/* (C) 1999-2001 Paul `Rusty' Russell
   * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
   *
   * This program is free software; you can redistribute it and/or modify
   * it under the terms of the GNU General Public License version 2 as
   * published by the Free Software Foundation.

   */

  #include <linux/types.h>

  #include <linux/timer.h>

  #include <linux/module.h>
  #include <linux/in.h>
  #include <linux/tcp.h>
  #include <linux/spinlock.h>
  #include <linux/skbuff.h>
  #include <linux/ipv6.h>
  #include <net/ip6_checksum.h>

  #include <asm/unaligned.h>

  
  #include <net/tcp.h>
  
  #include <linux/netfilter.h>
  #include <linux/netfilter_ipv4.h>
  #include <linux/netfilter_ipv6.h>
  #include <net/netfilter/nf_conntrack.h>

  #include <net/netfilter/nf_conntrack_l4proto.h>

  #include <net/netfilter/nf_conntrack_ecache.h>

  #include <net/netfilter/nf_log.h>

  #include <net/netfilter/ipv4/nf_conntrack_ipv4.h>
  #include <net/netfilter/ipv6/nf_conntrack_ipv6.h>

  /* "Be conservative in what you do,
      be liberal in what you accept from others."

      If it's non-zero, we mark only out of window RST segments as INVALID. */

  static int nf_ct_tcp_be_liberal __read_mostly = 0;

  /* If it is set to zero, we disable picking up already established

     connections. */

  static int nf_ct_tcp_loose __read_mostly = 1;

  /* Max number of the retransmitted packets without receiving an (acceptable)
     ACK from the destination. If this number is reached, a shorter timer

     will be started. */

  static int nf_ct_tcp_max_retrans __read_mostly = 3;

  
    /* FIXME: Examine ipfilter's timeouts and conntrack transitions more
       closely.  They're more complex. --RR */

  static const char *const tcp_conntrack_names[] = {

  	"NONE",
  	"SYN_SENT",
  	"SYN_RECV",
  	"ESTABLISHED",
  	"FIN_WAIT",
  	"CLOSE_WAIT",
  	"LAST_ACK",
  	"TIME_WAIT",
  	"CLOSE",

  	"SYN_SENT2",

  };

  #define SECS * HZ
  #define MINS * 60 SECS
  #define HOURS * 60 MINS
  #define DAYS * 24 HOURS

  /* RFC1122 says the R2 limit should be at least 100 seconds.

     Linux uses 15 packets as limit, which corresponds

     to ~13-30min depending on RTO. */

  static unsigned int nf_ct_tcp_timeout_max_retrans __read_mostly    =   5 MINS;
  static unsigned int nf_ct_tcp_timeout_unacknowledged __read_mostly =   5 MINS;

  static unsigned int tcp_timeouts[TCP_CONNTRACK_MAX] __read_mostly = {
  	[TCP_CONNTRACK_SYN_SENT]	= 2 MINS,
  	[TCP_CONNTRACK_SYN_RECV]	= 60 SECS,
  	[TCP_CONNTRACK_ESTABLISHED]	= 5 DAYS,
  	[TCP_CONNTRACK_FIN_WAIT]	= 2 MINS,
  	[TCP_CONNTRACK_CLOSE_WAIT]	= 60 SECS,
  	[TCP_CONNTRACK_LAST_ACK]	= 30 SECS,
  	[TCP_CONNTRACK_TIME_WAIT]	= 2 MINS,
  	[TCP_CONNTRACK_CLOSE]		= 10 SECS,

  	[TCP_CONNTRACK_SYN_SENT2]	= 2 MINS,

  };

  #define sNO TCP_CONNTRACK_NONE
  #define sSS TCP_CONNTRACK_SYN_SENT
  #define sSR TCP_CONNTRACK_SYN_RECV
  #define sES TCP_CONNTRACK_ESTABLISHED
  #define sFW TCP_CONNTRACK_FIN_WAIT
  #define sCW TCP_CONNTRACK_CLOSE_WAIT
  #define sLA TCP_CONNTRACK_LAST_ACK
  #define sTW TCP_CONNTRACK_TIME_WAIT
  #define sCL TCP_CONNTRACK_CLOSE

  #define sS2 TCP_CONNTRACK_SYN_SENT2

  #define sIV TCP_CONNTRACK_MAX
  #define sIG TCP_CONNTRACK_IGNORE
  
  /* What TCP flags are set from RST/SYN/FIN/ACK. */
  enum tcp_bit_set {
  	TCP_SYN_SET,
  	TCP_SYNACK_SET,
  	TCP_FIN_SET,
  	TCP_ACK_SET,
  	TCP_RST_SET,
  	TCP_NONE_SET,
  };

  /*
   * The TCP state transition table needs a few words...
   *
   * We are the man in the middle. All the packets go through us
   * but might get lost in transit to the destination.

   * It is assumed that the destinations can't receive segments

   * we haven't seen.
   *
   * The checked segment is in window, but our windows are *not*
   * equivalent with the ones of the sender/receiver. We always
   * try to guess the state of the current sender.
   *
   * The meaning of the states are:
   *
   * NONE:	initial state

   * SYN_SENT:	SYN-only packet seen

   * SYN_SENT2:	SYN-only packet seen from reply dir, simultaneous open

   * SYN_RECV:	SYN-ACK packet seen
   * ESTABLISHED:	ACK packet seen
   * FIN_WAIT:	FIN packet seen

   * CLOSE_WAIT:	ACK seen (after FIN)

   * LAST_ACK:	FIN seen (after FIN)
   * TIME_WAIT:	last ACK seen

   * CLOSE:	closed connection (RST)

   *

   * Packets marked as IGNORED (sIG):

   *	if they may be either invalid or valid
   *	and the receiver may send back a connection

   *	closing RST or a SYN/ACK.
   *
   * Packets marked as INVALID (sIV):

   *	if we regard them as truly invalid packets

   */

  static const u8 tcp_conntracks[2][6][TCP_CONNTRACK_MAX] = {

  	{
  /* ORIGINAL */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/
  /*syn*/	   { sSS, sSS, sIG, sIG, sIG, sIG, sIG, sSS, sSS, sS2 },

  /*
   *	sNO -> sSS	Initialize a new connection
   *	sSS -> sSS	Retransmitted SYN

   *	sS2 -> sS2	Late retransmitted SYN
   *	sSR -> sIG

   *	sES -> sIG	Error: SYNs in window outside the SYN_SENT state

   *			are errors. Receiver will reply with RST

   *			and close the connection.
   *			Or we are not in sync and hold a dead connection.
   *	sFW -> sIG
   *	sCW -> sIG
   *	sLA -> sIG
   *	sTW -> sSS	Reopened connection (RFC 1122).
   *	sCL -> sSS
   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/
  /*synack*/ { sIV, sIV, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR },

  /*

   *	sNO -> sIV	Too late and no reason to do anything
   *	sSS -> sIV	Client can't send SYN and then SYN/ACK
   *	sS2 -> sSR	SYN/ACK sent to SYN2 in simultaneous open
   *	sSR -> sIG
   *	sES -> sIG	Error: SYNs in window outside the SYN_SENT state
   *			are errors. Receiver will reply with RST
   *			and close the connection.
   *			Or we are not in sync and hold a dead connection.
   *	sFW -> sIG
   *	sCW -> sIG
   *	sLA -> sIG
   *	sTW -> sIG
   *	sCL -> sIG

   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/

  /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
  /*
   *	sNO -> sIV	Too late and no reason to do anything...
   *	sSS -> sIV	Client migth not send FIN in this state:
   *			we enforce waiting for a SYN/ACK reply first.

   *	sS2 -> sIV

   *	sSR -> sFW	Close started.
   *	sES -> sFW
   *	sFW -> sLA	FIN seen in both directions, waiting for

   *			the last ACK.

   *			Migth be a retransmitted FIN as well...
   *	sCW -> sLA
   *	sLA -> sLA	Retransmitted FIN. Remain in the same state.
   *	sTW -> sTW
   *	sCL -> sCL
   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/

  /*ack*/	   { sES, sIV, sES, sES, sCW, sCW, sTW, sTW, sCL, sIV },
  /*
   *	sNO -> sES	Assumed.
   *	sSS -> sIV	ACK is invalid: we haven't seen a SYN/ACK yet.

   *	sS2 -> sIV

   *	sSR -> sES	Established state is reached.
   *	sES -> sES	:-)
   *	sFW -> sCW	Normal close request answered by ACK.
   *	sCW -> sCW
   *	sLA -> sTW	Last ACK detected.
   *	sTW -> sTW	Retransmitted last ACK. Remain in the same state.
   *	sCL -> sCL
   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/
  /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },

  /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }
  	},
  	{
  /* REPLY */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/
  /*syn*/	   { sIV, sS2, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sS2 },

  /*
   *	sNO -> sIV	Never reached.

   *	sSS -> sS2	Simultaneous open
   *	sS2 -> sS2	Retransmitted simultaneous SYN
   *	sSR -> sIV	Invalid SYN packets sent by the server
   *	sES -> sIV

   *	sFW -> sIV
   *	sCW -> sIV
   *	sLA -> sIV
   *	sTW -> sIV	Reopened connection, but server may not do it.
   *	sCL -> sIV
   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/

  /*synack*/ { sIV, sSR, sIG, sIG, sIG, sIG, sIG, sIG, sIG, sSR },

  /*
   *	sSS -> sSR	Standard open.

   *	sS2 -> sSR	Simultaneous open

   *	sSR -> sIG	Retransmitted SYN/ACK, ignore it.

   *	sES -> sIG	Late retransmitted SYN/ACK?
   *	sFW -> sIG	Might be SYN/ACK answering ignored SYN
   *	sCW -> sIG
   *	sLA -> sIG
   *	sTW -> sIG
   *	sCL -> sIG
   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/

  /*fin*/    { sIV, sIV, sFW, sFW, sLA, sLA, sLA, sTW, sCL, sIV },
  /*
   *	sSS -> sIV	Server might not send FIN in this state.

   *	sS2 -> sIV

   *	sSR -> sFW	Close started.
   *	sES -> sFW
   *	sFW -> sLA	FIN seen in both directions.
   *	sCW -> sLA
   *	sLA -> sLA	Retransmitted FIN.
   *	sTW -> sTW
   *	sCL -> sCL
   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/
  /*ack*/	   { sIV, sIG, sSR, sES, sCW, sCW, sTW, sTW, sCL, sIG },

  /*

   *	sSS -> sIG	Might be a half-open connection.

   *	sS2 -> sIG

   *	sSR -> sSR	Might answer late resent SYN.
   *	sES -> sES	:-)
   *	sFW -> sCW	Normal close request answered by ACK.
   *	sCW -> sCW
   *	sLA -> sTW	Last ACK detected.
   *	sTW -> sTW	Retransmitted last ACK.
   *	sCL -> sCL
   */

  /* 	     sNO, sSS, sSR, sES, sFW, sCW, sLA, sTW, sCL, sS2	*/
  /*rst*/    { sIV, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL, sCL },

  /*none*/   { sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV, sIV }

  	}

  };

  static bool tcp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
  			     struct nf_conntrack_tuple *tuple)

  {

  	const struct tcphdr *hp;
  	struct tcphdr _hdr;

  
  	/* Actually only need first 8 bytes. */
  	hp = skb_header_pointer(skb, dataoff, 8, &_hdr);
  	if (hp == NULL)

  		return false;

  
  	tuple->src.u.tcp.port = hp->source;
  	tuple->dst.u.tcp.port = hp->dest;

  	return true;

  }

  static bool tcp_invert_tuple(struct nf_conntrack_tuple *tuple,
  			     const struct nf_conntrack_tuple *orig)

  {
  	tuple->src.u.tcp.port = orig->dst.u.tcp.port;
  	tuple->dst.u.tcp.port = orig->src.u.tcp.port;

  	return true;

  }
  
  /* Print out the per-protocol part of the tuple. */
  static int tcp_print_tuple(struct seq_file *s,
  			   const struct nf_conntrack_tuple *tuple)
  {
  	return seq_printf(s, "sport=%hu dport=%hu ",
  			  ntohs(tuple->src.u.tcp.port),
  			  ntohs(tuple->dst.u.tcp.port));
  }
  
  /* Print out the private part of the conntrack. */

  static int tcp_print_conntrack(struct seq_file *s, struct nf_conn *ct)

  {
  	enum tcp_conntrack state;

  	spin_lock_bh(&ct->lock);

  	state = ct->proto.tcp.state;

  	spin_unlock_bh(&ct->lock);

  
  	return seq_printf(s, "%s ", tcp_conntrack_names[state]);
  }
  
  static unsigned int get_conntrack_index(const struct tcphdr *tcph)
  {
  	if (tcph->rst) return TCP_RST_SET;
  	else if (tcph->syn) return (tcph->ack ? TCP_SYNACK_SET : TCP_SYN_SET);
  	else if (tcph->fin) return TCP_FIN_SET;
  	else if (tcph->ack) return TCP_ACK_SET;
  	else return TCP_NONE_SET;
  }
  
  /* TCP connection tracking based on 'Real Stateful TCP Packet Filtering
     in IP Filter' by Guido van Rooij.

     http://www.sane.nl/events/sane2000/papers.html
     http://www.darkart.com/mirrors/www.obfuscation.org/ipf/

     The boundaries and the conditions are changed according to RFC793:
     the packet must intersect the window (i.e. segments may be
     after the right or before the left edge) and thus receivers may ACK
     segments after the right edge of the window.

  	td_maxend = max(sack + max(win,1)) seen in reply packets

  	td_maxwin = max(max(win, 1)) + (sack - ack) seen in sent packets
  	td_maxwin += seq + len - sender.td_maxend
  			if seq + len > sender.td_maxend
  	td_end    = max(seq + len) seen in sent packets

     I.   Upper bound for valid data:	seq <= sender.td_maxend
     II.  Lower bound for valid data:	seq + len >= sender.td_end - receiver.td_maxwin

     III.	Upper bound for valid (s)ack:   sack <= receiver.td_end
     IV.	Lower bound for valid (s)ack:	sack >= receiver.td_end - MAXACKWINDOW

     where sack is the highest right edge of sack block found in the packet
     or ack in the case of packet without SACK option.

     The upper bound limit for a valid (s)ack is not ignored -

     we doesn't have to deal with fragments.

  */
  
  static inline __u32 segment_seq_plus_len(__u32 seq,
  					 size_t len,
  					 unsigned int dataoff,

  					 const struct tcphdr *tcph)

  {
  	/* XXX Should I use payload length field in IP/IPv6 header ?
  	 * - YK */
  	return (seq + len - dataoff - tcph->doff*4
  		+ (tcph->syn ? 1 : 0) + (tcph->fin ? 1 : 0));
  }

  /* Fixme: what about big packets? */
  #define MAXACKWINCONST			66000
  #define MAXACKWINDOW(sender)						\
  	((sender)->td_maxwin > MAXACKWINCONST ? (sender)->td_maxwin	\
  					      : MAXACKWINCONST)

  /*
   * Simplified tcp_parse_options routine from tcp_input.c
   */
  static void tcp_options(const struct sk_buff *skb,
  			unsigned int dataoff,

  			const struct tcphdr *tcph,

  			struct ip_ct_tcp_state *state)
  {
  	unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];

  	const unsigned char *ptr;

  	int length = (tcph->doff*4) - sizeof(struct tcphdr);
  
  	if (!length)
  		return;
  
  	ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
  				 length, buff);
  	BUG_ON(ptr == NULL);

  	state->td_scale =

  	state->flags = 0;
  
  	while (length > 0) {
  		int opcode=*ptr++;
  		int opsize;
  
  		switch (opcode) {
  		case TCPOPT_EOL:
  			return;
  		case TCPOPT_NOP:	/* Ref: RFC 793 section 3.1 */
  			length--;
  			continue;
  		default:
  			opsize=*ptr++;
  			if (opsize < 2) /* "silly options" */
  				return;
  			if (opsize > length)

  				return;	/* don't parse partial options */

  			if (opcode == TCPOPT_SACK_PERM

  			    && opsize == TCPOLEN_SACK_PERM)
  				state->flags |= IP_CT_TCP_FLAG_SACK_PERM;
  			else if (opcode == TCPOPT_WINDOW
  				 && opsize == TCPOLEN_WINDOW) {
  				state->td_scale = *(u_int8_t *)ptr;
  
  				if (state->td_scale > 14) {
  					/* See RFC1323 */
  					state->td_scale = 14;
  				}
  				state->flags |=
  					IP_CT_TCP_FLAG_WINDOW_SCALE;
  			}
  			ptr += opsize - 2;
  			length -= opsize;
  		}
  	}
  }
  
  static void tcp_sack(const struct sk_buff *skb, unsigned int dataoff,

                       const struct tcphdr *tcph, __u32 *sack)

  {

  	unsigned char buff[(15 * 4) - sizeof(struct tcphdr)];

  	const unsigned char *ptr;

  	int length = (tcph->doff*4) - sizeof(struct tcphdr);
  	__u32 tmp;
  
  	if (!length)
  		return;
  
  	ptr = skb_header_pointer(skb, dataoff + sizeof(struct tcphdr),
  				 length, buff);
  	BUG_ON(ptr == NULL);
  
  	/* Fast path for timestamp-only option */

  	if (length == TCPOLEN_TSTAMP_ALIGNED

  	    && *(__be32 *)ptr == htonl((TCPOPT_NOP << 24)
  				       | (TCPOPT_NOP << 16)
  				       | (TCPOPT_TIMESTAMP << 8)
  				       | TCPOLEN_TIMESTAMP))

  		return;
  
  	while (length > 0) {
  		int opcode = *ptr++;
  		int opsize, i;
  
  		switch (opcode) {
  		case TCPOPT_EOL:
  			return;
  		case TCPOPT_NOP:	/* Ref: RFC 793 section 3.1 */
  			length--;
  			continue;
  		default:
  			opsize = *ptr++;
  			if (opsize < 2) /* "silly options" */
  				return;
  			if (opsize > length)

  				return;	/* don't parse partial options */

  			if (opcode == TCPOPT_SACK
  			    && opsize >= (TCPOLEN_SACK_BASE
  					  + TCPOLEN_SACK_PERBLOCK)
  			    && !((opsize - TCPOLEN_SACK_BASE)
  				 % TCPOLEN_SACK_PERBLOCK)) {
  				for (i = 0;
  				     i < (opsize - TCPOLEN_SACK_BASE);
  				     i += TCPOLEN_SACK_PERBLOCK) {

  					tmp = get_unaligned_be32((__be32 *)(ptr+i)+1);

  
  					if (after(tmp, *sack))
  						*sack = tmp;
  				}
  				return;
  			}
  			ptr += opsize - 2;
  			length -= opsize;
  		}
  	}
  }

  #ifdef CONFIG_NF_NAT_NEEDED
  static inline s16 nat_offset(const struct nf_conn *ct,
  			     enum ip_conntrack_dir dir,
  			     u32 seq)
  {
  	typeof(nf_ct_nat_offset) get_offset = rcu_dereference(nf_ct_nat_offset);
  
  	return get_offset != NULL ? get_offset(ct, dir, seq) : 0;
  }
  #define NAT_OFFSET(pf, ct, dir, seq) \
  	(pf == NFPROTO_IPV4 ? nat_offset(ct, dir, seq) : 0)
  #else
  #define NAT_OFFSET(pf, ct, dir, seq)	0
  #endif

  static bool tcp_in_window(const struct nf_conn *ct,
  			  struct ip_ct_tcp *state,
  			  enum ip_conntrack_dir dir,
  			  unsigned int index,
  			  const struct sk_buff *skb,
  			  unsigned int dataoff,
  			  const struct tcphdr *tcph,

  			  u_int8_t pf)

  {

  	struct net *net = nf_ct_net(ct);

  	struct ip_ct_tcp_state *sender = &state->seen[dir];
  	struct ip_ct_tcp_state *receiver = &state->seen[!dir];

  	const struct nf_conntrack_tuple *tuple = &ct->tuplehash[dir].tuple;

  	__u32 seq, ack, sack, end, win, swin;

  	s16 receiver_offset;

  	bool res;

  
  	/*
  	 * Get the required data from the packet.
  	 */
  	seq = ntohl(tcph->seq);
  	ack = sack = ntohl(tcph->ack_seq);
  	win = ntohs(tcph->window);
  	end = segment_seq_plus_len(seq, skb->len, dataoff, tcph);
  
  	if (receiver->flags & IP_CT_TCP_FLAG_SACK_PERM)
  		tcp_sack(skb, dataoff, tcph, &sack);

  	/* Take into account NAT sequence number mangling */
  	receiver_offset = NAT_OFFSET(pf, ct, !dir, ack - 1);
  	ack -= receiver_offset;
  	sack -= receiver_offset;

  	pr_debug("tcp_in_window: START
  ");
  	pr_debug("tcp_in_window: ");

  	nf_ct_dump_tuple(tuple);

  	pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u
  ",
  		 seq, ack, receiver_offset, sack, receiver_offset, win, end);

  	pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
  		 "receiver end=%u maxend=%u maxwin=%u scale=%i
  ",
  		 sender->td_end, sender->td_maxend, sender->td_maxwin,
  		 sender->td_scale,
  		 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
  		 receiver->td_scale);

  	if (sender->td_maxwin == 0) {

  		/*
  		 * Initialize sender data.
  		 */

  		if (tcph->syn) {

  			/*

  			 * SYN-ACK in reply to a SYN
  			 * or SYN from reply direction in simultaneous open.

  			 */

  			sender->td_end =

  			sender->td_maxend = end;
  			sender->td_maxwin = (win == 0 ? 1 : win);
  
  			tcp_options(skb, dataoff, tcph, sender);

  			/*

  			 * RFC 1323:
  			 * Both sides must send the Window Scale option
  			 * to enable window scaling in either direction.
  			 */
  			if (!(sender->flags & IP_CT_TCP_FLAG_WINDOW_SCALE
  			      && receiver->flags & IP_CT_TCP_FLAG_WINDOW_SCALE))

  				sender->td_scale =

  				receiver->td_scale = 0;

  			if (!tcph->ack)
  				/* Simultaneous open */
  				return true;

  		} else {
  			/*
  			 * We are in the middle of a connection,
  			 * its history is lost for us.
  			 * Let's try to use the data from the packet.

  			 */

  			sender->td_end = end;

  			win <<= sender->td_scale;

  			sender->td_maxwin = (win == 0 ? 1 : win);
  			sender->td_maxend = end + sender->td_maxwin;

  			/*
  			 * We haven't seen traffic in the other direction yet
  			 * but we have to tweak window tracking to pass III
  			 * and IV until that happens.
  			 */
  			if (receiver->td_maxwin == 0)
  				receiver->td_end = receiver->td_maxend = sack;

  		}
  	} else if (((state->state == TCP_CONNTRACK_SYN_SENT
  		     && dir == IP_CT_DIR_ORIGINAL)
  		   || (state->state == TCP_CONNTRACK_SYN_RECV
  		     && dir == IP_CT_DIR_REPLY))
  		   && after(end, sender->td_end)) {
  		/*
  		 * RFC 793: "if a TCP is reinitialized ... then it need

  		 * not wait at all; it must only be sure to use sequence

  		 * numbers larger than those recently used."
  		 */
  		sender->td_end =
  		sender->td_maxend = end;
  		sender->td_maxwin = (win == 0 ? 1 : win);
  
  		tcp_options(skb, dataoff, tcph, sender);
  	}
  
  	if (!(tcph->ack)) {
  		/*
  		 * If there is no ACK, just pretend it was set and OK.
  		 */
  		ack = sack = receiver->td_end;

  	} else if (((tcp_flag_word(tcph) & (TCP_FLAG_ACK|TCP_FLAG_RST)) ==
  		    (TCP_FLAG_ACK|TCP_FLAG_RST))

  		   && (ack == 0)) {
  		/*
  		 * Broken TCP stacks, that set ACK in RST packets as well
  		 * with zero ack value.
  		 */
  		ack = sack = receiver->td_end;
  	}
  
  	if (seq == end
  	    && (!tcph->rst
  		|| (seq == 0 && state->state == TCP_CONNTRACK_SYN_SENT)))
  		/*
  		 * Packets contains no data: we assume it is valid
  		 * and check the ack value only.
  		 * However RST segments are always validated by their
  		 * SEQ number, except when seq == 0 (reset sent answering
  		 * SYN.
  		 */
  		seq = end = sender->td_end;

  	pr_debug("tcp_in_window: ");

  	nf_ct_dump_tuple(tuple);

  	pr_debug("seq=%u ack=%u+(%d) sack=%u+(%d) win=%u end=%u
  ",
  		 seq, ack, receiver_offset, sack, receiver_offset, win, end);

  	pr_debug("tcp_in_window: sender end=%u maxend=%u maxwin=%u scale=%i "
  		 "receiver end=%u maxend=%u maxwin=%u scale=%i
  ",
  		 sender->td_end, sender->td_maxend, sender->td_maxwin,
  		 sender->td_scale,
  		 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
  		 receiver->td_scale);
  
  	pr_debug("tcp_in_window: I=%i II=%i III=%i IV=%i
  ",
  		 before(seq, sender->td_maxend + 1),
  		 after(end, sender->td_end - receiver->td_maxwin - 1),
  		 before(sack, receiver->td_end + 1),

  		 after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1));

  	if (before(seq, sender->td_maxend + 1) &&
  	    after(end, sender->td_end - receiver->td_maxwin - 1) &&
  	    before(sack, receiver->td_end + 1) &&

  	    after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1)) {

  		/*

  		 * Take into account window scaling (RFC 1323).
  		 */
  		if (!tcph->syn)
  			win <<= sender->td_scale;
  
  		/*
  		 * Update sender data.
  		 */
  		swin = win + (sack - ack);
  		if (sender->td_maxwin < swin)
  			sender->td_maxwin = swin;

  		if (after(end, sender->td_end)) {

  			sender->td_end = end;

  			sender->flags |= IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;
  		}

  		if (tcph->ack) {
  			if (!(sender->flags & IP_CT_TCP_FLAG_MAXACK_SET)) {
  				sender->td_maxack = ack;
  				sender->flags |= IP_CT_TCP_FLAG_MAXACK_SET;
  			} else if (after(ack, sender->td_maxack))
  				sender->td_maxack = ack;
  		}

  		/*
  		 * Update receiver data.
  		 */

  		if (receiver->td_maxwin != 0 && after(end, sender->td_maxend))

  			receiver->td_maxwin += end - sender->td_maxend;
  		if (after(sack + win, receiver->td_maxend - 1)) {
  			receiver->td_maxend = sack + win;
  			if (win == 0)
  				receiver->td_maxend++;
  		}

  		if (ack == receiver->td_end)
  			receiver->flags &= ~IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED;

  		/*

  		 * Check retransmissions.
  		 */
  		if (index == TCP_ACK_SET) {
  			if (state->last_dir == dir
  			    && state->last_seq == seq
  			    && state->last_ack == ack

  			    && state->last_end == end
  			    && state->last_win == win)

  				state->retrans++;
  			else {
  				state->last_dir = dir;
  				state->last_seq = seq;
  				state->last_ack = ack;
  				state->last_end = end;

  				state->last_win = win;

  				state->retrans = 0;
  			}
  		}

  		res = true;

  	} else {

  		res = false;

  		if (sender->flags & IP_CT_TCP_FLAG_BE_LIBERAL ||
  		    nf_ct_tcp_be_liberal)

  			res = true;

  		if (!res && LOG_INVALID(net, IPPROTO_TCP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  			"nf_ct_tcp: %s ",
  			before(seq, sender->td_maxend + 1) ?
  			after(end, sender->td_end - receiver->td_maxwin - 1) ?
  			before(sack, receiver->td_end + 1) ?

  			after(sack, receiver->td_end - MAXACKWINDOW(sender) - 1) ? "BUG"

  			: "ACK is under the lower bound (possible overly delayed ACK)"
  			: "ACK is over the upper bound (ACKed data not seen yet)"
  			: "SEQ is under the lower bound (already ACKed data retransmitted)"
  			: "SEQ is over the upper bound (over the window of the receiver)");

  	}

  	pr_debug("tcp_in_window: res=%u sender end=%u maxend=%u maxwin=%u "

  		 "receiver end=%u maxend=%u maxwin=%u
  ",
  		 res, sender->td_end, sender->td_maxend, sender->td_maxwin,
  		 receiver->td_end, receiver->td_maxend, receiver->td_maxwin);

  
  	return res;
  }

  /* table of valid flag combinations - PUSH, ECE and CWR are always valid */

  static const u8 tcp_valid_flags[(TCPHDR_FIN|TCPHDR_SYN|TCPHDR_RST|TCPHDR_ACK|
  				 TCPHDR_URG) + 1] =

  {

  	[TCPHDR_SYN]				= 1,
  	[TCPHDR_SYN|TCPHDR_URG]			= 1,
  	[TCPHDR_SYN|TCPHDR_ACK]			= 1,
  	[TCPHDR_RST]				= 1,
  	[TCPHDR_RST|TCPHDR_ACK]			= 1,
  	[TCPHDR_FIN|TCPHDR_ACK]			= 1,
  	[TCPHDR_FIN|TCPHDR_ACK|TCPHDR_URG]	= 1,
  	[TCPHDR_ACK]				= 1,
  	[TCPHDR_ACK|TCPHDR_URG]			= 1,

  };
  
  /* Protect conntrack agaist broken packets. Code taken from ipt_unclean.c.  */

  static int tcp_error(struct net *net, struct nf_conn *tmpl,

  		     struct sk_buff *skb,

  		     unsigned int dataoff,
  		     enum ip_conntrack_info *ctinfo,

  		     u_int8_t pf,

  		     unsigned int hooknum)

  {

  	const struct tcphdr *th;
  	struct tcphdr _tcph;

  	unsigned int tcplen = skb->len - dataoff;
  	u_int8_t tcpflags;
  
  	/* Smaller that minimal TCP header? */
  	th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
  	if (th == NULL) {

  		if (LOG_INVALID(net, IPPROTO_TCP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				"nf_ct_tcp: short packet ");
  		return -NF_ACCEPT;

  	}

  	/* Not whole TCP header or malformed packet */
  	if (th->doff*4 < sizeof(struct tcphdr) || tcplen < th->doff*4) {

  		if (LOG_INVALID(net, IPPROTO_TCP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				"nf_ct_tcp: truncated/malformed packet ");
  		return -NF_ACCEPT;
  	}

  	/* Checksum invalid? Ignore.
  	 * We skip checking packets on the outgoing path

  	 * because the checksum is assumed to be correct.

  	 */
  	/* FIXME: Source route IP option packets --RR */

  	if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&

  	    nf_checksum(skb, hooknum, dataoff, IPPROTO_TCP, pf)) {

  		if (LOG_INVALID(net, IPPROTO_TCP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				  "nf_ct_tcp: bad TCP checksum ");
  		return -NF_ACCEPT;
  	}
  
  	/* Check TCP flags. */

  	tcpflags = (tcp_flag_byte(th) & ~(TCPHDR_ECE|TCPHDR_CWR|TCPHDR_PSH));

  	if (!tcp_valid_flags[tcpflags]) {

  		if (LOG_INVALID(net, IPPROTO_TCP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				  "nf_ct_tcp: invalid TCP flag combination ");
  		return -NF_ACCEPT;
  	}
  
  	return NF_ACCEPT;
  }

  /* Returns verdict for packet, or -1 for invalid. */

  static int tcp_packet(struct nf_conn *ct,

  		      const struct sk_buff *skb,
  		      unsigned int dataoff,
  		      enum ip_conntrack_info ctinfo,

  		      u_int8_t pf,

  		      unsigned int hooknum)
  {

  	struct net *net = nf_ct_net(ct);

  	struct nf_conntrack_tuple *tuple;

  	enum tcp_conntrack new_state, old_state;
  	enum ip_conntrack_dir dir;

  	const struct tcphdr *th;
  	struct tcphdr _tcph;

  	unsigned long timeout;
  	unsigned int index;
  
  	th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
  	BUG_ON(th == NULL);

  	spin_lock_bh(&ct->lock);

  	old_state = ct->proto.tcp.state;

  	dir = CTINFO2DIR(ctinfo);
  	index = get_conntrack_index(th);
  	new_state = tcp_conntracks[dir][index][old_state];

  	tuple = &ct->tuplehash[dir].tuple;

  
  	switch (new_state) {

  	case TCP_CONNTRACK_SYN_SENT:
  		if (old_state < TCP_CONNTRACK_TIME_WAIT)
  			break;

  		/* RFC 1122: "When a connection is closed actively,
  		 * it MUST linger in TIME-WAIT state for a time 2xMSL
  		 * (Maximum Segment Lifetime). However, it MAY accept
  		 * a new SYN from the remote TCP to reopen the connection
  		 * directly from TIME-WAIT state, if..."
  		 * We ignore the conditions because we are in the
  		 * TIME-WAIT state anyway.
  		 *
  		 * Handle aborted connections: we and the server
  		 * think there is an existing connection but the client
  		 * aborts it and starts a new one.
  		 */
  		if (((ct->proto.tcp.seen[dir].flags
  		      | ct->proto.tcp.seen[!dir].flags)
  		     & IP_CT_TCP_FLAG_CLOSE_INIT)

  		    || (ct->proto.tcp.last_dir == dir
  		        && ct->proto.tcp.last_index == TCP_RST_SET)) {

  			/* Attempt to reopen a closed/aborted connection.
  			 * Delete this connection and look up again. */

  			spin_unlock_bh(&ct->lock);

  			/* Only repeat if we can actually remove the timer.
  			 * Destruction may already be in progress in process
  			 * context and we must give it a chance to terminate.
  			 */

  			if (nf_ct_kill(ct))

  				return -NF_REPEAT;

  			return NF_DROP;

  		}
  		/* Fall through */

  	case TCP_CONNTRACK_IGNORE:

  		/* Ignored packets:
  		 *

  		 * Our connection entry may be out of sync, so ignore
  		 * packets which may signal the real connection between
  		 * the client and the server.
  		 *

  		 * a) SYN in ORIGINAL
  		 * b) SYN/ACK in REPLY

  		 * c) ACK in reply direction after initial SYN in original.

  		 *
  		 * If the ignored packet is invalid, the receiver will send
  		 * a RST we'll catch below.

  		 */

  		if (index == TCP_SYNACK_SET

  		    && ct->proto.tcp.last_index == TCP_SYN_SET
  		    && ct->proto.tcp.last_dir != dir
  		    && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {

  			/* b) This SYN/ACK acknowledges a SYN that we earlier

  			 * ignored as invalid. This means that the client and
  			 * the server are both in sync, while the firewall is

  			 * not. We get in sync from the previously annotated
  			 * values.

  			 */

  			old_state = TCP_CONNTRACK_SYN_SENT;
  			new_state = TCP_CONNTRACK_SYN_RECV;
  			ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_end =
  				ct->proto.tcp.last_end;
  			ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxend =
  				ct->proto.tcp.last_end;
  			ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_maxwin =
  				ct->proto.tcp.last_win == 0 ?
  					1 : ct->proto.tcp.last_win;
  			ct->proto.tcp.seen[ct->proto.tcp.last_dir].td_scale =
  				ct->proto.tcp.last_wscale;
  			ct->proto.tcp.seen[ct->proto.tcp.last_dir].flags =
  				ct->proto.tcp.last_flags;
  			memset(&ct->proto.tcp.seen[dir], 0,
  			       sizeof(struct ip_ct_tcp_state));
  			break;

  		}

  		ct->proto.tcp.last_index = index;
  		ct->proto.tcp.last_dir = dir;
  		ct->proto.tcp.last_seq = ntohl(th->seq);
  		ct->proto.tcp.last_end =

  		    segment_seq_plus_len(ntohl(th->seq), skb->len, dataoff, th);

  		ct->proto.tcp.last_win = ntohs(th->window);
  
  		/* a) This is a SYN in ORIGINAL. The client and the server
  		 * may be in sync but we are not. In that case, we annotate
  		 * the TCP options and let the packet go through. If it is a
  		 * valid SYN packet, the server will reply with a SYN/ACK, and
  		 * then we'll get in sync. Otherwise, the server ignores it. */
  		if (index == TCP_SYN_SET && dir == IP_CT_DIR_ORIGINAL) {
  			struct ip_ct_tcp_state seen = {};
  
  			ct->proto.tcp.last_flags =
  			ct->proto.tcp.last_wscale = 0;
  			tcp_options(skb, dataoff, th, &seen);
  			if (seen.flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {
  				ct->proto.tcp.last_flags |=
  					IP_CT_TCP_FLAG_WINDOW_SCALE;
  				ct->proto.tcp.last_wscale = seen.td_scale;
  			}
  			if (seen.flags & IP_CT_TCP_FLAG_SACK_PERM) {
  				ct->proto.tcp.last_flags |=
  					IP_CT_TCP_FLAG_SACK_PERM;
  			}
  		}

  		spin_unlock_bh(&ct->lock);

  		if (LOG_INVALID(net, IPPROTO_TCP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,

  				  "nf_ct_tcp: invalid packet ignored ");

  		return NF_ACCEPT;
  	case TCP_CONNTRACK_MAX:
  		/* Invalid packet */

  		pr_debug("nf_ct_tcp: Invalid dir=%i index=%u ostate=%u
  ",
  			 dir, get_conntrack_index(th), old_state);

  		spin_unlock_bh(&ct->lock);

  		if (LOG_INVALID(net, IPPROTO_TCP))

  			nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  				  "nf_ct_tcp: invalid state ");
  		return -NF_ACCEPT;

  	case TCP_CONNTRACK_CLOSE:
  		if (index == TCP_RST_SET

  		    && (ct->proto.tcp.seen[!dir].flags & IP_CT_TCP_FLAG_MAXACK_SET)
  		    && before(ntohl(th->seq), ct->proto.tcp.seen[!dir].td_maxack)) {
  			/* Invalid RST  */

  			spin_unlock_bh(&ct->lock);

  			if (LOG_INVALID(net, IPPROTO_TCP))
  				nf_log_packet(pf, 0, skb, NULL, NULL, NULL,
  					  "nf_ct_tcp: invalid RST ");
  			return -NF_ACCEPT;
  		}
  		if (index == TCP_RST_SET

  		    && ((test_bit(IPS_SEEN_REPLY_BIT, &ct->status)
  			 && ct->proto.tcp.last_index == TCP_SYN_SET)
  			|| (!test_bit(IPS_ASSURED_BIT, &ct->status)
  			    && ct->proto.tcp.last_index == TCP_ACK_SET))
  		    && ntohl(th->ack_seq) == ct->proto.tcp.last_end) {

  			/* RST sent to invalid SYN or ACK we had let through

  			 * at a) and c) above:
  			 *
  			 * a) SYN was in window then
  			 * c) we hold a half-open connection.
  			 *
  			 * Delete our connection entry.

  			 * We skip window checking, because packet might ACK

  			 * segments we ignored. */

  			goto in_window;
  		}

  		/* Just fall through */

  	default:
  		/* Keep compilers happy. */
  		break;
  	}

  	if (!tcp_in_window(ct, &ct->proto.tcp, dir, index,

  			   skb, dataoff, th, pf)) {

  		spin_unlock_bh(&ct->lock);

  		return -NF_ACCEPT;
  	}
       in_window:
  	/* From now on we have got in-window packets */

  	ct->proto.tcp.last_index = index;
  	ct->proto.tcp.last_dir = dir;

  	pr_debug("tcp_conntracks: ");

  	nf_ct_dump_tuple(tuple);

  	pr_debug("syn=%i ack=%i fin=%i rst=%i old=%i new=%i
  ",
  		 (th->syn ? 1 : 0), (th->ack ? 1 : 0),
  		 (th->fin ? 1 : 0), (th->rst ? 1 : 0),
  		 old_state, new_state);

  	ct->proto.tcp.state = new_state;

  	if (old_state != new_state

  	    && new_state == TCP_CONNTRACK_FIN_WAIT)

  		ct->proto.tcp.seen[dir].flags |= IP_CT_TCP_FLAG_CLOSE_INIT;

  
  	if (ct->proto.tcp.retrans >= nf_ct_tcp_max_retrans &&
  	    tcp_timeouts[new_state] > nf_ct_tcp_timeout_max_retrans)
  		timeout = nf_ct_tcp_timeout_max_retrans;
  	else if ((ct->proto.tcp.seen[0].flags | ct->proto.tcp.seen[1].flags) &
  		 IP_CT_TCP_FLAG_DATA_UNACKNOWLEDGED &&
  		 tcp_timeouts[new_state] > nf_ct_tcp_timeout_unacknowledged)
  		timeout = nf_ct_tcp_timeout_unacknowledged;
  	else
  		timeout = tcp_timeouts[new_state];

  	spin_unlock_bh(&ct->lock);

  	if (new_state != old_state)

  		nf_conntrack_event_cache(IPCT_PROTOINFO, ct);

  	if (!test_bit(IPS_SEEN_REPLY_BIT, &ct->status)) {

  		/* If only reply is a RST, we can consider ourselves not to
  		   have an established connection: this is a fairly common
  		   problem case, so we can delete the conntrack
  		   immediately.  --RR */
  		if (th->rst) {

  			nf_ct_kill_acct(ct, ctinfo, skb);

  			return NF_ACCEPT;
  		}

  	} else if (!test_bit(IPS_ASSURED_BIT, &ct->status)

  		   && (old_state == TCP_CONNTRACK_SYN_RECV
  		       || old_state == TCP_CONNTRACK_ESTABLISHED)
  		   && new_state == TCP_CONNTRACK_ESTABLISHED) {

  		/* Set ASSURED if we see see valid ack in ESTABLISHED
  		   after SYN_RECV or a valid answer for a picked up

  		   connection. */

  		set_bit(IPS_ASSURED_BIT, &ct->status);

  		nf_conntrack_event_cache(IPCT_ASSURED, ct);

  	}

  	nf_ct_refresh_acct(ct, ctinfo, skb, timeout);

  
  	return NF_ACCEPT;
  }

  /* Called when a new connection for this protocol found. */

  static bool tcp_new(struct nf_conn *ct, const struct sk_buff *skb,
  		    unsigned int dataoff)

  {
  	enum tcp_conntrack new_state;

  	const struct tcphdr *th;
  	struct tcphdr _tcph;
  	const struct ip_ct_tcp_state *sender = &ct->proto.tcp.seen[0];
  	const struct ip_ct_tcp_state *receiver = &ct->proto.tcp.seen[1];

  
  	th = skb_header_pointer(skb, dataoff, sizeof(_tcph), &_tcph);
  	BUG_ON(th == NULL);
  
  	/* Don't need lock here: this conntrack not in circulation yet */

  	new_state = tcp_conntracks[0][get_conntrack_index(th)][TCP_CONNTRACK_NONE];

  
  	/* Invalid: delete conntrack */
  	if (new_state >= TCP_CONNTRACK_MAX) {

  		pr_debug("nf_ct_tcp: invalid new deleting.
  ");

  		return false;

  	}
  
  	if (new_state == TCP_CONNTRACK_SYN_SENT) {

  		memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));

  		/* SYN packet */

  		ct->proto.tcp.seen[0].td_end =

  			segment_seq_plus_len(ntohl(th->seq), skb->len,
  					     dataoff, th);

  		ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
  		if (ct->proto.tcp.seen[0].td_maxwin == 0)
  			ct->proto.tcp.seen[0].td_maxwin = 1;
  		ct->proto.tcp.seen[0].td_maxend =
  			ct->proto.tcp.seen[0].td_end;
  
  		tcp_options(skb, dataoff, th, &ct->proto.tcp.seen[0]);

  	} else if (nf_ct_tcp_loose == 0) {
  		/* Don't try to pick up connections. */

  		return false;

  	} else {

  		memset(&ct->proto.tcp, 0, sizeof(ct->proto.tcp));

  		/*
  		 * We are in the middle of a connection,
  		 * its history is lost for us.
  		 * Let's try to use the data from the packet.
  		 */

  		ct->proto.tcp.seen[0].td_end =

  			segment_seq_plus_len(ntohl(th->seq), skb->len,
  					     dataoff, th);

  		ct->proto.tcp.seen[0].td_maxwin = ntohs(th->window);
  		if (ct->proto.tcp.seen[0].td_maxwin == 0)
  			ct->proto.tcp.seen[0].td_maxwin = 1;
  		ct->proto.tcp.seen[0].td_maxend =
  			ct->proto.tcp.seen[0].td_end +
  			ct->proto.tcp.seen[0].td_maxwin;

  		/* We assume SACK and liberal window checking to handle
  		 * window scaling */

  		ct->proto.tcp.seen[0].flags =
  		ct->proto.tcp.seen[1].flags = IP_CT_TCP_FLAG_SACK_PERM |
  					      IP_CT_TCP_FLAG_BE_LIBERAL;

  	}

  	/* tcp_packet will set them */

  	ct->proto.tcp.last_index = TCP_NONE_SET;

  	pr_debug("tcp_new: sender end=%u maxend=%u maxwin=%u scale=%i "
  		 "receiver end=%u maxend=%u maxwin=%u scale=%i
  ",
  		 sender->td_end, sender->td_maxend, sender->td_maxwin,
  		 sender->td_scale,
  		 receiver->td_end, receiver->td_maxend, receiver->td_maxwin,
  		 receiver->td_scale);

  	return true;

  }

  #if IS_ENABLED(CONFIG_NF_CT_NETLINK)

  
  #include <linux/netfilter/nfnetlink.h>
  #include <linux/netfilter/nfnetlink_conntrack.h>

  static int tcp_to_nlattr(struct sk_buff *skb, struct nlattr *nla,

  			 struct nf_conn *ct)

  {

  	struct nlattr *nest_parms;

  	struct nf_ct_tcp_flags tmp = {};

  	spin_lock_bh(&ct->lock);

  	nest_parms = nla_nest_start(skb, CTA_PROTOINFO_TCP | NLA_F_NESTED);
  	if (!nest_parms)
  		goto nla_put_failure;

  	NLA_PUT_U8(skb, CTA_PROTOINFO_TCP_STATE, ct->proto.tcp.state);

  	NLA_PUT_U8(skb, CTA_PROTOINFO_TCP_WSCALE_ORIGINAL,
  		   ct->proto.tcp.seen[0].td_scale);

  	NLA_PUT_U8(skb, CTA_PROTOINFO_TCP_WSCALE_REPLY,
  		   ct->proto.tcp.seen[1].td_scale);

  
  	tmp.flags = ct->proto.tcp.seen[0].flags;

  	NLA_PUT(skb, CTA_PROTOINFO_TCP_FLAGS_ORIGINAL,

  		sizeof(struct nf_ct_tcp_flags), &tmp);
  
  	tmp.flags = ct->proto.tcp.seen[1].flags;

  	NLA_PUT(skb, CTA_PROTOINFO_TCP_FLAGS_REPLY,

  		sizeof(struct nf_ct_tcp_flags), &tmp);

  	spin_unlock_bh(&ct->lock);

  	nla_nest_end(skb, nest_parms);

  
  	return 0;

  nla_put_failure:

  	spin_unlock_bh(&ct->lock);

  	return -1;
  }

  static const struct nla_policy tcp_nla_policy[CTA_PROTOINFO_TCP_MAX+1] = {
  	[CTA_PROTOINFO_TCP_STATE]	    = { .type = NLA_U8 },
  	[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] = { .type = NLA_U8 },
  	[CTA_PROTOINFO_TCP_WSCALE_REPLY]    = { .type = NLA_U8 },
  	[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]  = { .len = sizeof(struct nf_ct_tcp_flags) },
  	[CTA_PROTOINFO_TCP_FLAGS_REPLY]	    = { .len =  sizeof(struct nf_ct_tcp_flags) },

  };

  static int nlattr_to_tcp(struct nlattr *cda[], struct nf_conn *ct)

  {

  	struct nlattr *pattr = cda[CTA_PROTOINFO_TCP];

  	struct nlattr *tb[CTA_PROTOINFO_TCP_MAX+1];

  	int err;

  
  	/* updates could not contain anything about the private
  	 * protocol info, in that case skip the parsing */

  	if (!pattr)

  		return 0;

  	err = nla_parse_nested(tb, CTA_PROTOINFO_TCP_MAX, pattr, tcp_nla_policy);

  	if (err < 0)
  		return err;

  	if (tb[CTA_PROTOINFO_TCP_STATE] &&
  	    nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]) >= TCP_CONNTRACK_MAX)

  		return -EINVAL;

  	spin_lock_bh(&ct->lock);

  	if (tb[CTA_PROTOINFO_TCP_STATE])
  		ct->proto.tcp.state = nla_get_u8(tb[CTA_PROTOINFO_TCP_STATE]);

  	if (tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]) {

  		struct nf_ct_tcp_flags *attr =

  			nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_ORIGINAL]);

  		ct->proto.tcp.seen[0].flags &= ~attr->mask;
  		ct->proto.tcp.seen[0].flags |= attr->flags & attr->mask;
  	}

  	if (tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]) {

  		struct nf_ct_tcp_flags *attr =

  			nla_data(tb[CTA_PROTOINFO_TCP_FLAGS_REPLY]);

  		ct->proto.tcp.seen[1].flags &= ~attr->mask;
  		ct->proto.tcp.seen[1].flags |= attr->flags & attr->mask;
  	}

  	if (tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL] &&
  	    tb[CTA_PROTOINFO_TCP_WSCALE_REPLY] &&

  	    ct->proto.tcp.seen[0].flags & IP_CT_TCP_FLAG_WINDOW_SCALE &&
  	    ct->proto.tcp.seen[1].flags & IP_CT_TCP_FLAG_WINDOW_SCALE) {

  		ct->proto.tcp.seen[0].td_scale =
  			nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_ORIGINAL]);
  		ct->proto.tcp.seen[1].td_scale =
  			nla_get_u8(tb[CTA_PROTOINFO_TCP_WSCALE_REPLY]);

  	}

  	spin_unlock_bh(&ct->lock);

  
  	return 0;
  }

  
  static int tcp_nlattr_size(void)
  {
  	return nla_total_size(0)	   /* CTA_PROTOINFO_TCP */
  		+ nla_policy_len(tcp_nla_policy, CTA_PROTOINFO_TCP_MAX + 1);
  }
  
  static int tcp_nlattr_tuple_size(void)
  {
  	return nla_policy_len(nf_ct_port_nla_policy, CTA_PROTO_MAX + 1);
  }

  #endif

  
  #ifdef CONFIG_SYSCTL
  static unsigned int tcp_sysctl_table_users;
  static struct ctl_table_header *tcp_sysctl_header;
  static struct ctl_table tcp_sysctl_table[] = {
  	{

  		.procname	= "nf_conntrack_tcp_timeout_syn_sent",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_SYN_SENT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_syn_recv",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_SYN_RECV],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_established",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_ESTABLISHED],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_fin_wait",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_FIN_WAIT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_close_wait",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_CLOSE_WAIT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_last_ack",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_LAST_ACK],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_time_wait",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_TIME_WAIT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_close",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_CLOSE],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_max_retrans",
  		.data		= &nf_ct_tcp_timeout_max_retrans,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_timeout_unacknowledged",
  		.data		= &nf_ct_tcp_timeout_unacknowledged,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_loose",
  		.data		= &nf_ct_tcp_loose,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec,

  	},
  	{

  		.procname       = "nf_conntrack_tcp_be_liberal",
  		.data           = &nf_ct_tcp_be_liberal,
  		.maxlen         = sizeof(unsigned int),
  		.mode           = 0644,

  		.proc_handler   = proc_dointvec,

  	},
  	{

  		.procname	= "nf_conntrack_tcp_max_retrans",
  		.data		= &nf_ct_tcp_max_retrans,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec,

  	},

  	{ }

  };

  
  #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
  static struct ctl_table tcp_compat_sysctl_table[] = {
  	{

  		.procname	= "ip_conntrack_tcp_timeout_syn_sent",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_SYN_SENT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_syn_sent2",
  		.data		= &tcp_timeouts[TCP_CONNTRACK_SYN_SENT2],
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,
  		.proc_handler	= proc_dointvec_jiffies,
  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_syn_recv",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_SYN_RECV],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_established",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_ESTABLISHED],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_fin_wait",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_FIN_WAIT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_close_wait",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_CLOSE_WAIT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_last_ack",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_LAST_ACK],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_time_wait",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_TIME_WAIT],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_close",

  		.data		= &tcp_timeouts[TCP_CONNTRACK_CLOSE],

  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_timeout_max_retrans",
  		.data		= &nf_ct_tcp_timeout_max_retrans,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec_jiffies,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_loose",
  		.data		= &nf_ct_tcp_loose,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_be_liberal",
  		.data		= &nf_ct_tcp_be_liberal,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec,

  	},
  	{

  		.procname	= "ip_conntrack_tcp_max_retrans",
  		.data		= &nf_ct_tcp_max_retrans,
  		.maxlen		= sizeof(unsigned int),
  		.mode		= 0644,

  		.proc_handler	= proc_dointvec,

  	},

  	{ }

  };
  #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */

  #endif /* CONFIG_SYSCTL */

  struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp4 __read_mostly =

  {
  	.l3proto		= PF_INET,

  	.l4proto 		= IPPROTO_TCP,

  	.name 			= "tcp",
  	.pkt_to_tuple 		= tcp_pkt_to_tuple,
  	.invert_tuple 		= tcp_invert_tuple,
  	.print_tuple 		= tcp_print_tuple,
  	.print_conntrack 	= tcp_print_conntrack,
  	.packet 		= tcp_packet,
  	.new 			= tcp_new,

  	.error			= tcp_error,

  #if IS_ENABLED(CONFIG_NF_CT_NETLINK)

  	.to_nlattr		= tcp_to_nlattr,

  	.nlattr_size		= tcp_nlattr_size,

  	.from_nlattr		= nlattr_to_tcp,
  	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
  	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,

  	.nlattr_tuple_size	= tcp_nlattr_tuple_size,

  	.nla_policy		= nf_ct_port_nla_policy,

  #endif

  #ifdef CONFIG_SYSCTL
  	.ctl_table_users	= &tcp_sysctl_table_users,
  	.ctl_table_header	= &tcp_sysctl_header,
  	.ctl_table		= tcp_sysctl_table,

  #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
  	.ctl_compat_table	= tcp_compat_sysctl_table,
  #endif

  #endif

  };

  EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_tcp4);

  struct nf_conntrack_l4proto nf_conntrack_l4proto_tcp6 __read_mostly =

  {
  	.l3proto		= PF_INET6,

  	.l4proto 		= IPPROTO_TCP,

  	.name 			= "tcp",
  	.pkt_to_tuple 		= tcp_pkt_to_tuple,
  	.invert_tuple 		= tcp_invert_tuple,
  	.print_tuple 		= tcp_print_tuple,
  	.print_conntrack 	= tcp_print_conntrack,
  	.packet 		= tcp_packet,
  	.new 			= tcp_new,

  	.error			= tcp_error,

  #if IS_ENABLED(CONFIG_NF_CT_NETLINK)

  	.to_nlattr		= tcp_to_nlattr,

  	.nlattr_size		= tcp_nlattr_size,

  	.from_nlattr		= nlattr_to_tcp,
  	.tuple_to_nlattr	= nf_ct_port_tuple_to_nlattr,
  	.nlattr_to_tuple	= nf_ct_port_nlattr_to_tuple,

  	.nlattr_tuple_size	= tcp_nlattr_tuple_size,

  	.nla_policy		= nf_ct_port_nla_policy,

  #endif

  #ifdef CONFIG_SYSCTL
  	.ctl_table_users	= &tcp_sysctl_table_users,
  	.ctl_table_header	= &tcp_sysctl_header,
  	.ctl_table		= tcp_sysctl_table,
  #endif

  };

  EXPORT_SYMBOL_GPL(nf_conntrack_l4proto_tcp6);