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->parent->index;
  37                 dsa_header[1] = p->port << 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->parent->index;
  58                 dsa_header[1] = p->port << 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 >= dst->pd->nr_chips)
 111                 goto out_drop;
 112         ds = dst->ds[source_device];
 113         if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
 114                 goto out_drop;
 115
 116         /*
 117          * Convert the DSA header to an 802.1q header if the 'tagged'
 118          * bit in the DSA header is set.  If the 'tagged' bit is clear,
 119          * delete the DSA header entirely.
 120          */
 121         if (dsa_header[0] & 0x20) {
 122                 u8 new_header[4];
 123
 124                 /*
 125                  * Insert 802.1q ethertype and copy the VLAN-related
 126                  * fields, but clear the bit that will hold CFI (since
 127                  * DSA uses that bit location for another purpose).
 128                  */
 129                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 130                 new_header[1] = ETH_P_8021Q & 0xff;
 131                 new_header[2] = dsa_header[2] & ~0x10;
 132                 new_header[3] = dsa_header[3];
 133
 134                 /*
 135                  * Move CFI bit from its place in the DSA header to
 136                  * its 802.1q-designated place.
 137                  */
 138                 if (dsa_header[1] & 0x01)
 139                         new_header[2] |= 0x10;
 140
 141                 /*
 142                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 143                  */
 144                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 145                         __wsum c = skb->csum;
 146                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 147                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
 148                         skb->csum = c;
 149                 }
 150
 151                 memcpy(dsa_header, new_header, DSA_HLEN);
 152         } else {
 153                 /*
 154                  * Remove DSA tag and update checksum.
 155                  */
 156                 skb_pull_rcsum(skb, DSA_HLEN);
 157                 memmove(skb->data - ETH_HLEN,
 158                         skb->data - ETH_HLEN - DSA_HLEN,
 159                         2 * ETH_ALEN);
 160         }
 161
 162         skb->dev = ds->ports[source_port];
 163         skb_push(skb, ETH_HLEN);
 164         skb->pkt_type = PACKET_HOST;
 165         skb->protocol = eth_type_trans(skb, skb->dev);
 166
 167         skb->dev->stats.rx_packets++;
 168         skb->dev->stats.rx_bytes += skb->len;
 169
 170         netif_receive_skb(skb);
 171
 172         return 0;
 173
 174 out_drop:
 175         kfree_skb(skb);
 176 out:
 177         return 0;
 178 }
 179
 180 const struct dsa_device_ops dsa_netdev_ops = {
 181         .xmit   = dsa_xmit,
 182         .rcv    = dsa_rcv,
 183 };