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/*

 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.

 * All rights reserved.

 *

 * Redistribution and use in source and binary forms, with or without modification,

 * are permitted provided that the following conditions are met:

 *

 * 1. Redistributions of source code must retain the above copyright notice,

 *    this list of conditions and the following disclaimer.

 * 2. Redistributions in binary form must reproduce the above copyright notice,

 *    this list of conditions and the following disclaimer in the documentation

 *    and/or other materials provided with the distribution.

 * 3. The name of the author may not be used to endorse or promote products

 *    derived from this software without specific prior written permission.

 *

 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED

 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF

 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT

 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,

 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT

 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS

 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN

 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING

 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY

 * OF SUCH DAMAGE.

 *

 * This file is part of the lwIP TCP/IP stack.

 *

 * Author: Adam Dunkels <adam@sics.se>

 *

 */

#ifndef __LWIP_TCP_H__

#define __LWIP_TCP_H__

#include "lwip/opt.h"

#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */

#include "lwip/sys.h"

#include "lwip/mem.h"

#include "lwip/pbuf.h"

#include "lwip/ip.h"

#include "lwip/icmp.h"

#include "lwip/err.h"

#ifdef __cplusplus

extern "C" {

#endif

struct tcp_pcb;

/* Functions for interfacing with TCP: */

/* Lower layer interface to TCP: */

#define tcp_init() /* Compatibility define, not init needed. */

void             tcp_tmr     (void);  /* Must be called every

                                         TCP_TMR_INTERVAL

                                         ms. (Typically 250 ms). */

/* Application program's interface: */

struct tcp_pcb * tcp_new     (void);

struct tcp_pcb * tcp_alloc   (u8_t prio);

void             tcp_arg     (struct tcp_pcb *pcb, void *arg);

void             tcp_accept  (struct tcp_pcb *pcb,

                              err_t (* accept)(void *arg, struct tcp_pcb *newpcb,

                 err_t err));

void             tcp_recv    (struct tcp_pcb *pcb,

                              err_t (* recv)(void *arg, struct tcp_pcb *tpcb,

                              struct pbuf *p, err_t err));

void             tcp_sent    (struct tcp_pcb *pcb,

                              err_t (* sent)(void *arg, struct tcp_pcb *tpcb,

                              u16_t len));

void             tcp_poll    (struct tcp_pcb *pcb,

                              err_t (* poll)(void *arg, struct tcp_pcb *tpcb),

                              u8_t interval);

void             tcp_err     (struct tcp_pcb *pcb,

                              void (* err)(void *arg, err_t err));

#define          tcp_mss(pcb)      ((pcb)->mss)

#define          tcp_sndbuf(pcb)   ((pcb)->snd_buf)

#define          tcp_nagle_disable(pcb)  ((pcb)->flags |= TF_NODELAY)

#define          tcp_nagle_enable(pcb) ((pcb)->flags &= ~TF_NODELAY)

#define          tcp_nagle_disabled(pcb) (((pcb)->flags & TF_NODELAY) != 0)

#if TCP_LISTEN_BACKLOG

#define          tcp_accepted(pcb) (((struct tcp_pcb_listen *)(pcb))->accepts_pending--)

#else  /* TCP_LISTEN_BACKLOG */

#define          tcp_accepted(pcb)

#endif /* TCP_LISTEN_BACKLOG */

void             tcp_recved  (struct tcp_pcb *pcb, u16_t len);

err_t            tcp_bind    (struct tcp_pcb *pcb, struct ip_addr *ipaddr,

                              u16_t port);

err_t            tcp_connect (struct tcp_pcb *pcb, struct ip_addr *ipaddr,

                              u16_t port, err_t (* connected)(void *arg,

                              struct tcp_pcb *tpcb,

                              err_t err));

struct tcp_pcb * tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog);

#define          tcp_listen(pcb) tcp_listen_with_backlog(pcb, TCP_DEFAULT_LISTEN_BACKLOG)

void             tcp_abandon (struct tcp_pcb *pcb, int reset);

#define          tcp_abort(pcb) tcp_abandon((pcb), 1)

err_t            tcp_close   (struct tcp_pcb *pcb);

/* Flags for "apiflags" parameter in tcp_write and tcp_enqueue */

#define TCP_WRITE_FLAG_COPY 0x01

#define TCP_WRITE_FLAG_MORE 0x02

err_t            tcp_write   (struct tcp_pcb *pcb, const void *dataptr, u16_t len,

                              u8_t apiflags);

void             tcp_setprio (struct tcp_pcb *pcb, u8_t prio);

#define TCP_PRIO_MIN    1

#define TCP_PRIO_NORMAL 64

#define TCP_PRIO_MAX    127

/* It is also possible to call these two functions at the right

   intervals (instead of calling tcp_tmr()). */

void             tcp_slowtmr (void);

void             tcp_fasttmr (void);

/* Only used by IP to pass a TCP segment to TCP: */

void             tcp_input   (struct pbuf *p, struct netif *inp);

/* Used within the TCP code only: */

err_t            tcp_send_empty_ack(struct tcp_pcb *pcb);

err_t            tcp_output  (struct tcp_pcb *pcb);

void             tcp_rexmit  (struct tcp_pcb *pcb);

void             tcp_rexmit_rto  (struct tcp_pcb *pcb);

void             tcp_rexmit_fast (struct tcp_pcb *pcb);

u32_t            tcp_update_rcv_ann_wnd(struct tcp_pcb *pcb);

/**

 * This is the Nagle algorithm: try to combine user data to send as few TCP

 * segments as possible. Only send if

 * - no previously transmitted data on the connection remains unacknowledged or

 * - the TF_NODELAY flag is set (nagle algorithm turned off for this pcb) or

 * - the only unsent segment is at least pcb->mss bytes long (or there is more

 *   than one unsent segment - with lwIP, this can happen although unsent->len < mss)

 * - or if we are in fast-retransmit (TF_INFR)

 */

#define tcp_do_output_nagle(tpcb) ((((tpcb)->unacked == NULL) || \

                            ((tpcb)->flags & (TF_NODELAY | TF_INFR)) || \

                            (((tpcb)->unsent != NULL) && (((tpcb)->unsent->next != NULL) || \

                              ((tpcb)->unsent->len >= (tpcb)->mss))) \

                            ) ? 1 : 0)

#define tcp_output_nagle(tpcb) (tcp_do_output_nagle(tpcb) ? tcp_output(tpcb) : ERR_OK)

#define TCP_SEQ_LT(a,b)     ((s32_t)((a)-(b)) < 0)

#define TCP_SEQ_LEQ(a,b)    ((s32_t)((a)-(b)) <= 0)

#define TCP_SEQ_GT(a,b)     ((s32_t)((a)-(b)) > 0)

#define TCP_SEQ_GEQ(a,b)    ((s32_t)((a)-(b)) >= 0)

/* is b<=a<=c? */

#if 0 /* see bug #10548 */

#define TCP_SEQ_BETWEEN(a,b,c) ((c)-(b) >= (a)-(b))

#endif

#define TCP_SEQ_BETWEEN(a,b,c) (TCP_SEQ_GEQ(a,b) && TCP_SEQ_LEQ(a,c))

#define TCP_FIN 0x01U

#define TCP_SYN 0x02U

#define TCP_RST 0x04U

#define TCP_PSH 0x08U

#define TCP_ACK 0x10U

#define TCP_URG 0x20U

#define TCP_ECE 0x40U

#define TCP_CWR 0x80U

#define TCP_FLAGS 0x3fU

/* Length of the TCP header, excluding options. */

#define TCP_HLEN 20

#ifndef TCP_TMR_INTERVAL

#define TCP_TMR_INTERVAL       250  /* The TCP timer interval in milliseconds. */

#endif /* TCP_TMR_INTERVAL */

#ifndef TCP_FAST_INTERVAL

#define TCP_FAST_INTERVAL      TCP_TMR_INTERVAL /* the fine grained timeout in milliseconds */

#endif /* TCP_FAST_INTERVAL */

#ifndef TCP_SLOW_INTERVAL

#define TCP_SLOW_INTERVAL      (2*TCP_TMR_INTERVAL)  /* the coarse grained timeout in milliseconds */

#endif /* TCP_SLOW_INTERVAL */

#define TCP_FIN_WAIT_TIMEOUT 20000 /* milliseconds */

#define TCP_SYN_RCVD_TIMEOUT 20000 /* milliseconds */

#define TCP_OOSEQ_TIMEOUT        6U /* x RTO */

#ifndef TCP_MSL

#define TCP_MSL 60000UL /* The maximum segment lifetime in milliseconds */

#endif

/* Keepalive values, compliant with RFC 1122. Don't change this unless you know what you're doing */

#ifndef  TCP_KEEPIDLE_DEFAULT

#define  TCP_KEEPIDLE_DEFAULT     7200000UL /* Default KEEPALIVE timer in milliseconds */

#endif

#ifndef  TCP_KEEPINTVL_DEFAULT

#define  TCP_KEEPINTVL_DEFAULT    75000UL   /* Default Time between KEEPALIVE probes in milliseconds */

#endif

#ifndef  TCP_KEEPCNT_DEFAULT

#define  TCP_KEEPCNT_DEFAULT      9U        /* Default Counter for KEEPALIVE probes */

#endif

#define  TCP_MAXIDLE              TCP_KEEPCNT_DEFAULT * TCP_KEEPINTVL_DEFAULT  /* Maximum KEEPALIVE probe time */

/* Fields are (of course) in network byte order.

 * Some fields are converted to host byte order in tcp_input().

 */

#ifdef PACK_STRUCT_USE_INCLUDES

#  include "arch/bpstruct.h"

#endif

PACK_STRUCT_BEGIN

struct tcp_hdr {

  PACK_STRUCT_FIELD(u16_t src);

  PACK_STRUCT_FIELD(u16_t dest);

  PACK_STRUCT_FIELD(u32_t seqno);

  PACK_STRUCT_FIELD(u32_t ackno);

  PACK_STRUCT_FIELD(u16_t _hdrlen_rsvd_flags);

  PACK_STRUCT_FIELD(u16_t wnd);

  PACK_STRUCT_FIELD(u16_t chksum);

  PACK_STRUCT_FIELD(u16_t urgp);

} PACK_STRUCT_STRUCT;

PACK_STRUCT_END

#ifdef PACK_STRUCT_USE_INCLUDES

#  include "arch/epstruct.h"

#endif

#define TCPH_OFFSET(phdr) (ntohs((phdr)->_hdrlen_rsvd_flags) >> 8)

#define TCPH_HDRLEN(phdr) (ntohs((phdr)->_hdrlen_rsvd_flags) >> 12)

#define TCPH_FLAGS(phdr)  (ntohs((phdr)->_hdrlen_rsvd_flags) & TCP_FLAGS)

#define TCPH_OFFSET_SET(phdr, offset) (phdr)->_hdrlen_rsvd_flags = htons(((offset) << 8) | TCPH_FLAGS(phdr))

#define TCPH_HDRLEN_SET(phdr, len) (phdr)->_hdrlen_rsvd_flags = htons(((len) << 12) | TCPH_FLAGS(phdr))

#define TCPH_FLAGS_SET(phdr, flags) (phdr)->_hdrlen_rsvd_flags = (((phdr)->_hdrlen_rsvd_flags & htons((u16_t)(~(u16_t)(TCP_FLAGS)))) | htons(flags))

#define TCPH_SET_FLAG(phdr, flags ) (phdr)->_hdrlen_rsvd_flags = ((phdr)->_hdrlen_rsvd_flags | htons(flags))

#define TCPH_UNSET_FLAG(phdr, flags) (phdr)->_hdrlen_rsvd_flags = htons(ntohs((phdr)->_hdrlen_rsvd_flags) | (TCPH_FLAGS(phdr) & ~(flags)) )

#define TCP_TCPLEN(seg) ((seg)->len + ((TCPH_FLAGS((seg)->tcphdr) & (TCP_FIN | TCP_SYN)) != 0))

enum tcp_state {

  CLOSED      = 0,

  LISTEN      = 1,

  SYN_SENT    = 2,

  SYN_RCVD    = 3,

  ESTABLISHED = 4,

  FIN_WAIT_1  = 5,

  FIN_WAIT_2  = 6,

  CLOSE_WAIT  = 7,

  CLOSING     = 8,

  LAST_ACK    = 9,

  TIME_WAIT   = 10

};

/** Flags used on input processing, not on pcb->flags

*/

#define TF_RESET     (u8_t)0x08U   /* Connection was reset. */

#define TF_CLOSED    (u8_t)0x10U   /* Connection was sucessfully closed. */

#define TF_GOT_FIN   (u8_t)0x20U   /* Connection was closed by the remote end. */

#if LWIP_CALLBACK_API

  /* Function to call when a listener has been connected.

   * @param arg user-supplied argument (tcp_pcb.callback_arg)

   * @param pcb a new tcp_pcb that now is connected

   * @param err an error argument (TODO: that is current always ERR_OK?)

   * @return ERR_OK: accept the new connection,

   *                 any other err_t abortsthe new connection

   */

#define DEF_ACCEPT_CALLBACK  err_t (* accept)(void *arg, struct tcp_pcb *newpcb, err_t err)

#else /* LWIP_CALLBACK_API */

#define DEF_ACCEPT_CALLBACK

#endif /* LWIP_CALLBACK_API */

/**

 * members common to struct tcp_pcb and struct tcp_listen_pcb

 */

#define TCP_PCB_COMMON(type) \

  type *next; /* for the linked list */ \

  enum tcp_state state; /* TCP state */ \

  u8_t prio; \

  void *callback_arg; \

  /* ports are in host byte order */ \

  u16_t local_port; \

  /* the accept callback for listen- and normal pcbs, if LWIP_CALLBACK_API */ \

  DEF_ACCEPT_CALLBACK

/* the TCP protocol control block */

struct tcp_pcb {

/** common PCB members */

  IP_PCB;

/** protocol specific PCB members */

  TCP_PCB_COMMON(struct tcp_pcb);

  /* ports are in host byte order */

  u16_t remote_port;

  u8_t flags;

#define TF_ACK_DELAY   ((u8_t)0x01U)   /* Delayed ACK. */

#define TF_ACK_NOW     ((u8_t)0x02U)   /* Immediate ACK. */

#define TF_INFR        ((u8_t)0x04U)   /* In fast recovery. */

#define TF_TIMESTAMP   ((u8_t)0x08U)   /* Timestamp option enabled */

#define TF_FIN         ((u8_t)0x20U)   /* Connection was closed locally (FIN segment enqueued). */

#define TF_NODELAY     ((u8_t)0x40U)   /* Disable Nagle algorithm */

#define TF_NAGLEMEMERR ((u8_t)0x80U)   /* nagle enabled, memerr, try to output to prevent delayed ACK to happen */

  /* the rest of the fields are in host byte order

     as we have to do some math with them */

  /* receiver variables */

  u32_t rcv_nxt;   /* next seqno expected */

  u16_t rcv_wnd;   /* receiver window available */

  u16_t rcv_ann_wnd; /* receiver window to announce */

  u32_t rcv_ann_right_edge; /* announced right edge of window */

  /* Timers */

  u32_t tmr;

  u8_t polltmr, pollinterval;

  /* Retransmission timer. */

  s16_t rtime;

  u16_t mss;   /* maximum segment size */

  /* RTT (round trip time) estimation variables */

  u32_t rttest; /* RTT estimate in 500ms ticks */

  u32_t rtseq;  /* sequence number being timed */

  s16_t sa, sv; /* @todo document this */

  s16_t rto;    /* retransmission time-out */

  u8_t nrtx;    /* number of retransmissions */

  /* fast retransmit/recovery */

  u32_t lastack; /* Highest acknowledged seqno. */

  u8_t dupacks;

  /* congestion avoidance/control variables */

  u16_t cwnd;

  u16_t ssthresh;

  /* sender variables */

  u32_t snd_nxt;   /* next new seqno to be sent */

  u16_t snd_wnd;   /* sender window */

  u32_t snd_wl1, snd_wl2; /* Sequence and acknowledgement numbers of last

                             window update. */

  u32_t snd_lbb;       /* Sequence number of next byte to be buffered. */

  u16_t acked;

  u16_t snd_buf;   /* Available buffer space for sending (in bytes). */

#define TCP_SNDQUEUELEN_OVERFLOW (0xffff-3)

  u16_t snd_queuelen; /* Available buffer space for sending (in tcp_segs). */

  /* These are ordered by sequence number: */

  struct tcp_seg *unsent;   /* Unsent (queued) segments. */

  struct tcp_seg *unacked;  /* Sent but unacknowledged segments. */

#if TCP_QUEUE_OOSEQ  

  struct tcp_seg *ooseq;    /* Received out of sequence segments. */

#endif /* TCP_QUEUE_OOSEQ */

  struct pbuf *refused_data; /* Data previously received but not yet taken by upper layer */

#if LWIP_CALLBACK_API

  /* Function to be called when more send buffer space is available.

   * @param arg user-supplied argument (tcp_pcb.callback_arg)

   * @param pcb the tcp_pcb which has send buffer space available

   * @param space the amount of bytes available

   * @return ERR_OK: try to send some data by calling tcp_output

   */

  err_t (* sent)(void *arg, struct tcp_pcb *pcb, u16_t space);

  /* Function to be called when (in-sequence) data has arrived.

   * @param arg user-supplied argument (tcp_pcb.callback_arg)

   * @param pcb the tcp_pcb for which data has arrived

   * @param p the packet buffer which arrived

   * @param err an error argument (TODO: that is current always ERR_OK?)

   * @return ERR_OK: try to send some data by calling tcp_output

   */

  err_t (* recv)(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err);

  /* Function to be called when a connection has been set up.

   * @param arg user-supplied argument (tcp_pcb.callback_arg)

   * @param pcb the tcp_pcb that now is connected

   * @param err an error argument (TODO: that is current always ERR_OK?)

   * @return value is currently ignored

   */

  err_t (* connected)(void *arg, struct tcp_pcb *pcb, err_t err);

  /* Function which is called periodically.

   * The period can be adjusted in multiples of the TCP slow timer interval

   * by changing tcp_pcb.polltmr.

   * @param arg user-supplied argument (tcp_pcb.callback_arg)

   * @param pcb the tcp_pcb to poll for

   * @return ERR_OK: try to send some data by calling tcp_output

   */

  err_t (* poll)(void *arg, struct tcp_pcb *pcb);

  /* Function to be called whenever a fatal error occurs.

   * There is no pcb parameter since most of the times, the pcb is

   * already deallocated (or there is no pcb) when this function is called.

   * @param arg user-supplied argument (tcp_pcb.callback_arg)

   * @param err an indication why the error callback is called:

   *            ERR_ABRT: aborted through tcp_abort or by a TCP timer

   *            ERR_RST: the connection was reset by the remote host

   */

  void (* errf)(void *arg, err_t err);

#endif /* LWIP_CALLBACK_API */

#if LWIP_TCP_TIMESTAMPS

  u32_t ts_lastacksent;

  u32_t ts_recent;

#endif /* LWIP_TCP_TIMESTAMPS */

  /* idle time before KEEPALIVE is sent */

  u32_t keep_idle;

#if LWIP_TCP_KEEPALIVE

  u32_t keep_intvl;

  u32_t keep_cnt;

#endif /* LWIP_TCP_KEEPALIVE */

  /* Persist timer counter */

  u32_t persist_cnt;

  /* Persist timer back-off */

  u8_t persist_backoff;

  /* KEEPALIVE counter */

  u8_t keep_cnt_sent;

};

struct tcp_pcb_listen {

/* Common members of all PCB types */

  IP_PCB;

/* Protocol specific PCB members */

  TCP_PCB_COMMON(struct tcp_pcb_listen);

#if TCP_LISTEN_BACKLOG

  u8_t backlog;

  u8_t accepts_pending;

#endif /* TCP_LISTEN_BACKLOG */

};

#if LWIP_EVENT_API

enum lwip_event {

  LWIP_EVENT_ACCEPT,

  LWIP_EVENT_SENT,

  LWIP_EVENT_RECV,

  LWIP_EVENT_CONNECTED,

  LWIP_EVENT_POLL,

  LWIP_EVENT_ERR

};

err_t lwip_tcp_event(void *arg, struct tcp_pcb *pcb,

         enum lwip_event,

         struct pbuf *p,

         u16_t size,

         err_t err);

#define TCP_EVENT_ACCEPT(pcb,err,ret)    ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\

                LWIP_EVENT_ACCEPT, NULL, 0, err)

#define TCP_EVENT_SENT(pcb,space,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\

                   LWIP_EVENT_SENT, NULL, space, ERR_OK)

#define TCP_EVENT_RECV(pcb,p,err,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\

                LWIP_EVENT_RECV, (p), 0, (err))

#define TCP_EVENT_CONNECTED(pcb,err,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\

                LWIP_EVENT_CONNECTED, NULL, 0, (err))

#define TCP_EVENT_POLL(pcb,ret)       ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\

                LWIP_EVENT_POLL, NULL, 0, ERR_OK)

#define TCP_EVENT_ERR(errf,arg,err)  lwip_tcp_event((arg), NULL, \

                LWIP_EVENT_ERR, NULL, 0, (err))

#else /* LWIP_EVENT_API */

#define TCP_EVENT_ACCEPT(pcb,err,ret)                          \

  do {                                                         \

    if((pcb)->accept != NULL)                                  \

      (ret) = (pcb)->accept((pcb)->callback_arg,(pcb),(err));  \

    else (ret) = ERR_OK;                                       \

  } while (0)

#define TCP_EVENT_SENT(pcb,space,ret)                          \

  do {                                                         \

    if((pcb)->sent != NULL)                                    \

      (ret) = (pcb)->sent((pcb)->callback_arg,(pcb),(space));  \

    else (ret) = ERR_OK;                                       \

  } while (0)

#define TCP_EVENT_RECV(pcb,p,err,ret)                           \

  do {                                                          \

    if((pcb)->recv != NULL) {                                   \

      (ret) = (pcb)->recv((pcb)->callback_arg,(pcb),(p),(err)); \

    } else {                                                    \

      (ret) = tcp_recv_null(NULL, (pcb), (p), (err));           \

    }                                                           \

  } while (0)

#define TCP_EVENT_CONNECTED(pcb,err,ret)                         \

  do {                                                           \

    if((pcb)->connected != NULL)                                 \

      (ret) = (pcb)->connected((pcb)->callback_arg,(pcb),(err)); \

    else (ret) = ERR_OK;                                         \

  } while (0)

#define TCP_EVENT_POLL(pcb,ret)                                \

  do {                                                         \

    if((pcb)->poll != NULL)                                    \

      (ret) = (pcb)->poll((pcb)->callback_arg,(pcb));          \

    else (ret) = ERR_OK;                                       \

  } while (0)

#define TCP_EVENT_ERR(errf,arg,err)                            \

  do {                                                         \

    if((errf) != NULL)                                         \

      (errf)((arg),(err));                                     \

  } while (0)

#endif /* LWIP_EVENT_API */

/* This structure represents a TCP segment on the unsent and unacked queues */

struct tcp_seg {

  struct tcp_seg *next;    /* used when putting segements on a queue */

  struct pbuf *p;          /* buffer containing data + TCP header */

  void *dataptr;           /* pointer to the TCP data in the pbuf */

  u16_t len;               /* the TCP length of this segment */

  u8_t  flags;

#define TF_SEG_OPTS_MSS   (u8_t)0x01U   /* Include MSS option. */

#define TF_SEG_OPTS_TS    (u8_t)0x02U   /* Include timestamp option. */

  struct tcp_hdr *tcphdr;  /* the TCP header */

};

#define LWIP_TCP_OPT_LENGTH(flags)              \

  (flags & TF_SEG_OPTS_MSS ? 4  : 0) +          \

  (flags & TF_SEG_OPTS_TS  ? 12 : 0)

/** This returns a TCP header option for MSS in an u32_t */

#define TCP_BUILD_MSS_OPTION(x) (x) = htonl(((u32_t)2 << 24) |          \

                                            ((u32_t)4 << 16) |          \

                                            (((u32_t)TCP_MSS / 256) << 8) | \

                                            (TCP_MSS & 255))

/* Internal functions and global variables: */

struct tcp_pcb *tcp_pcb_copy(struct tcp_pcb *pcb);

void tcp_pcb_purge(struct tcp_pcb *pcb);

void tcp_pcb_remove(struct tcp_pcb **pcblist, struct tcp_pcb *pcb);

u8_t tcp_segs_free(struct tcp_seg *seg);

u8_t tcp_seg_free(struct tcp_seg *seg);

struct tcp_seg *tcp_seg_copy(struct tcp_seg *seg);

#define tcp_ack(pcb)                               \

  do {                                             \

    if((pcb)->flags & TF_ACK_DELAY) {              \

      (pcb)->flags &= ~TF_ACK_DELAY;               \

      (pcb)->flags |= TF_ACK_NOW;                  \

      tcp_output(pcb);                             \

    }                                              \

    else {                                         \

      (pcb)->flags |= TF_ACK_DELAY;                \

    }                                              \

  } while (0)

#define tcp_ack_now(pcb)                           \

  do {                                             \

    (pcb)->flags |= TF_ACK_NOW;                    \

    tcp_output(pcb);                               \

  } while (0)

err_t tcp_send_ctrl(struct tcp_pcb *pcb, u8_t flags);

err_t tcp_enqueue(struct tcp_pcb *pcb, void *dataptr, u16_t len,

                  u8_t flags, u8_t apiflags, u8_t optflags);

void tcp_rexmit_seg(struct tcp_pcb *pcb, struct tcp_seg *seg);

void tcp_rst(u32_t seqno, u32_t ackno,

       struct ip_addr *local_ip, struct ip_addr *remote_ip,

       u16_t local_port, u16_t remote_port);

u32_t tcp_next_iss(void);

void tcp_keepalive(struct tcp_pcb *pcb);

void tcp_zero_window_probe(struct tcp_pcb *pcb);

#if TCP_CALCULATE_EFF_SEND_MSS

u16_t tcp_eff_send_mss(u16_t sendmss, struct ip_addr *addr);

#endif /* TCP_CALCULATE_EFF_SEND_MSS */

#if LWIP_CALLBACK_API

err_t tcp_recv_null(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err);

#endif /* LWIP_CALLBACK_API */

extern struct tcp_pcb *tcp_input_pcb;

extern u32_t tcp_ticks;

const char* tcp_debug_state_str(enum tcp_state s);

#if TCP_DEBUG || TCP_INPUT_DEBUG || TCP_OUTPUT_DEBUG

void tcp_debug_print(struct tcp_hdr *tcphdr);

void tcp_debug_print_flags(u8_t flags);

void tcp_debug_print_state(enum tcp_state s);

void tcp_debug_print_pcbs(void);

s16_t tcp_pcbs_sane(void);

#else

#  define tcp_debug_print(tcphdr)

#  define tcp_debug_print_flags(flags)

#  define tcp_debug_print_state(s)

#  define tcp_debug_print_pcbs()

#  define tcp_pcbs_sane() 1

#endif /* TCP_DEBUG */

#if NO_SYS

#define tcp_timer_needed()

#else

void tcp_timer_needed(void);

#endif

/* The TCP PCB lists. */

union tcp_listen_pcbs_t { /* List of all TCP PCBs in LISTEN state. */

  struct tcp_pcb_listen *listen_pcbs;

  struct tcp_pcb *pcbs;

};

extern union tcp_listen_pcbs_t tcp_listen_pcbs;

extern struct tcp_pcb *tcp_active_pcbs;  /* List of all TCP PCBs that are in a

              state in which they accept or send

              data. */

extern struct tcp_pcb *tcp_tw_pcbs;      /* List of all TCP PCBs in TIME-WAIT. */

extern struct tcp_pcb *tcp_tmp_pcb;      /* Only used for temporary storage. */

/* Axioms about the above lists:

   1) Every TCP PCB that is not CLOSED is in one of the lists.

   2) A PCB is only in one of the lists.

   3) All PCBs in the tcp_listen_pcbs list is in LISTEN state.

   4) All PCBs in the tcp_tw_pcbs list is in TIME-WAIT state.

*/

/* Define two macros, TCP_REG and TCP_RMV that registers a TCP PCB

   with a PCB list or removes a PCB from a list, respectively. */

#if 0

#define TCP_REG(pcbs, npcb) do {\

                            LWIP_DEBUGF(TCP_DEBUG, ("TCP_REG %p local port %d\n", npcb, npcb->local_port)); \

                            for(tcp_tmp_pcb = *pcbs; \

          tcp_tmp_pcb != NULL; \

        tcp_tmp_pcb = tcp_tmp_pcb->next) { \

                                LWIP_ASSERT("TCP_REG: already registered\n", tcp_tmp_pcb != npcb); \

                            } \

                            LWIP_ASSERT("TCP_REG: pcb->state != CLOSED", npcb->state != CLOSED); \

                            npcb->next = *pcbs; \

                            LWIP_ASSERT("TCP_REG: npcb->next != npcb", npcb->next != npcb); \

                            *(pcbs) = npcb; \

                            LWIP_ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \

              tcp_timer_needed(); \

                            } while(0)

#define TCP_RMV(pcbs, npcb) do { \

                            LWIP_ASSERT("TCP_RMV: pcbs != NULL", *pcbs != NULL); \

                            LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removing %p from %p\n", npcb, *pcbs)); \

                            if(*pcbs == npcb) { \

                               *pcbs = (*pcbs)->next; \

                            } else for(tcp_tmp_pcb = *pcbs; tcp_tmp_pcb != NULL; tcp_tmp_pcb = tcp_tmp_pcb->next) { \

                               if(tcp_tmp_pcb->next == npcb) { \

                                  tcp_tmp_pcb->next = npcb->next; \

                                  break; \

                               } \

                            } \

                            npcb->next = NULL; \

                            LWIP_ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \

                            LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removed %p from %p\n", npcb, *pcbs)); \

                            } while(0)

#else /* LWIP_DEBUG */

#define TCP_REG(pcbs, npcb)                        \

  do {                                             \

    npcb->next = *pcbs;                            \

    *(pcbs) = npcb;                                \

    tcp_timer_needed();                            \

  } while (0)

#define TCP_RMV(pcbs, npcb)                        \

  do {                                             \

    if(*(pcbs) == npcb) {                          \

      (*(pcbs)) = (*pcbs)->next;                   \

    }                                              \

    else {                                         \

      for(tcp_tmp_pcb = *pcbs;                                         \

          tcp_tmp_pcb != NULL;                                         \

          tcp_tmp_pcb = tcp_tmp_pcb->next) {                           \

        if(tcp_tmp_pcb->next == npcb) {   \

          tcp_tmp_pcb->next = npcb->next;          \

          break;                                   \

        }                                          \

      }                                            \

    }                                              \

    npcb->next = NULL;                             \

  } while(0)

#endif /* LWIP_DEBUG */

#ifdef __cplusplus

}

#endif

#endif /* LWIP_TCP */

#endif /* __LWIP_TCP_H__ */