/*
 * Copyright (c) 2010 Nicira Networks.
 * Distributed under the terms of the GNU GPL version 2.
 *
 * Significant portions of this file may be copied from parts of the Linux
 * kernel, by Linus Torvalds and others.
 */

#include <linux/dcache.h>
#include <linux/kernel.h>
#include <linux/list.h>

#include "datapath.h"
#include "vport.h"
#include "vport-generic.h"

struct device_config {
	struct rcu_head rcu;

	unsigned char eth_addr[ETH_ALEN];
	unsigned int mtu;
};

struct patch_vport {
	char name[IFNAMSIZ];

	/* Protected by RTNL lock. */
	char peer_name[IFNAMSIZ];
	struct hlist_node hash_node;

	/* Protected by RCU. */
	struct vport *peer;

	/* Protected by RCU. */
	struct device_config *devconf;
};

/* Protected by RTNL lock. */
static struct hlist_head *peer_table;
#define PEER_HASH_BUCKETS 256

static inline struct patch_vport *patch_vport_priv(const struct vport *vport)
{
	return vport_priv(vport);
}

/* RCU callback. */
static void free_config(struct rcu_head *rcu)
{
	struct device_config *c = container_of(rcu, struct device_config, rcu);
	kfree(c);
}

static void assign_config_rcu(struct vport *vport,
			      struct device_config *new_config)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);
	struct device_config *old_config;

	old_config = rcu_dereference(patch_vport->devconf);
	rcu_assign_pointer(patch_vport->devconf, new_config);
	call_rcu(&old_config->rcu, free_config);
}

static struct hlist_head *hash_bucket(const char *name)
{
	unsigned int hash = full_name_hash(name, strlen(name));
	return &peer_table[hash & (PEER_HASH_BUCKETS - 1)];
}

static int patch_init(void)
{
	peer_table = kzalloc(PEER_HASH_BUCKETS * sizeof(struct hlist_head),
			    GFP_KERNEL);
	if (!peer_table)
		return -ENOMEM;

	return 0;
}

static void patch_exit(void)
{
	kfree(peer_table);
}

static int set_config(struct vport *vport, const void __user *uconfig)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);
	char peer_name[IFNAMSIZ];
	int retval;

	retval = strncpy_from_user(peer_name, uconfig, IFNAMSIZ);
	if (retval < 0)
		return -EFAULT;
	else if (retval >= IFNAMSIZ)
		return -ENAMETOOLONG;

	if (!strcmp(patch_vport->name, peer_name))
		return -EINVAL;

	strcpy(patch_vport->peer_name, peer_name);

	if (vport_get_dp_port(vport)) {
		hlist_del(&patch_vport->hash_node);
		rcu_assign_pointer(patch_vport->peer, vport_locate(patch_vport->peer_name));
		hlist_add_head(&patch_vport->hash_node, hash_bucket(patch_vport->peer_name));
	}

	return 0;
}

static struct vport *patch_create(const char *name, const void __user *config)
{
	struct vport *vport;
	struct patch_vport *patch_vport;
	int err;

	vport = vport_alloc(sizeof(struct patch_vport), &patch_vport_ops);
	if (IS_ERR(vport)) {
		err = PTR_ERR(vport);
		goto error;
	}

	patch_vport = patch_vport_priv(vport);

	strcpy(patch_vport->name, name);

	err = set_config(vport, config);
	if (err)
		goto error_free_vport;

	patch_vport->devconf = kmalloc(sizeof(struct device_config), GFP_KERNEL);
	if (!patch_vport->devconf) {
		err = -ENOMEM;
		goto error_free_vport;
	}

	vport_gen_rand_ether_addr(patch_vport->devconf->eth_addr);
	patch_vport->devconf->mtu = ETH_DATA_LEN;

	return vport;

error_free_vport:
	vport_free(vport);
error:
	return ERR_PTR(err);
}

static int patch_modify(struct vport *vport, const void __user *config)
{
	return set_config(vport, config);
}

static int patch_destroy(struct vport *vport)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);

	kfree(patch_vport->devconf);
	vport_free(vport);

	return 0;
}

static void update_peers(const char *name, struct vport *vport)
{
	struct hlist_head *bucket = hash_bucket(name);
	struct patch_vport *peer_vport;
	struct hlist_node *node;

	hlist_for_each_entry(peer_vport, node, bucket, hash_node)
		if (!strcmp(peer_vport->peer_name, name))
			rcu_assign_pointer(peer_vport->peer, vport);
}

static int patch_attach(struct vport *vport)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);

	hlist_add_head(&patch_vport->hash_node, hash_bucket(patch_vport->peer_name));

	rcu_assign_pointer(patch_vport->peer, vport_locate(patch_vport->peer_name));
	update_peers(patch_vport->name, vport);

	return 0;
}

static int patch_detach(struct vport *vport)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);

	update_peers(patch_vport->name, NULL);
	rcu_assign_pointer(patch_vport->peer, NULL);

	hlist_del(&patch_vport->hash_node);

	return 0;
}

static int patch_set_mtu(struct vport *vport, int mtu)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);
	struct device_config *devconf;

	devconf = kmemdup(patch_vport->devconf, sizeof(struct device_config), GFP_KERNEL);
	if (!devconf)
		return -ENOMEM;

	devconf->mtu = mtu;
	assign_config_rcu(vport, devconf);

	return 0;
}

static int patch_set_addr(struct vport *vport, const unsigned char *addr)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);
	struct device_config *devconf;

	devconf = kmemdup(patch_vport->devconf, sizeof(struct device_config), GFP_KERNEL);
	if (!devconf)
		return -ENOMEM;

	memcpy(devconf->eth_addr, addr, ETH_ALEN);
	assign_config_rcu(vport, devconf);

	return 0;
}


static const char *patch_get_name(const struct vport *vport)
{
	const struct patch_vport *patch_vport = patch_vport_priv(vport);
	return patch_vport->name;
}

static const unsigned char *patch_get_addr(const struct vport *vport)
{
	const struct patch_vport *patch_vport = patch_vport_priv(vport);
	return rcu_dereference(patch_vport->devconf)->eth_addr;
}

static int patch_get_mtu(const struct vport *vport)
{
	const struct patch_vport *patch_vport = patch_vport_priv(vport);
	return rcu_dereference(patch_vport->devconf)->mtu;
}

static int patch_send(struct vport *vport, struct sk_buff *skb)
{
	struct patch_vport *patch_vport = patch_vport_priv(vport);
	struct vport *peer = rcu_dereference(patch_vport->peer);
	int skb_len = skb->len;

	if (!peer) {
		kfree_skb(skb);
		vport_record_error(vport, VPORT_E_TX_DROPPED);

		return 0;
	}

	vport_receive(peer, skb);
	return skb_len;
}

struct vport_ops patch_vport_ops = {
	.type		= "patch",
	.flags		= VPORT_F_GEN_STATS,
	.init		= patch_init,
	.exit		= patch_exit,
	.create		= patch_create,
	.modify		= patch_modify,
	.destroy	= patch_destroy,
	.attach		= patch_attach,
	.detach		= patch_detach,
	.set_mtu	= patch_set_mtu,
	.set_addr	= patch_set_addr,
	.get_name	= patch_get_name,
	.get_addr	= patch_get_addr,
	.get_dev_flags	= vport_gen_get_dev_flags,
	.is_running	= vport_gen_is_running,
	.get_operstate	= vport_gen_get_operstate,
	.get_mtu	= patch_get_mtu,
	.send		= patch_send,
};