LXR linux/net/dsa/tag

   1/*
   2 * Copyright (C) 2017 Pengutronix, Juergen Borleis <jbe@pengutronix.de>
   3 *
   4 * This program is free software; you can redistribute it and/or
   5 * modify it under the terms of the GNU General Public License
   6 * version 2, as published by the Free Software Foundation.
   7 *
   8 * This program is distributed in the hope that it will be useful,
   9 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  10 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  11 * GNU General Public License for more details.
  12 *
  13 */
  14#include <linux/dsa/lan9303.h>
  15#include <linux/etherdevice.h>
  16#include <linux/list.h>
  17#include <linux/slab.h>
  18
  19#include "dsa_priv.h"
  20
  21/* To define the outgoing port and to discover the incoming port a regular
  22 * VLAN tag is used by the LAN9303. But its VID meaning is 'special':
  23 *
  24 *       Dest MAC       Src MAC        TAG    Type
  25 * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 | 1 2 |...
  26 *                                |<------->|
  27 * TAG:
  28 *    |<------------->|
  29 *    |  1  2 | 3  4  |
  30 *      TPID    VID
  31 *     0x8100
  32 *
  33 * VID bit 3 indicates a request for an ALR lookup.
  34 *
  35 * If VID bit 3 is zero, then bits 0 and 1 specify the destination port
  36 * (0, 1, 2) or broadcast (3) or the source port (1, 2).
  37 *
  38 * VID bit 4 is used to specify if the STP port state should be overridden.
  39 * Required when no forwarding between the external ports should happen.
  40 */
  41
  42#define LAN9303_TAG_LEN 4
  43# define LAN9303_TAG_TX_USE_ALR BIT(3)
  44# define LAN9303_TAG_TX_STP_OVERRIDE BIT(4)
  45# define LAN9303_TAG_RX_IGMP BIT(3)
  46# define LAN9303_TAG_RX_STP BIT(4)
  47# define LAN9303_TAG_RX_TRAPPED_TO_CPU (LAN9303_TAG_RX_IGMP | \
  48                                        LAN9303_TAG_RX_STP)
  49
  50/* Decide whether to transmit using ALR lookup, or transmit directly to
  51 * port using tag. ALR learning is performed only when using ALR lookup.
  52 * If the two external ports are bridged and the frame is unicast,
  53 * then use ALR lookup to allow ALR learning on CPU port.
  54 * Otherwise transmit directly to port with STP state override.
  55 * See also: lan9303_separate_ports() and lan9303.pdf 6.4.10.1
  56 */
  57static int lan9303_xmit_use_arl(struct dsa_port *dp, u8 *dest_addr)
  58{
  59        struct lan9303 *chip = dp->ds->priv;
  60
  61        return chip->is_bridged && !is_multicast_ether_addr(dest_addr);
  62}
  63
  64static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
  65{
  66        struct dsa_port *dp = dsa_slave_to_port(dev);
  67        u16 *lan9303_tag;
  68
  69        /* insert a special VLAN tag between the MAC addresses
  70         * and the current ethertype field.
  71         */
  72        if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
  73                dev_dbg(&dev->dev,
  74                        "Cannot make room for the special tag. Dropping packet\n");
  75                return NULL;
  76        }
  77
  78        /* provide 'LAN9303_TAG_LEN' bytes additional space */
  79        skb_push(skb, LAN9303_TAG_LEN);
  80
  81        /* make room between MACs and Ether-Type */
  82        memmove(skb->data, skb->data + LAN9303_TAG_LEN, 2 * ETH_ALEN);
  83
  84        lan9303_tag = (u16 *)(skb->data + 2 * ETH_ALEN);
  85        lan9303_tag[0] = htons(ETH_P_8021Q);
  86        lan9303_tag[1] = lan9303_xmit_use_arl(dp, skb->data) ?
  87                                LAN9303_TAG_TX_USE_ALR :
  88                                dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
  89        lan9303_tag[1] = htons(lan9303_tag[1]);
  90
  91        return skb;
  92}
  93
  94static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev,
  95                                   struct packet_type *pt)
  96{
  97        u16 *lan9303_tag;
  98        u16 lan9303_tag1;
  99        unsigned int source_port;
 100
 101        if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
 102                dev_warn_ratelimited(&dev->dev,
 103                                     "Dropping packet, cannot pull\n");
 104                return NULL;
 105        }
 106
 107        /* '->data' points into the middle of our special VLAN tag information:
 108         *
 109         * ~ MAC src   | 0x81 | 0x00 | 0xyy | 0xzz | ether type
 110         *                           ^
 111         *                        ->data
 112         */
 113        lan9303_tag = (u16 *)(skb->data - 2);
 114
 115        if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
 116                dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
 117                return NULL;
 118        }
 119
 120        lan9303_tag1 = ntohs(lan9303_tag[1]);
 121        source_port = lan9303_tag1 & 0x3;
 122
 123        skb->dev = dsa_master_find_slave(dev, 0, source_port);
 124        if (!skb->dev) {
 125                dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
 126                return NULL;
 127        }
 128
 129        /* remove the special VLAN tag between the MAC addresses
 130         * and the current ethertype field.
 131         */
 132        skb_pull_rcsum(skb, 2 + 2);
 133        memmove(skb->data - ETH_HLEN, skb->data - (ETH_HLEN + LAN9303_TAG_LEN),
 134                2 * ETH_ALEN);
 135        skb->offload_fwd_mark = !(lan9303_tag1 & LAN9303_TAG_RX_TRAPPED_TO_CPU);
 136
 137        return skb;
 138}
 139
 140const struct dsa_device_ops lan9303_netdev_ops = {
 141        .xmit = lan9303_xmit,
 142        .rcv = lan9303_rcv,
 143        .overhead = LAN9303_TAG_LEN,
 144};
 145