LXR linux/net/dsa/tag

   1/*
   2 * net/dsa/tag_trailer.c - Trailer tag format handling
   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
  17static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
  18{
  19        struct dsa_port *dp = dsa_slave_to_port(dev);
  20        struct sk_buff *nskb;
  21        int padlen;
  22        u8 *trailer;
  23
  24        /*
  25         * We have to make sure that the trailer ends up as the very
  26         * last 4 bytes of the packet.  This means that we have to pad
  27         * the packet to the minimum ethernet frame size, if necessary,
  28         * before adding the trailer.
  29         */
  30        padlen = 0;
  31        if (skb->len < 60)
  32                padlen = 60 - skb->len;
  33
  34        nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
  35        if (!nskb)
  36                return NULL;
  37        skb_reserve(nskb, NET_IP_ALIGN);
  38
  39        skb_reset_mac_header(nskb);
  40        skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
  41        skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
  42        skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
  43        consume_skb(skb);
  44
  45        if (padlen) {
  46                skb_put_zero(nskb, padlen);
  47        }
  48
  49        trailer = skb_put(nskb, 4);
  50        trailer[0] = 0x80;
  51        trailer[1] = 1 << dp->index;
  52        trailer[2] = 0x10;
  53        trailer[3] = 0x00;
  54
  55        return nskb;
  56}
  57
  58static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev,
  59                                   struct packet_type *pt)
  60{
  61        u8 *trailer;
  62        int source_port;
  63
  64        if (skb_linearize(skb))
  65                return NULL;
  66
  67        trailer = skb_tail_pointer(skb) - 4;
  68        if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
  69            (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
  70                return NULL;
  71
  72        source_port = trailer[1] & 7;
  73
  74        skb->dev = dsa_master_find_slave(dev, 0, source_port);
  75        if (!skb->dev)
  76                return NULL;
  77
  78        pskb_trim_rcsum(skb, skb->len - 4);
  79
  80        return skb;
  81}
  82
  83const struct dsa_device_ops trailer_netdev_ops = {
  84        .xmit   = trailer_xmit,
  85        .rcv    = trailer_rcv,
  86};
  87