/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		The Internet Protocol (IP) module.
 *
 * Version:	$Id: ip_input.c,v 1.24 1997/10/24 17:15:58 kuznet Exp $
 *
 * Authors:	Ross Biro, <bir7@leland.Stanford.Edu>
 *		Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 *		Donald Becker, <becker@super.org>
 *		Alan Cox, <Alan.Cox@linux.org>
 *		Richard Underwood
 *		Stefan Becker, <stefanb@yello.ping.de>
 *		Jorge Cwik, <jorge@laser.satlink.net>
 *		Arnt Gulbrandsen, <agulbra@nvg.unit.no>
 *		
 *
 * Fixes:
 *		Alan Cox	:	Commented a couple of minor bits of surplus code
 *		Alan Cox	:	Undefining IP_FORWARD doesn't include the code
 *					(just stops a compiler warning).
 *		Alan Cox	:	Frames with >=MAX_ROUTE record routes, strict routes or loose routes
 *					are junked rather than corrupting things.
 *		Alan Cox	:	Frames to bad broadcast subnets are dumped
 *					We used to process them non broadcast and
 *					boy could that cause havoc.
 *		Alan Cox	:	ip_forward sets the free flag on the
 *					new frame it queues. Still crap because
 *					it copies the frame but at least it
 *					doesn't eat memory too.
 *		Alan Cox	:	Generic queue code and memory fixes.
 *		Fred Van Kempen :	IP fragment support (borrowed from NET2E)
 *		Gerhard Koerting:	Forward fragmented frames correctly.
 *		Gerhard Koerting: 	Fixes to my fix of the above 8-).
 *		Gerhard Koerting:	IP interface addressing fix.
 *		Linus Torvalds	:	More robustness checks
 *		Alan Cox	:	Even more checks: Still not as robust as it ought to be
 *		Alan Cox	:	Save IP header pointer for later
 *		Alan Cox	:	ip option setting
 *		Alan Cox	:	Use ip_tos/ip_ttl settings
 *		Alan Cox	:	Fragmentation bogosity removed
 *					(Thanks to Mark.Bush@prg.ox.ac.uk)
 *		Dmitry Gorodchanin :	Send of a raw packet crash fix.
 *		Alan Cox	:	Silly ip bug when an overlength
 *					fragment turns up. Now frees the
 *					queue.
 *		Linus Torvalds/ :	Memory leakage on fragmentation
 *		Alan Cox	:	handling.
 *		Gerhard Koerting:	Forwarding uses IP priority hints
 *		Teemu Rantanen	:	Fragment problems.
 *		Alan Cox	:	General cleanup, comments and reformat
 *		Alan Cox	:	SNMP statistics
 *		Alan Cox	:	BSD address rule semantics. Also see
 *					UDP as there is a nasty checksum issue
 *					if you do things the wrong way.
 *		Alan Cox	:	Always defrag, moved IP_FORWARD to the config.in file
 *		Alan Cox	: 	IP options adjust sk->priority.
 *		Pedro Roque	:	Fix mtu/length error in ip_forward.
 *		Alan Cox	:	Avoid ip_chk_addr when possible.
 *	Richard Underwood	:	IP multicasting.
 *		Alan Cox	:	Cleaned up multicast handlers.
 *		Alan Cox	:	RAW sockets demultiplex in the BSD style.
 *		Gunther Mayer	:	Fix the SNMP reporting typo
 *		Alan Cox	:	Always in group 224.0.0.1
 *	Pauline Middelink	:	Fast ip_checksum update when forwarding
 *					Masquerading support.
 *		Alan Cox	:	Multicast loopback error for 224.0.0.1
 *		Alan Cox	:	IP_MULTICAST_LOOP option.
 *		Alan Cox	:	Use notifiers.
 *		Bjorn Ekwall	:	Removed ip_csum (from slhc.c too)
 *		Bjorn Ekwall	:	Moved ip_fast_csum to ip.h (inline!)
 *		Stefan Becker   :       Send out ICMP HOST REDIRECT
 *	Arnt Gulbrandsen	:	ip_build_xmit
 *		Alan Cox	:	Per socket routing cache
 *		Alan Cox	:	Fixed routing cache, added header cache.
 *		Alan Cox	:	Loopback didn't work right in original ip_build_xmit - fixed it.
 *		Alan Cox	:	Only send ICMP_REDIRECT if src/dest are the same net.
 *		Alan Cox	:	Incoming IP option handling.
 *		Alan Cox	:	Set saddr on raw output frames as per BSD.
 *		Alan Cox	:	Stopped broadcast source route explosions.
 *		Alan Cox	:	Can disable source routing
 *		Takeshi Sone    :	Masquerading didn't work.
 *	Dave Bonn,Alan Cox	:	Faster IP forwarding whenever possible.
 *		Alan Cox	:	Memory leaks, tramples, misc debugging.
 *		Alan Cox	:	Fixed multicast (by popular demand 8))
 *		Alan Cox	:	Fixed forwarding (by even more popular demand 8))
 *		Alan Cox	:	Fixed SNMP statistics [I think]
 *	Gerhard Koerting	:	IP fragmentation forwarding fix
 *		Alan Cox	:	Device lock against page fault.
 *		Alan Cox	:	IP_HDRINCL facility.
 *	Werner Almesberger	:	Zero fragment bug
 *		Alan Cox	:	RAW IP frame length bug
 *		Alan Cox	:	Outgoing firewall on build_xmit
 *		A.N.Kuznetsov	:	IP_OPTIONS support throughout the kernel
 *		Alan Cox	:	Multicast routing hooks
 *		Jos Vos		:	Do accounting *before* call_in_firewall
 *	Willy Konynenberg	:	Transparent proxying support
 *
 *  
 *
 * To Fix:
 *		IP fragmentation wants rewriting cleanly. The RFC815 algorithm is much more efficient
 *		and could be made very efficient with the addition of some virtual memory hacks to permit
 *		the allocation of a buffer that can then be 'grown' by twiddling page tables.
 *		Output fragmentation wants updating along with the buffer management to use a single 
 *		interleaved copy algorithm so that fragmenting has a one copy overhead. Actual packet
 *		output should probably do its own fragmentation at the UDP/RAW layer. TCP shouldn't cause
 *		fragmentation anyway.
 *
 *		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.
 */

#include <asm/uaccess.h>
#include <asm/system.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/errno.h>
#include <linux/config.h>

#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/etherdevice.h>
#include <linux/proc_fs.h>
#include <linux/stat.h>

#include <net/snmp.h>
#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <linux/skbuff.h>
#include <net/sock.h>
#include <net/arp.h>
#include <net/icmp.h>
#include <net/raw.h>
#include <net/checksum.h>
#include <linux/igmp.h>
#include <linux/ip_fw.h>
#ifdef CONFIG_IP_MASQUERADE
#include <net/ip_masq.h>
#endif
#include <linux/firewall.h>
#include <linux/mroute.h>
#include <linux/netlink.h>
#include <linux/ipsec.h>

/*
 *	SNMP management statistics
 */

struct ip_mib ip_statistics={2,IPDEFTTL,};	/* Forwarding=No, Default TTL=64 */


/*
 *	Handle the issuing of an ioctl() request
 *	for the ip device. This is scheduled to
 *	disappear
 */

int ip_ioctl(struct sock *sk, int cmd, unsigned long arg)
{
	switch(cmd)
	{
		default:
			return(-EINVAL);
	}
}


#if defined(CONFIG_IP_TRANSPARENT_PROXY) && !defined(CONFIG_IP_ALWAYS_DEFRAG)
#define CONFIG_IP_ALWAYS_DEFRAG 1
#endif

/*
 *	0 - deliver
 *	1 - block
 */
static __inline__ int icmp_filter(struct sock *sk, struct sk_buff *skb)
{
	int    type;

	type = skb->h.icmph->type;
	if (type < 32)
		return test_bit(type, &sk->tp_pinfo.tp_raw4.filter);

	/* Do not block unknown ICMP types */
	return 0;
}

int ip_call_ra_chain(struct sk_buff *skb)
{
	struct ip_ra_chain *ra;
	u8 protocol = skb->nh.iph->protocol;
	struct sock *last = NULL;

	for (ra = ip_ra_chain; ra; ra = ra->next) {
		struct sock *sk = ra->sk;
		if (sk && sk->num == protocol) {
			if (skb->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
				skb = ip_defrag(skb);
				if (skb == NULL)
					return 1;
			}
			if (last) {
				struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
				if (skb2)
					raw_rcv(last, skb2);
			}
			last = sk;
		}
	}

	if (last) {
		raw_rcv(last, skb);
		return 1;
	}
	return 0;
}

int ip_local_deliver(struct sk_buff *skb)
{
	struct iphdr *iph = skb->nh.iph;
	struct inet_protocol *ipprot;
	struct sock *raw_sk=NULL;
	unsigned char hash;
	int flag = 0;

#ifndef CONFIG_IP_ALWAYS_DEFRAG
	/*
	 *	Reassemble IP fragments.
	 */

	if (iph->frag_off & htons(IP_MF|IP_OFFSET)) {
		skb = ip_defrag(skb);
		if (!skb)
			return 0;
		iph = skb->nh.iph;
	}
#endif

#ifdef CONFIG_IP_MASQUERADE
	/*
	 * Do we need to de-masquerade this packet?
	 */
        {
		int ret = ip_fw_demasquerade(&skb);
		if (ret < 0) {
			kfree_skb(skb, FREE_WRITE);
			return 0;
		}

		if (ret) {
			iph=skb->nh.iph;
			IPCB(skb)->flags |= IPSKB_MASQUERADED;
			dst_release(skb->dst);
			skb->dst = NULL;
			if (ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, skb->dev)) {
				kfree_skb(skb, FREE_WRITE);
				return 0;
			}
			return skb->dst->input(skb);
		}
        }
#endif

        /*
	 *	Point into the IP datagram, just past the header.
	 */

        skb->h.raw = skb->nh.raw + iph->ihl*4;

	/*
	 *	Deliver to raw sockets. This is fun as to avoid copies we want to make no surplus copies.
	 *
	 *	RFC 1122: SHOULD pass TOS value up to the transport layer.
	 */
 
	/* Note: See raw.c and net/raw.h, RAWV4_HTABLE_SIZE==MAX_INET_PROTOS */
	hash = iph->protocol & (MAX_INET_PROTOS - 1);

	/* 
	 *	If there maybe a raw socket we must check - if not we don't care less 
	 */
		 
	if((raw_sk = raw_v4_htable[hash]) != NULL) {
		struct sock *sknext = NULL;
		struct sk_buff *skb1;
		raw_sk = raw_v4_lookup(raw_sk, iph->protocol, iph->saddr, iph->daddr, skb->dev->ifindex);
		if(raw_sk) {	/* Any raw sockets */
			do {
				/* Find the next */
				sknext = raw_v4_lookup(raw_sk->next, iph->protocol,
						       iph->saddr, iph->daddr, skb->dev->ifindex);
				if (iph->protocol != IPPROTO_ICMP || !icmp_filter(raw_sk, skb)) {
					if (sknext == NULL)
						break;
					skb1 = skb_clone(skb, GFP_ATOMIC);
					if(skb1)
					{
						if(ipsec_sk_policy(raw_sk,skb1))	
							raw_rcv(raw_sk, skb1);
						else
							kfree_skb(skb1, FREE_WRITE);
					}
				}
				raw_sk = sknext;
			} while(raw_sk!=NULL);
				
			/*	Here either raw_sk is the last raw socket, or NULL if
			 *	none.  We deliver to the last raw socket AFTER the
			 *	protocol checks as it avoids a surplus copy.
			 */
		}
	}
	
	/*
	 *	skb->h.raw now points at the protocol beyond the IP header.
	 */
	
	for (ipprot = (struct inet_protocol *)inet_protos[hash];ipprot != NULL;ipprot=(struct inet_protocol *)ipprot->next)
	{
		struct sk_buff *skb2;
	
		if (ipprot->protocol != iph->protocol)
			continue;
		/*
		 * 	See if we need to make a copy of it.  This will
		 * 	only be set if more than one protocol wants it.
		 * 	and then not for the last one. If there is a pending
		 *	raw delivery wait for that
		 */
	
		if (ipprot->copy || raw_sk)
		{
			skb2 = skb_clone(skb, GFP_ATOMIC);
			if(skb2==NULL)
				continue;
		}
		else
		{
			skb2 = skb;
		}
		flag = 1;

		/*
		 *	Pass on the datagram to each protocol that wants it,
		 *	based on the datagram protocol.  We should really
		 *	check the protocol handler's return values here...
		 */

		ipprot->handler(skb2, ntohs(iph->tot_len) - (iph->ihl * 4));
	}

	/*
	 *	All protocols checked.
	 *	If this packet was a broadcast, we may *not* reply to it, since that
	 *	causes (proven, grin) ARP storms and a leakage of memory (i.e. all
	 *	ICMP reply messages get queued up for transmission...)
	 */

	if(raw_sk!=NULL)	/* Shift to last raw user */
	{
		if(ipsec_sk_policy(raw_sk, skb))
			raw_rcv(raw_sk, skb);
		else
			kfree_skb(skb, FREE_WRITE);
	}
	else if (!flag)		/* Free and report errors */
	{
		icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PROT_UNREACH, 0);	
		kfree_skb(skb, FREE_WRITE);
	}

	return(0);
}

int ip_rcv(struct sk_buff *skb, struct device *dev, struct packet_type *pt)
{
	struct iphdr *iph = skb->nh.iph;
	struct ip_options * opt = NULL;
	int err;

	/*
	 * When interface is in promisc. mode, drop all the crap
	 * that it receives, do not truing to analyse it.
	 */
	if (skb->pkt_type == PACKET_OTHERHOST)
		goto drop;

	ip_statistics.IpInReceives++;

	/*
	 *	Account for the packet (even if the packet is
	 *	not accepted by the firewall!).
	 */

#ifdef CONFIG_IP_ACCT
	ip_fw_chk(iph,dev,NULL,ip_acct_chain,0,IP_FW_MODE_ACCT_IN);
#endif	

	/*
	 *	RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum.
	 *
	 *	Is the datagram acceptable?
	 *
	 *	1.	Length at least the size of an ip header
	 *	2.	Version of 4
	 *	3.	Checksums correctly. [Speed optimisation for later, skip loopback checksums]
	 *	4.	Doesn't have a bogus length
	 */

	if (skb->len<sizeof(struct iphdr) || iph->ihl<5 || iph->version != 4
	    || ip_fast_csum((unsigned char *)iph, iph->ihl) !=0
		|| skb->len < ntohs(iph->tot_len))
		goto inhdr_error;

	/*
	 *	Our transport medium may have padded the buffer out. Now we know it
	 *	is IP we can trim to the true length of the frame.
	 *	Note this now means skb->len holds ntohs(iph->tot_len).
	 */
	__skb_trim(skb, ntohs(iph->tot_len));

	if (skb->dst == NULL) {
		err = ip_route_input(skb, iph->daddr, iph->saddr, iph->tos, dev);
		if (err)
			goto drop;
#ifdef CONFIG_CPU_IS_SLOW
		if (net_cpu_congestion > 10 && !(iph->tos&IPTOS_RELIABILITY) &&
		    IPTOS_PREC(iph->tos) < IPTOS_PREC_INTERNETCONTROL) {
			goto drop;
		}
#endif
	}

#ifdef CONFIG_IP_ALWAYS_DEFRAG
	if (iph->frag_off & htons(IP_MF|IP_OFFSET)) {
		skb = ip_defrag(skb);
		if (!skb)
			return 0;
		iph = skb->nh.iph;
		ip_send_check(iph);
	}
#endif

	if (iph->ihl > 5) {
		skb->ip_summed = 0;
		if (ip_options_compile(NULL, skb))
			goto inhdr_error;

		opt = &(IPCB(skb)->opt);
		if (opt->srr) {
			if (!ipv4_config.source_route) {
				if (ipv4_config.log_martians && net_ratelimit())
					printk(KERN_INFO "source route option %08lx -> %08lx\n",
					       ntohl(iph->saddr), ntohl(iph->daddr));
				goto drop;
			}
			if (((struct rtable*)skb->dst)->rt_type == RTN_LOCAL &&
			    ip_options_rcv_srr(skb))
				goto drop;
		}
	}
	
	/*
	 *	See if the firewall wants to dispose of the packet. 
	 */
	
#ifdef	CONFIG_FIREWALL
        {
		int fwres;
		u16 rport;

		if ((fwres=call_in_firewall(PF_INET, skb->dev, iph, &rport, &skb))<FW_ACCEPT) {
			if (fwres==FW_REJECT)
				icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
			goto drop;
		}

#ifdef	CONFIG_IP_TRANSPARENT_PROXY
		if (fwres==FW_REDIRECT && (IPCB(skb)->redirport = rport) != 0)
			return ip_local_deliver(skb);
#endif
	}
#endif

	return skb->dst->input(skb);

inhdr_error:
	ip_statistics.IpInHdrErrors++;
drop:
        kfree_skb(skb, FREE_WRITE);
        return(0);
}