/* (C) 1999-2001 Paul `Rusty' Russell
 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * 16 Dec 2003: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 *	- move L3 protocol dependent part to this file.
 * 23 Mar 2004: Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 *	- add get_features() to support various size of conntrack
 *	  structures.
 *
 * Derived from net/ipv4/netfilter/ip_conntrack_standalone.c
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/ip.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/icmp.h>
#include <linux/sysctl.h>
#include <net/ip.h>

#include <linux/netfilter_ipv4.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_protocol.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/ipv4/nf_conntrack_ipv4.h>

#if 0
#define DEBUGP printk
#else
#define DEBUGP(format, args...)
#endif

DECLARE_PER_CPU(struct nf_conntrack_stat, nf_conntrack_stat);

static int ipv4_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
			     struct nf_conntrack_tuple *tuple)
{
	u_int32_t _addrs[2], *ap;
	ap = skb_header_pointer(skb, nhoff + offsetof(struct iphdr, saddr),
				sizeof(u_int32_t) * 2, _addrs);
	if (ap == NULL)
		return 0;

	tuple->src.u3.ip = ap[0];
	tuple->dst.u3.ip = ap[1];

	return 1;
}

static int ipv4_invert_tuple(struct nf_conntrack_tuple *tuple,
			   const struct nf_conntrack_tuple *orig)
{
	tuple->src.u3.ip = orig->dst.u3.ip;
	tuple->dst.u3.ip = orig->src.u3.ip;

	return 1;
}

static int ipv4_print_tuple(struct seq_file *s,
			    const struct nf_conntrack_tuple *tuple)
{
	return seq_printf(s, "src=%u.%u.%u.%u dst=%u.%u.%u.%u ",
		          NIPQUAD(tuple->src.u3.ip),
			  NIPQUAD(tuple->dst.u3.ip));
}

static int ipv4_print_conntrack(struct seq_file *s,
				const struct nf_conn *conntrack)
{
	return 0;
}

/* Returns new sk_buff, or NULL */
static struct sk_buff *
nf_ct_ipv4_gather_frags(struct sk_buff *skb, u_int32_t user)
{
	skb_orphan(skb);

        local_bh_disable();
        skb = ip_defrag(skb, user);
        local_bh_enable();

        if (skb)
		ip_send_check(skb->nh.iph);

        return skb;
}

static int
ipv4_prepare(struct sk_buff **pskb, unsigned int hooknum, unsigned int *dataoff,
	     u_int8_t *protonum)
{
	/* Never happen */
	if ((*pskb)->nh.iph->frag_off & htons(IP_OFFSET)) {
		if (net_ratelimit()) {
			printk(KERN_ERR "ipv4_prepare: Frag of proto %u (hook=%u)\n",
			(*pskb)->nh.iph->protocol, hooknum);
		}
		return -NF_DROP;
	}

	*dataoff = (*pskb)->nh.raw - (*pskb)->data + (*pskb)->nh.iph->ihl*4;
	*protonum = (*pskb)->nh.iph->protocol;

	return NF_ACCEPT;
}

int nat_module_is_loaded = 0;
static u_int32_t ipv4_get_features(const struct nf_conntrack_tuple *tuple)
{
	if (nat_module_is_loaded)
		return NF_CT_F_NAT;

	return NF_CT_F_BASIC;
}

static unsigned int ipv4_confirm(unsigned int hooknum,
				 struct sk_buff **pskb,
				 const struct net_device *in,
				 const struct net_device *out,
				 int (*okfn)(struct sk_buff *))
{
	/* We've seen it coming out the other side: confirm it */
	return nf_conntrack_confirm(pskb);
}

static unsigned int ipv4_conntrack_help(unsigned int hooknum,
				      struct sk_buff **pskb,
				      const struct net_device *in,
				      const struct net_device *out,
				      int (*okfn)(struct sk_buff *))
{
	struct nf_conn *ct;
	enum ip_conntrack_info ctinfo;

	/* This is where we call the helper: as the packet goes out. */
	ct = nf_ct_get(*pskb, &ctinfo);
	if (ct && ct->helper) {
		unsigned int ret;
		ret = ct->helper->help(pskb,
				       (*pskb)->nh.raw - (*pskb)->data
						       + (*pskb)->nh.iph->ihl*4,
				       ct, ctinfo);
		if (ret != NF_ACCEPT)
			return ret;
	}
	return NF_ACCEPT;
}

static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
					  struct sk_buff **pskb,
					  const struct net_device *in,
					  const struct net_device *out,
					  int (*okfn)(struct sk_buff *))
{
#if !defined(CONFIG_IP_NF_NAT) && !defined(CONFIG_IP_NF_NAT_MODULE)
	/* Previously seen (loopback)?  Ignore.  Do this before
	   fragment check. */
	if ((*pskb)->nfct)
		return NF_ACCEPT;
#endif

	/* Gather fragments. */
	if ((*pskb)->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
		*pskb = nf_ct_ipv4_gather_frags(*pskb,
						hooknum == NF_IP_PRE_ROUTING ?
						IP_DEFRAG_CONNTRACK_IN :
						IP_DEFRAG_CONNTRACK_OUT);
		if (!*pskb)
			return NF_STOLEN;
	}
	return NF_ACCEPT;
}

static unsigned int ipv4_refrag(unsigned int hooknum,
				struct sk_buff **pskb,
				const struct net_device *in,
				const struct net_device *out,
				int (*okfn)(struct sk_buff *))
{
	struct rtable *rt = (struct rtable *)(*pskb)->dst;

	/* We've seen it coming out the other side: confirm */
	if (ipv4_confirm(hooknum, pskb, in, out, okfn) != NF_ACCEPT)
		return NF_DROP;

	/* Local packets are never produced too large for their
	   interface.  We degfragment them at LOCAL_OUT, however,
	   so we have to refragment them here. */
	if ((*pskb)->len > dst_mtu(&rt->u.dst) &&
	    !skb_shinfo(*pskb)->tso_size) {
		/* No hook can be after us, so this should be OK. */
		ip_fragment(*pskb, okfn);
		return NF_STOLEN;
	}
	return NF_ACCEPT;
}

static unsigned int ipv4_conntrack_in(unsigned int hooknum,
				      struct sk_buff **pskb,
				      const struct net_device *in,
				      const struct net_device *out,
				      int (*okfn)(struct sk_buff *))
{
	return nf_conntrack_in(PF_INET, hooknum, pskb);
}

static unsigned int ipv4_conntrack_local(unsigned int hooknum,
				         struct sk_buff **pskb,
				         const struct net_device *in,
				         const struct net_device *out,
				         int (*okfn)(struct sk_buff *))
{
	/* root is playing with raw sockets. */
	if ((*pskb)->len < sizeof(struct iphdr)
	    || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr)) {
		if (net_ratelimit())
			printk("ipt_hook: happy cracking.\n");
		return NF_ACCEPT;
	}
	return nf_conntrack_in(PF_INET, hooknum, pskb);
}

/* Connection tracking may drop packets, but never alters them, so
   make it the first hook. */
static struct nf_hook_ops ipv4_conntrack_defrag_ops = {
	.hook		= ipv4_conntrack_defrag,
	.owner		= THIS_MODULE,
	.pf		= PF_INET,
	.hooknum	= NF_IP_PRE_ROUTING,
	.priority	= NF_IP_PRI_CONNTRACK_DEFRAG,
};

static struct nf_hook_ops ipv4_conntrack_in_ops = {
	.hook		= ipv4_conntrack_in,
	.owner		= THIS_MODULE,
	.pf		= PF_INET,
	.hooknum	= NF_IP_PRE_ROUTING,
	.priority	= NF_IP_PRI_CONNTRACK,
};

static struct nf_hook_ops ipv4_conntrack_defrag_local_out_ops = {
	.hook           = ipv4_conntrack_defrag,
	.owner          = THIS_MODULE,
	.pf             = PF_INET,
	.hooknum        = NF_IP_LOCAL_OUT,
	.priority       = NF_IP_PRI_CONNTRACK_DEFRAG,
};

static struct nf_hook_ops ipv4_conntrack_local_out_ops = {
	.hook		= ipv4_conntrack_local,
	.owner		= THIS_MODULE,
	.pf		= PF_INET,
	.hooknum	= NF_IP_LOCAL_OUT,
	.priority	= NF_IP_PRI_CONNTRACK,
};

/* helpers */
static struct nf_hook_ops ipv4_conntrack_helper_out_ops = {
	.hook		= ipv4_conntrack_help,
	.owner		= THIS_MODULE,
	.pf		= PF_INET,
	.hooknum	= NF_IP_POST_ROUTING,
	.priority	= NF_IP_PRI_CONNTRACK_HELPER,
};

static struct nf_hook_ops ipv4_conntrack_helper_in_ops = {
	.hook		= ipv4_conntrack_help,
	.owner		= THIS_MODULE,
	.pf		= PF_INET,
	.hooknum	= NF_IP_LOCAL_IN,
	.priority	= NF_IP_PRI_CONNTRACK_HELPER,
};


/* Refragmenter; last chance. */
static struct nf_hook_ops ipv4_conntrack_out_ops = {
	.hook		= ipv4_refrag,
	.owner		= THIS_MODULE,
	.pf		= PF_INET,
	.hooknum	= NF_IP_POST_ROUTING,
	.priority	= NF_IP_PRI_CONNTRACK_CONFIRM,
};

static struct nf_hook_ops ipv4_conntrack_local_in_ops = {
	.hook		= ipv4_confirm,
	.owner		= THIS_MODULE,
	.pf		= PF_INET,
	.hooknum	= NF_IP_LOCAL_IN,
	.priority	= NF_IP_PRI_CONNTRACK_CONFIRM,
};

#ifdef CONFIG_SYSCTL
/* From nf_conntrack_proto_icmp.c */
extern unsigned long nf_ct_icmp_timeout;
static struct ctl_table_header *nf_ct_ipv4_sysctl_header;

static ctl_table nf_ct_sysctl_table[] = {
	{
		.ctl_name	= NET_NF_CONNTRACK_ICMP_TIMEOUT,
		.procname	= "nf_conntrack_icmp_timeout",
		.data		= &nf_ct_icmp_timeout,
		.maxlen		= sizeof(unsigned int),
		.mode		= 0644,
		.proc_handler	= &proc_dointvec_jiffies,
	},
        { .ctl_name = 0 }
};

static ctl_table nf_ct_netfilter_table[] = {
	{
		.ctl_name       = NET_NETFILTER,
		.procname       = "netfilter",
		.mode           = 0555,
		.child          = nf_ct_sysctl_table,
	},
	{ .ctl_name = 0 }
};

static ctl_table nf_ct_net_table[] = {
	{
		.ctl_name       = CTL_NET,
		.procname       = "net",
		.mode           = 0555,
		.child          = nf_ct_netfilter_table,
	},
	{ .ctl_name = 0 }
};
#endif

/* Fast function for those who don't want to parse /proc (and I don't
   blame them). */
/* Reversing the socket's dst/src point of view gives us the reply
   mapping. */
static int
getorigdst(struct sock *sk, int optval, void __user *user, int *len)
{
	struct inet_sock *inet = inet_sk(sk);
	struct nf_conntrack_tuple_hash *h;
	struct nf_conntrack_tuple tuple;
	
	NF_CT_TUPLE_U_BLANK(&tuple);
	tuple.src.u3.ip = inet->rcv_saddr;
	tuple.src.u.tcp.port = inet->sport;
	tuple.dst.u3.ip = inet->daddr;
	tuple.dst.u.tcp.port = inet->dport;
	tuple.src.l3num = PF_INET;
	tuple.dst.protonum = IPPROTO_TCP;

	/* We only do TCP at the moment: is there a better way? */
	if (strcmp(sk->sk_prot->name, "TCP")) {
		DEBUGP("SO_ORIGINAL_DST: Not a TCP socket\n");
		return -ENOPROTOOPT;
	}

	if ((unsigned int) *len < sizeof(struct sockaddr_in)) {
		DEBUGP("SO_ORIGINAL_DST: len %u not %u\n",
		       *len, sizeof(struct sockaddr_in));
		return -EINVAL;
	}

	h = nf_conntrack_find_get(&tuple, NULL);
	if (h) {
		struct sockaddr_in sin;
		struct nf_conn *ct = nf_ct_tuplehash_to_ctrack(h);

		sin.sin_family = AF_INET;
		sin.sin_port = ct->tuplehash[IP_CT_DIR_ORIGINAL]
			.tuple.dst.u.tcp.port;
		sin.sin_addr.s_addr = ct->tuplehash[IP_CT_DIR_ORIGINAL]
			.tuple.dst.u3.ip;

		DEBUGP("SO_ORIGINAL_DST: %u.%u.%u.%u %u\n",
		       NIPQUAD(sin.sin_addr.s_addr), ntohs(sin.sin_port));
		nf_ct_put(ct);
		if (copy_to_user(user, &sin, sizeof(sin)) != 0)
			return -EFAULT;
		else
			return 0;
	}
	DEBUGP("SO_ORIGINAL_DST: Can't find %u.%u.%u.%u/%u-%u.%u.%u.%u/%u.\n",
	       NIPQUAD(tuple.src.u3.ip), ntohs(tuple.src.u.tcp.port),
	       NIPQUAD(tuple.dst.u3.ip), ntohs(tuple.dst.u.tcp.port));
	return -ENOENT;
}

static struct nf_sockopt_ops so_getorigdst = {
	.pf		= PF_INET,
	.get_optmin	= SO_ORIGINAL_DST,
	.get_optmax	= SO_ORIGINAL_DST+1,
	.get		= &getorigdst,
};

struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv4 = {
	.l3proto	 = PF_INET,
	.name		 = "ipv4",
	.pkt_to_tuple	 = ipv4_pkt_to_tuple,
	.invert_tuple	 = ipv4_invert_tuple,
	.print_tuple	 = ipv4_print_tuple,
	.print_conntrack = ipv4_print_conntrack,
	.prepare	 = ipv4_prepare,
	.get_features	 = ipv4_get_features,
	.me		 = THIS_MODULE,
};

extern struct nf_conntrack_protocol nf_conntrack_protocol_tcp4;
extern struct nf_conntrack_protocol nf_conntrack_protocol_udp4;
extern struct nf_conntrack_protocol nf_conntrack_protocol_icmp;
static int init_or_cleanup(int init)
{
	int ret = 0;

	if (!init) goto cleanup;

	ret = nf_register_sockopt(&so_getorigdst);
	if (ret < 0) {
		printk(KERN_ERR "Unable to register netfilter socket option\n");
		goto cleanup_nothing;
	}

	ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_tcp4);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register tcp.\n");
		goto cleanup_sockopt;
	}

	ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_udp4);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register udp.\n");
		goto cleanup_tcp;
	}

	ret = nf_conntrack_protocol_register(&nf_conntrack_protocol_icmp);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register icmp.\n");
		goto cleanup_udp;
	}

	ret = nf_conntrack_l3proto_register(&nf_conntrack_l3proto_ipv4);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register ipv4\n");
		goto cleanup_icmp;
	}

	ret = nf_register_hook(&ipv4_conntrack_defrag_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register pre-routing defrag hook.\n");
		goto cleanup_ipv4;
	}
	ret = nf_register_hook(&ipv4_conntrack_defrag_local_out_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register local_out defrag hook.\n");
		goto cleanup_defragops;
	}

	ret = nf_register_hook(&ipv4_conntrack_in_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register pre-routing hook.\n");
		goto cleanup_defraglocalops;
	}

	ret = nf_register_hook(&ipv4_conntrack_local_out_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register local out hook.\n");
		goto cleanup_inops;
	}

	ret = nf_register_hook(&ipv4_conntrack_helper_in_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register local helper hook.\n");
		goto cleanup_inandlocalops;
	}

	ret = nf_register_hook(&ipv4_conntrack_helper_out_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register postrouting helper hook.\n");
		goto cleanup_helperinops;
	}

	ret = nf_register_hook(&ipv4_conntrack_out_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register post-routing hook.\n");
		goto cleanup_helperoutops;
	}

	ret = nf_register_hook(&ipv4_conntrack_local_in_ops);
	if (ret < 0) {
		printk("nf_conntrack_ipv4: can't register local in hook.\n");
		goto cleanup_inoutandlocalops;
	}

#ifdef CONFIG_SYSCTL
	nf_ct_ipv4_sysctl_header = register_sysctl_table(nf_ct_net_table, 0);
	if (nf_ct_ipv4_sysctl_header == NULL) {
		printk("nf_conntrack: can't register to sysctl.\n");
		ret = -ENOMEM;
		goto cleanup_localinops;
	}
#endif

	/* For use by REJECT target */
	ip_ct_attach = __nf_conntrack_attach;

	return ret;

 cleanup:
	synchronize_net();
	ip_ct_attach = NULL;
#ifdef CONFIG_SYSCTL
 	unregister_sysctl_table(nf_ct_ipv4_sysctl_header);
 cleanup_localinops:
#endif
	nf_unregister_hook(&ipv4_conntrack_local_in_ops);
 cleanup_inoutandlocalops:
	nf_unregister_hook(&ipv4_conntrack_out_ops);
 cleanup_helperoutops:
	nf_unregister_hook(&ipv4_conntrack_helper_out_ops);
 cleanup_helperinops:
	nf_unregister_hook(&ipv4_conntrack_helper_in_ops);
 cleanup_inandlocalops:
	nf_unregister_hook(&ipv4_conntrack_local_out_ops);
 cleanup_inops:
	nf_unregister_hook(&ipv4_conntrack_in_ops);
 cleanup_defraglocalops:
	nf_unregister_hook(&ipv4_conntrack_defrag_local_out_ops);
 cleanup_defragops:
	nf_unregister_hook(&ipv4_conntrack_defrag_ops);
 cleanup_ipv4:
	nf_conntrack_l3proto_unregister(&nf_conntrack_l3proto_ipv4);
 cleanup_icmp:
	nf_conntrack_protocol_unregister(&nf_conntrack_protocol_icmp);
 cleanup_udp:
	nf_conntrack_protocol_unregister(&nf_conntrack_protocol_udp4);
 cleanup_tcp:
	nf_conntrack_protocol_unregister(&nf_conntrack_protocol_tcp4);
 cleanup_sockopt:
	nf_unregister_sockopt(&so_getorigdst);
 cleanup_nothing:
	return ret;
}

MODULE_LICENSE("GPL");

static int __init init(void)
{
	need_nf_conntrack();
	return init_or_cleanup(1);
}

static void __exit fini(void)
{
	init_or_cleanup(0);
}

module_init(init);
module_exit(fini);

void need_ip_conntrack(void)
{
}

EXPORT_SYMBOL(need_ip_conntrack);
EXPORT_SYMBOL(nf_ct_ipv4_gather_frags);