/*
 * net/dsa/tag_edsa.c - 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 "dsa_priv.h"

#define DSA_HLEN        4
#define EDSA_HLEN       8

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

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

        /*
         * Convert the outermost 802.1q tag to a DSA tag and prepend
         * a DSA ethertype field is the packet is tagged, or insert
         * a DSA ethertype plus DSA tag between the addresses and the
         * current ethertype field if the packet is untagged.
         */
        if (skb->protocol == htons(ETH_P_8021Q)) {
                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 tagged FROM_CPU DSA tag from 802.1q tag.
                 */
                edsa_header = skb->data + 2 * ETH_ALEN;
                edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
                edsa_header[1] = ETH_P_EDSA & 0xff;
                edsa_header[2] = 0x00;
                edsa_header[3] = 0x00;
                edsa_header[4] = 0x60 | p->parent->index;
                edsa_header[5] = p->port << 3;

                /*
                 * Move CFI field from byte 6 to byte 5.
                 */
                if (edsa_header[6] & 0x10) {
                        edsa_header[5] |= 0x01;
                        edsa_header[6] &= ~0x10;
                }
        } else {
                if (skb_cow_head(skb, EDSA_HLEN) < 0)
                        goto out_free;
                skb_push(skb, EDSA_HLEN);

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

                /*
                 * Construct untagged FROM_CPU DSA tag.
                 */
                edsa_header = skb->data + 2 * ETH_ALEN;
                edsa_header[0] = (ETH_P_EDSA >> 8) & 0xff;
                edsa_header[1] = ETH_P_EDSA & 0xff;
                edsa_header[2] = 0x00;
                edsa_header[3] = 0x00;
                edsa_header[4] = 0x40 | p->parent->index;
                edsa_header[5] = p->port << 3;
                edsa_header[6] = 0x00;
                edsa_header[7] = 0x00;
        }

        skb->protocol = htons(ETH_P_EDSA);

        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 edsa_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 *edsa_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, EDSA_HLEN)))
                goto out_drop;

        /*
         * Skip the two null bytes after the ethertype.
         */
        edsa_header = skb->data + 2;

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

        /*
         * Determine source device and port.
         */
        source_device = edsa_header[0] & 0x1f;
        source_port = (edsa_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;

        /*
         * If the 'tagged' bit is set, convert the DSA tag to a 802.1q
         * tag and delete the ethertype part.  If the 'tagged' bit is
         * clear, delete the ethertype and the DSA tag parts.
         */
        if (edsa_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] = edsa_header[2] & ~0x10;
                new_header[3] = edsa_header[3];

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

                skb_pull_rcsum(skb, DSA_HLEN);

                /*
                 * 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(edsa_header + 2, 2, 0));
                        skb->csum = c;
                }

                memcpy(edsa_header, new_header, DSA_HLEN);

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

static struct packet_type edsa_packet_type __read_mostly = {
        .type   = cpu_to_be16(ETH_P_EDSA),
        .func   = edsa_rcv,
};

static int __init edsa_init_module(void)
{
        dev_add_pack(&edsa_packet_type);
        return 0;
}
module_init(edsa_init_module);

static void __exit edsa_cleanup_module(void)
{
        dev_remove_pack(&edsa_packet_type);
}
module_exit(edsa_cleanup_module);