/* A simple network driver for lguest.
 *
 * Copyright 2006 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
 *
 * 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.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */
//#define DEBUG
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/module.h>
#include <linux/mm_types.h>
#include <linux/io.h>
#include <linux/lguest_bus.h>

#define SHARED_SIZE		PAGE_SIZE
#define MAX_LANS		4
#define NUM_SKBS		8

struct lguestnet_info
{
	/* The shared page(s). */
	struct lguest_net *peer;
	unsigned long peer_phys;
	unsigned long mapsize;

	/* The lguest_device I come from */
	struct lguest_device *lgdev;

	/* My peerid. */
	unsigned int me;

	/* Receive queue. */
	struct sk_buff *skb[NUM_SKBS];
	struct lguest_dma dma[NUM_SKBS];
};

/* How many bytes left in this page. */
static unsigned int rest_of_page(void *data)
{
	return PAGE_SIZE - ((unsigned long)data % PAGE_SIZE);
}

/* Simple convention: offset 4 * peernum. */
static unsigned long peer_key(struct lguestnet_info *info, unsigned peernum)
{
	return info->peer_phys + 4 * peernum;
}

static void skb_to_dma(const struct sk_buff *skb, unsigned int headlen,
		       struct lguest_dma *dma)
{
	unsigned int i, seg;

	for (i = seg = 0; i < headlen; seg++, i += rest_of_page(skb->data+i)) {
		dma->addr[seg] = virt_to_phys(skb->data + i);
		dma->len[seg] = min((unsigned)(headlen - i),
				    rest_of_page(skb->data + i));
	}
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++, seg++) {
		const skb_frag_t *f = &skb_shinfo(skb)->frags[i];
		/* Should not happen with MTU less than 64k - 2 * PAGE_SIZE. */
		if (seg == LGUEST_MAX_DMA_SECTIONS) {
			printk("Woah dude!  Megapacket!\n");
			break;
		}
		dma->addr[seg] = page_to_phys(f->page) + f->page_offset;
		dma->len[seg] = f->size;
	}
	if (seg < LGUEST_MAX_DMA_SECTIONS)
		dma->len[seg] = 0;
}

/* We overload multicast bit to show promiscuous mode. */
#define PROMISC_BIT		0x01

static void lguestnet_set_multicast(struct net_device *dev)
{
	struct lguestnet_info *info = netdev_priv(dev);

	if ((dev->flags & (IFF_PROMISC|IFF_ALLMULTI)) || dev->mc_count)
		info->peer[info->me].mac[0] |= PROMISC_BIT;
	else
		info->peer[info->me].mac[0] &= ~PROMISC_BIT;
}

static int promisc(struct lguestnet_info *info, unsigned int peer)
{
	return info->peer[peer].mac[0] & PROMISC_BIT;
}

static int mac_eq(const unsigned char mac[ETH_ALEN],
		  struct lguestnet_info *info, unsigned int peer)
{
	/* Ignore multicast bit, which peer turns on to mean promisc. */
	if ((info->peer[peer].mac[0] & (~PROMISC_BIT)) != mac[0])
		return 0;
	return memcmp(mac+1, info->peer[peer].mac+1, ETH_ALEN-1) == 0;
}

static void transfer_packet(struct net_device *dev,
			    struct sk_buff *skb,
			    unsigned int peernum)
{
	struct lguestnet_info *info = netdev_priv(dev);
	struct lguest_dma dma;

	skb_to_dma(skb, skb_headlen(skb), &dma);
	pr_debug("xfer length %04x (%u)\n", htons(skb->len), skb->len);

	lguest_send_dma(peer_key(info, peernum), &dma);
	if (dma.used_len != skb->len) {
		dev->stats.tx_carrier_errors++;
		pr_debug("Bad xfer to peer %i: %i of %i (dma %p/%i)\n",
			 peernum, dma.used_len, skb->len,
			 (void *)dma.addr[0], dma.len[0]);
	} else {
		dev->stats.tx_bytes += skb->len;
		dev->stats.tx_packets++;
	}
}

static int unused_peer(const struct lguest_net peer[], unsigned int num)
{
	return peer[num].mac[0] == 0;
}

static int lguestnet_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	unsigned int i;
	int broadcast;
	struct lguestnet_info *info = netdev_priv(dev);
	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;

	pr_debug("%s: xmit %02x:%02x:%02x:%02x:%02x:%02x\n",
		 dev->name, dest[0],dest[1],dest[2],dest[3],dest[4],dest[5]);

	broadcast = is_multicast_ether_addr(dest);
	for (i = 0; i < info->mapsize/sizeof(struct lguest_net); i++) {
		if (i == info->me || unused_peer(info->peer, i))
			continue;

		if (!broadcast && !promisc(info, i) && !mac_eq(dest, info, i))
			continue;

		pr_debug("lguestnet %s: sending from %i to %i\n",
			 dev->name, info->me, i);
		transfer_packet(dev, skb, i);
	}
	dev_kfree_skb(skb);
	return 0;
}

/* Find a new skb to put in this slot in shared mem. */
static int fill_slot(struct net_device *dev, unsigned int slot)
{
	struct lguestnet_info *info = netdev_priv(dev);
	/* Try to create and register a new one. */
	info->skb[slot] = netdev_alloc_skb(dev, ETH_HLEN + ETH_DATA_LEN);
	if (!info->skb[slot]) {
		printk("%s: could not fill slot %i\n", dev->name, slot);
		return -ENOMEM;
	}

	skb_to_dma(info->skb[slot], ETH_HLEN + ETH_DATA_LEN, &info->dma[slot]);
	wmb();
	/* Now we tell hypervisor it can use the slot. */
	info->dma[slot].used_len = 0;
	return 0;
}

static irqreturn_t lguestnet_rcv(int irq, void *dev_id)
{
	struct net_device *dev = dev_id;
	struct lguestnet_info *info = netdev_priv(dev);
	unsigned int i, done = 0;

	for (i = 0; i < ARRAY_SIZE(info->dma); i++) {
		unsigned int length;
		struct sk_buff *skb;

		length = info->dma[i].used_len;
		if (length == 0)
			continue;

		done++;
		skb = info->skb[i];
		fill_slot(dev, i);

		if (length < ETH_HLEN || length > ETH_HLEN + ETH_DATA_LEN) {
			pr_debug(KERN_WARNING "%s: unbelievable skb len: %i\n",
				 dev->name, length);
			dev_kfree_skb(skb);
			continue;
		}

		skb_put(skb, length);
		skb->protocol = eth_type_trans(skb, dev);
		/* This is a reliable transport. */
		if (dev->features & NETIF_F_NO_CSUM)
			skb->ip_summed = CHECKSUM_UNNECESSARY;
		pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
			 ntohs(skb->protocol), skb->len, skb->pkt_type);

		dev->stats.rx_bytes += skb->len;
		dev->stats.rx_packets++;
		netif_rx(skb);
	}
	return done ? IRQ_HANDLED : IRQ_NONE;
}

static int lguestnet_open(struct net_device *dev)
{
	int i;
	struct lguestnet_info *info = netdev_priv(dev);

	/* Set up our MAC address */
	memcpy(info->peer[info->me].mac, dev->dev_addr, ETH_ALEN);

	/* Turn on promisc mode if needed */
	lguestnet_set_multicast(dev);

	for (i = 0; i < ARRAY_SIZE(info->dma); i++) {
		if (fill_slot(dev, i) != 0)
			goto cleanup;
	}
	if (lguest_bind_dma(peer_key(info,info->me), info->dma,
			    NUM_SKBS, lgdev_irq(info->lgdev)) != 0)
		goto cleanup;
	return 0;

cleanup:
	while (--i >= 0)
		dev_kfree_skb(info->skb[i]);
	return -ENOMEM;
}

static int lguestnet_close(struct net_device *dev)
{
	unsigned int i;
	struct lguestnet_info *info = netdev_priv(dev);

	/* Clear all trace: others might deliver packets, we'll ignore it. */
	memset(&info->peer[info->me], 0, sizeof(info->peer[info->me]));

	/* Deregister sg lists. */
	lguest_unbind_dma(peer_key(info, info->me), info->dma);
	for (i = 0; i < ARRAY_SIZE(info->dma); i++)
		dev_kfree_skb(info->skb[i]);
	return 0;
}

static int lguestnet_probe(struct lguest_device *lgdev)
{
	int err, irqf = IRQF_SHARED;
	struct net_device *dev;
	struct lguestnet_info *info;
	struct lguest_device_desc *desc = &lguest_devices[lgdev->index];

	pr_debug("lguest_net: probing for device %i\n", lgdev->index);

	dev = alloc_etherdev(sizeof(struct lguestnet_info));
	if (!dev)
		return -ENOMEM;

	SET_MODULE_OWNER(dev);

	/* Ethernet defaults with some changes */
	ether_setup(dev);
	dev->set_mac_address = NULL;

	dev->dev_addr[0] = 0x02; /* set local assignment bit (IEEE802) */
	dev->dev_addr[1] = 0x00;
	memcpy(&dev->dev_addr[2], &lguest_data.guestid, 2);
	dev->dev_addr[4] = 0x00;
	dev->dev_addr[5] = 0x00;

	dev->open = lguestnet_open;
	dev->stop = lguestnet_close;
	dev->hard_start_xmit = lguestnet_start_xmit;

	/* Turning on/off promisc will call dev->set_multicast_list.
	 * We don't actually support multicast yet */
	dev->set_multicast_list = lguestnet_set_multicast;
	SET_NETDEV_DEV(dev, &lgdev->dev);
	if (desc->features & LGUEST_NET_F_NOCSUM)
		dev->features = NETIF_F_SG|NETIF_F_NO_CSUM;

	info = netdev_priv(dev);
	info->mapsize = PAGE_SIZE * desc->num_pages;
	info->peer_phys = ((unsigned long)desc->pfn << PAGE_SHIFT);
	info->lgdev = lgdev;
	info->peer = lguest_map(info->peer_phys, desc->num_pages);
	if (!info->peer) {
		err = -ENOMEM;
		goto free;
	}

	/* This stores our peerid (upper bits reserved for future). */
	info->me = (desc->features & (info->mapsize-1));

	err = register_netdev(dev);
	if (err) {
		pr_debug("lguestnet: registering device failed\n");
		goto unmap;
	}

	if (lguest_devices[lgdev->index].features & LGUEST_DEVICE_F_RANDOMNESS)
		irqf |= IRQF_SAMPLE_RANDOM;
	if (request_irq(lgdev_irq(lgdev), lguestnet_rcv, irqf, "lguestnet",
			dev) != 0) {
		pr_debug("lguestnet: cannot get irq %i\n", lgdev_irq(lgdev));
		goto unregister;
	}

	pr_debug("lguestnet: registered device %s\n", dev->name);
	lgdev->private = dev;
	return 0;

unregister:
	unregister_netdev(dev);
unmap:
	lguest_unmap(info->peer);
free:
	free_netdev(dev);
	return err;
}

static struct lguest_driver lguestnet_drv = {
	.name = "lguestnet",
	.owner = THIS_MODULE,
	.device_type = LGUEST_DEVICE_T_NET,
	.probe = lguestnet_probe,
};

static __init int lguestnet_init(void)
{
	return register_lguest_driver(&lguestnet_drv);
}
module_init(lguestnet_init);

MODULE_DESCRIPTION("Lguest network driver");
MODULE_LICENSE("GPL");