/*
   * net/dsa/tag_trailer.c - Trailer tag format handling

   * 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/slab.h>

  #include "dsa_priv.h"

  static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)

  {
  	struct dsa_slave_priv *p = netdev_priv(dev);
  	struct sk_buff *nskb;
  	int padlen;
  	u8 *trailer;

  	/*
  	 * We have to make sure that the trailer ends up as the very
  	 * last 4 bytes of the packet.  This means that we have to pad
  	 * the packet to the minimum ethernet frame size, if necessary,
  	 * before adding the trailer.
  	 */
  	padlen = 0;
  	if (skb->len < 60)
  		padlen = 60 - skb->len;
  
  	nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
  	if (nskb == NULL) {
  		kfree_skb(skb);

  		return NULL;

  	}
  	skb_reserve(nskb, NET_IP_ALIGN);
  
  	skb_reset_mac_header(nskb);
  	skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
  	skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
  	skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
  	kfree_skb(skb);
  
  	if (padlen) {
  		u8 *pad = skb_put(nskb, padlen);
  		memset(pad, 0, padlen);
  	}
  
  	trailer = skb_put(nskb, 4);
  	trailer[0] = 0x80;
  	trailer[1] = 1 << p->port;
  	trailer[2] = 0x10;
  	trailer[3] = 0x00;

  	return nskb;

  }
  
  static int trailer_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 *trailer;
  	int source_port;

  	if (unlikely(dst == NULL))

  		goto out_drop;

  	ds = dst->ds[0];

  
  	skb = skb_unshare(skb, GFP_ATOMIC);
  	if (skb == NULL)
  		goto out;
  
  	if (skb_linearize(skb))
  		goto out_drop;
  
  	trailer = skb_tail_pointer(skb) - 4;
  	if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||

  	    (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)

  		goto out_drop;
  
  	source_port = trailer[1] & 7;

  	if (source_port >= DSA_MAX_PORTS || !ds->ports[source_port].netdev)

  		goto out_drop;
  
  	pskb_trim_rcsum(skb, skb->len - 4);

  	skb->dev = ds->ports[source_port].netdev;

  	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;
  }

  const struct dsa_device_ops trailer_netdev_ops = {
  	.xmit	= trailer_xmit,
  	.rcv	= trailer_rcv,

  };