version.
   */
  
  #include <linux/etherdevice.h>
  #include <linux/list.h>
  #include <linux/netdevice.h>

  #include <linux/slab.h>

  #include "dsa_priv.h"
  
  #define DSA_HLEN	4
  #define EDSA_HLEN	8

  netdev_tx_t edsa_xmit(struct sk_buff *skb, struct net_device *dev)

  {
  	struct dsa_slave_priv *p = netdev_priv(dev);
  	u8 *edsa_header;
  
  	dev->stats.tx_packets++;
  	dev->stats.tx_bytes += skb->len;
  
  	/*
  	 * Convert the outermost 802.1q tag to a DSA tag and prepend
  	 * a DSA ethertype field is the packet is tagged, or insert
  	 * a DSA ethertype plus DSA tag between the addresses and the
  	 * current ethertype field if the packet is untagged.
  	 */
  	if (skb->protocol == htons(ETH_P_8021Q)) {
  		if (skb_cow_head(skb, DSA_HLEN) < 0)
  			goto out_free;
  		skb_push(skb, DSA_HLEN);
  
  		memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
  
  		/*
  		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  		 */
  		edsa_header = skb->data + 2 * ETH_ALEN;
  		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  		edsa_header[1] = ETH_P_EDSA & 0xff;
  		edsa_header[2] = 0x00;
  		edsa_header[3] = 0x00;

  		edsa_header[4] = 0x60 | p->parent->index;

  		edsa_header[5] = p->port << 3;
  
  		/*
  		 * Move CFI field from byte 6 to byte 5.
  		 */
  		if (edsa_header[6] & 0x10) {
  			edsa_header[5] |= 0x01;
  			edsa_header[6] &= ~0x10;
  		}
  	} else {
  		if (skb_cow_head(skb, EDSA_HLEN) < 0)
  			goto out_free;
  		skb_push(skb, EDSA_HLEN);
  
  		memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
  
  		/*
  		 * Construct untagged FROM_CPU DSA tag.
  		 */
  		edsa_header = skb->data + 2 * ETH_ALEN;
  		edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  		edsa_header[1] = ETH_P_EDSA & 0xff;
  		edsa_header[2] = 0x00;
  		edsa_header[3] = 0x00;

  		edsa_header[4] = 0x40 | p->parent->index;

  		edsa_header[5] = p->port << 3;
  		edsa_header[6] = 0x00;
  		edsa_header[7] = 0x00;
  	}
  
  	skb->protocol = htons(ETH_P_EDSA);

  	skb->dev = p->parent->dst->master_netdev;

  	dev_queue_xmit(skb);
  
  	return NETDEV_TX_OK;
  
  out_free:
  	kfree_skb(skb);
  	return NETDEV_TX_OK;
  }
  
  static int edsa_rcv(struct sk_buff *skb, struct net_device *dev,
  		    struct packet_type *pt, struct net_device *orig_dev)
  {

  	struct dsa_switch_tree *dst = dev->dsa_ptr;
  	struct dsa_switch *ds;

  	u8 *edsa_header;

  	int source_device;

  	int source_port;

  	if (unlikely(dst == NULL))

  		goto out_drop;
  
  	skb = skb_unshare(skb, GFP_ATOMIC);
  	if (skb == NULL)
  		goto out;
  
  	if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
  		goto out_drop;
  
  	/*
  	 * Skip the two null bytes after the ethertype.
  	 */
  	edsa_header = skb->data + 2;
  
  	/*

  	 * Check that frame type is either TO_CPU or FORWARD.

  	 */

  	if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)

  		goto out_drop;
  
  	/*

  	 * Determine source device and port.

  	 */

  	source_device = edsa_header[0] & 0x1f;

  	source_port = (edsa_header[1] >> 3) & 0x1f;

  
  	/*
  	 * Check that the source device exists and that the source
  	 * port is a registered DSA port.
  	 */
  	if (source_device >= dst->pd->nr_chips)
  		goto out_drop;
  	ds = dst->ds[source_device];

  	if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
  		goto out_drop;
  
  	/*
  	 * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
  	 * tag and delete the ethertype part.  If the 'tagged' bit is
  	 * clear, delete the ethertype and the DSA tag parts.
  	 */
  	if (edsa_header[0] & 0x20) {
  		u8 new_header[4];
  
  		/*
  		 * Insert 802.1q ethertype and copy the VLAN-related
  		 * fields, but clear the bit that will hold CFI (since
  		 * DSA uses that bit location for another purpose).
  		 */
  		new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
  		new_header[1] = ETH_P_8021Q & 0xff;
  		new_header[2] = edsa_header[2] & ~0x10;
  		new_header[3] = edsa_header[3];
  
  		/*
  		 * Move CFI bit from its place in the DSA header to
  		 * its 802.1q-designated place.
  		 */
  		if (edsa_header[1] & 0x01)
  			new_header[2] |= 0x10;
  
  		skb_pull_rcsum(skb, DSA_HLEN);
  
  		/*
  		 * Update packet checksum if skb is CHECKSUM_COMPLETE.
  		 */
  		if (skb->ip_summed == CHECKSUM_COMPLETE) {
  			__wsum c = skb->csum;
  			c = csum_add(c, csum_partial(new_header + 2, 2, 0));
  			c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
  			skb->csum = c;
  		}
  
  		memcpy(edsa_header, new_header, DSA_HLEN);
  
  		memmove(skb->data - ETH_HLEN,
  			skb->data - ETH_HLEN - DSA_HLEN,
  			2 * ETH_ALEN);
  	} else {
  		/*
  		 * Remove DSA tag and update checksum.
  		 */
  		skb_pull_rcsum(skb, EDSA_HLEN);
  		memmove(skb->data - ETH_HLEN,
  			skb->data - ETH_HLEN - EDSA_HLEN,
  			2 * ETH_ALEN);
  	}
  
  	skb->dev = ds->ports[source_port];
  	skb_push(skb, ETH_HLEN);

  	skb->pkt_type = PACKET_HOST;

  	skb->protocol = eth_type_trans(skb, skb->dev);

  	skb->dev->stats.rx_packets++;
  	skb->dev->stats.rx_bytes += skb->len;
  
  	netif_receive_skb(skb);
  
  	return 0;
  
  out_drop:
  	kfree_skb(skb);
  out:
  	return 0;
  }

  struct packet_type edsa_packet_type __read_mostly = {

  	.type	= cpu_to_be16(ETH_P_EDSA),

  	.func	= edsa_rcv,
  };