LXR linux/net/dsa/tag

   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
  15static 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
  63static 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
 145static 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
 153static 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
 162MODULE_LICENSE("GPL");
 163MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_DSA);
 164
 165module_dsa_tag_driver(dsa_netdev_ops);
 166