net/dsa/tag_trailer.c

   1 // SPDX-License-Identifier: GPL-2.0+
   2 /*
   3  * net/dsa/tag_trailer.c - Trailer tag format handling
   4  * Copyright (c) 2008-2009 Marvell Semiconductor
   5  */
   6
   7 #include <linux/etherdevice.h>
   8 #include <linux/list.h>
   9 #include <linux/slab.h>
  10
  11 #include "dsa_priv.h"
  12
  13 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
  14 {
  15         struct dsa_port *dp = dsa_slave_to_port(dev);
  16         u8 *trailer;
  17
  18         trailer = skb_put(skb, 4);
  19         trailer[0] = 0x80;
  20         trailer[1] = 1 << dp->index;
  21         trailer[2] = 0x10;
  22         trailer[3] = 0x00;
  23
  24         return skb;
  25 }
  26
  27 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev)
  28 {
  29         u8 *trailer;
  30         int source_port;
  31
  32         if (skb_linearize(skb))
  33                 return NULL;
  34
  35         trailer = skb_tail_pointer(skb) - 4;
  36         if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
  37             (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
  38                 return NULL;
  39
  40         source_port = trailer[1] & 7;
  41
  42         skb->dev = dsa_master_find_slave(dev, 0, source_port);
  43         if (!skb->dev)
  44                 return NULL;
  45
  46         if (pskb_trim_rcsum(skb, skb->len - 4))
  47                 return NULL;
  48
  49         return skb;
  50 }
  51
  52 static const struct dsa_device_ops trailer_netdev_ops = {
  53         .name   = "trailer",
  54         .proto  = DSA_TAG_PROTO_TRAILER,
  55         .xmit   = trailer_xmit,
  56         .rcv    = trailer_rcv,
  57         .needed_tailroom = 4,
  58 };
  59
  60 MODULE_LICENSE("GPL");
  61 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER);
  62
  63 module_dsa_tag_driver(trailer_netdev_ops);