net/dsa/tag_dsa.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * net/dsa/tag_dsa.c - (Non-ethertype) DSA tagging
   4  * Copyright (c) 2008-2009 Marvell Semiconductor
   5  */
   6
   7 #include <linux/etherdevice.h>
   8 #include <linux/list.h>
   9 #include <linux/slab.h>
  10
  11 #include "dsa_priv.h"
  12
  13 #define DSA_HLEN        4
  14
  15 static struct sk_buff *dsa_xmit(struct sk_buff *skb, struct net_device *dev)
  16 {
  17         struct dsa_port *dp = dsa_slave_to_port(dev);
  18         u8 *dsa_header;
  19
  20         /*
  21          * Convert the outermost 802.1q tag to a DSA tag for tagged
  22          * packets, or insert a DSA tag between the addresses and
  23          * the ethertype field for untagged packets.
  24          */
  25         if (skb->protocol == htons(ETH_P_8021Q)) {
  26                 /*
  27                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  28                  */
  29                 dsa_header = skb->data + 2 * ETH_ALEN;
  30                 dsa_header[0] = 0x60 | dp->ds->index;
  31                 dsa_header[1] = dp->index << 3;
  32
  33                 /*
  34                  * Move CFI field from byte 2 to byte 1.
  35                  */
  36                 if (dsa_header[2] & 0x10) {
  37                         dsa_header[1] |= 0x01;
  38                         dsa_header[2] &= ~0x10;
  39                 }
  40         } else {
  41                 skb_push(skb, DSA_HLEN);
  42
  43                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
  44
  45                 /*
  46                  * Construct untagged FROM_CPU DSA tag.
  47                  */
  48                 dsa_header = skb->data + 2 * ETH_ALEN;
  49                 dsa_header[0] = 0x40 | dp->ds->index;
  50                 dsa_header[1] = dp->index << 3;
  51                 dsa_header[2] = 0x00;
  52                 dsa_header[3] = 0x00;
  53         }
  54
  55         return skb;
  56 }
  57
  58 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
  59                                struct packet_type *pt)
  60 {
  61         u8 *dsa_header;
  62         int source_device;
  63         int source_port;
  64
  65         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
  66                 return NULL;
  67
  68         /*
  69          * The ethertype field is part of the DSA header.
  70          */
  71         dsa_header = skb->data - 2;
  72
  73         /*
  74          * Check that frame type is either TO_CPU or FORWARD.
  75          */
  76         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
  77                 return NULL;
  78
  79         /*
  80          * Determine source device and port.
  81          */
  82         source_device = dsa_header[0] & 0x1f;
  83         source_port = (dsa_header[1] >> 3) & 0x1f;
  84
  85         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
  86         if (!skb->dev)
  87                 return NULL;
  88
  89         /*
  90          * Convert the DSA header to an 802.1q header if the 'tagged'
  91          * bit in the DSA header is set.  If the 'tagged' bit is clear,
  92          * delete the DSA header entirely.
  93          */
  94         if (dsa_header[0] & 0x20) {
  95                 u8 new_header[4];
  96
  97                 /*
  98                  * Insert 802.1q ethertype and copy the VLAN-related
  99                  * fields, but clear the bit that will hold CFI (since
 100                  * DSA uses that bit location for another purpose).
 101                  */
 102                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 103                 new_header[1] = ETH_P_8021Q & 0xff;
 104                 new_header[2] = dsa_header[2] & ~0x10;
 105                 new_header[3] = dsa_header[3];
 106
 107                 /*
 108                  * Move CFI bit from its place in the DSA header to
 109                  * its 802.1q-designated place.
 110                  */
 111                 if (dsa_header[1] & 0x01)
 112                         new_header[2] |= 0x10;
 113
 114                 /*
 115                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 116                  */
 117                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 118                         __wsum c = skb->csum;
 119                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 120                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
 121                         skb->csum = c;
 122                 }
 123
 124                 memcpy(dsa_header, new_header, DSA_HLEN);
 125         } else {
 126                 /*
 127                  * Remove DSA tag and update checksum.
 128                  */
 129                 skb_pull_rcsum(skb, DSA_HLEN);
 130                 memmove(skb->data - ETH_HLEN,
 131                         skb->data - ETH_HLEN - DSA_HLEN,
 132                         2 * ETH_ALEN);
 133         }
 134
 135         skb->offload_fwd_mark = 1;
 136
 137         return skb;
 138 }
 139
 140 static const struct dsa_device_ops dsa_netdev_ops = {
 141         .name   = "dsa",
 142         .proto  = DSA_TAG_PROTO_DSA,
 143         .xmit   = dsa_xmit,
 144         .rcv    = dsa_rcv,
 145         .overhead = DSA_HLEN,
 146 };
 147
 148 MODULE_LICENSE("GPL");
 149 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
 150
 151 module_dsa_tag_driver(dsa_netdev_ops);