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_port *dp = dsa_slave_to_port(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 | dp->ds->index;
  38                 dsa_header[1] = 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 | dp->ds->index;
  59                 dsa_header[1] = 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         u8 *dsa_header;
  71         int source_device;
  72         int source_port;
  73
  74         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
  75                 return NULL;
  76
  77         /*
  78          * The ethertype field is part of the DSA header.
  79          */
  80         dsa_header = skb->data - 2;
  81
  82         /*
  83          * Check that frame type is either TO_CPU or FORWARD.
  84          */
  85         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
  86                 return NULL;
  87
  88         /*
  89          * Determine source device and port.
  90          */
  91         source_device = dsa_header[0] & 0x1f;
  92         source_port = (dsa_header[1] >> 3) & 0x1f;
  93
  94         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
  95         if (!skb->dev)
  96                 return NULL;
  97
  98         /*
  99          * Convert the DSA header to an 802.1q header if the 'tagged'
 100          * bit in the DSA header is set.  If the 'tagged' bit is clear,
 101          * delete the DSA header entirely.
 102          */
 103         if (dsa_header[0] & 0x20) {
 104                 u8 new_header[4];
 105
 106                 /*
 107                  * Insert 802.1q ethertype and copy the VLAN-related
 108                  * fields, but clear the bit that will hold CFI (since
 109                  * DSA uses that bit location for another purpose).
 110                  */
 111                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 112                 new_header[1] = ETH_P_8021Q & 0xff;
 113                 new_header[2] = dsa_header[2] & ~0x10;
 114                 new_header[3] = dsa_header[3];
 115
 116                 /*
 117                  * Move CFI bit from its place in the DSA header to
 118                  * its 802.1q-designated place.
 119                  */
 120                 if (dsa_header[1] & 0x01)
 121                         new_header[2] |= 0x10;
 122
 123                 /*
 124                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 125                  */
 126                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 127                         __wsum c = skb->csum;
 128                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 129                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
 130                         skb->csum = c;
 131                 }
 132
 133                 memcpy(dsa_header, new_header, DSA_HLEN);
 134         } else {
 135                 /*
 136                  * Remove DSA tag and update checksum.
 137                  */
 138                 skb_pull_rcsum(skb, DSA_HLEN);
 139                 memmove(skb->data - ETH_HLEN,
 140                         skb->data - ETH_HLEN - DSA_HLEN,
 141                         2 * ETH_ALEN);
 142         }
 143
 144         skb->offload_fwd_mark = 1;
 145
 146         return skb;
 147 }
 148
 149 const struct dsa_device_ops dsa_netdev_ops = {
 150         .xmit   = dsa_xmit,
 151         .rcv    = dsa_rcv,
 152 };