/*
 *	TCP over IPv6
 *	Linux INET6 implementation 
 *
 *	Authors:
 *	Pedro Roque		<roque@di.fc.ul.pt>	
 *
 *	$Id: tcp_ipv6.c,v 1.112 1999/08/31 07:04:19 davem Exp $
 *
 *	Based on: 
 *	linux/net/ipv4/tcp.c
 *	linux/net/ipv4/tcp_input.c
 *	linux/net/ipv4/tcp_output.c
 *
 *	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.
 */

#define __NO_VERSION__
#include <linux/module.h>
#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/ipsec.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;
extern int sysctl_tcp_tw_recycle;
extern __u32 sysctl_wmem_max;
extern __u32 sysctl_rmem_max;

static void	tcp_v6_send_reset(struct sk_buff *skb);
static void	tcp_v6_or_send_ack(struct sk_buff *skb, struct open_request *req);
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 int	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]);
	hashent ^= hashent>>16;
	hashent ^= hashent>>8;
	return (hashent & (tcp_ehash_size - 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_hashbucket *head;
	struct tcp_bind_bucket *tb;
	int ret;

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

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

		/* Exhausted local port range during search? */
		ret = 1;
		if (remaining <= 0)
			goto fail;

		/* OK, here is the one we will use. */
		snum = rover;
		tb = NULL;
	} else {
		head = &tcp_bhash[tcp_bhashfn(snum)];
		spin_lock(&head->lock);
		for (tb = head->chain; tb != NULL; tb = tb->next)
			if (tb->port == snum)
				break;
	}
	if (tb != NULL && tb->owners != NULL) {
		if (tb->fastreuse != 0 && sk->reuse != 0) {
			goto success;
		} else {
			struct sock *sk2 = tb->owners;
			int sk_reuse = sk->reuse;
			int addr_type = ipv6_addr_type(&sk->net_pinfo.af_inet6.rcv_saddr);

			/* We must walk the whole port owner list in this case. -DaveM */
			for( ; sk2 != NULL; sk2 = sk2->bind_next) {
				if (sk->bound_dev_if == sk2->bound_dev_if) {
					if (!sk_reuse	||
					    !sk2->reuse	||
					    sk2->state == TCP_LISTEN) {
						/* NOTE: IPv6 tw bucket have different format */
						if (!sk2->rcv_saddr	||
						    addr_type == IPV6_ADDR_ANY ||
						    !ipv6_addr_cmp(&sk->net_pinfo.af_inet6.rcv_saddr,
								   sk2->state != TCP_TIME_WAIT ?
								   &sk2->net_pinfo.af_inet6.rcv_saddr :
								   &((struct tcp_tw_bucket*)sk)->v6_rcv_saddr))
							break;
					}
				}
			}
			/* If we found a conflict, fail. */
			ret = 1;
			if (sk2 != NULL)
				goto fail_unlock;
		}
	}
	ret = 1;
	if (tb == NULL &&
	    (tb = tcp_bucket_create(head, snum)) == NULL)
			goto fail_unlock;
	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;

success:
	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;
	ret = 0;

fail_unlock:
	spin_unlock(&head->lock);
fail:
	local_bh_enable();
	return ret;
}

static __inline__ void __tcp_v6_hash(struct sock *sk)
{
	struct sock **skp;
	rwlock_t *lock;

	BUG_TRAP(sk->pprev==NULL);

	if(sk->state == TCP_LISTEN) {
		skp = &tcp_listening_hash[tcp_sk_listen_hashfn(sk)];
		lock = &tcp_lhash_lock;
		tcp_listen_wlock();
	} else {
		skp = &tcp_ehash[(sk->hashent = tcp_v6_sk_hashfn(sk))].chain;
		lock = &tcp_ehash[sk->hashent].lock;
		write_lock(lock);
	}

	if((sk->next = *skp) != NULL)
		(*skp)->pprev = &sk->next;
	*skp = sk;
	sk->pprev = skp;
	sk->prot->inuse++;
	if(sk->prot->highestinuse < sk->prot->inuse)
		sk->prot->highestinuse = sk->prot->inuse;
	write_unlock(lock);
}


static void tcp_v6_hash(struct sock *sk)
{
	if(sk->state != TCP_CLOSE) {
		if (sk->tp_pinfo.af_tcp.af_specific == &ipv6_mapped) {
			tcp_prot.hash(sk);
			return;
		}
		local_bh_disable();
		__tcp_v6_hash(sk);
		local_bh_enable();
	}
}

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;
	read_lock(&tcp_lhash_lock);
	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) {
				result = sk;
				break;
			}
			if (score > hiscore) {
				hiscore = score;
				result = sk;
			}
		}
	}
	if (sk)
		sock_hold(sk);
	read_unlock(&tcp_lhash_lock);
	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
 *
 * The sockhash lock must be held as a reader here.
 */
static inline struct sock *__tcp_v6_lookup(struct in6_addr *saddr, u16 sport,
					   struct in6_addr *daddr, u16 hnum,
					   int dif)
{
	struct tcp_ehash_bucket *head;
	struct sock *sk;
	__u32 ports = TCP_COMBINED_PORTS(sport, hnum);
	int hash;

	/* Optimize here for direct hit, only listening connections can
	 * have wildcards anyways.
	 */
	hash = tcp_v6_hashfn(daddr, hnum, saddr, sport);
	head = &tcp_ehash[hash];
	read_lock(&head->lock);
	for(sk = head->chain; sk; sk = sk->next) {
		/* For IPV6 do the cheaper port and family tests first. */
		if(TCP_IPV6_MATCH(sk, saddr, daddr, ports, dif))
			goto hit; /* You sunk my battleship! */
	}
	/* Must check for a TIME_WAIT'er before going to listener hash. */
	for(sk = (head + tcp_ehash_size)->chain; 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;
		}
	}
	read_unlock(&head->lock);

	return tcp_v6_lookup_listener(daddr, hnum, dif);

hit:
	sock_hold(sk);
	read_unlock(&head->lock);
	return sk;
}

#define tcp_v6_lookup(sa, sp, da, dp, dif) \
({	struct sock *___sk; \
	local_bh_disable(); \
	___sk = __tcp_v6_lookup((sa),(sp),(da),ntohs(dp),(dif)); \
	local_bh_enable(); \
	___sk; \
})

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_check_established(struct sock *sk)
{
	struct in6_addr *daddr = &sk->net_pinfo.af_inet6.rcv_saddr;
	struct in6_addr *saddr = &sk->net_pinfo.af_inet6.daddr;
	int dif = sk->bound_dev_if;
	u32 ports = TCP_COMBINED_PORTS(sk->dport, sk->num);
	int hash = tcp_v6_hashfn(daddr, sk->num, saddr, sk->dport);
	struct tcp_ehash_bucket *head = &tcp_ehash[hash];
	struct sock *sk2, **skp;
	struct tcp_tw_bucket *tw;

	write_lock(&head->lock);

	for(skp = &(head + tcp_ehash_size)->chain; (sk2=*skp)!=NULL; skp = &sk2->next) {
		tw = (struct tcp_tw_bucket*)sk2;

		if(*((__u32 *)&(sk2->dport))	== ports	&&
		   sk2->family			== PF_INET6	&&
		   !ipv6_addr_cmp(&tw->v6_daddr, saddr)		&&
		   !ipv6_addr_cmp(&tw->v6_rcv_saddr, daddr)	&&
		   sk2->bound_dev_if == sk->bound_dev_if) {
#ifdef CONFIG_TCP_TW_RECYCLE
			struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);

			if (sysctl_tcp_tw_recycle && tw->ts_recent_stamp) {
				/* See comment in tcp_ipv4.c */
				if ((tp->write_seq = tw->snd_nxt + 2) == 0)
					tp->write_seq = 1;
				tp->ts_recent = tw->ts_recent;
				tp->ts_recent_stamp = tw->ts_recent_stamp;
				sock_hold(sk2);
				skp = &head->chain;
				goto unique;
			} else
#endif
			goto not_unique;
		}
	}
	tw = NULL;

	for(skp = &head->chain; (sk2=*skp)!=NULL; skp = &sk2->next) {
		if(TCP_IPV6_MATCH(sk, saddr, daddr, ports, dif))
			goto not_unique;
	}

#ifdef CONFIG_TCP_TW_RECYCLE
unique:
#endif
	BUG_TRAP(sk->pprev==NULL);
	if ((sk->next = *skp) != NULL)
		(*skp)->pprev = &sk->next;

	*skp = sk;
	sk->pprev = skp;
	sk->prot->inuse++;
	if(sk->prot->highestinuse < sk->prot->inuse)
		sk->prot->highestinuse = sk->prot->inuse;
	write_unlock_bh(&head->lock);

#ifdef CONFIG_TCP_TW_RECYCLE
	if (tw) {
		/* Silly. Should hash-dance instead... */
		local_bh_disable();
		tcp_tw_deschedule(tw);
		tcp_timewait_kill(tw);
		local_bh_enable();

		tcp_tw_put(tw);
	}
#endif
	return 0;

not_unique:
	write_unlock_bh(&head->lock);
	return -EADDRNOTAVAIL;
}

static int tcp_v6_hash_connecting(struct sock *sk)
{
	unsigned short snum = sk->num;
	struct tcp_bind_hashbucket *head = &tcp_bhash[tcp_bhashfn(snum)];
	struct tcp_bind_bucket *tb = head->chain;

	spin_lock_bh(&head->lock);

	if (tb->owners == sk && sk->bind_next == NULL) {
		__tcp_v6_hash(sk);
		spin_unlock_bh(&head->lock);
		return 0;
	} else {
		spin_unlock_bh(&head->lock);
		return tcp_v6_check_established(sk);
	}
}

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);

	if (addr_len < sizeof(struct sockaddr_in6)) 
		return(-EINVAL);

	if (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;

	/* We may need to bind the socket. */
	if (sk->num==0 && sk->prot->get_port(sk, 0))
		return -EAGAIN;
	sk->sport = htons(sk->num);

#ifdef CONFIG_TCP_TW_RECYCLE
	if (tp->ts_recent_stamp && ipv6_addr_cmp(&np->daddr, &usin->sin6_addr)) {
		tp->ts_recent = 0;
		tp->ts_recent_stamp = 0;
		tp->write_seq = 0;
	}
#endif

	ipv6_addr_copy(&np->daddr, &usin->sin6_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");

		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;
	tp->mss_clamp = IPV6_MIN_MTU - sizeof(struct tcphdr) - sizeof(struct ipv6hdr);

	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;

	/*
	 *	Init variables
	 */

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

	err = tcp_connect(sk, buff);
	if (err == 0)
		return 0;

failure:
	__sk_dst_reset(sk);
	sk->dport = 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;

	lock_sock(sk);
	/*
	 *	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:
	release_sock(sk);
	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) {
		icmpv6_statistics.Icmp6InErrors++;
		return;
	}

	if (sk->state == TCP_TIME_WAIT) {
		tcp_tw_put((struct tcp_tw_bucket*)sk);
		return;
	}

	bh_lock_sock(sk);
	if (sk->lock.users)
		net_statistics.LockDroppedIcmps++;

	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++;
		goto out;
	}

	np = &sk->net_pinfo.af_inet6;

	if (type == ICMPV6_PKT_TOOBIG) {
		struct dst_entry *dst = NULL;

		if (sk->lock.users)
			goto out;
		if ((1<<sk->state)&(TCPF_LISTEN|TCPF_CLOSE))
			goto out;

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

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

			/* 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);
		}

		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);
		goto out;
	}

	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 (sk->lock.users)
			goto out;

		/* 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)
			goto out;

		if (req->sk) {
			struct sock *nsk = req->sk;

			sock_hold(nsk);
			bh_unlock_sock(sk);
			sock_put(sk);
			sk = nsk;

			BUG_TRAP(sk->lock.users==0);

			tp = &sk->tp_pinfo.af_tcp;
			if (!between(seq, tp->snd_una, tp->snd_nxt)) {
				net_statistics.OutOfWindowIcmps++;
				goto out;
			}
		} else {
			if (seq != req->snt_isn) {
				net_statistics.OutOfWindowIcmps++;
				goto out;
			}

			tp->syn_backlog--;
			tcp_synq_unlink(tp, req, prev);
			tcp_dec_slow_timer(TCP_SLT_SYNACK);
			req->class->destructor(req);
			tcp_openreq_free(req);
			goto out;
		}
		break;
	case TCP_SYN_SENT:
	case TCP_SYN_RECV:  /* Cannot happen.
			       It can, it SYNs are crossed. --ANK */ 
		if (sk->lock.users == 0) {
			tcp_statistics.TcpAttemptFails++;
			sk->err = err;
			sk->error_report(sk);		/* Wake people up to see the error (see connect in sock.c) */

			tcp_set_state(sk, TCP_CLOSE);
			tcp_done(sk);
		} else {
			sk->err_soft = err;
		}
		goto out;
	}

	if (sk->lock.users == 0 && np->recverr) {
		sk->err = err;
		sk->error_report(sk);
	} else {
		sk->err_soft = err;
	}

out:
	bh_unlock_sock(sk);
	sock_put(sk);
}


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;

	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;

	skb = tcp_make_synack(sk, dst, req);
	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 = {
	AF_INET6,
	tcp_v6_send_synack,
	tcp_v6_or_send_ack,
	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)
{
	struct tcp_opt tp;
	struct open_request *req;
	__u32 isn = TCP_SKB_CB(skb)->when;

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

	/* 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 = IPV6_MIN_MTU - sizeof(struct tcphdr) - sizeof(struct ipv6hdr);
	tp.user_mss = sk->tp_pinfo.af_tcp.user_mss;

	tcp_parse_options(NULL, skb->h.th, &tp, 0);

	req->mss = tp.mss_clamp;
	req->ts_recent = tp.saw_tstamp ? tp.rcv_tsval : 0;
	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) ||
	    sk->net_pinfo.af_inet6.rxopt.bits.rxinfo ||
	    sk->net_pinfo.af_inet6.rxopt.bits.rxhlim) {
		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;
		newsk->net_pinfo.af_inet6.mcast_oif = tcp_v6_iif(skb);
		newsk->net_pinfo.af_inet6.mcast_hops = skb->nh.ipv6h->hop_limit;

		/* Charge newly allocated IPv6 socket. Though it is mapped,
		 * it is IPv6 yet.
		 */
		atomic_inc(&inet6_sock_nr);
		MOD_INC_USE_COUNT;

		/* 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;

	/* Charge newly allocated IPv6 socket */
	atomic_inc(&inet6_sock_nr);
	MOD_INC_USE_COUNT;

	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->protinfo.af_inet.opt = NULL;

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

	/* Clone pktoptions received with SYN */
	np->pktoptions = NULL;
	if (req->af.v6_req.pktopts) {
		np->pktoptions = skb_clone(req->af.v6_req.pktopts, GFP_ATOMIC);
		if (np->pktoptions)
			skb_set_owner_r(np->pktoptions, newsk);
	}
	np->opt = NULL;
	np->mcast_oif = tcp_v6_iif(skb);
	np->mcast_hops = skb->nh.ipv6h->hop_limit;

	/* 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);
	tcp_initialize_rcv_mss(newsk);

	if (newsk->rcvbuf < (3 * (dst->advmss+60+MAX_HEADER+15)))
		newsk->rcvbuf = min ((3 * (dst->advmss+60+MAX_HEADER+15)), sysctl_rmem_max);
	if (newsk->sndbuf < (3 * (newtp->mss_clamp+60+MAX_HEADER+15)))
		newsk->sndbuf = min ((3 * (newtp->mss_clamp+60+MAX_HEADER+15)), sysctl_wmem_max);

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

	bh_lock_sock(newsk);

	__tcp_v6_hash(newsk);
	tcp_inherit_port(sk, newsk);

	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;
		t1->ack_seq = htonl(ntohl(th->seq) + th->syn + th->fin
				    + skb->len - (th->doff<<2));
	}

	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, u32 win, u32 ts)
{
	struct tcphdr *th = skb->h.th, *t1;
	struct sk_buff *buff;
	struct flowi fl;
	int tot_len = sizeof(struct tcphdr);

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

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

	if (ts)
		tot_len += 3*4;

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

	/* Swap the send and the receive. */
	memset(t1, 0, sizeof(*t1));
	t1->dest = th->source;
	t1->source = th->dest;
	t1->doff = tot_len/4;
	t1->seq = htonl(seq);
	t1->ack_seq = htonl(ack);
	t1->ack = 1;
	t1->window = htons(win);
	
	if (ts) {
		u32 *ptr = (u32*)(t1 + 1);
		*ptr++ = __constant_htonl((TCPOPT_NOP << 24) |
					  (TCPOPT_NOP << 16) |
					  (TCPOPT_TIMESTAMP << 8) |
					  TCPOLEN_TIMESTAMP);
		*ptr++ = htonl(tcp_time_stamp);
		*ptr = htonl(ts);
	}

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

	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 void tcp_v6_timewait_ack(struct sock *sk, struct sk_buff *skb)
{
	struct tcp_tw_bucket *tw = (struct tcp_tw_bucket *)sk;

	tcp_v6_send_ack(skb, tw->snd_nxt, tw->rcv_nxt, 0, tw->ts_recent);

	tcp_tw_put(tw);
}

static void tcp_v6_or_send_ack(struct sk_buff *skb, struct open_request *req)
{
	tcp_v6_send_ack(skb, req->snt_isn+1, req->rcv_isn+1, req->rcv_wnd, req->ts_recent);
}

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 (req->rmt_port == rport &&
		    req->class->family == AF_INET6 &&
		    !ipv6_addr_cmp(&req->af.v6_req.rmt_addr, &ip6h->saddr) &&
		    !ipv6_addr_cmp(&req->af.v6_req.loc_addr, &ip6h->daddr) &&
		    (!req->af.v6_req.iif || req->af.v6_req.iif == iif)) {
			if (req->sk) {
				bh_lock_sock(req->sk);
				BUG_TRAP(req->sk->lock.users==0);
				if (req->sk->state == TCP_CLOSE) {
					bh_unlock_sock(req->sk);
					prev = req;
					continue;
				}
			}
			*prevp = prev;
			return req;
		}
		prev = req; 
	}
	return NULL; 
}


static struct sock *tcp_v6_hnd_req(struct sock *sk,struct sk_buff *skb)
{
	struct open_request *req, *prev;
	struct tcphdr *th = skb->h.th;
	struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);

	/* Find possible connection requests. */
	req = tcp_v6_search_req(tp, skb->nh.ipv6h, th, tcp_v6_iif(skb), &prev);
	if (req)
		return tcp_check_req(sk, skb, req, prev);

#if 0 /*def CONFIG_SYN_COOKIES*/
	if (!th->rst && (th->syn || th->ack))
		sk = cookie_v6_check(sk, skb, &(IPCB(skb)->opt));
#endif
	return sk;
}


static int tcp_v6_csum_verify(struct sk_buff *skb)
{
	switch (skb->ip_summed) {
	case CHECKSUM_NONE:
		skb->csum = csum_partial((char *)skb->h.th, skb->len, 0);
	case CHECKSUM_HW:
		if (tcp_v6_check(skb->h.th,skb->len,&skb->nh.ipv6h->saddr,
				 &skb->nh.ipv6h->daddr,skb->csum)) {
			printk(KERN_DEBUG "tcp v6 csum failed\n");
			return 1;
		}
		skb->ip_summed = CHECKSUM_UNNECESSARY;
	default:
		/* CHECKSUM_UNNECESSARY */
	};
	return 0;
}

/* The socket must have it's spinlock held when we get
 * here.
 *
 * We have a potential double-lock case here, so even when
 * doing backlog processing we use the BH locking scheme.
 * This is because we cannot sleep with the original spinlock
 * held.
 */
static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
{
#ifdef CONFIG_FILTER
	struct sk_filter *filter;
#endif
	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.
	 */

  	ipv6_statistics.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 */
		/* Ready to move deeper ... */
		if (tcp_v6_csum_verify(skb))
			goto csum_err;
		if (tcp_rcv_established(sk, skb, skb->h.th, skb->len))
			goto reset;
		if (users)
			goto ipv6_pktoptions;
		return 0;
	}

	if (tcp_v6_csum_verify(skb))
		goto csum_err;

	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(nsk != sk) {
			int ret;
			int state = nsk->state;

			skb_orphan(skb);
			BUG_TRAP(nsk->lock.users == 0);
			skb_set_owner_r(skb, nsk);
			ret = tcp_rcv_state_process(nsk, skb, skb->h.th, skb->len);

			/* Wakeup parent, send SIGIO */
			if (state == TCP_SYN_RECV && nsk->state != state)
				sk->data_ready(sk, 0);
			bh_unlock_sock(nsk);

			if (ret)
				goto reset;
			if (users)
				kfree_skb(skb);
			return 0;
		}
	}

	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;
csum_err:
	tcp_statistics.TcpInErrs++;
	goto discard;


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 (sk->net_pinfo.af_inet6.rxopt.bits.rxinfo)
			sk->net_pinfo.af_inet6.mcast_oif = tcp_v6_iif(skb);
		if (sk->net_pinfo.af_inet6.rxopt.bits.rxhlim)
			sk->net_pinfo.af_inet6.mcast_hops = skb->nh.ipv6h->hop_limit;
		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;
	int ret;

	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++;

	if (len < sizeof(struct tcphdr))
		goto bad_packet;

	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);
	TCP_SKB_CB(skb)->when = 0;
	skb->used = 0;

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

	if (!sk)
		goto no_tcp_socket;

process:
	if(!ipsec_sk_policy(sk,skb))
		goto discard_and_relse;
	if(sk->state == TCP_TIME_WAIT)
		goto do_time_wait;

	bh_lock_sock(sk);
	ret = 0;
	if (!sk->lock.users)
		ret = tcp_v6_do_rcv(sk, skb);
	else
		sk_add_backlog(sk, skb);
	bh_unlock_sock(sk);

	sock_put(sk);
	return ret;

no_tcp_socket:
	if (tcp_v6_csum_verify(skb)) {
bad_packet:
		tcp_statistics.TcpInErrs++;
	} else {
		tcp_v6_send_reset(skb);
	}

discard_it:

	/*
	 *	Discard frame
	 */

	kfree_skb(skb);
	return 0;

discard_and_relse:
	sock_put(sk);
	goto discard_it;

do_time_wait:
	if (tcp_v6_csum_verify(skb)) {
		tcp_statistics.TcpInErrs++;
		sock_put(sk);
		goto discard_it;
	}

	switch(tcp_timewait_state_process((struct tcp_tw_bucket *)sk,
					  skb, th, skb->len)) {
	case TCP_TW_SYN:
	{
		struct sock *sk2;

		sk2 = tcp_v6_lookup_listener(&skb->nh.ipv6h->daddr, ntohs(th->dest), tcp_v6_iif(skb));
		if (sk2 != NULL) {
			tcp_tw_deschedule((struct tcp_tw_bucket *)sk);
			tcp_timewait_kill((struct tcp_tw_bucket *)sk);
			tcp_tw_put((struct tcp_tw_bucket *)sk);
			sk = sk2;
			goto process;
		}
		/* Fall through to ACK */
	}
	case TCP_TW_ACK:
		tcp_v6_timewait_ack(sk, skb);
		break;
	case TCP_TW_RST:
		goto no_tcp_socket;
	case TCP_TW_SUCCESS:
	}
	goto discard_it;
}

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

	dst = sk_dst_check(sk, 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) {
			err = dst->error;
			dst_release(dst);
			return err;
		}

		ip6_dst_store(sk, dst, NULL);
		return 0;
	}

	err = dst->error;
	dst_release(dst);
	return err;
}

static int 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;

	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;
	}

	dst = sk_dst_check(sk, np->dst_cookie);

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

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

		dst_clone(dst);
		ip6_dst_store(sk, dst, NULL);
	}

	skb->dst = dst;

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

	return 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;
}

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_hash_connecting,
	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_v4_hash_connecting,
	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;
	tp->mdev = TCP_TIMEOUT_INIT;

	/* 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;
	tp->snd_cwnd_clamp = ~0;
	tp->mss_cache = 536;

	sk->state = TCP_CLOSE;
	sk->max_ack_backlog = SOMAXCONN;

	/* 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);

	/*
	 *	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);
}

/* Proc filesystem TCPv6 sock list dumping. */
static void get_openreq6(struct sock *sk, struct open_request *req, char *tmpbuf, int i)
{
	struct in6_addr *dest, *src;

	src = &req->af.v6_req.loc_addr;
	dest = &req->af.v6_req.rmt_addr;
	sprintf(tmpbuf,
		"%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
		"%02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %p",
		i,
		src->s6_addr32[0], src->s6_addr32[1],
		src->s6_addr32[2], src->s6_addr32[3],
		ntohs(sk->sport),
		dest->s6_addr32[0], dest->s6_addr32[1],
		dest->s6_addr32[2], dest->s6_addr32[3],
		ntohs(req->rmt_port),
		TCP_SYN_RECV,
		0,0, /* could print option size, but that is af dependent. */
		1,   /* timers active (only the expire timer) */  
		(unsigned long)(req->expires - jiffies), 
		req->retrans,
		sk->socket ? sk->socket->inode->i_uid : 0,
		0,  /* non standard timer */  
		0, /* open_requests have no inode */
		0, req);
}

static void get_tcp6_sock(struct sock *sp, char *tmpbuf, int i)
{
	struct in6_addr *dest, *src;
	__u16 destp, srcp;
	int timer_active, timer_active1, timer_active2;
	unsigned long timer_expires;
	struct tcp_opt *tp = &sp->tp_pinfo.af_tcp;

	dest  = &sp->net_pinfo.af_inet6.daddr;
	src   = &sp->net_pinfo.af_inet6.rcv_saddr;
	destp = ntohs(sp->dport);
	srcp  = ntohs(sp->sport);
	timer_active1 = tp->retransmit_timer.prev != NULL;
	timer_active2 = sp->timer.prev != NULL;
	timer_active	= 0;
	timer_expires	= (unsigned) -1;
	if (timer_active1 && tp->retransmit_timer.expires < timer_expires) {
		timer_active	= 1;
		timer_expires	= tp->retransmit_timer.expires;
	}
	if (timer_active2 && sp->timer.expires < timer_expires) {
		timer_active	= 2;
		timer_expires	= sp->timer.expires;
	}
	if(timer_active == 0)
		timer_expires = jiffies;

	sprintf(tmpbuf,
		"%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
		"%02X %08X:%08X %02X:%08lX %08X %5d %8d %ld %d %p",
		i,
		src->s6_addr32[0], src->s6_addr32[1],
		src->s6_addr32[2], src->s6_addr32[3], srcp,
		dest->s6_addr32[0], dest->s6_addr32[1],
		dest->s6_addr32[2], dest->s6_addr32[3], destp,
		sp->state, 
		tp->write_seq-tp->snd_una, tp->rcv_nxt-tp->copied_seq,
		timer_active, timer_expires-jiffies,
		tp->retransmits,
		sp->socket ? sp->socket->inode->i_uid : 0,
		0,
		sp->socket ? sp->socket->inode->i_ino : 0,
		atomic_read(&sp->refcnt), sp);
}

static void get_timewait6_sock(struct tcp_tw_bucket *tw, char *tmpbuf, int i)
{
	struct in6_addr *dest, *src;
	__u16 destp, srcp;
	int slot_dist;

	dest  = &tw->v6_daddr;
	src   = &tw->v6_rcv_saddr;
	destp = ntohs(tw->dport);
	srcp  = ntohs(tw->sport);

	slot_dist = tw->death_slot;
	if(slot_dist > tcp_tw_death_row_slot)
		slot_dist = (TCP_TWKILL_SLOTS - slot_dist) + tcp_tw_death_row_slot;
	else
		slot_dist = tcp_tw_death_row_slot - slot_dist;

	sprintf(tmpbuf,
		"%4d: %08X%08X%08X%08X:%04X %08X%08X%08X%08X:%04X "
		"%02X %08X:%08X %02X:%08X %08X %5d %8d %d %d %p",
		i,
		src->s6_addr32[0], src->s6_addr32[1],
		src->s6_addr32[2], src->s6_addr32[3], srcp,
		dest->s6_addr32[0], dest->s6_addr32[1],
		dest->s6_addr32[2], dest->s6_addr32[3], destp,
		TCP_TIME_WAIT, 0, 0,
		3, slot_dist * TCP_TWKILL_PERIOD, 0, 0, 0, 0,
		atomic_read(&tw->refcnt), tw);
}

#define LINE_LEN 190
#define LINE_FMT "%-190s\n"

int tcp6_get_info(char *buffer, char **start, off_t offset, int length, int dummy)
{
	int len = 0, num = 0, i;
	off_t begin, pos = 0;
	char tmpbuf[LINE_LEN+2];

	if(offset < LINE_LEN+1)
		len += sprintf(buffer, LINE_FMT,
			       "  sl  "						/* 6 */
			       "local_address                         "		/* 38 */
			       "remote_address                        "		/* 38 */
			       "st tx_queue rx_queue tr tm->when retrnsmt"	/* 41 */
			       "   uid  timeout inode");			/* 21 */
										/*----*/
										/*144 */

	pos = LINE_LEN+1;

	/* First, walk listening socket table. */
	tcp_listen_lock();
	for(i = 0; i < TCP_LHTABLE_SIZE; i++) {
		struct sock *sk = tcp_listening_hash[i];

		for (sk = tcp_listening_hash[i]; sk; sk = sk->next, num++) {
			struct open_request *req;
			struct tcp_opt *tp = &(sk->tp_pinfo.af_tcp);

			if (sk->family != PF_INET6)
				continue;
			pos += LINE_LEN+1;
			if (pos >= offset) {
				get_tcp6_sock(sk, tmpbuf, num);
				len += sprintf(buffer+len, LINE_FMT, tmpbuf);
				if (len >= length) {
					tcp_listen_unlock();
					goto out_no_bh;
				}
			}

			lock_sock(sk);
			for (req = tp->syn_wait_queue; req; req = req->dl_next, num++) {
				if (req->sk)
					continue;
				if (req->class->family != PF_INET6)
					continue;
				pos += LINE_LEN+1;
				if (pos < offset)
					continue;
				get_openreq6(sk, req, tmpbuf, num);
				len += sprintf(buffer+len, LINE_FMT, tmpbuf);
				if(len >= length) { 
					release_sock(sk);
					tcp_listen_unlock();
					goto out_no_bh;
				}
			}
			release_sock(sk);
		}
	}
	tcp_listen_unlock();

	local_bh_disable();

	/* Next, walk established hash chain. */
	for (i = 0; i < tcp_ehash_size; i++) {
		struct tcp_ehash_bucket *head = &tcp_ehash[i];
		struct sock *sk;
		struct tcp_tw_bucket *tw;

		read_lock(&head->lock);
		for(sk = head->chain; sk; sk = sk->next, num++) {
			if (sk->family != PF_INET6)
				continue;
			pos += LINE_LEN+1;
			if (pos < offset)
				continue;
			get_tcp6_sock(sk, tmpbuf, num);
			len += sprintf(buffer+len, LINE_FMT, tmpbuf);
			if(len >= length) {
				read_unlock(&head->lock);
				goto out;
			}
		}
		for (tw = (struct tcp_tw_bucket *)tcp_ehash[i+tcp_ehash_size].chain;
		     tw != NULL;
		     tw = (struct tcp_tw_bucket *)tw->next, num++) {
			if (tw->family != PF_INET6)
				continue;
			pos += LINE_LEN+1;
			if (pos < offset)
				continue;
			get_timewait6_sock(tw, tmpbuf, num);
			len += sprintf(buffer+len, LINE_FMT, tmpbuf);
			if(len >= length) {
				read_unlock(&head->lock);
				goto out;
			}
		}
		read_unlock(&head->lock);
	}

out:
	local_bh_enable();
out_no_bh:

	begin = len - (pos - offset);
	*start = buffer + begin;
	len -= begin;
	if(len > length)
		len = length;
	if (len < 0)
		len = 0; 
	return len;
}

struct proto tcpv6_prot = {
	tcp_close,			/* close */
	tcp_v6_connect,			/* connect */
	tcp_disconnect,			/* disconnect */
	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_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			*/
};

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