net/dsa/tag_lan9303.c

   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  */
  57 static 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
  64 static 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
  94 static 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
 140 const struct dsa_device_ops lan9303_netdev_ops = {
 141         .xmit = lan9303_xmit,
 142         .rcv = lan9303_rcv,
 143 };