/*
 * 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,
};