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                 if (skb_cow_head(skb, 0) < 0)
  27                         return NULL;
  28
  29                 /*
  30                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  31                  */
  32                 dsa_header = skb->data + 2 * ETH_ALEN;
  33                 dsa_header[0] = 0x60 | dp->ds->index;
  34                 dsa_header[1] = dp->index << 3;
  35
  36                 /*
  37                  * Move CFI field from byte 2 to byte 1.
  38                  */
  39                 if (dsa_header[2] & 0x10) {
  40                         dsa_header[1] |= 0x01;
  41                         dsa_header[2] &= ~0x10;
  42                 }
  43         } else {
  44                 if (skb_cow_head(skb, DSA_HLEN) < 0)
  45                         return NULL;
  46                 skb_push(skb, DSA_HLEN);
  47
  48                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
  49
  50                 /*
  51                  * Construct untagged FROM_CPU DSA tag.
  52                  */
  53                 dsa_header = skb->data + 2 * ETH_ALEN;
  54                 dsa_header[0] = 0x40 | dp->ds->index;
  55                 dsa_header[1] = dp->index << 3;
  56                 dsa_header[2] = 0x00;
  57                 dsa_header[3] = 0x00;
  58         }
  59
  60         return skb;
  61 }
  62
  63 static struct sk_buff *dsa_rcv(struct sk_buff *skb, struct net_device *dev,
  64                                struct packet_type *pt)
  65 {
  66         u8 *dsa_header;
  67         int source_device;
  68         int source_port;
  69
  70         if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
  71                 return NULL;
  72
  73         /*
  74          * The ethertype field is part of the DSA header.
  75          */
  76         dsa_header = skb->data - 2;
  77
  78         /*
  79          * Check that frame type is either TO_CPU or FORWARD.
  80          */
  81         if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
  82                 return NULL;
  83
  84         /*
  85          * Determine source device and port.
  86          */
  87         source_device = dsa_header[0] & 0x1f;
  88         source_port = (dsa_header[1] >> 3) & 0x1f;
  89
  90         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
  91         if (!skb->dev)
  92                 return NULL;
  93
  94         /*
  95          * Convert the DSA header to an 802.1q header if the 'tagged'
  96          * bit in the DSA header is set.  If the 'tagged' bit is clear,
  97          * delete the DSA header entirely.
  98          */
  99         if (dsa_header[0] & 0x20) {
 100                 u8 new_header[4];
 101
 102                 /*
 103                  * Insert 802.1q ethertype and copy the VLAN-related
 104                  * fields, but clear the bit that will hold CFI (since
 105                  * DSA uses that bit location for another purpose).
 106                  */
 107                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 108                 new_header[1] = ETH_P_8021Q & 0xff;
 109                 new_header[2] = dsa_header[2] & ~0x10;
 110                 new_header[3] = dsa_header[3];
 111
 112                 /*
 113                  * Move CFI bit from its place in the DSA header to
 114                  * its 802.1q-designated place.
 115                  */
 116                 if (dsa_header[1] & 0x01)
 117                         new_header[2] |= 0x10;
 118
 119                 /*
 120                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 121                  */
 122                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 123                         __wsum c = skb->csum;
 124                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 125                         c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
 126                         skb->csum = c;
 127                 }
 128
 129                 memcpy(dsa_header, new_header, DSA_HLEN);
 130         } else {
 131                 /*
 132                  * Remove DSA tag and update checksum.
 133                  */
 134                 skb_pull_rcsum(skb, DSA_HLEN);
 135                 memmove(skb->data - ETH_HLEN,
 136                         skb->data - ETH_HLEN - DSA_HLEN,
 137                         2 * ETH_ALEN);
 138         }
 139
 140         skb->offload_fwd_mark = 1;
 141
 142         return skb;
 143 }
 144
 145 static int dsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 146                                 int *offset)
 147 {
 148         *offset = 4;
 149         *proto = ((__be16 *)skb->data)[1];
 150         return 0;
 151 }
 152
 153 static const struct dsa_device_ops dsa_netdev_ops = {
 154         .name   = "dsa",
 155         .proto  = DSA_TAG_PROTO_DSA,
 156         .xmit   = dsa_xmit,
 157         .rcv    = dsa_rcv,
 158         .flow_dissect   = dsa_tag_flow_dissect,
 159         .overhead = DSA_HLEN,
 160 };
 161
 162 MODULE_LICENSE("GPL");
 163 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
 164
 165 module_dsa_tag_driver(dsa_netdev_ops);