net/dsa/tag_edsa.c

   1 /*
   2  * net/dsa/tag_edsa.c - 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 #define EDSA_HLEN       8
  19
  20 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
  21 {
  22         struct dsa_port *dp = dsa_slave_to_port(dev);
  23         u8 *edsa_header;
  24
  25         /*
  26          * Convert the outermost 802.1q tag to a DSA tag and prepend
  27          * a DSA ethertype field is the packet is tagged, or insert
  28          * a DSA ethertype plus DSA tag between the addresses and the
  29          * current ethertype field if the packet is untagged.
  30          */
  31         if (skb->protocol == htons(ETH_P_8021Q)) {
  32                 if (skb_cow_head(skb, DSA_HLEN) < 0)
  33                         return NULL;
  34                 skb_push(skb, DSA_HLEN);
  35
  36                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
  37
  38                 /*
  39                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  40                  */
  41                 edsa_header = skb->data + 2 * ETH_ALEN;
  42                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  43                 edsa_header[1] = ETH_P_EDSA & 0xff;
  44                 edsa_header[2] = 0x00;
  45                 edsa_header[3] = 0x00;
  46                 edsa_header[4] = 0x60 | dp->ds->index;
  47                 edsa_header[5] = dp->index << 3;
  48
  49                 /*
  50                  * Move CFI field from byte 6 to byte 5.
  51                  */
  52                 if (edsa_header[6] & 0x10) {
  53                         edsa_header[5] |= 0x01;
  54                         edsa_header[6] &= ~0x10;
  55                 }
  56         } else {
  57                 if (skb_cow_head(skb, EDSA_HLEN) < 0)
  58                         return NULL;
  59                 skb_push(skb, EDSA_HLEN);
  60
  61                 memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
  62
  63                 /*
  64                  * Construct untagged FROM_CPU DSA tag.
  65                  */
  66                 edsa_header = skb->data + 2 * ETH_ALEN;
  67                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  68                 edsa_header[1] = ETH_P_EDSA & 0xff;
  69                 edsa_header[2] = 0x00;
  70                 edsa_header[3] = 0x00;
  71                 edsa_header[4] = 0x40 | dp->ds->index;
  72                 edsa_header[5] = dp->index << 3;
  73                 edsa_header[6] = 0x00;
  74                 edsa_header[7] = 0x00;
  75         }
  76
  77         return skb;
  78 }
  79
  80 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
  81                                 struct packet_type *pt)
  82 {
  83         u8 *edsa_header;
  84         int source_device;
  85         int source_port;
  86
  87         if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
  88                 return NULL;
  89
  90         /*
  91          * Skip the two null bytes after the ethertype.
  92          */
  93         edsa_header = skb->data + 2;
  94
  95         /*
  96          * Check that frame type is either TO_CPU or FORWARD.
  97          */
  98         if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
  99                 return NULL;
 100
 101         /*
 102          * Determine source device and port.
 103          */
 104         source_device = edsa_header[0] & 0x1f;
 105         source_port = (edsa_header[1] >> 3) & 0x1f;
 106
 107         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
 108         if (!skb->dev)
 109                 return NULL;
 110
 111         /*
 112          * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
 113          * tag and delete the ethertype part.  If the 'tagged' bit is
 114          * clear, delete the ethertype and the DSA tag parts.
 115          */
 116         if (edsa_header[0] & 0x20) {
 117                 u8 new_header[4];
 118
 119                 /*
 120                  * Insert 802.1q ethertype and copy the VLAN-related
 121                  * fields, but clear the bit that will hold CFI (since
 122                  * DSA uses that bit location for another purpose).
 123                  */
 124                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 125                 new_header[1] = ETH_P_8021Q & 0xff;
 126                 new_header[2] = edsa_header[2] & ~0x10;
 127                 new_header[3] = edsa_header[3];
 128
 129                 /*
 130                  * Move CFI bit from its place in the DSA header to
 131                  * its 802.1q-designated place.
 132                  */
 133                 if (edsa_header[1] & 0x01)
 134                         new_header[2] |= 0x10;
 135
 136                 skb_pull_rcsum(skb, DSA_HLEN);
 137
 138                 /*
 139                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 140                  */
 141                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 142                         __wsum c = skb->csum;
 143                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 144                         c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
 145                         skb->csum = c;
 146                 }
 147
 148                 memcpy(edsa_header, new_header, DSA_HLEN);
 149
 150                 memmove(skb->data - ETH_HLEN,
 151                         skb->data - ETH_HLEN - DSA_HLEN,
 152                         2 * ETH_ALEN);
 153         } else {
 154                 /*
 155                  * Remove DSA tag and update checksum.
 156                  */
 157                 skb_pull_rcsum(skb, EDSA_HLEN);
 158                 memmove(skb->data - ETH_HLEN,
 159                         skb->data - ETH_HLEN - EDSA_HLEN,
 160                         2 * ETH_ALEN);
 161         }
 162
 163         skb->offload_fwd_mark = 1;
 164
 165         return skb;
 166 }
 167
 168 const struct dsa_device_ops edsa_netdev_ops = {
 169         .xmit   = edsa_xmit,
 170         .rcv    = edsa_rcv,
 171 };