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 #include "dsa_priv.h"
  15
  16 #define DSA_HLEN        4
  17 #define EDSA_HLEN       8
  18
  19 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
  20 {
  21         struct dsa_slave_priv *p = netdev_priv(dev);
  22         u8 *edsa_header;
  23
  24         /*
  25          * Convert the outermost 802.1q tag to a DSA tag and prepend
  26          * a DSA ethertype field is the packet is tagged, or insert
  27          * a DSA ethertype plus DSA tag between the addresses and the
  28          * current ethertype field if the packet is untagged.
  29          */
  30         if (skb->protocol == htons(ETH_P_8021Q)) {
  31                 if (skb_cow_head(skb, DSA_HLEN) < 0)
  32                         goto out_free;
  33                 skb_push(skb, DSA_HLEN);
  34
  35                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
  36
  37                 /*
  38                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  39                  */
  40                 edsa_header = skb->data + 2 * ETH_ALEN;
  41                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  42                 edsa_header[1] = ETH_P_EDSA & 0xff;
  43                 edsa_header[2] = 0x00;
  44                 edsa_header[3] = 0x00;
  45                 edsa_header[4] = 0x60 | p->parent->index;
  46                 edsa_header[5] = p->port << 3;
  47
  48                 /*
  49                  * Move CFI field from byte 6 to byte 5.
  50                  */
  51                 if (edsa_header[6] & 0x10) {
  52                         edsa_header[5] |= 0x01;
  53                         edsa_header[6] &= ~0x10;
  54                 }
  55         } else {
  56                 if (skb_cow_head(skb, EDSA_HLEN) < 0)
  57                         goto out_free;
  58                 skb_push(skb, EDSA_HLEN);
  59
  60                 memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
  61
  62                 /*
  63                  * Construct untagged FROM_CPU DSA tag.
  64                  */
  65                 edsa_header = skb->data + 2 * ETH_ALEN;
  66                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  67                 edsa_header[1] = ETH_P_EDSA & 0xff;
  68                 edsa_header[2] = 0x00;
  69                 edsa_header[3] = 0x00;
  70                 edsa_header[4] = 0x40 | p->parent->index;
  71                 edsa_header[5] = p->port << 3;
  72                 edsa_header[6] = 0x00;
  73                 edsa_header[7] = 0x00;
  74         }
  75
  76         return skb;
  77
  78 out_free:
  79         kfree_skb(skb);
  80         return NULL;
  81 }
  82
  83 static int edsa_rcv(struct sk_buff *skb, struct net_device *dev,
  84                     struct packet_type *pt, struct net_device *orig_dev)
  85 {
  86         struct dsa_switch_tree *dst = dev->dsa_ptr;
  87         struct dsa_switch *ds;
  88         u8 *edsa_header;
  89         int source_device;
  90         int source_port;
  91
  92         if (unlikely(dst == NULL))
  93                 goto out_drop;
  94
  95         skb = skb_unshare(skb, GFP_ATOMIC);
  96         if (skb == NULL)
  97                 goto out;
  98
  99         if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
 100                 goto out_drop;
 101
 102         /*
 103          * Skip the two null bytes after the ethertype.
 104          */
 105         edsa_header = skb->data + 2;
 106
 107         /*
 108          * Check that frame type is either TO_CPU or FORWARD.
 109          */
 110         if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
 111                 goto out_drop;
 112
 113         /*
 114          * Determine source device and port.
 115          */
 116         source_device = edsa_header[0] & 0x1f;
 117         source_port = (edsa_header[1] >> 3) & 0x1f;
 118
 119         /*
 120          * Check that the source device exists and that the source
 121          * port is a registered DSA port.
 122          */
 123         if (source_device >= DSA_MAX_SWITCHES)
 124                 goto out_drop;
 125
 126         ds = dst->ds[source_device];
 127         if (!ds)
 128                 goto out_drop;
 129
 130         if (source_port >= DSA_MAX_PORTS || !ds->ports[source_port].netdev)
 131                 goto out_drop;
 132
 133         /*
 134          * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
 135          * tag and delete the ethertype part.  If the 'tagged' bit is
 136          * clear, delete the ethertype and the DSA tag parts.
 137          */
 138         if (edsa_header[0] & 0x20) {
 139                 u8 new_header[4];
 140
 141                 /*
 142                  * Insert 802.1q ethertype and copy the VLAN-related
 143                  * fields, but clear the bit that will hold CFI (since
 144                  * DSA uses that bit location for another purpose).
 145                  */
 146                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 147                 new_header[1] = ETH_P_8021Q & 0xff;
 148                 new_header[2] = edsa_header[2] & ~0x10;
 149                 new_header[3] = edsa_header[3];
 150
 151                 /*
 152                  * Move CFI bit from its place in the DSA header to
 153                  * its 802.1q-designated place.
 154                  */
 155                 if (edsa_header[1] & 0x01)
 156                         new_header[2] |= 0x10;
 157
 158                 skb_pull_rcsum(skb, DSA_HLEN);
 159
 160                 /*
 161                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 162                  */
 163                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 164                         __wsum c = skb->csum;
 165                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 166                         c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
 167                         skb->csum = c;
 168                 }
 169
 170                 memcpy(edsa_header, new_header, DSA_HLEN);
 171
 172                 memmove(skb->data - ETH_HLEN,
 173                         skb->data - ETH_HLEN - DSA_HLEN,
 174                         2 * ETH_ALEN);
 175         } else {
 176                 /*
 177                  * Remove DSA tag and update checksum.
 178                  */
 179                 skb_pull_rcsum(skb, EDSA_HLEN);
 180                 memmove(skb->data - ETH_HLEN,
 181                         skb->data - ETH_HLEN - EDSA_HLEN,
 182                         2 * ETH_ALEN);
 183         }
 184
 185         skb->dev = ds->ports[source_port].netdev;
 186         skb_push(skb, ETH_HLEN);
 187         skb->pkt_type = PACKET_HOST;
 188         skb->protocol = eth_type_trans(skb, skb->dev);
 189
 190         skb->dev->stats.rx_packets++;
 191         skb->dev->stats.rx_bytes += skb->len;
 192
 193         netif_receive_skb(skb);
 194
 195         return 0;
 196
 197 out_drop:
 198         kfree_skb(skb);
 199 out:
 200         return 0;
 201 }
 202
 203 const struct dsa_device_ops edsa_netdev_ops = {
 204         .xmit   = edsa_xmit,
 205         .rcv    = edsa_rcv,
 206 };