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 <net/dsa.h>
  15 #include "dsa_priv.h"
  16
  17 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
  18 {
  19         struct dsa_slave_priv *p = netdev_priv(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 == NULL) {
  36                 kfree_skb(skb);
  37                 return NULL;
  38         }
  39         skb_reserve(nskb, NET_IP_ALIGN);
  40
  41         skb_reset_mac_header(nskb);
  42         skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
  43         skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
  44         skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
  45         kfree_skb(skb);
  46
  47         if (padlen) {
  48                 u8 *pad = skb_put(nskb, padlen);
  49                 memset(pad, 0, padlen);
  50         }
  51
  52         trailer = skb_put(nskb, 4);
  53         trailer[0] = 0x80;
  54         trailer[1] = 1 << p->dp->index;
  55         trailer[2] = 0x10;
  56         trailer[3] = 0x00;
  57
  58         return nskb;
  59 }
  60
  61 static int trailer_rcv(struct sk_buff *skb, struct net_device *dev,
  62                        struct packet_type *pt, struct net_device *orig_dev)
  63 {
  64         struct dsa_switch_tree *dst = dev->dsa_ptr;
  65         struct dsa_switch *ds;
  66         u8 *trailer;
  67         int source_port;
  68
  69         if (unlikely(dst == NULL))
  70                 goto out_drop;
  71         ds = dst->cpu_switch;
  72
  73         skb = skb_unshare(skb, GFP_ATOMIC);
  74         if (skb == NULL)
  75                 goto out;
  76
  77         if (skb_linearize(skb))
  78                 goto out_drop;
  79
  80         trailer = skb_tail_pointer(skb) - 4;
  81         if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
  82             (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
  83                 goto out_drop;
  84
  85         source_port = trailer[1] & 7;
  86         if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
  87                 goto out_drop;
  88
  89         pskb_trim_rcsum(skb, skb->len - 4);
  90
  91         skb->dev = ds->ports[source_port].netdev;
  92         skb_push(skb, ETH_HLEN);
  93         skb->pkt_type = PACKET_HOST;
  94         skb->protocol = eth_type_trans(skb, skb->dev);
  95
  96         skb->dev->stats.rx_packets++;
  97         skb->dev->stats.rx_bytes += skb->len;
  98
  99         netif_receive_skb(skb);
 100
 101         return 0;
 102
 103 out_drop:
 104         kfree_skb(skb);
 105 out:
 106         return 0;
 107 }
 108
 109 const struct dsa_device_ops trailer_netdev_ops = {
 110         .xmit   = trailer_xmit,
 111         .rcv    = trailer_rcv,
 112 };