text: /*
   * net/dsa/tag_dsa.c - (Non-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 "dsa_priv.h"
  
  #define DSA_HLEN	4
  
  netdev_tx_t dsa_xmit(struct sk_buff *skb, struct net_device *dev)
  {
  	struct dsa_slave_priv *p = netdev_priv(dev);
  	u8 *dsa_header;
  
  	dev->stats.tx_packets++;
  	dev->stats.tx_bytes += skb->len;
  
  	/*
  	 * Convert the outermost 802.1q tag to a DSA tag for tagged
  	 * packets, or insert a DSA tag between the addresses and
  	 * the ethertype field for untagged packets.
  	 */
  	if (skb->protocol == htons(ETH_P_8021Q)) {
  		if (skb_cow_head(skb, 0) < 0)
  			goto out_free;
  
  		/*
  		 * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  		 */
  		dsa_header = skb->data + 2 * ETH_ALEN;
  		dsa_header[0] = 0x60 | p->parent->index;
  		dsa_header[1] = p->port << 3;
  
  		/*
  		 * Move CFI field from byte 2 to byte 1.
  		 */
  		if (dsa_header[2] & 0x10) {
  			dsa_header[1] |= 0x01;
  			dsa_header[2] &= ~0x10;
  		}
  	} else {
  		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 untagged FROM_CPU DSA tag.
  		 */
  		dsa_header = skb->data + 2 * ETH_ALEN;
  		dsa_header[0] = 0x40 | p->parent->index;
  		dsa_header[1] = p->port << 3;
  		dsa_header[2] = 0x00;
  		dsa_header[3] = 0x00;
  	}
  
  	skb->protocol = htons(ETH_P_DSA);
  
  	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 dsa_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 *dsa_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, DSA_HLEN)))
  		goto out_drop;
  
  	/*
  	 * The ethertype field is part of the DSA header.
  	 */
  	dsa_header = skb->data - 2;
  
  	/*
  	 * Check that frame type is either TO_CPU or FORWARD.
  	 */
  	if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
  		goto out_drop;
  
  	/*
  	 * Determine source device and port.
  	 */
  	source_device = dsa_header[0] & 0x1f;
  	source_port = (dsa_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;
  
  	/*
  	 * Convert the DSA header to an 802.1q header if the 'tagged'
  	 * bit in the DSA header is set.  If the 'tagged' bit is clear,
  	 * delete the DSA header entirely.
  	 */
  	if (dsa_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] = dsa_header[2] & ~0x10;
  		new_header[3] = dsa_header[3];
  
  		/*
  		 * Move CFI bit from its place in the DSA header to
  		 * its 802.1q-designated place.
  		 */
  		if (dsa_header[1] & 0x01)
  			new_header[2] |= 0x10;
  
  		/*
  		 * 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(dsa_header + 2, 2, 0));
  			skb->csum = c;
  		}
  
  		memcpy(dsa_header, new_header, DSA_HLEN);
  	} else {
  		/*
  		 * Remove DSA tag and update checksum.
  		 */
  		skb_pull_rcsum(skb, DSA_HLEN);
  		memmove(skb->data - ETH_HLEN,
  			skb->data - ETH_HLEN - DSA_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;
  }
  
  static struct packet_type dsa_packet_type __read_mostly = {
  	.type	= cpu_to_be16(ETH_P_DSA),
  	.func	= dsa_rcv,
  };
  
  static int __init dsa_init_module(void)
  {
  	dev_add_pack(&dsa_packet_type);
  	return 0;
  }
  module_init(dsa_init_module);
  
  static void __exit dsa_cleanup_module(void)
  {
  	dev_remove_pack(&dsa_packet_type);
  }
  module_exit(dsa_cleanup_module);
  