net/dsa/tag_lan9303.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2017 Pengutronix, Juergen Borleis <jbe@pengutronix.de>
   4  */
   5 #include <linux/dsa/lan9303.h>
   6 #include <linux/etherdevice.h>
   7 #include <linux/list.h>
   8 #include <linux/slab.h>
   9
  10 #include "dsa_priv.h"
  11
  12 /* To define the outgoing port and to discover the incoming port a regular
  13  * VLAN tag is used by the LAN9303. But its VID meaning is 'special':
  14  *
  15  *       Dest MAC       Src MAC        TAG    Type
  16  * ...| 1 2 3 4 5 6 | 1 2 3 4 5 6 | 1 2 3 4 | 1 2 |...
  17  *                                |<------->|
  18  * TAG:
  19  *    |<------------->|
  20  *    |  1  2 | 3  4  |
  21  *      TPID    VID
  22  *     0x8100
  23  *
  24  * VID bit 3 indicates a request for an ALR lookup.
  25  *
  26  * If VID bit 3 is zero, then bits 0 and 1 specify the destination port
  27  * (0, 1, 2) or broadcast (3) or the source port (1, 2).
  28  *
  29  * VID bit 4 is used to specify if the STP port state should be overridden.
  30  * Required when no forwarding between the external ports should happen.
  31  */
  32
  33 #define LAN9303_TAG_LEN 4
  34 # define LAN9303_TAG_TX_USE_ALR BIT(3)
  35 # define LAN9303_TAG_TX_STP_OVERRIDE BIT(4)
  36 # define LAN9303_TAG_RX_IGMP BIT(3)
  37 # define LAN9303_TAG_RX_STP BIT(4)
  38 # define LAN9303_TAG_RX_TRAPPED_TO_CPU (LAN9303_TAG_RX_IGMP | \
  39                                         LAN9303_TAG_RX_STP)
  40
  41 /* Decide whether to transmit using ALR lookup, or transmit directly to
  42  * port using tag. ALR learning is performed only when using ALR lookup.
  43  * If the two external ports are bridged and the frame is unicast,
  44  * then use ALR lookup to allow ALR learning on CPU port.
  45  * Otherwise transmit directly to port with STP state override.
  46  * See also: lan9303_separate_ports() and lan9303.pdf 6.4.10.1
  47  */
  48 static int lan9303_xmit_use_arl(struct dsa_port *dp, u8 *dest_addr)
  49 {
  50         struct lan9303 *chip = dp->ds->priv;
  51
  52         return chip->is_bridged && !is_multicast_ether_addr(dest_addr);
  53 }
  54
  55 static struct sk_buff *lan9303_xmit(struct sk_buff *skb, struct net_device *dev)
  56 {
  57         struct dsa_port *dp = dsa_slave_to_port(dev);
  58         u16 *lan9303_tag;
  59
  60         /* insert a special VLAN tag between the MAC addresses
  61          * and the current ethertype field.
  62          */
  63         if (skb_cow_head(skb, LAN9303_TAG_LEN) < 0) {
  64                 dev_dbg(&dev->dev,
  65                         "Cannot make room for the special tag. Dropping packet\n");
  66                 return NULL;
  67         }
  68
  69         /* provide 'LAN9303_TAG_LEN' bytes additional space */
  70         skb_push(skb, LAN9303_TAG_LEN);
  71
  72         /* make room between MACs and Ether-Type */
  73         memmove(skb->data, skb->data + LAN9303_TAG_LEN, 2 * ETH_ALEN);
  74
  75         lan9303_tag = (u16 *)(skb->data + 2 * ETH_ALEN);
  76         lan9303_tag[0] = htons(ETH_P_8021Q);
  77         lan9303_tag[1] = lan9303_xmit_use_arl(dp, skb->data) ?
  78                                 LAN9303_TAG_TX_USE_ALR :
  79                                 dp->index | LAN9303_TAG_TX_STP_OVERRIDE;
  80         lan9303_tag[1] = htons(lan9303_tag[1]);
  81
  82         return skb;
  83 }
  84
  85 static struct sk_buff *lan9303_rcv(struct sk_buff *skb, struct net_device *dev,
  86                                    struct packet_type *pt)
  87 {
  88         u16 *lan9303_tag;
  89         u16 lan9303_tag1;
  90         unsigned int source_port;
  91
  92         if (unlikely(!pskb_may_pull(skb, LAN9303_TAG_LEN))) {
  93                 dev_warn_ratelimited(&dev->dev,
  94                                      "Dropping packet, cannot pull\n");
  95                 return NULL;
  96         }
  97
  98         /* '->data' points into the middle of our special VLAN tag information:
  99          *
 100          * ~ MAC src   | 0x81 | 0x00 | 0xyy | 0xzz | ether type
 101          *                           ^
 102          *                        ->data
 103          */
 104         lan9303_tag = (u16 *)(skb->data - 2);
 105
 106         if (lan9303_tag[0] != htons(ETH_P_8021Q)) {
 107                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid VLAN marker\n");
 108                 return NULL;
 109         }
 110
 111         lan9303_tag1 = ntohs(lan9303_tag[1]);
 112         source_port = lan9303_tag1 & 0x3;
 113
 114         skb->dev = dsa_master_find_slave(dev, 0, source_port);
 115         if (!skb->dev) {
 116                 dev_warn_ratelimited(&dev->dev, "Dropping packet due to invalid source port\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         skb->offload_fwd_mark = !(lan9303_tag1 & LAN9303_TAG_RX_TRAPPED_TO_CPU);
 127
 128         return skb;
 129 }
 130
 131 static const struct dsa_device_ops lan9303_netdev_ops = {
 132         .name = "lan9303",
 133         .proto  = DSA_TAG_PROTO_LAN9303,
 134         .xmit = lan9303_xmit,
 135         .rcv = lan9303_rcv,
 136         .overhead = LAN9303_TAG_LEN,
 137 };
 138
 139 MODULE_LICENSE("GPL");
 140 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_LAN9303);
 141
 142 module_dsa_tag_driver(lan9303_netdev_ops);