net/dsa/tag_edsa.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * net/dsa/tag_edsa.c - 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 #define EDSA_HLEN       8
  15
  16 static struct sk_buff *edsa_xmit(struct sk_buff *skb, struct net_device *dev)
  17 {
  18         struct dsa_port *dp = dsa_slave_to_port(dev);
  19         u8 *edsa_header;
  20
  21         /*
  22          * Convert the outermost 802.1q tag to a DSA tag and prepend
  23          * a DSA ethertype field is the packet is tagged, or insert
  24          * a DSA ethertype plus DSA tag between the addresses and the
  25          * current ethertype field if the packet is untagged.
  26          */
  27         if (skb->protocol == htons(ETH_P_8021Q)) {
  28                 if (skb_cow_head(skb, DSA_HLEN) < 0)
  29                         return NULL;
  30                 skb_push(skb, DSA_HLEN);
  31
  32                 memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);
  33
  34                 /*
  35                  * Construct tagged FROM_CPU DSA tag from 802.1q tag.
  36                  */
  37                 edsa_header = skb->data + 2 * ETH_ALEN;
  38                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  39                 edsa_header[1] = ETH_P_EDSA & 0xff;
  40                 edsa_header[2] = 0x00;
  41                 edsa_header[3] = 0x00;
  42                 edsa_header[4] = 0x60 | dp->ds->index;
  43                 edsa_header[5] = dp->index << 3;
  44
  45                 /*
  46                  * Move CFI field from byte 6 to byte 5.
  47                  */
  48                 if (edsa_header[6] & 0x10) {
  49                         edsa_header[5] |= 0x01;
  50                         edsa_header[6] &= ~0x10;
  51                 }
  52         } else {
  53                 if (skb_cow_head(skb, EDSA_HLEN) < 0)
  54                         return NULL;
  55                 skb_push(skb, EDSA_HLEN);
  56
  57                 memmove(skb->data, skb->data + EDSA_HLEN, 2 * ETH_ALEN);
  58
  59                 /*
  60                  * Construct untagged FROM_CPU DSA tag.
  61                  */
  62                 edsa_header = skb->data + 2 * ETH_ALEN;
  63                 edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
  64                 edsa_header[1] = ETH_P_EDSA & 0xff;
  65                 edsa_header[2] = 0x00;
  66                 edsa_header[3] = 0x00;
  67                 edsa_header[4] = 0x40 | dp->ds->index;
  68                 edsa_header[5] = dp->index << 3;
  69                 edsa_header[6] = 0x00;
  70                 edsa_header[7] = 0x00;
  71         }
  72
  73         return skb;
  74 }
  75
  76 static struct sk_buff *edsa_rcv(struct sk_buff *skb, struct net_device *dev,
  77                                 struct packet_type *pt)
  78 {
  79         u8 *edsa_header;
  80         int source_device;
  81         int source_port;
  82
  83         if (unlikely(!pskb_may_pull(skb, EDSA_HLEN)))
  84                 return NULL;
  85
  86         /*
  87          * Skip the two null bytes after the ethertype.
  88          */
  89         edsa_header = skb->data + 2;
  90
  91         /*
  92          * Check that frame type is either TO_CPU or FORWARD.
  93          */
  94         if ((edsa_header[0] & 0xc0) != 0x00 && (edsa_header[0] & 0xc0) != 0xc0)
  95                 return NULL;
  96
  97         /*
  98          * Determine source device and port.
  99          */
 100         source_device = edsa_header[0] & 0x1f;
 101         source_port = (edsa_header[1] >> 3) & 0x1f;
 102
 103         skb->dev = dsa_master_find_slave(dev, source_device, source_port);
 104         if (!skb->dev)
 105                 return NULL;
 106
 107         /*
 108          * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
 109          * tag and delete the ethertype part.  If the 'tagged' bit is
 110          * clear, delete the ethertype and the DSA tag parts.
 111          */
 112         if (edsa_header[0] & 0x20) {
 113                 u8 new_header[4];
 114
 115                 /*
 116                  * Insert 802.1q ethertype and copy the VLAN-related
 117                  * fields, but clear the bit that will hold CFI (since
 118                  * DSA uses that bit location for another purpose).
 119                  */
 120                 new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
 121                 new_header[1] = ETH_P_8021Q & 0xff;
 122                 new_header[2] = edsa_header[2] & ~0x10;
 123                 new_header[3] = edsa_header[3];
 124
 125                 /*
 126                  * Move CFI bit from its place in the DSA header to
 127                  * its 802.1q-designated place.
 128                  */
 129                 if (edsa_header[1] & 0x01)
 130                         new_header[2] |= 0x10;
 131
 132                 skb_pull_rcsum(skb, DSA_HLEN);
 133
 134                 /*
 135                  * Update packet checksum if skb is CHECKSUM_COMPLETE.
 136                  */
 137                 if (skb->ip_summed == CHECKSUM_COMPLETE) {
 138                         __wsum c = skb->csum;
 139                         c = csum_add(c, csum_partial(new_header + 2, 2, 0));
 140                         c = csum_sub(c, csum_partial(edsa_header + 2, 2, 0));
 141                         skb->csum = c;
 142                 }
 143
 144                 memcpy(edsa_header, new_header, DSA_HLEN);
 145
 146                 memmove(skb->data - ETH_HLEN,
 147                         skb->data - ETH_HLEN - DSA_HLEN,
 148                         2 * ETH_ALEN);
 149         } else {
 150                 /*
 151                  * Remove DSA tag and update checksum.
 152                  */
 153                 skb_pull_rcsum(skb, EDSA_HLEN);
 154                 memmove(skb->data - ETH_HLEN,
 155                         skb->data - ETH_HLEN - EDSA_HLEN,
 156                         2 * ETH_ALEN);
 157         }
 158
 159         skb->offload_fwd_mark = 1;
 160
 161         return skb;
 162 }
 163
 164 static int edsa_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 165                                  int *offset)
 166 {
 167         *offset = 8;
 168         *proto = ((__be16 *)skb->data)[3];
 169         return 0;
 170 }
 171
 172 static const struct dsa_device_ops edsa_netdev_ops = {
 173         .name   = "edsa",
 174         .proto  = DSA_TAG_PROTO_EDSA,
 175         .xmit   = edsa_xmit,
 176         .rcv    = edsa_rcv,
 177         .flow_dissect   = edsa_tag_flow_dissect,
 178         .overhead = EDSA_HLEN,
 179 };
 180
 181 MODULE_LICENSE("GPL");
 182 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_EDSA);
 183
 184 module_dsa_tag_driver(edsa_netdev_ops);