/* $USAGI: tcp_ipv6.c,v 1.25 2001/11/19 14:12:04 yoshfuji Exp $ */

/*
 *	TCP over IPv6
 *	Linux INET6 implementation 
 *
 *	Authors:
 *	Pedro Roque		<roque@di.fc.ul.pt>	
 *
 *	$Id: tcp_ipv6.c,v 1.104.2.11 1999/12/03 09:30:29 davem Exp $
 *
 *	Based on: 
 *	linux/net/ipv4/tcp.c
 *	linux/net/ipv4/tcp_input.c
 *	linux/net/ipv4/tcp_output.c
 *
 *	Fixes:
 *	Hideaki YOSHIFUJI	:	sin6_scope_id support
 *	yoshfuji@USAGI		:	Reworked bind(2) behavior, including:
 *					- Allow ipv6 and ipv4 bind(2) to the
 *					  same port.
 *					- Don't allow narrow binding unless
 *					  later uid is the same as before:
 *					  CONFIG_NET_MODERATE_REUSE
 *					- Don't allow binding to the same
 *					  address unless it is one of multi-
 *					  cast address even if SO_REUSEADDR 
 *					  is set.
 *
 *	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 <linux/config.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/sched.h>
#include <linux/in.h>
#include <linux/in6.h>
#include <linux/netdevice.h>
#include <linux/init.h>

#include <linux/ipv6.h>
#include <linux/icmpv6.h>
#include <linux/random.h>

#include <net/tcp.h>
#include <net/ndisc.h>
#include <net/ipv6.h>
#include <net/transp_v6.h>
#include <net/addrconf.h>
#include <net/ip6_route.h>

#include <asm/uaccess.h>

extern int sysctl_max_syn_backlog;

static void	tcp_v6_send_reset(struct sk_buff *skb);
static void	tcp_v6_send_check(struct sock *sk, struct tcphdr *th, int len, 
				  struct sk_buff *skb);

static int	tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb);
static void	tcp_v6_xmit(struct sk_buff *skb);
static struct open_request *tcp_v6_search_req(struct tcp_opt *tp,
					      struct ipv6hdr *ip6h,
					      struct tcphdr *th,
					      int iif,
					      struct open_request **prevp);

static struct tcp_func ipv6_mapped;
static struct tcp_func ipv6_specific;

/* I have no idea if this is a good hash for v6 or not. -DaveM */
static __inline__ int tcp_v6_hashfn(struct in6_addr *laddr, u16 lport,
				    struct in6_addr *faddr, u16 fport)
{
	int hashent = (lport ^ fport);

	hashent ^= (laddr->s6_addr32[3] ^ faddr->s6_addr32[3]);
	return (hashent & ((tcp_ehash_size/2) - 1));
}

static __inline__ int tcp_v6_sk_hashfn(struct sock *sk)
{
	struct in6_addr *laddr = &sk->net_pinfo.af_inet6.rcv_saddr;
	struct in6_addr *faddr = &sk->net_pinfo.af_inet6.daddr;
	__u16 lport = sk->num;
	__u16 fport = sk->dport;
	return tcp_v6_hashfn(laddr, lport, faddr, fport);
}

/* Grrr, addr_type already calculated by caller, but I don't want
 * to add some silly "cookie" argument to this method just for that.
 * But it doesn't matter, the recalculation is in the rarest path
 * this function ever takes.
 */
static int tcp_v6_get_port(struct sock *sk, unsigned short snum)
{
	struct tcp_bind_bucket *tb;

	SOCKHASH_LOCK();
	if (snum == 0) {
		int rover = tcp_port_rover;
		int low = sysctl_local_port_range[0];
		int high = sysctl_local_port_range[1];
		int remaining = (high - low) + 1;

		do {	rover++;
			if ((rover < low) || (rover > high))
				rover = low;
			tb = tcp_bhash[tcp_bhashfn(rover)];
			for ( ; tb; tb = tb->next)
				if (tb->port == rover)
					goto next;
			break;
		next:
		} while (--remaining > 0);
		tcp_port_rover = rover;

		/* Exhausted local port range during search? */
		if (remaining <= 0)
			goto fail;

		/* OK, here is the one we will use. */
		snum = rover;
		tb = NULL;
	} else {
		for (tb = tcp_bhash[tcp_bhashfn(snum)];
		     tb != NULL;
		     tb = tb->next)
			if (tb->port == snum)
				break;
	}
	if (tb != NULL && tb->owners != NULL) {
		{
			struct sock *sk2 = tb->owners;
			int sk_reuse, sk2_reuse;
			int addr_type2;
			struct in6_addr *sk_rcv_saddr6 = sk->state != TCP_TIME_WAIT ? 
								&sk->net_pinfo.af_inet6.rcv_saddr:
								&((struct tcp_tw_bucket*)sk2)->v6_rcv_saddr;
			int addr_type = ipv6_addr_type(sk_rcv_saddr6);
#if defined(CONFIG_NET_MODERATE_REUSE) || defined(CONFIG_IPV6_MODERATE_DOUBLE_BIND)
			uid_t sk_uid = sk->state != TCP_TIME_WAIT ? sock_i_uid_t(sk) : ((struct tcp_tw_bucket *)sk)->uid,
			      sk2_uid;
#endif

			sk_reuse = 0;
#ifdef SO_REUSEPORT
			if (sk->reuseport)
				sk_reuse |= 2;
#endif
			if (sk->reuse)
				sk_reuse |= addr_type != IPV6_ADDR_MAPPED ?
						((addr_type & IPV6_ADDR_MULTICAST) ? 3 : 1) :
						(MULTICAST(sk->rcv_saddr) ? 3 : 1);

			/* We must walk the whole port owner list in this case. -DaveM */
			for( ; sk2 != NULL; sk2 = sk2->bind_next) {
#if defined(CONFIG_NET_MODERATE_REUSE) || defined(CONFIG_IPV6_MODERATE_DOUBLE_BIND)
				int uid_ok;
#endif
				int both_specified = 0;
				struct in6_addr *sk2_rcv_saddr6;
				if (sk2 == sk ||
				    (sk2->bound_dev_if && sk->bound_dev_if &&
				     sk2->bound_dev_if != sk->bound_dev_if))
					continue;
#if 0
				if (sk2->family != AF_INET6 && sk2->family != AF_INET)
					continue;
#endif
				sk2_rcv_saddr6 = sk2->state != TCP_TIME_WAIT ?
							&sk2->net_pinfo.af_inet6.rcv_saddr :
							&((struct tcp_tw_bucket*)sk2)->v6_rcv_saddr;
				addr_type2 = sk2->family == AF_INET6 ? ipv6_addr_type(sk2_rcv_saddr6) : IPV6_ADDR_MAPPED;
#if defined(CONFIG_NET_MODERATE_REUSE) || defined(CONFIG_IPV6_MODERATE_DOUBLE_BIND)
				sk2_uid = sk2->state != TCP_TIME_WAIT ? sock_i_uid_t(sk2) : ((struct tcp_tw_bucket *)sk2)->uid;
#endif

				if ((addr_type2 != IPV6_ADDR_MAPPED ? addr_type2 != IPV6_ADDR_ANY : sk2->rcv_saddr) &&
				    (addr_type != IPV6_ADDR_MAPPED ? addr_type != IPV6_ADDR_ANY : sk->rcv_saddr)) {
					if (addr_type2 == IPV6_ADDR_MAPPED || addr_type == IPV6_ADDR_MAPPED) {
						if (addr_type2 != addr_type ||
						    sk2->rcv_saddr != sk->rcv_saddr)
							continue;
					} else {
						if (ipv6_addr_cmp(sk2_rcv_saddr6, sk_rcv_saddr6))
							continue;
					}
					both_specified = 1;
				}

#if defined(CONFIG_NET_MODERATE_REUSE) || defined(CONFIG_IPV6_MODERATE_DOUBLE_BIND)
				uid_ok = sk2_uid == (uid_t) -1 || sk_uid == sk2_uid;
#endif

				if ((addr_type2 == IPV6_ADDR_MAPPED && 
				     addr_type != IPV6_ADDR_MAPPED && sk->net_pinfo.af_inet6.ipv6only) ||
				    (addr_type == IPV6_ADDR_MAPPED &&
				     addr_type2 != IPV6_ADDR_MAPPED && sk2->net_pinfo.af_inet6.ipv6only)) {
#ifdef CONFIG_IPV6_MODERATE_DOUBLE_BIND
					if (uid_ok)
						continue;
#else
					continue;
#endif
				}

				sk2_reuse = 0;
#ifdef SO_REUSEPORT
				if (sk2->reuseport)
					sk2_reuse |= 2;
#endif
				if (sk2->reuse)
					sk2_reuse |= addr_type2 != IPV6_ADDR_MAPPED ?
							((addr_type2 & IPV6_ADDR_MULTICAST) ? 3 : 1) :
							(MULTICAST(sk2->rcv_saddr) ? 3 : 1);

				if (sk2_reuse & sk_reuse) {	/* NOT && */
#ifdef CONFIG_NET_MODERATE_REUSE
					if (!uid_ok)
						goto fail;
#endif
					if (sk2_reuse & sk_reuse & 2) {
						continue;
					} else {
						if (both_specified) {
							struct in6_addr *sk2_daddr6 = sk2->state != TCP_TIME_WAIT ?
											&sk2->net_pinfo.af_inet6.daddr :
											&((struct tcp_tw_bucket*)sk2)->v6_daddr;
							int addr_type2d = sk2->family == AF_INET6 ? ipv6_addr_type(sk2_daddr6) : IPV6_ADDR_MAPPED;
							if (addr_type2d != IPV6_ADDR_MAPPED ? addr_type2d != IPV6_ADDR_ANY : sk2->daddr)
								continue;
						} else {
							if ((addr_type2 != IPV6_ADDR_MAPPED ? addr_type2 != IPV6_ADDR_ANY : sk2->rcv_saddr) || 
							    (addr_type != IPV6_ADDR_MAPPED ? addr_type != IPV6_ADDR_ANY : sk->rcv_saddr))
								continue;
						}
					}
				}
				goto fail;
			}
			/* If we found a conflict, fail. */
			if (sk2 != NULL)
				goto fail;
		}
	}
	if (tb == NULL &&
	    (tb = tcp_bucket_create(snum)) == NULL)
			goto fail;
	if (tb->owners == NULL) {
		if (sk->reuse && sk->state != TCP_LISTEN)
			tb->fastreuse = 1;
		else
			tb->fastreuse = 0;
	} else if (tb->fastreuse &&
		   ((sk->reuse == 0) || (sk->state == TCP_LISTEN)))
		tb->fastreuse = 0;

#if !defined(CONFIG_NET_NEW_BIND_SEMANTICS) && !defined(CONFIG_IPV6_DOUBLE_BIND)
success:
#endif
	sk->num = snum;
	if ((sk->bind_next = tb->owners) != NULL)
		tb->owners->bind_pprev = &sk->bind_next;
	tb->owners = sk;
	sk->bind_pprev = &tb->owners;
	sk->prev = (struct sock *) tb;

	SOCKHASH_UNLOCK();
	return 0;

fail:
	SOCKHASH_UNLOCK();
	return 1;
}

static void tcp_v6_hash(struct sock *sk)
{
	if(sk->state != TCP_CLOSE) {
		struct sock **skp;

		/* Well, I know that it is ugly...
		 * All this ->prot, ->af_specific etc. need LARGE cleanup --ANK
		 */
		if (sk->tp_pinfo.af_tcp.af_specific == &ipv6_mapped) {
			tcp_prot.hash(sk);
			return;
		}

		if(sk->state == TCP_LISTEN)
			skp = &tcp_listening_hash[tcp_sk_listen_hashfn(sk)];
		else
			skp = &tcp_ehash[(sk->hashent = tcp_v6_sk_hashfn(sk))];

		SOCKHASH_LOCK();
		if((sk->next = *skp) != NULL)
			(*skp)->pprev = &sk->next;
		*skp = sk;
		sk->pprev = skp;
		SOCKHASH_UNLOCK();
	}
}

static void tcp_v6_unhash(struct sock *sk)
{
	SOCKHASH_LOCK();
	if(sk->pprev) {
		if(sk->next)
			sk->next->pprev = sk->pprev;
		*sk->pprev = sk->next;
		sk->pprev = NULL;
		tcp_reg_zap(sk);
		__tcp_put_port(sk);
	}
	SOCKHASH_UNLOCK();
}

static struct sock *tcp_v6_lookup_listener(struct in6_addr *daddr, unsigned short hnum, int dif)
{
	struct sock *sk;
	struct sock *result = NULL;
	int score, hiscore;

	hiscore=0;
	sk = tcp_listening_hash[tcp_lhashfn(hnum)];
	for(; sk; sk = sk->next) {
		if((sk->num == hnum) && (sk->family == PF_INET6)) {
			struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;
			
			score = 1;
			if(!ipv6_addr_any(&np->rcv_saddr)) {
				if(ipv6_addr_cmp(&np->rcv_saddr, daddr))
					continue;
				score++;
			}
			if (sk->bound_dev_if) {
				if (sk->bound_dev_if != dif)
					continue;
				score++;
			}
			if (score == 3)
				return sk;
			if (score > hiscore) {
				hiscore = score;
				result = sk;
			}
		}
	}
	return result;
}

/* Sockets in TCP_CLOSE state are _always_ taken out of the hash, so
 * we need not check it for TCP lookups anymore, thanks Alexey. -DaveM
 * It is assumed that this code only gets called from within NET_BH.
 */
static inline struct sock *__tcp_v6_lookup(struct tcphdr *th,
					   struct in6_addr *saddr, u16 sport,
					   struct in6_addr *daddr, u16 dport,
					   int dif)
{
	struct sock *sk;
	__u16 hnum = ntohs(dport);
	__u32 ports = TCP_COMBINED_PORTS(sport, hnum);
	int hash;

	/* Check TCP register quick cache first. */
	sk = TCP_RHASH(sport);
	if(sk && TCP_IPV6_MATCH(sk, saddr, daddr, ports, dif))
		goto hit;

	/* Optimize here for direct hit, only listening connections can
	 * have wildcards anyways.
	 */
	hash = tcp_v6_hashfn(daddr, hnum, saddr, sport);
	for(sk = tcp_ehash[hash]; sk; sk = sk->next) {
		/* For IPV6 do the cheaper port and family tests first. */
		if(TCP_IPV6_MATCH(sk, saddr, daddr, ports, dif)) {
			if (sk->state == TCP_ESTABLISHED)
				TCP_RHASH(sport) = sk;
			goto hit; /* You sunk my battleship! */
		}
	}
	/* Must check for a TIME_WAIT'er before going to listener hash. */
	for(sk = tcp_ehash[hash+(tcp_ehash_size/2)]; sk; sk = sk->next) {
		if(*((__u32 *)&(sk->dport))	== ports	&&
		   sk->family			== PF_INET6) {
			struct tcp_tw_bucket *tw = (struct tcp_tw_bucket *)sk;
			if(!ipv6_addr_cmp(&tw->v6_daddr, saddr)	&&
			   !ipv6_addr_cmp(&tw->v6_rcv_saddr, daddr) &&
			   (!sk->bound_dev_if || sk->bound_dev_if == dif))
				goto hit;
		}
	}
	sk = tcp_v6_lookup_listener(daddr, hnum, dif);
hit:
	return sk;
}

#define tcp_v6_lookup(sa, sp, da, dp, dif) __tcp_v6_lookup((0),(sa),(sp),(da),(dp),(dif))

static __inline__ u16 tcp_v6_check(struct tcphdr *th, int len,
				   struct in6_addr *saddr, 
				   struct in6_addr *daddr, 
				   unsigned long base)
{
	return csum_ipv6_magic(saddr, daddr, len, IPPROTO_TCP, base);
}

static __u32 tcp_v6_init_sequence(struct sock *sk, struct sk_buff *skb)
{
	__u32 si;
	__u32 di;

	if (skb->protocol == __constant_htons(ETH_P_IPV6)) {
		si = skb->nh.ipv6h->saddr.s6_addr32[3];
		di = skb->nh.ipv6h->daddr.s6_addr32[3];
	} else {
		si = skb->nh.iph->saddr;
		di = skb->nh.iph->daddr;
	}

	return secure_tcp_sequence_number(di, si,
					  skb->h.th->dest,
					  skb->h.th->source);
}

static int tcp_v6_unique_address(struct sock *sk)
{
	struct tcp_bind_bucket *tb;
	unsigned short snum = sk->num;
	int retval = 1;

	/* Freeze the hash while we snoop around. */
	SOCKHASH_LOCK();
	tb = tcp_bhash[tcp_bhashfn(snum)];
	for(; tb; tb = tb->next) {
		if(tb->port == snum && tb->owners != NULL) {
			/* Almost certainly the re-use port case, search the real hashes
			 * so it actually scales.  (we hope that all ipv6 ftp servers will
			 * use passive ftp, I just cover this case for completeness)
			 */
			sk = __tcp_v6_lookup(NULL, &sk->net_pinfo.af_inet6.daddr,
					     sk->dport,
					     &sk->net_pinfo.af_inet6.rcv_saddr,
					     htons(snum),
					     sk->bound_dev_if);
			if((sk != NULL) && (sk->state != TCP_LISTEN))
				retval = 0;
			break;
		}
	}
	SOCKHASH_UNLOCK();
	return retval;
}

static __inline__ int tcp_v6_iif(struct sk_buff *skb)
{
	struct inet6_skb_parm *opt = (struct inet6_skb_parm *) skb->cb;
	return opt->iif;
}

static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr, 
			  int addr_len)
{
	struct sockaddr_in6 *usin = (struct sockaddr_in6 *) uaddr;
	struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;
	struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
	struct in6_addr *saddr = NULL;
	struct in6_addr saddr_buf;
	struct flowi fl;
	struct dst_entry *dst;
	struct sk_buff *buff;
	int addr_type;
	int err;

	if (sk->state != TCP_CLOSE) 
		return(-EISCONN);

	/*
	 *	Don't allow a double connect.
	 */
	 	
	if(!ipv6_addr_any(&np->daddr))
		return -EINVAL;
	
	if (addr_len < SIN6_LEN_RFC2133)
		return(-EINVAL);

	if (usin->sin6_family && usin->sin6_family != AF_INET6) 
		return(-EAFNOSUPPORT);

	fl.fl6_flowlabel = 0;
	if (np->sndflow) {
		fl.fl6_flowlabel = usin->sin6_flowinfo&IPV6_FLOWINFO_MASK;
		if (fl.fl6_flowlabel&IPV6_FLOWLABEL_MASK) {
			struct ip6_flowlabel *flowlabel;
			flowlabel = fl6_sock_lookup(sk, fl.fl6_flowlabel);
			if (flowlabel == NULL)
				return -EINVAL;
			ipv6_addr_copy(&usin->sin6_addr, &flowlabel->dst);
			fl6_sock_release(flowlabel);
		}
	}

	/*
  	 *	connect() to INADDR_ANY means loopback (BSD'ism).
  	 */
  	
  	if(ipv6_addr_any(&usin->sin6_addr))
		usin->sin6_addr.s6_addr[15] = 0x1; 

	addr_type = ipv6_addr_type(&usin->sin6_addr);

	if(addr_type & IPV6_ADDR_MULTICAST)
		return -ENETUNREACH;

#ifdef CONFIG_IPV6_SCOPE_ID
	if (addr_type&IPV6_ADDR_LINKLOCAL) {
		if (addr_len >= sizeof(struct sockaddr_in6) &&
		    usin->sin6_scope_id) {
			/* If interface is set while binding, indices
			 * must coincide.
			 */
			if (sk->bound_dev_if &&
			    sk->bound_dev_if != usin->sin6_scope_id)
				return -EINVAL;
			sk->bound_dev_if = usin->sin6_scope_id;
		}

#ifndef CONFIG_IPV6_LOOSE_SCOPE_ID
		/* Connect to link-local address requires an interface */
		if (sk->bound_dev_if == 0)
 			return -EINVAL;
#endif
	}
#endif

	/*
	 *	connect to self not allowed
	 */

	if (ipv6_addr_cmp(&usin->sin6_addr, &np->saddr) == 0 &&
	    usin->sin6_port == sk->sport)
		return (-EINVAL);

	memcpy(&np->daddr, &usin->sin6_addr, sizeof(struct in6_addr));
	np->flow_label = fl.fl6_flowlabel;

	/*
	 *	TCP over IPv4
	 */

	if (addr_type == IPV6_ADDR_MAPPED) {
		u32 exthdrlen = tp->ext_header_len;
		struct sockaddr_in sin;

		SOCK_DEBUG(sk, "connect: ipv4 mapped\n");

		if (sk->net_pinfo.af_inet6.ipv6only)
			return -ENETUNREACH;

		sin.sin_family = AF_INET;
		sin.sin_port = usin->sin6_port;
		sin.sin_addr.s_addr = usin->sin6_addr.s6_addr32[3];

		sk->tp_pinfo.af_tcp.af_specific = &ipv6_mapped;
		sk->backlog_rcv = tcp_v4_do_rcv;

		err = tcp_v4_connect(sk, (struct sockaddr *)&sin, sizeof(sin));

		if (err) {
			tp->ext_header_len = exthdrlen;
			sk->tp_pinfo.af_tcp.af_specific = &ipv6_specific;
			sk->backlog_rcv = tcp_v6_do_rcv;
			goto failure;
		} else {
			ipv6_addr_set(&np->saddr, 0, 0, __constant_htonl(0x0000FFFF),
				      sk->saddr);
			ipv6_addr_set(&np->rcv_saddr, 0, 0, __constant_htonl(0x0000FFFF),
				      sk->rcv_saddr);
		}

		return err;
	}

	if (!ipv6_addr_any(&np->rcv_saddr))
		saddr = &np->rcv_saddr;

	fl.proto = IPPROTO_TCP;
	fl.fl6_dst = &np->daddr;
	fl.fl6_src = saddr;
	fl.oif = sk->bound_dev_if;
	fl.uli_u.ports.dport = usin->sin6_port;
	fl.uli_u.ports.sport = sk->sport;

	if (np->opt && np->opt->srcrt) {
		struct rt0_hdr *rt0 = (struct rt0_hdr *) np->opt->srcrt;
		fl.nl_u.ip6_u.daddr = rt0->addr;
	}

	dst = ip6_route_output(sk, &fl);

	if ((err = dst->error) != 0) {
		dst_release(dst);
		goto failure;
	}

	if (fl.oif == 0 && addr_type&IPV6_ADDR_LINKLOCAL) {
		/* Ough! This guy tries to connect to link local
		 * address and did not specify interface.
		 * Actually we should kick him out, but
		 * we will be patient :) --ANK
		 */
		sk->bound_dev_if = dst->dev->ifindex;
	}

	ip6_dst_store(sk, dst, NULL);

	if (saddr == NULL) {
		err = ipv6_get_saddr(dst, &np->daddr, &saddr_buf);
		if (err)
			goto failure;

		saddr = &saddr_buf;
	}

	/* set the source address */
	ipv6_addr_copy(&np->rcv_saddr, saddr);
	ipv6_addr_copy(&np->saddr, saddr);

	tp->ext_header_len = 0;
	if (np->opt)
		tp->ext_header_len = np->opt->opt_flen+np->opt->opt_nflen;
	/* Reset mss clamp */
	tp->mss_clamp = ~0;

	err = -ENOBUFS;
	buff = sock_wmalloc(sk, (MAX_HEADER + sk->prot->max_header),
			    0, GFP_KERNEL);

	if (buff == NULL)
		goto failure;

	sk->dport = usin->sin6_port;

	if (!tcp_v6_unique_address(sk)) {
		kfree_skb(buff);
		err = -EADDRNOTAVAIL;
		goto failure;
	}

	/*
	 *	Init variables
	 */

	tp->write_seq = secure_tcp_sequence_number(np->saddr.s6_addr32[3],
						   np->daddr.s6_addr32[3],
						   sk->sport, sk->dport);

	tcp_connect(sk, buff, dst->pmtu);

	return 0;

failure:
	dst_release(xchg(&sk->dst_cache, NULL));
	memset(&np->daddr, 0, sizeof(struct in6_addr));
	sk->daddr = 0;
	return err;
}

static int tcp_v6_sendmsg(struct sock *sk, struct msghdr *msg, int len)
{
	struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;
	int retval = -EINVAL;

	/*
	 *	Do sanity checking for sendmsg/sendto/send
	 */

	if (msg->msg_flags & ~(MSG_OOB|MSG_DONTROUTE|MSG_DONTWAIT|MSG_NOSIGNAL))
		goto out;
	if (msg->msg_name) {
		struct sockaddr_in6 *addr=(struct sockaddr_in6 *)msg->msg_name;

		if (msg->msg_namelen < sizeof(*addr))
			goto out;

		if (addr->sin6_family && addr->sin6_family != AF_INET6)
			goto out;
		retval = -ENOTCONN;

		if(sk->state == TCP_CLOSE)
			goto out;
		retval = -EISCONN;
		if (addr->sin6_port != sk->dport)
			goto out;
		if (ipv6_addr_cmp(&addr->sin6_addr, &np->daddr))
			goto out;
		if (np->sndflow && np->flow_label != (addr->sin6_flowinfo&IPV6_FLOWINFO_MASK))
			goto out;
	}

	retval = tcp_do_sendmsg(sk, msg);

out:
	return retval;
}

void tcp_v6_err(struct sk_buff *skb, struct ipv6hdr *hdr,
		struct inet6_skb_parm *opt,
		int type, int code, unsigned char *header, __u32 info)
{
	struct in6_addr *saddr = &hdr->saddr;
	struct in6_addr *daddr = &hdr->daddr;
	struct tcphdr *th = (struct tcphdr *)header;
	struct ipv6_pinfo *np;
	struct sock *sk;
	int err;
	struct tcp_opt *tp; 
	__u32 seq; 

	if (header + 8 > skb->tail)
		return;

	sk = tcp_v6_lookup(daddr, th->dest, saddr, th->source, skb->dev->ifindex);

	if (sk == NULL) {
		struct inet6_dev *idev = ipv6_get_idev(skb->dev);
		ICMP6_INC_STATS_BH(idev,Icmp6InErrors);
		return;
	}

	if (sk->state == TCP_TIME_WAIT)
		return;

	tp = &sk->tp_pinfo.af_tcp;
	seq = ntohl(th->seq); 
	if (sk->state != TCP_LISTEN && !between(seq, tp->snd_una, tp->snd_nxt)) {
		net_statistics.OutOfWindowIcmps++;
		return; 
	}

	np = &sk->net_pinfo.af_inet6;
	if (type == ICMPV6_PKT_TOOBIG) {
		struct dst_entry *dst = NULL;

		if (atomic_read(&sk->sock_readers))
			return;

		if (sk->state == TCP_LISTEN)
			return;

		/* icmp should have updated the destination cache entry */
		if (sk->dst_cache)
			dst = dst_check(&sk->dst_cache, np->dst_cookie);

		if (dst == NULL) {
			struct flowi fl;

			/* BUGGG_FUTURE: Again, it is not clear how
			   to handle rthdr case. Ignore this complexity
			   for now.
			 */
			fl.proto = IPPROTO_TCP;
			fl.nl_u.ip6_u.daddr = &np->daddr;
			fl.nl_u.ip6_u.saddr = &np->saddr;
			fl.oif = sk->bound_dev_if;
			fl.uli_u.ports.dport = sk->dport;
			fl.uli_u.ports.sport = sk->sport;

			dst = ip6_route_output(sk, &fl);
		} else
			dst = dst_clone(dst);

		if (dst->error) {
			sk->err_soft = -dst->error;
		} else if (tp->pmtu_cookie > dst->pmtu) {
			tcp_sync_mss(sk, dst->pmtu);
			tcp_simple_retransmit(sk);
		} /* else let the usual retransmit timer handle it */
		dst_release(dst);
		return;
	}

	icmpv6_err_convert(type, code, &err);

	/* Might be for an open_request */
	switch (sk->state) {
		struct open_request *req, *prev;
		struct ipv6hdr hd;
	case TCP_LISTEN:
		if (atomic_read(&sk->sock_readers)) {
			net_statistics.LockDroppedIcmps++;
			 /* If too many ICMPs get dropped on busy
			  * servers this needs to be solved differently.
			  */
 			return;
		}

		/* Grrrr - fix this later. */
		ipv6_addr_copy(&hd.saddr, saddr);
		ipv6_addr_copy(&hd.daddr, daddr); 
		req = tcp_v6_search_req(tp, &hd, th, tcp_v6_iif(skb), &prev);
		if (!req)
			return;
		if (seq != req->snt_isn) {
			net_statistics.OutOfWindowIcmps++;
			return;
		}
		if (req->sk) {
			sk = req->sk; /* report error in accept */
		} else {
			tp->syn_backlog--;
			tcp_synq_unlink(tp, req, prev);
			req->class->destructor(req);
			tcp_openreq_free(req);
		}
		/* FALL THROUGH */ 
	case TCP_SYN_SENT:
	case TCP_SYN_RECV:  /* Cannot happen */ 
		tcp_statistics.TcpAttemptFails++;
		sk->err = err;
		sk->zapped = 1;
		mb();
		sk->error_report(sk);
		return;
	}

	if (np->recverr) {
		/* This code isn't serialized with the socket code */
		/* ANK (980927) ... which is harmless now,
		   sk->err's may be safely lost.
		 */
		sk->err = err;
		mb();
		sk->error_report(sk);
	} else {
		sk->err_soft = err;
		mb();
	}
}


static void tcp_v6_send_synack(struct sock *sk, struct open_request *req)
{
	struct sk_buff * skb;
	struct dst_entry *dst;
	struct ipv6_txoptions *opt = NULL;
	struct flowi fl;
	int mss;

	fl.proto = IPPROTO_TCP;
	fl.nl_u.ip6_u.daddr = &req->af.v6_req.rmt_addr;
	fl.nl_u.ip6_u.saddr = &req->af.v6_req.loc_addr;
	fl.fl6_flowlabel = 0;
	fl.oif = req->af.v6_req.iif;
	fl.uli_u.ports.dport = req->rmt_port;
	fl.uli_u.ports.sport = sk->sport;

	opt = sk->net_pinfo.af_inet6.opt;
	if (opt == NULL &&
	    sk->net_pinfo.af_inet6.rxopt.bits.srcrt == 2 &&
	    req->af.v6_req.pktopts) {
		struct sk_buff *pktopts = req->af.v6_req.pktopts;
		struct inet6_skb_parm *rxopt = (struct inet6_skb_parm *)pktopts->cb;
		if (rxopt->srcrt)
			opt = ipv6_invert_rthdr(sk, (struct ipv6_rt_hdr*)(pktopts->nh.raw + rxopt->srcrt));
	}

	if (opt && opt->srcrt) {
		struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
		fl.nl_u.ip6_u.daddr = rt0->addr;
	}

	dst = ip6_route_output(sk, &fl);
	if (dst->error)
		goto done;

	mss = dst->pmtu - sizeof(struct ipv6hdr) - sizeof(struct tcphdr);

	skb = tcp_make_synack(sk, dst, req, mss);
	if (skb) {
		struct tcphdr *th = skb->h.th;

		th->check = tcp_v6_check(th, skb->len,
					 &req->af.v6_req.loc_addr, &req->af.v6_req.rmt_addr,
					 csum_partial((char *)th, skb->len, skb->csum));

		fl.nl_u.ip6_u.daddr = &req->af.v6_req.rmt_addr;
		ip6_xmit(sk, skb, &fl, opt);
	}

done:
	dst_release(dst);
        if (opt && opt != sk->net_pinfo.af_inet6.opt)
		sock_kfree_s(sk, opt, opt->tot_len);
}

static void tcp_v6_or_free(struct open_request *req)
{
	if (req->af.v6_req.pktopts) {
		kfree_skb(req->af.v6_req.pktopts);
		req->af.v6_req.pktopts = NULL;
	}
}

static struct or_calltable or_ipv6 = {
	tcp_v6_send_synack,
	tcp_v6_or_free,
	tcp_v6_send_reset
};

static int ipv6_opt_accepted(struct sock *sk, struct sk_buff *skb)
{
	struct inet6_skb_parm *opt = (struct inet6_skb_parm *)skb->cb;

	if (sk->net_pinfo.af_inet6.rxopt.all) {
		if ((opt->hop && sk->net_pinfo.af_inet6.rxopt.bits.hopopts) ||
		    ((IPV6_FLOWINFO_MASK&*(u32*)skb->nh.raw) &&
		     sk->net_pinfo.af_inet6.rxopt.bits.rxflow) ||
		    (opt->srcrt && sk->net_pinfo.af_inet6.rxopt.bits.srcrt) ||
		    ((opt->dst1 || opt->dst0) && sk->net_pinfo.af_inet6.rxopt.bits.dstopts))
			return 1;
	}
	return 0;
}


#define BACKLOG(sk) ((sk)->tp_pinfo.af_tcp.syn_backlog) /* lvalue! */
#define BACKLOGMAX(sk) sysctl_max_syn_backlog

/* FIXME: this is substantially similar to the ipv4 code.
 * Can some kind of merge be done? -- erics
 */
static int tcp_v6_conn_request(struct sock *sk, struct sk_buff *skb, __u32 isn)
{
	struct tcp_opt tp;
	struct open_request *req;
	
	/* If the socket is dead, don't accept the connection.	*/
	if (sk->dead) {
		SOCK_DEBUG(sk, "Reset on %p: Connect on dead socket.\n", sk);
		tcp_statistics.TcpAttemptFails++;
		return -ENOTCONN;
	}

	if (skb->protocol == __constant_htons(ETH_P_IP))
		return tcp_v4_conn_request(sk, skb, isn);

	/* FIXME: do the same check for anycast */
	if (ipv6_addr_is_multicast(&skb->nh.ipv6h->daddr))
		goto drop; 

	if (isn == 0) 
		isn = tcp_v6_init_sequence(sk,skb);

	/*
	 *	There are no SYN attacks on IPv6, yet...	
	 */
	if (BACKLOG(sk) >= BACKLOGMAX(sk)) {
		(void)(net_ratelimit() && 
		       printk(KERN_INFO "droping syn ack:%d max:%d\n",
			       BACKLOG(sk), BACKLOGMAX(sk)));
		goto drop;		
	}

	req = tcp_openreq_alloc();
	if (req == NULL) {
		goto drop;
	}

	BACKLOG(sk)++;

	req->rcv_wnd = 0;		/* So that tcp_send_synack() knows! */

	req->rcv_isn = TCP_SKB_CB(skb)->seq;
	req->snt_isn = isn;
	tp.tstamp_ok = tp.sack_ok = tp.wscale_ok = tp.snd_wscale = 0;
	tp.mss_clamp = 65535;
	tcp_parse_options(NULL, skb->h.th, &tp, 0);
	if (tp.mss_clamp == 65535)
		tp.mss_clamp = 576 - sizeof(struct ipv6hdr) - sizeof(struct iphdr);
	if (sk->tp_pinfo.af_tcp.user_mss && sk->tp_pinfo.af_tcp.user_mss < tp.mss_clamp)
		tp.mss_clamp = sk->tp_pinfo.af_tcp.user_mss;

        req->mss = tp.mss_clamp;
	if (tp.saw_tstamp)
                req->ts_recent = tp.rcv_tsval;
        req->tstamp_ok = tp.tstamp_ok;
	req->sack_ok = tp.sack_ok;
        req->snd_wscale = tp.snd_wscale;
        req->wscale_ok = tp.wscale_ok;
	req->rmt_port = skb->h.th->source;
	ipv6_addr_copy(&req->af.v6_req.rmt_addr, &skb->nh.ipv6h->saddr);
	ipv6_addr_copy(&req->af.v6_req.loc_addr, &skb->nh.ipv6h->daddr);
	req->af.v6_req.pktopts = NULL;
	if (ipv6_opt_accepted(sk, skb)) {
		atomic_inc(&skb->users);
		req->af.v6_req.pktopts = skb;
	}
	req->af.v6_req.iif = sk->bound_dev_if;

	/* So that link locals have meaning */
	if (!sk->bound_dev_if && ipv6_addr_type(&req->af.v6_req.rmt_addr)&IPV6_ADDR_LINKLOCAL)
		req->af.v6_req.iif = tcp_v6_iif(skb);

	req->class = &or_ipv6;
	req->retrans = 0;
	req->sk = NULL;

	tcp_v6_send_synack(sk, req);

	req->expires = jiffies + TCP_TIMEOUT_INIT;
	tcp_inc_slow_timer(TCP_SLT_SYNACK);
	tcp_synq_queue(&sk->tp_pinfo.af_tcp, req);	

	return 0;

drop:
	tcp_statistics.TcpAttemptFails++;
	return 0; /* don't send reset */
}

static void tcp_v6_send_check(struct sock *sk, struct tcphdr *th, int len, 
			      struct sk_buff *skb)
{
	struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;
	th->check = 0;
	
	th->check = csum_ipv6_magic(&np->saddr, &np->daddr, len, IPPROTO_TCP, 
				    csum_partial((char *)th, th->doff<<2, 
						 skb->csum));
}

static struct sock * tcp_v6_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
					  struct open_request *req,
					  struct dst_entry *dst)
{
	struct ipv6_pinfo *np;
	struct flowi fl;
	struct tcp_opt *newtp;
	struct sock *newsk;
	struct ipv6_txoptions *opt;

	if (skb->protocol == __constant_htons(ETH_P_IP)) {
		/*
		 *	v6 mapped
		 */

		newsk = tcp_v4_syn_recv_sock(sk, skb, req, dst);

		if (newsk == NULL) 
			return NULL;
	
		np = &newsk->net_pinfo.af_inet6;

		ipv6_addr_set(&np->daddr, 0, 0, __constant_htonl(0x0000FFFF),
			      newsk->daddr);

		ipv6_addr_set(&np->saddr, 0, 0, __constant_htonl(0x0000FFFF),
			      newsk->saddr);

		ipv6_addr_copy(&np->rcv_saddr, &np->saddr);

		newsk->tp_pinfo.af_tcp.af_specific = &ipv6_mapped;
		newsk->backlog_rcv = tcp_v4_do_rcv;
		newsk->net_pinfo.af_inet6.pktoptions = NULL;
		newsk->net_pinfo.af_inet6.opt = NULL;

		/* It is tricky place. Until this moment IPv4 tcp
		   worked with IPv6 af_tcp.af_specific.
		   Sync it now.
		 */
		tcp_sync_mss(newsk, newsk->tp_pinfo.af_tcp.pmtu_cookie);

		return newsk;
	}

	opt = sk->net_pinfo.af_inet6.opt;

	if (sk->ack_backlog > sk->max_ack_backlog)
		goto out;

	if (sk->net_pinfo.af_inet6.rxopt.bits.srcrt == 2 &&
	    opt == NULL && req->af.v6_req.pktopts) {
		struct inet6_skb_parm *rxopt = (struct inet6_skb_parm *)req->af.v6_req.pktopts->cb;
		if (rxopt->srcrt)
			opt = ipv6_invert_rthdr(sk, (struct ipv6_rt_hdr*)(req->af.v6_req.pktopts->nh.raw+rxopt->srcrt));
	}

	if (dst == NULL) {
		fl.proto = IPPROTO_TCP;
		fl.nl_u.ip6_u.daddr = &req->af.v6_req.rmt_addr;
		if (opt && opt->srcrt) {
			struct rt0_hdr *rt0 = (struct rt0_hdr *) opt->srcrt;
			fl.nl_u.ip6_u.daddr = rt0->addr;
		}
		fl.nl_u.ip6_u.saddr = &req->af.v6_req.loc_addr;
		fl.fl6_flowlabel = 0;
		fl.oif = sk->bound_dev_if;
		fl.uli_u.ports.dport = req->rmt_port;
		fl.uli_u.ports.sport = sk->sport;

		dst = ip6_route_output(sk, &fl);
	}

	if (dst->error)
		goto out;

	sk->tp_pinfo.af_tcp.syn_backlog--;
	sk->ack_backlog++;

	newsk = tcp_create_openreq_child(sk, req, skb);
	if (newsk == NULL)
		goto out;

	ip6_dst_store(newsk, dst, NULL);

	newtp = &(newsk->tp_pinfo.af_tcp);

	np = &newsk->net_pinfo.af_inet6;
	ipv6_addr_copy(&np->daddr, &req->af.v6_req.rmt_addr);
	ipv6_addr_copy(&np->saddr, &req->af.v6_req.loc_addr);
	ipv6_addr_copy(&np->rcv_saddr, &req->af.v6_req.loc_addr);
	newsk->bound_dev_if = req->af.v6_req.iif;

	/* Now IPv6 options... 

	   First: no IPv4 options.
	 */
	newsk->opt = NULL;

	/* Clone RX bits */
	np->rxopt.all = sk->net_pinfo.af_inet6.rxopt.all;

	/* Clone pktoptions received with SYN */
	np->pktoptions = req->af.v6_req.pktopts;
	if (np->pktoptions)
		atomic_inc(&np->pktoptions->users);
	np->opt = NULL;

	/* Clone native IPv6 options from listening socket (if any)

	   Yes, keeping reference count would be much more clever,
	   but we make one more one thing there: reattach optmem
	   to newsk.
	 */
	if (opt) {
		np->opt = ipv6_dup_options(newsk, opt);
		if (opt != sk->net_pinfo.af_inet6.opt)
			sock_kfree_s(sk, opt, opt->tot_len);
	}

	newtp->ext_header_len = 0;
	if (np->opt)
		newtp->ext_header_len = np->opt->opt_nflen + np->opt->opt_flen;

	tcp_sync_mss(newsk, dst->pmtu);
	newtp->rcv_mss = newtp->mss_clamp;

	newsk->daddr	= LOOPBACK4_IPV6;
	newsk->saddr	= LOOPBACK4_IPV6;
	newsk->rcv_saddr= LOOPBACK4_IPV6;

	newsk->prot->hash(newsk);
	tcp_inherit_port(sk, newsk);
	add_to_prot_sklist(newsk);
	sk->data_ready(sk, 0); /* Deliver SIGIO */ 

	return newsk;

out:
	if (opt && opt != sk->net_pinfo.af_inet6.opt)
		sock_kfree_s(sk, opt, opt->tot_len);
	dst_release(dst);
	return NULL;
}

static void tcp_v6_send_reset(struct sk_buff *skb)
{
	struct tcphdr *th = skb->h.th, *t1; 
	struct sk_buff *buff;
	struct flowi fl;

	if (th->rst)
		return;

	if (ipv6_addr_is_multicast(&skb->nh.ipv6h->daddr))
		return; 

	/*
	 * We need to grab some memory, and put together an RST,
	 * and then put it into the queue to be sent.
	 */

	buff = alloc_skb(MAX_HEADER + sizeof(struct ipv6hdr), GFP_ATOMIC);
	if (buff == NULL) 
	  	return;

	skb_reserve(buff, MAX_HEADER + sizeof(struct ipv6hdr));

	t1 = (struct tcphdr *) skb_push(buff,sizeof(struct tcphdr));

	/* Swap the send and the receive. */
	memset(t1, 0, sizeof(*t1));
	t1->dest = th->source;
	t1->source = th->dest;
	t1->doff = sizeof(*t1)/4;
	t1->rst = 1;
  
	if(th->ack) {
	  	t1->seq = th->ack_seq;
	} else {
		t1->ack = 1;
	  	if(!th->syn)
			t1->ack_seq = th->seq;
		else
			t1->ack_seq = htonl(ntohl(th->seq)+1);
	}

	buff->csum = csum_partial((char *)t1, sizeof(*t1), 0);

	fl.nl_u.ip6_u.daddr = &skb->nh.ipv6h->saddr;
	fl.nl_u.ip6_u.saddr = &skb->nh.ipv6h->daddr;
	fl.fl6_flowlabel = 0;

	t1->check = csum_ipv6_magic(fl.nl_u.ip6_u.saddr,
				    fl.nl_u.ip6_u.daddr, 
				    sizeof(*t1), IPPROTO_TCP,
				    buff->csum);

	fl.proto = IPPROTO_TCP;
	fl.oif = tcp_v6_iif(skb);
	fl.uli_u.ports.dport = t1->dest;
	fl.uli_u.ports.sport = t1->source;

	/* sk = NULL, but it is safe for now. RST socket required. */
	buff->dst = ip6_route_output(NULL, &fl);

	if (buff->dst->error == 0) {
		ip6_xmit(NULL, buff, &fl, NULL);
		tcp_statistics.TcpOutSegs++;
		tcp_statistics.TcpOutRsts++;
		return;
	}

	kfree_skb(buff);
}

static void tcp_v6_send_ack(struct sk_buff *skb, __u32 seq, __u32 ack, __u16 window)
{
	struct tcphdr *th = skb->h.th, *t1; 
	struct sk_buff *buff;
	struct flowi fl;

	buff = alloc_skb(MAX_HEADER + sizeof(struct ipv6hdr), GFP_ATOMIC);
	if (buff == NULL) 
	  	return;

	skb_reserve(buff, MAX_HEADER + sizeof(struct ipv6hdr));

	t1 = (struct tcphdr *) skb_push(buff,sizeof(struct tcphdr));

	/* Swap the send and the receive. */
	memset(t1, 0, sizeof(*t1));
	t1->dest = th->source;
	t1->source = th->dest;
	t1->doff = sizeof(*t1)/4;
	t1->ack = 1;
	t1->seq = seq;
	t1->ack_seq = ack; 

	t1->window = htons(window);

	buff->csum = csum_partial((char *)t1, sizeof(*t1), 0);

	fl.nl_u.ip6_u.daddr = &skb->nh.ipv6h->saddr;
	fl.nl_u.ip6_u.saddr = &skb->nh.ipv6h->daddr;
	fl.fl6_flowlabel = 0;

	t1->check = csum_ipv6_magic(fl.nl_u.ip6_u.saddr,
				    fl.nl_u.ip6_u.daddr, 
				    sizeof(*t1), IPPROTO_TCP,
				    buff->csum);

	fl.proto = IPPROTO_TCP;
	fl.oif = tcp_v6_iif(skb);
	fl.uli_u.ports.dport = t1->dest;
	fl.uli_u.ports.sport = t1->source;

	/* sk = NULL, but it is safe for now. static socket required. */
	buff->dst = ip6_route_output(NULL, &fl);

	if (buff->dst->error == 0) {
		ip6_xmit(NULL, buff, &fl, NULL);
		tcp_statistics.TcpOutSegs++;
		return;
	}

	kfree_skb(buff);
}

static struct open_request *tcp_v6_search_req(struct tcp_opt *tp,
					      struct ipv6hdr *ip6h,
					      struct tcphdr *th,
					      int iif,
					      struct open_request **prevp)
{
	struct open_request *req, *prev; 
	__u16 rport = th->source;

	/*	assumption: the socket is not in use.
	 *	as we checked the user count on tcp_rcv and we're
	 *	running from a soft interrupt.
	 */
	prev = (struct open_request *) (&tp->syn_wait_queue); 
	for (req = prev->dl_next; req; req = req->dl_next) {
		if (!ipv6_addr_cmp(&req->af.v6_req.rmt_addr, &ip6h->saddr) &&
		    !ipv6_addr_cmp(&req->af.v6_req.loc_addr, &ip6h->daddr) &&
		    req->rmt_port == rport &&
		    (!req->af.v6_req.iif || req->af.v6_req.iif == iif)) {
			*prevp = prev;
			return req;
		}
		prev = req; 
	}
	return NULL; 
}

static void tcp_v6_rst_req(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_opt *tp = &sk->tp_pinfo.af_tcp;
	struct open_request *req, *prev;

	req = tcp_v6_search_req(tp,skb->nh.ipv6h,skb->h.th,tcp_v6_iif(skb),&prev);
	if (!req)
		return;
	/* Sequence number check required by RFC793 */
	if (before(TCP_SKB_CB(skb)->seq, req->rcv_isn) ||
	    after(TCP_SKB_CB(skb)->seq, req->rcv_isn+1))
		return;
	if(req->sk)
		sk->ack_backlog--;
	else
		tp->syn_backlog--;
	tcp_synq_unlink(tp, req, prev);
	req->class->destructor(req);
	tcp_openreq_free(req); 
	net_statistics.EmbryonicRsts++; 
}

static inline struct sock *tcp_v6_hnd_req(struct sock *sk, struct sk_buff *skb)
{
	struct tcphdr *th = skb->h.th; 
	u32 flg = ((u32 *)th)[3]; 

	/* Check for RST */
	if (flg & __constant_htonl(0x00040000)) {
		tcp_v6_rst_req(sk, skb);
		return NULL;
	}
		
	/* Check SYN|ACK */
	if (flg & __constant_htonl(0x00120000)) {
		struct open_request *req, *dummy;
		struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
			
		req = tcp_v6_search_req(tp, skb->nh.ipv6h, th, tcp_v6_iif(skb), &dummy);
		if (req) {
			sk = tcp_check_req(sk, skb, req);
		}
#if 0 /*def CONFIG_SYN_COOKIES */
		 else {
			sk = cookie_v6_check(sk, skb);
		 }
#endif
	}
	return sk;
}

static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
{
#ifdef CONFIG_FILTER
	struct sk_filter *filter;
#endif
	struct device *dev;
	struct inet6_dev *idev;
	int users = 0;

	/* Imagine: socket is IPv6. IPv4 packet arrives,
	   goes to IPv4 receive handler and backlogged.
	   From backlog it always goes here. Kerboom...
	   Fortunately, tcp_rcv_established and rcv_established
	   handle them correctly, but it is not case with
	   tcp_v6_hnd_req and tcp_v6_send_reset().   --ANK
	 */

	if (skb->protocol == __constant_htons(ETH_P_IP))
		return tcp_v4_do_rcv(sk, skb);

#ifdef CONFIG_FILTER
	filter = sk->filter;
	if (filter && sk_filter(skb, filter))
		goto discard;
#endif /* CONFIG_FILTER */

	/*
	 *	socket locking is here for SMP purposes as backlog rcv
	 *	is currently called with bh processing disabled.
	 */

	dev = dev_get_by_index(tcp_v6_iif(skb));
	idev = dev ? ipv6_get_idev(dev) : NULL;
	IP6_INC_STATS_BH(idev,Ip6InDelivers);

	/* 
	 * This doesn't check if the socket has enough room for the packet.
	 * Either process the packet _without_ queueing it and then free it,
	 * or do the check later.
	 */
	skb_set_owner_r(skb, sk);

	/* Do Stevens' IPV6_PKTOPTIONS.

	   Yes, guys, it is the only place in our code, where we
	   may make it not affecting IPv4.
	   The rest of code is protocol independent,
	   and I do not like idea to uglify IPv4.

	   Actually, all the idea behind IPV6_PKTOPTIONS
	   looks not very well thought. For now we latch
	   options, received in the last packet, enqueued
	   by tcp. Feel free to propose better solution.
	                                       --ANK (980728)
	 */
	if (sk->net_pinfo.af_inet6.rxopt.all) {
		users = atomic_read(&skb->users);
		atomic_inc(&skb->users);
	}

	if (sk->state == TCP_ESTABLISHED) { /* Fast path */
		if (tcp_rcv_established(sk, skb, skb->h.th, skb->len))
			goto reset;
		if (users)
			goto ipv6_pktoptions;
		return 0;
	}

	if (sk->state == TCP_LISTEN) { 
		struct sock *nsk;
		
		nsk = tcp_v6_hnd_req(sk, skb);
		if (!nsk)
			goto discard;

		/*
		 * Queue it on the new socket if the new socket is active,
		 * otherwise we just shortcircuit this and continue with
		 * the new socket..
		 */
		if (atomic_read(&nsk->sock_readers)) {
			skb_orphan(skb);
			__skb_queue_tail(&nsk->back_log, skb);
			return 0;
		}
		sk = nsk;
	}

	if (tcp_rcv_state_process(sk, skb, skb->h.th, skb->len))
		goto reset;
	if (users)
		goto ipv6_pktoptions;
	return 0;

reset:
	tcp_v6_send_reset(skb);
discard:
	if (users)
		kfree_skb(skb);
	kfree_skb(skb);
	return 0;

ipv6_pktoptions:
	/* Do you ask, what is it?

	   1. skb was enqueued by tcp.
	   2. skb is added to tail of read queue, rather than out of order.
	   3. socket is not in passive state.
	   4. Finally, it really contains options, which user wants to receive.
	 */
	if (atomic_read(&skb->users) > users &&
	    TCP_SKB_CB(skb)->end_seq == sk->tp_pinfo.af_tcp.rcv_nxt &&
	    !((1<<sk->state)&(TCPF_CLOSE|TCPF_LISTEN))) {
		if (ipv6_opt_accepted(sk, skb)) {
			struct sk_buff *skb2 = skb_clone(skb, GFP_ATOMIC);
			kfree_skb(skb);
			skb = NULL;
			if (skb2) {
				skb_set_owner_r(skb2, sk);
				skb = xchg(&sk->net_pinfo.af_inet6.pktoptions, skb2);
			}
		} else {
			kfree_skb(skb);
			skb = xchg(&sk->net_pinfo.af_inet6.pktoptions, NULL);
		}
	}

	if (skb)
		kfree_skb(skb);
	return 0;
}

int tcp_v6_rcv(struct sk_buff *skb, unsigned long len)
{
	struct tcphdr *th;	
	struct sock *sk;
	struct in6_addr *saddr = &skb->nh.ipv6h->saddr;
	struct in6_addr *daddr = &skb->nh.ipv6h->daddr;

	th = skb->h.th;

	if (skb->pkt_type != PACKET_HOST)
		goto discard_it;

	/*
	 *	Pull up the IP header.
	 */

	__skb_pull(skb, skb->h.raw - skb->data);

	/*
	 *	Count it even if it's bad.
	 */

	tcp_statistics.TcpInSegs++;

	len = skb->len;
	if (len < sizeof(struct tcphdr))
		goto bad_packet;

	/*
	 *	Try to use the device checksum if provided.
	 */

	switch (skb->ip_summed) {
	case CHECKSUM_NONE:
		skb->csum = csum_partial((char *)th, len, 0);
	case CHECKSUM_HW:
		if (tcp_v6_check(th,len,saddr,daddr,skb->csum)) {
			printk(KERN_DEBUG "tcp csum failed\n");
	bad_packet:		
			tcp_statistics.TcpInErrs++;
			goto discard_it;
		}
	default:
		/* CHECKSUM_UNNECESSARY */
	};

	if((th->doff * 4) < sizeof(struct tcphdr) ||
	   len < (th->doff * 4))
		goto bad_packet;

	sk = __tcp_v6_lookup(th, saddr, th->source, daddr, th->dest, tcp_v6_iif(skb));

	if (!sk)
		goto no_tcp_socket;

	TCP_SKB_CB(skb)->seq = ntohl(th->seq);
	TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
				    len - th->doff*4);
	TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
	skb->used = 0;
	if(sk->state == TCP_TIME_WAIT)
		goto do_time_wait;

	if (!atomic_read(&sk->sock_readers))
		return tcp_v6_do_rcv(sk, skb);

	__skb_queue_tail(&sk->back_log, skb);
	return(0);

no_tcp_socket:
	tcp_v6_send_reset(skb);

discard_it:

	/*
	 *	Discard frame
	 */

	kfree_skb(skb);
	return 0;

do_time_wait:
	switch (tcp_timewait_state_process((struct tcp_tw_bucket *)sk,
					   skb, th, skb->len)) {
	case TCP_TW_ACK:
		tcp_v6_send_ack(skb,
				((struct tcp_tw_bucket *)sk)->snd_nxt,
				((struct tcp_tw_bucket *)sk)->rcv_nxt,
				((struct tcp_tw_bucket *)sk)->window);
		goto discard_it; 
	case TCP_TW_RST:
		goto no_tcp_socket;
	default:
		goto discard_it; 
	}
}

static int tcp_v6_rebuild_header(struct sock *sk)
{
	struct dst_entry *dst = NULL;
	struct ipv6_pinfo *np = &sk->net_pinfo.af_inet6;

	if (sk->dst_cache)
		dst = dst_check(&sk->dst_cache, np->dst_cookie);

	if (dst == NULL) {
		struct flowi fl;

		fl.proto = IPPROTO_TCP;
		fl.nl_u.ip6_u.daddr = &np->daddr;
		fl.nl_u.ip6_u.saddr = &np->saddr;
		fl.fl6_flowlabel = np->flow_label;
		fl.oif = sk->bound_dev_if;
		fl.uli_u.ports.dport = sk->dport;
		fl.uli_u.ports.sport = sk->sport;

		if (np->opt && np->opt->srcrt) {
			struct rt0_hdr *rt0 = (struct rt0_hdr *) np->opt->srcrt;
			fl.nl_u.ip6_u.daddr = rt0->addr;
		}


		dst = ip6_route_output(sk, &fl);

		if (dst->error) {
			dst_release(dst);
			return dst->error;
		}

		ip6_dst_store(sk, dst, NULL);
	}

	return dst->error;
}

static struct sock * tcp_v6_get_sock(struct sk_buff *skb, struct tcphdr *th)
{
	struct in6_addr *saddr;
	struct in6_addr *daddr;

	if (skb->protocol == __constant_htons(ETH_P_IP))
		return ipv4_specific.get_sock(skb, th);

	saddr = &skb->nh.ipv6h->saddr;
	daddr = &skb->nh.ipv6h->daddr;
	return tcp_v6_lookup(saddr, th->source, daddr, th->dest, tcp_v6_iif(skb));
}

static void tcp_v6_xmit(struct sk_buff *skb)
{
	struct sock *sk = skb->sk;
	struct ipv6_pinfo * np = &sk->net_pinfo.af_inet6;
	struct flowi fl;
	struct dst_entry *dst = sk->dst_cache;

	fl.proto = IPPROTO_TCP;
	fl.fl6_dst = &np->daddr;
	fl.fl6_src = &np->saddr;
	fl.fl6_flowlabel = np->flow_label;
	fl.oif = sk->bound_dev_if;
	fl.uli_u.ports.sport = sk->sport;
	fl.uli_u.ports.dport = sk->dport;

	if (np->opt && np->opt->srcrt) {
		struct rt0_hdr *rt0 = (struct rt0_hdr *) np->opt->srcrt;
		fl.nl_u.ip6_u.daddr = rt0->addr;
	}

	if (sk->dst_cache)
		dst = dst_check(&sk->dst_cache, np->dst_cookie);

	if (dst == NULL) {
		dst = ip6_route_output(sk, &fl);

		if (dst->error) {
			sk->err_soft = -dst->error;
			dst_release(dst);
			return;
		}

		ip6_dst_store(sk, dst, NULL);
	}

	skb->dst = dst_clone(dst);

	/* Restore final destination back after routing done */
	fl.nl_u.ip6_u.daddr = &np->daddr;

	ip6_xmit(sk, skb, &fl, np->opt);
}

static void v6_addr2sockaddr(struct sock *sk, struct sockaddr * uaddr)
{
	struct ipv6_pinfo * np = &sk->net_pinfo.af_inet6;
	struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) uaddr;

	sin6->sin6_family = AF_INET6;
	memcpy(&sin6->sin6_addr, &np->daddr, sizeof(struct in6_addr));
	sin6->sin6_port	= sk->dport;
	/* We do not store received flowlabel for TCP */
	sin6->sin6_flowinfo = 0;
#ifdef CONFIG_IPV6_SCOPE_ID
	sin6->sin6_scope_id = 0;
	if (sk->bound_dev_if && ipv6_addr_type(&sin6->sin6_addr)&IPV6_ADDR_LINKLOCAL)
		sin6->sin6_scope_id = sk->bound_dev_if;
#endif
}

static struct tcp_func ipv6_specific = {
	tcp_v6_xmit,
	tcp_v6_send_check,
	tcp_v6_rebuild_header,
	tcp_v6_conn_request,
	tcp_v6_syn_recv_sock,
	tcp_v6_get_sock,
	sizeof(struct ipv6hdr),

	ipv6_setsockopt,
	ipv6_getsockopt,
	v6_addr2sockaddr,
	sizeof(struct sockaddr_in6)
};

/*
 *	TCP over IPv4 via INET6 API
 */

static struct tcp_func ipv6_mapped = {
	ip_queue_xmit,
	tcp_v4_send_check,
	tcp_v4_rebuild_header,
	tcp_v6_conn_request,
	tcp_v6_syn_recv_sock,
	tcp_v6_get_sock,
	sizeof(struct iphdr),

	ipv6_setsockopt,
	ipv6_getsockopt,
	v6_addr2sockaddr,
	sizeof(struct sockaddr_in6)
};

/* NOTE: A lot of things set to zero explicitly by call to
 *       sk_alloc() so need not be done here.
 */
static int tcp_v6_init_sock(struct sock *sk)
{
	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);

	skb_queue_head_init(&tp->out_of_order_queue);
	tcp_init_xmit_timers(sk);

	tp->rto  = TCP_TIMEOUT_INIT;		/*TCP_WRITE_TIME*/
	tp->mdev = TCP_TIMEOUT_INIT;
	tp->mss_clamp = ~0;

	/* So many TCP implementations out there (incorrectly) count the
	 * initial SYN frame in their delayed-ACK and congestion control
	 * algorithms that we must have the following bandaid to talk
	 * efficiently to them.  -DaveM
	 */
	tp->snd_cwnd = 2;

	/* See draft-stevens-tcpca-spec-01 for discussion of the
	 * initialization of these values.
	 */
	tp->snd_cwnd_cnt = 0;
	tp->snd_ssthresh = 0x7fffffff;

	sk->state = TCP_CLOSE;
	sk->max_ack_backlog = SOMAXCONN;
	tp->rcv_mss = 536; 

	/* Init SYN queue. */
	tcp_synq_init(tp);

	sk->tp_pinfo.af_tcp.af_specific = &ipv6_specific;

	sk->write_space = tcp_write_space;

	return 0;
}

static int tcp_v6_destroy_sock(struct sock *sk)
{
	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);
	struct sk_buff *skb;

	tcp_clear_xmit_timers(sk);

	if (sk->keepopen)
		tcp_dec_slow_timer(TCP_SLT_KEEPALIVE);

	/*
	 *	Cleanup up the write buffer.
	 */

  	while((skb = __skb_dequeue(&sk->write_queue)) != NULL)
		kfree_skb(skb);

	/*
	 *  Cleans up our, hopefuly empty, out_of_order_queue
	 */

  	while((skb = __skb_dequeue(&tp->out_of_order_queue)) != NULL)
		kfree_skb(skb);

	/* Clean up a locked TCP bind bucket, this only happens if a
	 * port is allocated for a socket, but it never fully connects.
	 */
	if(sk->prev != NULL)
		tcp_put_port(sk);

	return inet6_destroy_sock(sk);
}

struct proto tcpv6_prot = {
	(struct sock *)&tcpv6_prot,	/* sklist_next */
	(struct sock *)&tcpv6_prot,	/* sklist_prev */
	tcp_close,			/* close */
	tcp_v6_connect,			/* connect */
	tcp_accept,			/* accept */
	NULL,				/* retransmit */
	tcp_write_wakeup,		/* write_wakeup */
	tcp_read_wakeup,		/* read_wakeup */
	tcp_poll,			/* poll */
	tcp_ioctl,			/* ioctl */
	tcp_v6_init_sock,		/* init */
	tcp_v6_destroy_sock,		/* destroy */
	tcp_shutdown,			/* shutdown */
	tcp_setsockopt,			/* setsockopt */
	tcp_getsockopt,			/* getsockopt */
	tcp_v6_sendmsg,			/* sendmsg */
	tcp_recvmsg,			/* recvmsg */
	NULL,				/* bind */
	tcp_v6_do_rcv,			/* backlog_rcv */
	tcp_v6_hash,			/* hash */
	tcp_v6_unhash,			/* unhash */
	tcp_v6_get_port,		/* get_port */
	128,				/* max_header */
	0,				/* retransmits */
	"TCPv6",			/* name */
	0,				/* inuse */
	0				/* highestinuse */
};

static struct inet6_protocol tcpv6_protocol =
{
	tcp_v6_rcv,		/* TCP handler		*/
	tcp_v6_err,		/* TCP error control	*/
	NULL,			/* next			*/
	IPPROTO_TCP,		/* protocol ID		*/
	0,			/* copy			*/
	NULL,			/* data			*/
	"TCPv6"			/* name			*/
};

__initfunc(void tcpv6_init(void))
{
	/* register inet6 protocol */
	inet6_add_protocol(&tcpv6_protocol);
}
