LXR linux/net/dsa/tag

   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Mediatek DSA Tag support
   4 * Copyright (C) 2017 Landen Chao <landen.chao@mediatek.com>
   5 *                    Sean Wang <sean.wang@mediatek.com>
   6 */
   7
   8#include <linux/etherdevice.h>
   9#include <linux/if_vlan.h>
  10
  11#include "dsa_priv.h"
  12
  13#define MTK_HDR_LEN             4
  14#define MTK_HDR_XMIT_UNTAGGED           0
  15#define MTK_HDR_XMIT_TAGGED_TPID_8100   1
  16#define MTK_HDR_RECV_SOURCE_PORT_MASK   GENMASK(2, 0)
  17#define MTK_HDR_XMIT_DP_BIT_MASK        GENMASK(5, 0)
  18
  19static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  20                                    struct net_device *dev)
  21{
  22        struct dsa_port *dp = dsa_slave_to_port(dev);
  23        u8 *mtk_tag;
  24        bool is_vlan_skb = true;
  25
  26        /* Build the special tag after the MAC Source Address. If VLAN header
  27         * is present, it's required that VLAN header and special tag is
  28         * being combined. Only in this way we can allow the switch can parse
  29         * the both special and VLAN tag at the same time and then look up VLAN
  30         * table with VID.
  31         */
  32        if (!skb_vlan_tagged(skb)) {
  33                if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  34                        return NULL;
  35
  36                skb_push(skb, MTK_HDR_LEN);
  37                memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  38                is_vlan_skb = false;
  39        }
  40
  41        mtk_tag = skb->data + 2 * ETH_ALEN;
  42
  43        /* Mark tag attribute on special tag insertion to notify hardware
  44         * whether that's a combined special tag with 802.1Q header.
  45         */
  46        mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
  47                     MTK_HDR_XMIT_UNTAGGED;
  48        mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  49
  50        /* Tag control information is kept for 802.1Q */
  51        if (!is_vlan_skb) {
  52                mtk_tag[2] = 0;
  53                mtk_tag[3] = 0;
  54        }
  55
  56        return skb;
  57}
  58
  59static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  60                                   struct packet_type *pt)
  61{
  62        int port;
  63        __be16 *phdr, hdr;
  64
  65        if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  66                return NULL;
  67
  68        /* The MTK header is added by the switch between src addr
  69         * and ethertype at this point, skb->data points to 2 bytes
  70         * after src addr so header should be 2 bytes right before.
  71         */
  72        phdr = (__be16 *)(skb->data - 2);
  73        hdr = ntohs(*phdr);
  74
  75        /* Remove MTK tag and recalculate checksum. */
  76        skb_pull_rcsum(skb, MTK_HDR_LEN);
  77
  78        memmove(skb->data - ETH_HLEN,
  79                skb->data - ETH_HLEN - MTK_HDR_LEN,
  80                2 * ETH_ALEN);
  81
  82        /* Get source port information */
  83        port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  84
  85        skb->dev = dsa_master_find_slave(dev, 0, port);
  86        if (!skb->dev)
  87                return NULL;
  88
  89        return skb;
  90}
  91
  92static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
  93                                int *offset)
  94{
  95        *offset = 4;
  96        *proto = ((__be16 *)skb->data)[1];
  97
  98        return 0;
  99}
 100
 101static const struct dsa_device_ops mtk_netdev_ops = {
 102        .name           = "mtk",
 103        .proto          = DSA_TAG_PROTO_MTK,
 104        .xmit           = mtk_tag_xmit,
 105        .rcv            = mtk_tag_rcv,
 106        .flow_dissect   = mtk_tag_flow_dissect,
 107        .overhead       = MTK_HDR_LEN,
 108};
 109
 110MODULE_LICENSE("GPL");
 111MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_MTK);
 112
 113module_dsa_tag_driver(mtk_netdev_ops);
 114