tag_dsa.c

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/*
 * net/dsa/tag_dsa.c - (Non-ethertype) DSA tagging
 * 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"

#define DSA_HLEN    4

netdev_tx_t dsa_xmit(struct sk_buff *skb, struct net_device *dev)
{
    struct dsa_slave_priv *p = netdev_priv(dev);
    u8 *dsa_header;

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

    /*
     * Convert the outermost 802.1q tag to a DSA tag for tagged
     * packets, or insert a DSA tag between the addresses and
     * the ethertype field for untagged packets.
     */
    if (skb->protocol == htons(ETH_P_8021Q)) {
        if (skb_cow_head(skb, 0) < 0)
            goto out_free;

        /*
         * Construct tagged FROM_CPU DSA tag from 802.1q tag.
         */
        dsa_header = skb->data + 2 * ETH_ALEN;
        dsa_header[0] = 0x60 | p->parent->index;
        dsa_header[1] = p->port << 3;

        /*
         * Move CFI field from byte 2 to byte 1.
         */
        if (dsa_header[2] & 0x10) {
            dsa_header[1] |= 0x01;
            dsa_header[2] &= ~0x10;
        }
    } else {
        if (skb_cow_head(skb, DSA_HLEN) < 0)
            goto out_free;
        skb_push(skb, DSA_HLEN);

        memmove(skb->data, skb->data + DSA_HLEN, 2 * ETH_ALEN);

        /*
         * Construct untagged FROM_CPU DSA tag.
         */
        dsa_header = skb->data + 2 * ETH_ALEN;
        dsa_header[0] = 0x40 | p->parent->index;
        dsa_header[1] = p->port << 3;
        dsa_header[2] = 0x00;
        dsa_header[3] = 0x00;
    }

    skb->protocol = htons(ETH_P_DSA);

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

    return NETDEV_TX_OK;

out_free:
    kfree_skb(skb);
    return NETDEV_TX_OK;
}

static int dsa_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 *dsa_header;
    int source_device;
    int source_port;

    if (unlikely(dst == NULL))
        goto out_drop;

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

    if (unlikely(!pskb_may_pull(skb, DSA_HLEN)))
        goto out_drop;

    /*
     * The ethertype field is part of the DSA header.
     */
    dsa_header = skb->data - 2;

    /*
     * Check that frame type is either TO_CPU or FORWARD.
     */
    if ((dsa_header[0] & 0xc0) != 0x00 && (dsa_header[0] & 0xc0) != 0xc0)
        goto out_drop;

    /*
     * Determine source device and port.
     */
    source_device = dsa_header[0] & 0x1f;
    source_port = (dsa_header[1] >> 3) & 0x1f;

    /*
     * Check that the source device exists and that the source
     * port is a registered DSA port.
     */
    if (source_device >= dst->pd->nr_chips)
        goto out_drop;
    ds = dst->ds[source_device];
    if (source_port >= DSA_MAX_PORTS || ds->ports[source_port] == NULL)
        goto out_drop;

    /*
     * Convert the DSA header to an 802.1q header if the 'tagged'
     * bit in the DSA header is set.  If the 'tagged' bit is clear,
     * delete the DSA header entirely.
     */
    if (dsa_header[0] & 0x20) {
        u8 new_header[4];

        /*
         * Insert 802.1q ethertype and copy the VLAN-related
         * fields, but clear the bit that will hold CFI (since
         * DSA uses that bit location for another purpose).
         */
        new_header[0] = (ETH_P_8021Q >> 8) & 0xff;
        new_header[1] = ETH_P_8021Q & 0xff;
        new_header[2] = dsa_header[2] & ~0x10;
        new_header[3] = dsa_header[3];

        /*
         * Move CFI bit from its place in the DSA header to
         * its 802.1q-designated place.
         */
        if (dsa_header[1] & 0x01)
            new_header[2] |= 0x10;

        /*
         * Update packet checksum if skb is CHECKSUM_COMPLETE.
         */
        if (skb->ip_summed == CHECKSUM_COMPLETE) {
            __wsum c = skb->csum;
            c = csum_add(c, csum_partial(new_header + 2, 2, 0));
            c = csum_sub(c, csum_partial(dsa_header + 2, 2, 0));
            skb->csum = c;
        }

        memcpy(dsa_header, new_header, DSA_HLEN);
    } else {
        /*
         * Remove DSA tag and update checksum.
         */
        skb_pull_rcsum(skb, DSA_HLEN);
        memmove(skb->data - ETH_HLEN,
            skb->data - ETH_HLEN - DSA_HLEN,
            2 * ETH_ALEN);
    }

    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 dsa_packet_type __read_mostly = {
    .type   = cpu_to_be16(ETH_P_DSA),
    .func   = dsa_rcv,
};