net/dsa/tag_trailer.c

   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 #include "dsa_priv.h"
  15
  16 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
  17 {
  18         struct dsa_slave_priv *p = netdev_priv(dev);
  19         struct sk_buff *nskb;
  20         int padlen;
  21         u8 *trailer;
  22
  23         /*
  24          * We have to make sure that the trailer ends up as the very
  25          * last 4 bytes of the packet.  This means that we have to pad
  26          * the packet to the minimum ethernet frame size, if necessary,
  27          * before adding the trailer.
  28          */
  29         padlen = 0;
  30         if (skb->len < 60)
  31                 padlen = 60 - skb->len;
  32
  33         nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
  34         if (nskb == NULL) {
  35                 kfree_skb(skb);
  36                 return NULL;
  37         }
  38         skb_reserve(nskb, NET_IP_ALIGN);
  39
  40         skb_reset_mac_header(nskb);
  41         skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
  42         skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
  43         skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
  44         kfree_skb(skb);
  45
  46         if (padlen) {
  47                 u8 *pad = skb_put(nskb, padlen);
  48                 memset(pad, 0, padlen);
  49         }
  50
  51         trailer = skb_put(nskb, 4);
  52         trailer[0] = 0x80;
  53         trailer[1] = 1 << p->port;
  54         trailer[2] = 0x10;
  55         trailer[3] = 0x00;
  56
  57         return nskb;
  58 }
  59
  60 static int trailer_rcv(struct sk_buff *skb, struct net_device *dev,
  61                        struct packet_type *pt, struct net_device *orig_dev)
  62 {
  63         struct dsa_switch_tree *dst = dev->dsa_ptr;
  64         struct dsa_switch *ds;
  65         u8 *trailer;
  66         int source_port;
  67
  68         if (unlikely(dst == NULL))
  69                 goto out_drop;
  70         ds = dst->ds[0];
  71
  72         skb = skb_unshare(skb, GFP_ATOMIC);
  73         if (skb == NULL)
  74                 goto out;
  75
  76         if (skb_linearize(skb))
  77                 goto out_drop;
  78
  79         trailer = skb_tail_pointer(skb) - 4;
  80         if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
  81             (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
  82                 goto out_drop;
  83
  84         source_port = trailer[1] & 7;
  85         if (source_port >= DSA_MAX_PORTS || !ds->ports[source_port].netdev)
  86                 goto out_drop;
  87
  88         pskb_trim_rcsum(skb, skb->len - 4);
  89
  90         skb->dev = ds->ports[source_port].netdev;
  91         skb_push(skb, ETH_HLEN);
  92         skb->pkt_type = PACKET_HOST;
  93         skb->protocol = eth_type_trans(skb, skb->dev);
  94
  95         skb->dev->stats.rx_packets++;
  96         skb->dev->stats.rx_bytes += skb->len;
  97
  98         netif_receive_skb(skb);
  99
 100         return 0;
 101
 102 out_drop:
 103         kfree_skb(skb);
 104 out:
 105         return 0;
 106 }
 107
 108 const struct dsa_device_ops trailer_netdev_ops = {
 109         .xmit   = trailer_xmit,
 110         .rcv    = trailer_rcv,
 111 };