LXR linux/net/dsa/tag

   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
  13static 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
  54static 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
  80static 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
  88MODULE_LICENSE("GPL");
  89MODULE_ALIAS_DSA_TAG_DRIVER(DSA_TAG_PROTO_TRAILER);
  90
  91module_dsa_tag_driver(trailer_netdev_ops);
  92