tag_trailer.c

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/*
 * net/dsa/tag_trailer.c - Trailer tag format handling
 * Copyright (c) 2008-2009 Marvell Semiconductor
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 */

#include <linux/etherdevice.h>
#include <linux/list.h>
#include <linux/netdevice.h>
#include <linux/slab.h>
#include "dsa_priv.h"

netdev_tx_t trailer_xmit(struct sk_buff *skb, struct net_device *dev)
{
    struct dsa_slave_priv *p = netdev_priv(dev);
    struct sk_buff *nskb;
    int padlen;
    u8 *trailer;

    dev->stats.tx_packets++;
    dev->stats.tx_bytes += skb->len;

    /*
     * We have to make sure that the trailer ends up as the very
     * last 4 bytes of the packet.  This means that we have to pad
     * the packet to the minimum ethernet frame size, if necessary,
     * before adding the trailer.
     */
    padlen = 0;
    if (skb->len < 60)
        padlen = 60 - skb->len;

    nskb = alloc_skb(NET_IP_ALIGN + skb->len + padlen + 4, GFP_ATOMIC);
    if (nskb == NULL) {
        kfree_skb(skb);
        return NETDEV_TX_OK;
    }
    skb_reserve(nskb, NET_IP_ALIGN);

    skb_reset_mac_header(nskb);
    skb_set_network_header(nskb, skb_network_header(skb) - skb->head);
    skb_set_transport_header(nskb, skb_transport_header(skb) - skb->head);
    skb_copy_and_csum_dev(skb, skb_put(nskb, skb->len));
    kfree_skb(skb);

    if (padlen) {
        u8 *pad = skb_put(nskb, padlen);
        memset(pad, 0, padlen);
    }

    trailer = skb_put(nskb, 4);
    trailer[0] = 0x80;
    trailer[1] = 1 << p->port;
    trailer[2] = 0x10;
    trailer[3] = 0x00;

    nskb->protocol = htons(ETH_P_TRAILER);

    nskb->dev = p->parent->dst->master_netdev;
    dev_queue_xmit(nskb);

    return NETDEV_TX_OK;
}

static int trailer_rcv(struct sk_buff *skb, struct net_device *dev,
               struct packet_type *pt, struct net_device *orig_dev)
{
    struct dsa_switch_tree *dst = dev->dsa_ptr;
    struct dsa_switch *ds;
    u8 *trailer;
    int source_port;

    if (unlikely(dst == NULL))
        goto out_drop;
    ds = dst->ds[0];

    skb = skb_unshare(skb, GFP_ATOMIC);
    if (skb == NULL)
        goto out;

    if (skb_linearize(skb))
        goto out_drop;

    trailer = skb_tail_pointer(skb) - 4;
    if (trailer[0] != 0x80 || (trailer[1] & 0xf8) != 0x00 ||
        (trailer[3] & 0xef) != 0x00 || trailer[3] != 0x00)
        goto out_drop;

    source_port = trailer[1] & 7;
    if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
        goto out_drop;

    pskb_trim_rcsum(skb, skb->len - 4);

    skb->dev = ds->ports[source_port];
    skb_push(skb, ETH_HLEN);
    skb->pkt_type = PACKET_HOST;
    skb->protocol = eth_type_trans(skb, skb->dev);

    skb->dev->stats.rx_packets++;
    skb->dev->stats.rx_bytes += skb->len;

    netif_receive_skb(skb);

    return 0;

out_drop:
    kfree_skb(skb);
out:
    return 0;
}

struct packet_type trailer_packet_type __read_mostly = {
    .type   = cpu_to_be16(ETH_P_TRAILER),
    .func   = trailer_rcv,
};