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 "tag.h"
  12
  13 #define TRAILER_NAME "trailer"
  14
  15 static struct sk_buff *trailer_xmit(struct sk_buff *skb, struct net_device *dev)
  16 {
  17         struct dsa_port *dp = dsa_slave_to_port(dev);
  18         u8 *trailer;
  19
  20         trailer = skb_put(skb, 4);
  21         trailer[0] = 0x80;
  22         trailer[1] = 1 << dp->index;
  23         trailer[2] = 0x10;
  24         trailer[3] = 0x00;
  25
  26         return skb;
  27 }
  28
  29 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev)
  30 {
  31         u8 *trailer;
  32         int source_port;
  33
  34         if (skb_linearize(skb))
  35                 return NULL;
  36
  37         trailer = skb_tail_pointer(skb) - 4;
  38         if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
  39             (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
  40                 return NULL;
  41
  42         source_port = trailer[1] & 7;
  43
  44         skb->dev = dsa_master_find_slave(dev, 0, source_port);
  45         if (!skb->dev)
  46                 return NULL;
  47
  48         if (pskb_trim_rcsum(skb, skb->len - 4))
  49                 return NULL;
  50
  51         return skb;
  52 }
  53
  54 static const struct dsa_device_ops trailer_netdev_ops = {
  55         .name   = TRAILER_NAME,
  56         .proto  = DSA_TAG_PROTO_TRAILER,
  57         .xmit   = trailer_xmit,
  58         .rcv    = trailer_rcv,
  59         .needed_tailroom = 4,
  60 };
  61
  62 MODULE_LICENSE("GPL");
  63 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER, TRAILER_NAME);
  64
  65 module_dsa_tag_driver(trailer_netdev_ops);