LXR linux/net/dsa/tag

   1/*
   2 * Mediatek DSA Tag support
   3 * Copyright (C) 2017 Landen Chao <landen.chao@mediatek.com>
   4 *                    Sean Wang <sean.wang@mediatek.com>
   5 * This program is free software; you can redistribute it and/or modify
   6 * it under the terms of the GNU General Public License version 2 and
   7 * only version 2 as published by the Free Software Foundation.
   8 *
   9 * This program is distributed in the hope that it will be useful,
  10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 * GNU General Public License for more details.
  13 */
  14
  15#include <linux/etherdevice.h>
  16#include <linux/if_vlan.h>
  17
  18#include "dsa_priv.h"
  19
  20#define MTK_HDR_LEN             4
  21#define MTK_HDR_XMIT_UNTAGGED           0
  22#define MTK_HDR_XMIT_TAGGED_TPID_8100   1
  23#define MTK_HDR_RECV_SOURCE_PORT_MASK   GENMASK(2, 0)
  24#define MTK_HDR_XMIT_DP_BIT_MASK        GENMASK(5, 0)
  25
  26static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  27                                    struct net_device *dev)
  28{
  29        struct dsa_port *dp = dsa_slave_to_port(dev);
  30        u8 *mtk_tag;
  31        bool is_vlan_skb = true;
  32
  33        /* Build the special tag after the MAC Source Address. If VLAN header
  34         * is present, it's required that VLAN header and special tag is
  35         * being combined. Only in this way we can allow the switch can parse
  36         * the both special and VLAN tag at the same time and then look up VLAN
  37         * table with VID.
  38         */
  39        if (!skb_vlan_tagged(skb)) {
  40                if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  41                        return NULL;
  42
  43                skb_push(skb, MTK_HDR_LEN);
  44                memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  45                is_vlan_skb = false;
  46        }
  47
  48        mtk_tag = skb->data + 2 * ETH_ALEN;
  49
  50        /* Mark tag attribute on special tag insertion to notify hardware
  51         * whether that's a combined special tag with 802.1Q header.
  52         */
  53        mtk_tag[0] = is_vlan_skb ? MTK_HDR_XMIT_TAGGED_TPID_8100 :
  54                     MTK_HDR_XMIT_UNTAGGED;
  55        mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  56
  57        /* Tag control information is kept for 802.1Q */
  58        if (!is_vlan_skb) {
  59                mtk_tag[2] = 0;
  60                mtk_tag[3] = 0;
  61        }
  62
  63        return skb;
  64}
  65
  66static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  67                                   struct packet_type *pt)
  68{
  69        int port;
  70        __be16 *phdr, hdr;
  71
  72        if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  73                return NULL;
  74
  75        /* The MTK header is added by the switch between src addr
  76         * and ethertype at this point, skb->data points to 2 bytes
  77         * after src addr so header should be 2 bytes right before.
  78         */
  79        phdr = (__be16 *)(skb->data - 2);
  80        hdr = ntohs(*phdr);
  81
  82        /* Remove MTK tag and recalculate checksum. */
  83        skb_pull_rcsum(skb, MTK_HDR_LEN);
  84
  85        memmove(skb->data - ETH_HLEN,
  86                skb->data - ETH_HLEN - MTK_HDR_LEN,
  87                2 * ETH_ALEN);
  88
  89        /* Get source port information */
  90        port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  91
  92        skb->dev = dsa_master_find_slave(dev, 0, port);
  93        if (!skb->dev)
  94                return NULL;
  95
  96        return skb;
  97}
  98
  99static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
 100                                int *offset)
 101{
 102        *offset = 4;
 103        *proto = ((__be16 *)skb->data)[1];
 104
 105        return 0;
 106}
 107
 108const struct dsa_device_ops mtk_netdev_ops = {
 109        .xmit           = mtk_tag_xmit,
 110        .rcv            = mtk_tag_rcv,
 111        .flow_dissect   = mtk_tag_flow_dissect,
 112};
 113