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 #include <net/dsa.h>
  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 #define LAN9303_MAX_PORTS 3
  43
  44 static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
  45 {
  46         struct dsa_slave_priv *p = netdev_priv(dev);
  47         u16 *lan9303_tag;
  48
  49         /* insert a special VLAN tag between the MAC addresses
  50          * and the current ethertype field.
  51          */
  52         if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
  53                 dev_dbg(&dev->dev,
  54                         "Cannot make room for the special tag. Dropping packet\n");
  55                 goto out_free;
  56         }
  57
  58         /* provide 'LAN9303_TAG_LEN' bytes additional space */
  59         skb_push(skb, LAN9303_TAG_LEN);
  60
  61         /* make room between MACs and Ether-Type */
  62         memmove(skb->data, skb->data + LAN9303_TAG_LEN, 2 * ETH_ALEN);
  63
  64         lan9303_tag = (u16 *)(skb->data + 2 * ETH_ALEN);
  65         lan9303_tag[0] = htons(ETH_P_8021Q);
  66         lan9303_tag[1] = htons(p->dp->index | BIT(4));
  67
  68         return skb;
  69 out_free:
  70         kfree_skb(skb);
  71         return NULL;
  72 }
  73
  74 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev,
  75                         struct packet_type *pt, struct net_device *orig_dev)
  76 {
  77         u16 *lan9303_tag;
  78         struct dsa_switch_tree *dst = dev->dsa_ptr;
  79         struct dsa_switch *ds;
  80         unsigned int source_port;
  81
  82         ds = dst->ds[0];
  83
  84         if (unlikely(!ds)) {
  85                 dev_warn_ratelimited(&dev->dev, "Dropping packet, due to missing DSA switch device\n");
  86                 return NULL;
  87         }
  88
  89         if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
  90                 dev_warn_ratelimited(&dev->dev,
  91                                      "Dropping packet, cannot pull\n");
  92                 return NULL;
  93         }
  94
  95         /* '->data' points into the middle of our special VLAN tag information:
  96          *
  97          * ~ MAC src   | 0x81 | 0x00 | 0xyy | 0xzz | ether type
  98          *                           ^
  99          *                        ->data
 100          */
 101         lan9303_tag = (u16 *)(skb->data - 2);
 102
 103         if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
 104                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
 105                 return NULL;
 106         }
 107
 108         source_port = ntohs(lan9303_tag[1]) & 0x3;
 109
 110         if (source_port >= LAN9303_MAX_PORTS) {
 111                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\n");
 112                 return NULL;
 113         }
 114
 115         if (!ds->ports[source_port].netdev) {
 116                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid netdev or device\n");
 117                 return NULL;
 118         }
 119
 120         /* remove the special VLAN tag between the MAC addresses
 121          * and the current ethertype field.
 122          */
 123         skb_pull_rcsum(skb, 2 + 2);
 124         memmove(skb->data - ETH_HLEN, skb->data - (ETH_HLEN + LAN9303_TAG_LEN),
 125                 2 * ETH_ALEN);
 126
 127         /* forward the packet to the dedicated interface */
 128         skb->dev = ds->ports[source_port].netdev;
 129
 130         return skb;
 131 }
 132
 133 const struct dsa_device_ops lan9303_netdev_ops = {
 134         .xmit = lan9303_xmit,
 135         .rcv = lan9303_rcv,
 136 };