net/dsa/tag_mtk.c

   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
  17 #include "dsa_priv.h"
  18
  19 #define MTK_HDR_LEN             4
  20 #define MTK_HDR_RECV_SOURCE_PORT_MASK   GENMASK(2, 0)
  21 #define MTK_HDR_XMIT_DP_BIT_MASK        GENMASK(5, 0)
  22
  23 static struct sk_buff *mtk_tag_xmit(struct sk_buff *skb,
  24                                     struct net_device *dev)
  25 {
  26         struct dsa_port *dp = dsa_slave_to_port(dev);
  27         u8 *mtk_tag;
  28
  29         if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  30                 return NULL;
  31
  32         skb_push(skb, MTK_HDR_LEN);
  33
  34         memmove(skb->data, skb->data + MTK_HDR_LEN, 2 * ETH_ALEN);
  35
  36         /* Build the tag after the MAC Source Address */
  37         mtk_tag = skb->data + 2 * ETH_ALEN;
  38         mtk_tag[0] = 0;
  39         mtk_tag[1] = (1 << dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  40         mtk_tag[2] = 0;
  41         mtk_tag[3] = 0;
  42
  43         return skb;
  44 }
  45
  46 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  47                                    struct packet_type *pt)
  48 {
  49         int port;
  50         __be16 *phdr, hdr;
  51
  52         if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  53                 return NULL;
  54
  55         /* The MTK header is added by the switch between src addr
  56          * and ethertype at this point, skb->data points to 2 bytes
  57          * after src addr so header should be 2 bytes right before.
  58          */
  59         phdr = (__be16 *)(skb->data - 2);
  60         hdr = ntohs(*phdr);
  61
  62         /* Remove MTK tag and recalculate checksum. */
  63         skb_pull_rcsum(skb, MTK_HDR_LEN);
  64
  65         memmove(skb->data - ETH_HLEN,
  66                 skb->data - ETH_HLEN - MTK_HDR_LEN,
  67                 2 * ETH_ALEN);
  68
  69         /* Get source port information */
  70         port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  71
  72         skb->dev = dsa_master_find_slave(dev, 0, port);
  73         if (!skb->dev)
  74                 return NULL;
  75
  76         return skb;
  77 }
  78
  79 static int mtk_tag_flow_dissect(const struct sk_buff *skb, __be16 *proto,
  80                                 int *offset)
  81 {
  82         *offset = 4;
  83         *proto = ((__be16 *)skb->data)[1];
  84
  85         return 0;
  86 }
  87
  88 const struct dsa_device_ops mtk_netdev_ops = {
  89         .xmit           = mtk_tag_xmit,
  90         .rcv            = mtk_tag_rcv,
  91         .flow_dissect   = mtk_tag_flow_dissect,
  92 };