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 #include <net/dsa.h>
  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_slave_priv *p = netdev_priv(dev);
  27         u8 *mtk_tag;
  28
  29         if (skb_cow_head(skb, MTK_HDR_LEN) < 0)
  30                 goto out_free;
  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 << p->dp->index) & MTK_HDR_XMIT_DP_BIT_MASK;
  40         mtk_tag[2] = 0;
  41         mtk_tag[3] = 0;
  42
  43         return skb;
  44
  45 out_free:
  46         kfree_skb(skb);
  47         return NULL;
  48 }
  49
  50 static struct sk_buff *mtk_tag_rcv(struct sk_buff *skb, struct net_device *dev,
  51                                    struct packet_type *pt,
  52                                    struct net_device *orig_dev)
  53 {
  54         struct dsa_switch_tree *dst = dev->dsa_ptr;
  55         struct dsa_switch *ds;
  56         int port;
  57         __be16 *phdr, hdr;
  58
  59         if (unlikely(!pskb_may_pull(skb, MTK_HDR_LEN)))
  60                 goto out_drop;
  61
  62         /* The MTK header is added by the switch between src addr
  63          * and ethertype at this point, skb->data points to 2 bytes
  64          * after src addr so header should be 2 bytes right before.
  65          */
  66         phdr = (__be16 *)(skb->data - 2);
  67         hdr = ntohs(*phdr);
  68
  69         /* Remove MTK tag and recalculate checksum. */
  70         skb_pull_rcsum(skb, MTK_HDR_LEN);
  71
  72         memmove(skb->data - ETH_HLEN,
  73                 skb->data - ETH_HLEN - MTK_HDR_LEN,
  74                 2 * ETH_ALEN);
  75
  76         /* This protocol doesn't support cascading multiple
  77          * switches so it's safe to assume the switch is first
  78          * in the tree.
  79          */
  80         ds = dst->ds[0];
  81         if (!ds)
  82                 goto out_drop;
  83
  84         /* Get source port information */
  85         port = (hdr & MTK_HDR_RECV_SOURCE_PORT_MASK);
  86         if (!ds->ports[port].netdev)
  87                 goto out_drop;
  88
  89         skb->dev = ds->ports[port].netdev;
  90
  91         return skb;
  92
  93 out_drop:
  94         return NULL;
  95 }
  96
  97 const struct dsa_device_ops mtk_netdev_ops = {
  98         .xmit   = mtk_tag_xmit,
  99         .rcv    = mtk_tag_rcv,
 100 };