net/dsa/tag_dsa.c

   1 /*
   2  * net/dsa/tag_dsa.c - (Non-ethertype) DSA tagging
   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
  17 #define DSA_HLEN        4
  18
  19 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
  20 {
  21         struct dsa_slave_priv *p = netdev_priv(dev);
  22         u8 *dsa_header;
  23
  24         /*
  25          * Convert the outermost 802.1q tag to a DSA tag for tagged
  26          * packets, or insert a DSA tag between the addresses and
  27          * the ethertype field for untagged packets.
  28          */
  29         if (skb->protocol == htons(ETH_P_8021Q)) {
  30                 if (skb_cow_head(skb, 0) < 0)
  31                         return NULL;
  32
  33                 /*
  34                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  35                  */
  36                 dsa_header = skb->data + 2 * ETH_ALEN;
  37                 dsa_header[0] = 0x60 | p->dp->ds->index;
  38                 dsa_header[1] = p->dp->index << 3;
  39
  40                 /*
  41                  * Move CFI field from byte 2 to byte 1.
  42                  */
  43                 if (dsa_header[2] & 0x10) {
  44                         dsa_header[1] |= 0x01;
  45                         dsa_header[2] &= ~0x10;
  46                 }
  47         } else {
  48                 if (skb_cow_head(skb, DSA_HLEN) < 0)
  49                         return NULL;
  50                 skb_push(skb, DSA_HLEN);
  51
  52                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
  53
  54                 /*
  55                  * Construct untagged FROM_CPU DSA tag.
  56                  */
  57                 dsa_header = skb->data + 2 * ETH_ALEN;
  58                 dsa_header[0] = 0x40 | p->dp->ds->index;
  59                 dsa_header[1] = p->dp->index << 3;
  60                 dsa_header[2] = 0x00;
  61                 dsa_header[3] = 0x00;
  62         }
  63
  64         return skb;
  65 }
  66
  67 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
  68                                struct packet_type *pt)
  69 {
  70         struct dsa_switch_tree *dst = dev->dsa_ptr;
  71         struct dsa_switch *ds;
  72         u8 *dsa_header;
  73         int source_device;
  74         int source_port;
  75
  76         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
  77                 return NULL;
  78
  79         /*
  80          * The ethertype field is part of the DSA header.
  81          */
  82         dsa_header = skb->data - 2;
  83
  84         /*
  85          * Check that frame type is either TO_CPU or FORWARD.
  86          */
  87         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
  88                 return NULL;
  89
  90         /*
  91          * Determine source device and port.
  92          */
  93         source_device = dsa_header[0] & 0x1f;
  94         source_port = (dsa_header[1] >> 3) & 0x1f;
  95
  96         /*
  97          * Check that the source device exists and that the source
  98          * port is a registered DSA port.
  99          */
 100         if (source_device >= DSA_MAX_SWITCHES)
 101                 return NULL;
 102
 103         ds = dst->ds[source_device];
 104         if (!ds)
 105                 return NULL;
 106
 107         if (source_port >= ds->num_ports || !ds->ports[source_port].netdev)
 108                 return NULL;
 109
 110         /*
 111          * Convert the DSA header to an 802.1q header if the 'tagged'
 112          * bit in the DSA header is set.  If the 'tagged' bit is clear,
 113          * delete the DSA header entirely.
 114          */
 115         if (dsa_header[0] & 0x20) {
 116                 u8 new_header[4];
 117
 118                 /*
 119                  * Insert 802.1q ethertype and copy the VLAN-related
 120                  * fields, but clear the bit that will hold CFI (since
 121                  * DSA uses that bit location for another purpose).
 122                  */
 123                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 124                 new_header[1] = ETH_P_8021Q & 0xff;
 125                 new_header[2] = dsa_header[2] & ~0x10;
 126                 new_header[3] = dsa_header[3];
 127
 128                 /*
 129                  * Move CFI bit from its place in the DSA header to
 130                  * its 802.1q-designated place.
 131                  */
 132                 if (dsa_header[1] & 0x01)
 133                         new_header[2] |= 0x10;
 134
 135                 /*
 136                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 137                  */
 138                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 139                         __wsum c = skb->csum;
 140                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 141                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
 142                         skb->csum = c;
 143                 }
 144
 145                 memcpy(dsa_header, new_header, DSA_HLEN);
 146         } else {
 147                 /*
 148                  * Remove DSA tag and update checksum.
 149                  */
 150                 skb_pull_rcsum(skb, DSA_HLEN);
 151                 memmove(skb->data - ETH_HLEN,
 152                         skb->data - ETH_HLEN - DSA_HLEN,
 153                         2 * ETH_ALEN);
 154         }
 155
 156         skb->dev = ds->ports[source_port].netdev;
 157
 158         return skb;
 159 }
 160
 161 const struct dsa_device_ops dsa_netdev_ops = {
 162         .xmit   = dsa_xmit,
 163         .rcv    = dsa_rcv,
 164 };