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         struct sk_buff *nskb;
  17         int padlen;
  18         u8 *trailer;
  19
  20         /*
  21          * We have to make sure that the trailer ends up as the very
  22          * last 4 bytes of the packet.  This means that we have to pad
  23          * the packet to the minimum ethernet frame size, if necessary,
  24          * before adding the trailer.
  25          */
  26         padlen = 0;
  27         if (skb->len < 60)
  28                 padlen = 60 - skb->len;
  29
  30         nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
  31         if (!nskb)
  32                 return NULL;
  33         skb_reserve(nskb, NET_IP_ALIGN);
  34
  35         skb_reset_mac_header(nskb);
  36         skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
  37         skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
  38         skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
  39         consume_skb(skb);
  40
  41         if (padlen) {
  42                 skb_put_zero(nskb, padlen);
  43         }
  44
  45         trailer = skb_put(nskb, 4);
  46         trailer[0] = 0x80;
  47         trailer[1] = 1 << dp->index;
  48         trailer[2] = 0x10;
  49         trailer[3] = 0x00;
  50
  51         return nskb;
  52 }
  53
  54 static struct sk_buff *trailer_rcv(struct sk_buff *skb, struct net_device *dev,
  55                                    struct packet_type *pt)
  56 {
  57         u8 *trailer;
  58         int source_port;
  59
  60         if (skb_linearize(skb))
  61                 return NULL;
  62
  63         trailer = skb_tail_pointer(skb) - 4;
  64         if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
  65             (trailer[2] & 0xef) != 0x00 || trailer[3] != 0x00)
  66                 return NULL;
  67
  68         source_port = trailer[1] & 7;
  69
  70         skb->dev = dsa_master_find_slave(dev, 0, source_port);
  71         if (!skb->dev)
  72                 return NULL;
  73
  74         if (pskb_trim_rcsum(skb, skb->len - 4))
  75                 return NULL;
  76
  77         return skb;
  78 }
  79
  80 static const struct dsa_device_ops trailer_netdev_ops = {
  81         .name   = "trailer",
  82         .proto  = DSA_TAG_PROTO_TRAILER,
  83         .xmit   = trailer_xmit,
  84         .rcv    = trailer_rcv,
  85         .overhead = 4,
  86 };
  87
  88 MODULE_LICENSE("GPL");
  89 MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER);
  90
  91 module_dsa_tag_driver(trailer_netdev_ops);