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