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/etherdevice.h>
  15 #include <linux/list.h>
  16 #include <linux/slab.h>
  17
  18 #include "dsa_priv.h"
  19
  20 /* To define the outgoing port and to discover the incoming port a regular
  21  * VLAN tag is used by the LAN9303. But its VID meaning is 'special':
  22  *
  23  *       Dest MAC       Src MAC        TAG    Type
  24  * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 | 1 2 |...
  25  *                                |<------->|
  26  * TAG:
  27  *    |<------------->|
  28  *    |  1  2 | 3  4  |
  29  *      TPID    VID
  30  *     0x8100
  31  *
  32  * VID bit 3 indicates a request for an ALR lookup.
  33  *
  34  * If VID bit 3 is zero, then bits 0 and 1 specify the destination port
  35  * (0, 1, 2) or broadcast (3) or the source port (1, 2).
  36  *
  37  * VID bit 4 is used to specify if the STP port state should be overridden.
  38  * Required when no forwarding between the external ports should happen.
  39  */
  40
  41 #define LAN9303_TAG_LEN 4
  42
  43 static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
  44 {
  45         struct dsa_slave_priv *p = netdev_priv(dev);
  46         u16 *lan9303_tag;
  47
  48         /* insert a special VLAN tag between the MAC addresses
  49          * and the current ethertype field.
  50          */
  51         if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
  52                 dev_dbg(&dev->dev,
  53                         "Cannot make room for the special tag. Dropping packet\n");
  54                 return NULL;
  55         }
  56
  57         /* provide 'LAN9303_TAG_LEN' bytes additional space */
  58         skb_push(skb, LAN9303_TAG_LEN);
  59
  60         /* make room between MACs and Ether-Type */
  61         memmove(skb->data, skb->data + LAN9303_TAG_LEN, 2 * ETH_ALEN);
  62
  63         lan9303_tag = (u16 *)(skb->data + 2 * ETH_ALEN);
  64         lan9303_tag[0] = htons(ETH_P_8021Q);
  65         lan9303_tag[1] = htons(p->dp->index | BIT(4));
  66
  67         return skb;
  68 }
  69
  70 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev,
  71                         struct packet_type *pt)
  72 {
  73         u16 *lan9303_tag;
  74         struct dsa_switch_tree *dst = dev->dsa_ptr;
  75         struct dsa_switch *ds;
  76         unsigned int source_port;
  77
  78         ds = dst->ds[0];
  79
  80         if (unlikely(!ds)) {
  81                 dev_warn_ratelimited(&dev->dev, "Dropping packet, due to missing DSA switch device\n");
  82                 return NULL;
  83         }
  84
  85         if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
  86                 dev_warn_ratelimited(&dev->dev,
  87                                      "Dropping packet, cannot pull\n");
  88                 return NULL;
  89         }
  90
  91         /* '->data' points into the middle of our special VLAN tag information:
  92          *
  93          * ~ MAC src   | 0x81 | 0x00 | 0xyy | 0xzz | ether type
  94          *                           ^
  95          *                        ->data
  96          */
  97         lan9303_tag = (u16 *)(skb->data - 2);
  98
  99         if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
 100                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
 101                 return NULL;
 102         }
 103
 104         source_port = ntohs(lan9303_tag[1]) & 0x3;
 105
 106         if (source_port >= ds->num_ports) {
 107                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
 108                 return NULL;
 109         }
 110
 111         if (!ds->ports[source_port].netdev) {
 112                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid netdev or device\n");
 113                 return NULL;
 114         }
 115
 116         /* remove the special VLAN tag between the MAC addresses
 117          * and the current ethertype field.
 118          */
 119         skb_pull_rcsum(skb, 2 + 2);
 120         memmove(skb->data - ETH_HLEN, skb->data - (ETH_HLEN + LAN9303_TAG_LEN),
 121                 2 * ETH_ALEN);
 122
 123         /* forward the packet to the dedicated interface */
 124         skb->dev = ds->ports[source_port].netdev;
 125
 126         return skb;
 127 }
 128
 129 const struct dsa_device_ops lan9303_netdev_ops = {
 130         .xmit = lan9303_xmit,
 131         .rcv = lan9303_rcv,
 132 };