/*
 * Copyright (c) 2012 GCT Semiconductor, Inc. All rights reserved.
 *
 * This software is licensed under the terms of the GNU General Public
 * License version 2, as published by the Free Software Foundation, and
 * may be copied, distributed, and modified under those terms.
 *
 * 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.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/etherdevice.h>
#include <linux/netlink.h>
#include <asm/byteorder.h>
#include <net/sock.h>

#if !defined(NLMSG_HDRLEN)
#define NLMSG_HDRLEN	 ((int) NLMSG_ALIGN(sizeof(struct nlmsghdr)))
#endif

#define ND_MAX_GROUP			30
#define ND_IFINDEX_LEN			sizeof(int)
#define ND_NLMSG_SPACE(len)		(NLMSG_SPACE(len) + ND_IFINDEX_LEN)
#define ND_NLMSG_DATA(nlh) \
	((void *)((char *)NLMSG_DATA(nlh) + ND_IFINDEX_LEN))
#define ND_NLMSG_S_LEN(len)		(len+ND_IFINDEX_LEN)
#define ND_NLMSG_R_LEN(nlh)		(nlh->nlmsg_len-ND_IFINDEX_LEN)
#define ND_NLMSG_IFIDX(nlh)		NLMSG_DATA(nlh)
#define ND_MAX_MSG_LEN			8096

#if defined(DEFINE_MUTEX)
static DEFINE_MUTEX(netlink_mutex);
#else
static struct semaphore netlink_mutex;
#define mutex_lock(x)		down(x)
#define mutex_unlock(x)		up(x)
#endif

static void (*rcv_cb)(struct net_device *dev, u16 type, void *msg, int len);

static void netlink_rcv_cb(struct sk_buff *skb)
{
	struct nlmsghdr *nlh;
	struct net_device *dev;
	u32 mlen;
	void *msg;
	int ifindex;

	if (skb->len >= NLMSG_SPACE(0)) {
		nlh = (struct nlmsghdr *)skb->data;

		if (skb->len < nlh->nlmsg_len ||
		nlh->nlmsg_len > ND_MAX_MSG_LEN) {
			netdev_err(skb->dev, "Invalid length (%d,%d)\n",
				   skb->len, nlh->nlmsg_len);
			return;
		}

		memcpy(&ifindex, ND_NLMSG_IFIDX(nlh), ND_IFINDEX_LEN);
		msg = ND_NLMSG_DATA(nlh);
		mlen = ND_NLMSG_R_LEN(nlh);

		if (rcv_cb) {
			dev = dev_get_by_index(&init_net, ifindex);
			if (dev) {
				rcv_cb(dev, nlh->nlmsg_type, msg, mlen);
				dev_put(dev);
			} else
				netdev_err(skb->dev,
					   "dev_get_by_index(%d) is not found.\n",
					   ifindex);
		} else
			netdev_err(skb->dev, "Unregistered Callback\n");
	}
}

static void netlink_rcv(struct sk_buff *skb)
{
	mutex_lock(&netlink_mutex);
	netlink_rcv_cb(skb);
	mutex_unlock(&netlink_mutex);
}

struct sock *netlink_init(int unit, void (*cb)(struct net_device *dev, u16 type,
						void *msg, int len))
{
	struct sock *sock;
	struct netlink_kernel_cfg cfg = {
		.input  = netlink_rcv,
	};

#if !defined(DEFINE_MUTEX)
	init_MUTEX(&netlink_mutex);
#endif

	sock = netlink_kernel_create(&init_net, unit, &cfg);

	if (sock)
		rcv_cb = cb;

	return sock;
}

void netlink_exit(struct sock *sock)
{
	netlink_kernel_release(sock);
}

int netlink_send(struct sock *sock, int group, u16 type, void *msg, int len)
{
	static u32 seq;
	struct sk_buff *skb = NULL;
	struct nlmsghdr *nlh;
	int ret = 0;

	if (group > ND_MAX_GROUP) {
		pr_err("Group %d is invalied.\n", group);
		pr_err("Valid group is 0 ~ %d.\n", ND_MAX_GROUP);
		return -EINVAL;
	}

	skb = alloc_skb(NLMSG_SPACE(len), GFP_ATOMIC);
	if (!skb) {
		pr_err("netlink_broadcast ret=%d\n", ret);
		return -ENOMEM;
	}

	seq++;
	nlh = nlmsg_put(skb, 0, seq, type, len, 0);
	if (!nlh) {
		kfree_skb(skb);
		return -EMSGSIZE;
	}
	memcpy(nlmsg_data(nlh), msg, len);

	NETLINK_CB(skb).portid = 0;
	NETLINK_CB(skb).dst_group = 0;

	ret = netlink_broadcast(sock, skb, 0, group+1, GFP_ATOMIC);

	if (!ret)
		return len;
	else {
		if (ret != -ESRCH) {
			pr_err("netlink_broadcast g=%d, t=%d, l=%d, r=%d\n",
			       group, type, len, ret);
		}
		ret = 0;
	}
	return ret;
}