#include <linux/module.h>
#include <linux/init.h>
#include <linux/netdevice.h>    /* struct device, and other headers */
#include <linux/etherdevice.h>  /* eth_type_trans */
#include <linux/ip.h>           /* struct iphdr */
#include <linux/ipv6.h>         /* struct ipv6hdr */
#include <linux/in.h>

#include "smskdefs.h" // page, scatterlist, kmutex
#include "smscoreapi.h"
#include "smstypes.h"

#define IPV4VERSION			0x40
#define IPV6VERSION			0x60
#define GETIPVERSION(_x_)	((_x_) & 0xf0)

typedef struct _smsnet_client
{
	struct list_head entry;

	smscore_device_t *coredev;
	smscore_client_t *smsclient;

	int				packet_length, splitpacket_length;
	int				header_length, splitheader_length;
	u8				splitpacket[ETH_DATA_LEN];
} smsnet_client_t;

struct list_head g_smsnet_clients;
kmutex_t g_smsnet_clientslock;

struct net_device *g_smsnet_device = NULL;
struct net_device_stats g_smsnet_stats;

int	g_smsnet_inuse = 0;

void smsnet_send_packet(u8* buffer, int length)
{
	u8 *eth;
	struct sk_buff *skb = dev_alloc_skb(length + ETH_HLEN + NET_IP_ALIGN);

	if (!skb)
	{
		g_smsnet_stats.rx_dropped++;
		return;
	}

	skb_reserve(skb, NET_IP_ALIGN);

	eth = (u8 *) skb_put(skb, length + ETH_HLEN);
	memcpy(eth + ETH_HLEN, buffer, length);

	eth[6] = 0;
	eth[7] = 1;
	eth[8] = 1;
	eth[9] = 3;
	eth[10] = 4;
	eth[11] = 5;

	if (GETIPVERSION(*buffer) == IPV4VERSION)
	{
		eth[0] = 1;
		eth[1] = 0;
		eth[2] = 0x5e;
		eth[3] = buffer[17] & 0x7f;
		eth[4] = buffer[18];
		eth[5] = buffer[19];

		eth[12] = 0x08;
		eth[13] = 0x00;
	}
	else
	{
		// todo: ip6 mcast address

		eth[12] = 0x86;
		eth[13] = 0xdd;
	}

	skb->dev = g_smsnet_device;
	skb->protocol = eth_type_trans(skb, g_smsnet_device);
	skb->ip_summed = CHECKSUM_UNNECESSARY;

	g_smsnet_stats.rx_packets ++;
	g_smsnet_stats.rx_bytes += skb->len;

	netif_rx(skb);
}

int check_header(smsnet_client_t* client, u8* buffer)
{
	struct iphdr *ip4_hdr;
	struct ipv6hdr *ip6_hdr;
	struct udphdr *udp_hdr;
	u16 csum;

	// check if packet header is valid and it is a UDP
	if (GETIPVERSION(*buffer) == IPV4VERSION)
	{
		ip4_hdr = (struct iphdr*) buffer;
		csum = ip4_hdr->check;

		ip4_hdr->check = 0;

		// check header checksum for IPv4 packets
		if(ip4_hdr->protocol != IPPROTO_UDP || csum != ip_fast_csum(buffer, ip4_hdr->ihl))
		{
			ip4_hdr->check = csum;
			return 0;
		}

		ip4_hdr->check = csum;
		client->packet_length = ntohs(ip4_hdr->tot_len);
	}
	else
	{
		ip6_hdr = (struct ipv6hdr *) buffer;
		udp_hdr = (struct udphdr *)(ip6_hdr + 1);

		if ((ip6_hdr->nexthdr != IPPROTO_UDP) ||
			(ip6_hdr->payload_len != udp_hdr->len))
		{
			return 0;
		}

		client->packet_length = ntohs(ip6_hdr->payload_len) + sizeof(struct ipv6hdr);
	}

	// check for abnormal packet length
	if (client->packet_length > ETH_DATA_LEN)
		return 0;

	return 1;
}

int smsnet_onresponse(void *context, smscore_buffer_t *cb)
{
	smsnet_client_t *client = (smsnet_client_t *) context;
	int				length, rest;
	u8				ip_ver, *buffer;

	buffer = ((u8*) cb->p) + cb->offset + sizeof(SmsMsgHdr_ST);
	length = cb->size - sizeof(SmsMsgHdr_ST);

	if (client->splitheader_length)
	{
		// how much data is missing ?
		rest = client->header_length - client->splitheader_length;

		// do we have enough in this buffer ?
		rest = min(rest, length);

		memcpy(&client->splitpacket[client->splitheader_length], buffer, rest);

		client->splitheader_length += rest;

		if (client->splitheader_length != client->header_length)
			goto exit;

		if (check_header(client, client->splitpacket))
		{
			buffer += rest;
			length -= rest;

			client->splitpacket_length = client->header_length;
		}

		client->splitheader_length = 0;
	}

	if (client->splitpacket_length)
	{
		// how much data is missing ?
		rest = client->packet_length - client->splitpacket_length;

		// do we have enough in this buffer ?
		rest = min(rest, length);

		memcpy(&client->splitpacket[client->splitpacket_length], buffer, rest);

		client->splitpacket_length += rest;

		if (client->splitpacket_length != client->packet_length)
			goto exit;

		client->splitpacket_length = 0;

		smsnet_send_packet(client->splitpacket, client->packet_length);

		buffer += rest;
		length -= rest;
	}

	while (length > 0)
	{
		ip_ver = GETIPVERSION(*buffer);
		while (length && (ip_ver != IPV4VERSION) && (ip_ver != IPV6VERSION))
		{
			buffer++;
			length--;
			ip_ver = GETIPVERSION(*buffer);
		}

		// No more data in section
		if (!length)
			break;

		// Set the header length at start of packet according to the version
		// no problem with the IP header cast, since we have at least 1 byte (we use only the first byte)
		client->header_length = (ip_ver == IPV4VERSION) ? (((struct iphdr *) buffer)->ihl * 4) : (sizeof(struct ipv6hdr) + sizeof(struct udphdr));

		// Check that Header length is at least 20 (min IPv4 length)
		if (client->header_length < 20)
		{
			length--;
			buffer++;
			continue;
		}

		// check split header case
		if (client->header_length > length)
		{
			memcpy(client->splitpacket, buffer, length);
			client->splitheader_length = length;
			break;
		}

		if (check_header(client, buffer))
		{
			// check split packet case
			if (client->packet_length > length)
			{
				memcpy(client->splitpacket, buffer, length);
				client->splitpacket_length = length;
				break;
			}
		}
		else
		{
			length --;
			buffer ++;
			continue;
		}

		smsnet_send_packet(buffer, client->packet_length);

		buffer += client->packet_length;
		length -= client->packet_length;
	}

exit:
	smscore_putbuffer(client->coredev, cb);

	return 0;
}

void smsnet_unregister_client(smsnet_client_t* client)
{
	// must be called under clientslock

	list_del(&client->entry);

	smscore_unregister_client(client->smsclient);
	kfree(client);
}

void smsnet_onremove(void *context)
{
	kmutex_lock(&g_smsnet_clientslock);

	smsnet_unregister_client((smsnet_client_t*) context);

	kmutex_unlock(&g_smsnet_clientslock);
}

int smsnet_hotplug(smscore_device_t *coredev, struct device* device, int arrival)
{
	smsclient_params_t params;
	smsnet_client_t* client;
	int rc;

	// device removal handled by onremove callback
	if (!arrival)
		return 0;

	client = kzalloc(sizeof(smsnet_client_t), GFP_KERNEL);
	if (!client)
	{
		printk(KERN_INFO "%s kmalloc() failed\n", __FUNCTION__);
		return -ENOMEM;
	}

	params.initial_id = 0;
	params.data_type = MSG_SMS_DATA_MSG;
	params.onresponse_handler = smsnet_onresponse;
	params.onremove_handler = smsnet_onremove;
	params.context = client;

	rc = smscore_register_client(coredev, &params, &client->smsclient);
	if (rc < 0)
	{
		printk(KERN_INFO "%s smscore_register_client() failed %d\n", __FUNCTION__, rc);
		kfree(client);
		return rc;
	}

	client->coredev = coredev;

	kmutex_lock(&g_smsnet_clientslock);

	list_add(&client->entry, &g_smsnet_clients);

	kmutex_unlock(&g_smsnet_clientslock);

	printk(KERN_INFO "%s success\n", __FUNCTION__);

	return 0;
}

static int smsnet_open(struct net_device *dev)
{
	g_smsnet_inuse ++;

	netif_start_queue(dev);

	printk(KERN_INFO "%s, %d\n", __FUNCTION__, g_smsnet_inuse);

	return 0;
}

static int smsnet_stop(struct net_device *dev)
{
	netif_stop_queue(dev);

	g_smsnet_inuse --;

	printk(KERN_INFO "%s, %d\n", __FUNCTION__, g_smsnet_inuse);

	return 0;
}

static int smsnet_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	printk(KERN_INFO "%s\n", __FUNCTION__);

	dev_kfree_skb(skb);
	return 0;
}

static struct net_device_stats * smsnet_get_stats(struct net_device *dev)
{
	return &g_smsnet_stats;
}

static void smsnet_set_multicast_list(struct net_device *dev)
{
	printk(KERN_INFO "%s %d\n", __FUNCTION__, dev->mc_count);
	if (dev->mc_count)
	{
		struct dev_mc_list	*p;

		for (p = dev->mc_list; p; p = p->next)
			printk(KERN_INFO "%s %d %02x %02x %02x %02x %02x %02x %02x %02x\n", __FUNCTION__, p->dmi_addrlen,
				p->dmi_addr[0], p->dmi_addr[1], p->dmi_addr[2], p->dmi_addr[3],
				p->dmi_addr[4], p->dmi_addr[5], p->dmi_addr[6], p->dmi_addr[7]
			);
	}
}

static void smsnet_setup_device(struct net_device *dev)
{
	ether_setup(dev);

	dev->open				= smsnet_open;
	dev->stop				= smsnet_stop;
	dev->hard_start_xmit	= smsnet_hard_start_xmit;
	dev->get_stats			= smsnet_get_stats;
	dev->set_multicast_list = smsnet_set_multicast_list;

	dev->mc_count = 0;
	dev->hard_header_cache  = NULL;

	memcpy(dev->dev_addr, "\0SIANO", ETH_ALEN);

	dev->flags |= IFF_NOARP;
    dev->features |= NETIF_F_NO_CSUM;
}

int smsnet_module_init(void)
{
	int rc;

	INIT_LIST_HEAD(&g_smsnet_clients);
	kmutex_init(&g_smsnet_clientslock);

	memset(&g_smsnet_stats, 0, sizeof(g_smsnet_stats));

	g_smsnet_device = alloc_netdev(0, "sms", smsnet_setup_device);
	if (!g_smsnet_device)
	{
		printk(KERN_INFO "%s alloc_netdev() failed\n", __FUNCTION__);
		return -ENOMEM;
	}

	rc = register_netdev(g_smsnet_device);
	if (rc < 0)
	{
		printk(KERN_INFO "%s register_netdev() failed %d\n", __FUNCTION__, rc);
		free_netdev(g_smsnet_device);
		return rc;
	}

	rc = smscore_register_hotplug(smsnet_hotplug);

	printk(KERN_INFO "%s, rc %d\n", __FUNCTION__, rc);

	return rc;
}

void smsnet_module_exit(void)
{
	if (g_smsnet_device)
	{
		unregister_netdev(g_smsnet_device);
		free_netdev(g_smsnet_device);

		g_smsnet_device = NULL;
	}

	smscore_unregister_hotplug(smsnet_hotplug);

	kmutex_lock(&g_smsnet_clientslock);

	while (!list_empty(&g_smsnet_clients))
		smsnet_unregister_client((smsnet_client_t*) g_smsnet_clients.next);

	kmutex_unlock(&g_smsnet_clientslock);

	printk(KERN_INFO "%s\n", __FUNCTION__);
}

module_init(smsnet_module_init);
module_exit(smsnet_module_exit);

MODULE_DESCRIPTION("smsnet dvb-h ip sink module");
MODULE_AUTHOR("Anatoly Greenblatt,,, (anatolyg@siano-ms.com)");
MODULE_LICENSE("GPL");