src/include/lwip/tcp.h - third_party/lwip - Git at Google

 /*
  * Copyright (c) 2001, 2002 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/sys.h"
 #include "lwip/mem.h"

 #include "lwip/pbuf.h"
 #include "lwip/opt.h"
 #include "lwip/ip.h"
 #include "lwip/icmp.h"

 #include "lwip/sys.h"

 #include "lwip/err.h"

 #include "lwip/event.h"

 struct tcp_pcb;

 /* Functions for interfacing with TCP: */

 /* Lower layer interface to TCP: */
 void             tcp_init    (void);  /* Must be called first to
 					 initialize TCP. */
 void             tcp_tmr     (void);  /* Must be called every
 					 TCP_TMR_INTERVAL
 					 ms. (Typically 100 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)

 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  (struct tcp_pcb *pcb);
 void             tcp_abort   (struct tcp_pcb *pcb);
 err_t            tcp_close   (struct tcp_pcb *pcb);
 err_t            tcp_write   (struct tcp_pcb *pcb, const void *dataptr, u16_t len,
 			      u8_t copy);

 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_output  (struct tcp_pcb *pcb);
 void             tcp_rexmit  (struct tcp_pcb *pcb);


 #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)

 #define TCP_FIN 0x01
 #define TCP_SYN 0x02
 #define TCP_RST 0x04
 #define TCP_PSH 0x08
 #define TCP_ACK 0x10
 #define TCP_URG 0x20

 #define TCP_FLAGS 0x3f

 /* Length of the TCP header, excluding options. */
 #define TCP_HLEN 20

 #define TCP_TMR_INTERVAL       100  /* The TCP timer interval in
 				       milliseconds. */

 #define TCP_FAST_INTERVAL      200  /* the fine grained timeout in
 				       milliseconds */
 #define TCP_SLOW_INTERVAL      500  /* the coarse grained timeout in
 				       milliseconds */
 #define TCP_FIN_WAIT_TIMEOUT 20000 /* milliseconds */
 #define TCP_SYN_RCVD_TIMEOUT 20000 /* milliseconds */

 #define TCP_OOSEQ_TIMEOUT        6 /* x RTO */

 #define TCP_MSL 60000  /* The maximum segment lifetime in microseconds */

 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 _offset_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

 #define TCPH_OFFSET(hdr) (NTOHS((hdr)->_offset_flags) >> 8)
 #define TCPH_FLAGS(hdr) (NTOHS((hdr)->_offset_flags) & 0xff)

 #define TCPH_OFFSET_SET(hdr, offset) (hdr)->_offset_flags = HTONS(((offset) << 8) | TCPH_FLAGS(hdr))
 #define TCPH_FLAGS_SET(hdr, flags) (hdr)->_offset_flags = HTONS((TCPH_OFFSET(hdr) << 8) | (flags))

 #define TCP_TCPLEN(seg) ((seg)->len + ((TCPH_FLAGS((seg)->tcphdr) & TCP_FIN || \
 					TCPH_FLAGS((seg)->tcphdr) & TCP_SYN)? 1: 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
 };


 /* the TCP protocol control block */
 struct tcp_pcb {
   struct tcp_pcb *next;   /* for the linked list */
   u8_t prio;
   void *callback_arg;

   struct ip_addr local_ip;
   u16_t local_port;

   struct ip_addr remote_ip;
   u16_t remote_port;

   /* receiver varables */
   u32_t rcv_nxt;   /* next seqno expected */
   u16_t rcv_wnd;   /* receiver window */

   enum tcp_state state;   /* TCP state */

   /* Timers */
   u16_t tmr;
   u8_t polltmr, pollinterval;

   /* Retransmission timer. */
   u8_t rtime;

   u16_t mss;   /* maximum segment size */

   u8_t flags;
 #define TF_ACK_DELAY 0x01U   /* Delayed ACK. */
 #define TF_ACK_NOW   0x02U   /* Immediate ACK. */
 #define TF_INFR      0x04U   /* In fast recovery. */
 #define TF_RESET     0x08U   /* Connection was reset. */
 #define TF_CLOSED    0x10U   /* Connection was sucessfully closed. */
 #define TF_GOT_FIN   0x20U   /* Connection was closed by the remote end. */

   /* RTT estimation variables. */
   u16_t rttest; /* RTT estimate in 500ms ticks */
   u32_t rtseq;  /* sequence number being timed */
   s16_t sa, sv;

   u16_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 seqno to be sent */
     snd_max,       /* Highest seqno sent. */
     snd_wnd,       /* sender window */
     snd_wl1, snd_wl2, /* Sequence and acknowledgement numbers of last
 			 window update. */
     snd_lbb;       /* Sequence number of next byte to be buffered. */

   u16_t acked;

   u16_t snd_buf;   /* Avaliable buffer space for sending (in bytes). */
   u8_t snd_queuelen; /* Avaliable 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 */

 #if LWIP_CALLBACK_API
   /* Function to be called when more send buffer space is avaliable. */
   err_t (* sent)(void *arg, struct tcp_pcb *pcb, u16_t space);

   /* Function to be called when (in-sequence) data has arrived. */
   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. */
   err_t (* connected)(void *arg, struct tcp_pcb *pcb, err_t err);

   /* Function to call when a listener has been connected. */
   err_t (* accept)(void *arg, struct tcp_pcb *newpcb, err_t err);

   /* Function which is called periodically. */
   err_t (* poll)(void *arg, struct tcp_pcb *pcb);

   /* Function to be called whenever a fatal error occurs. */
   void (* errf)(void *arg, err_t err);
 #endif /* LWIP_CALLBACK_API */
 };

 struct tcp_pcb_listen {
   struct tcp_pcb_listen *next;   /* for the linked list */
   u8_t prio;
   void *callback_arg;

   struct ip_addr local_ip;
   u16_t local_port;

 #if LWIP_CALLBACK_API
   /* Function to call when a listener has been connected. */
   err_t (* accept)(void *arg, struct tcp_pcb *newpcb, err_t err);
 #endif /* LWIP_CALLBACK_API */
 };

 #if LWIP_EVENT_API
 #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)     \
                         if((pcb)->accept != NULL) \
                         (ret = (pcb)->accept((pcb)->callback_arg,(pcb),(err)))
 #define TCP_EVENT_SENT(pcb,space,ret) \
                         if((pcb)->sent != NULL) \
                         (ret = (pcb)->sent((pcb)->callback_arg,(pcb),(space)))
 #define TCP_EVENT_RECV(pcb,p,err,ret) \
                         if((pcb)->recv != NULL) \
                         (ret = (pcb)->recv((pcb)->callback_arg,(pcb),(p),(err)))
 #define TCP_EVENT_CONNECTED(pcb,err,ret) \
                         if((pcb)->connected != NULL) \
                         (ret = (pcb)->connected((pcb)->callback_arg,(pcb),(err)))
 #define TCP_EVENT_POLL(pcb,ret) \
                         if((pcb)->poll != NULL) \
                         (ret = (pcb)->poll((pcb)->callback_arg,(pcb)))
 #define TCP_EVENT_ERR(errf,arg,err) \
                         if((errf) != NULL) \
                         (errf)((arg),(err))
 #endif /* LWIP_EVENT_API */

 /* This structure is used to repressent TCP segments when queued. */
 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 */
   struct tcp_hdr *tcphdr;  /* the TCP header */
 };

 /* 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)     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; \
                          }

 #define tcp_ack_now(pcb) (pcb)->flags |= TF_ACK_NOW; \
                          tcp_output(pcb)

 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 copy,
                 u8_t *optdata, u8_t optlen);

 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);

 extern struct tcp_pcb *tcp_input_pcb;
 extern u32_t tcp_ticks;

 #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);
 int tcp_pcbs_sane(void);
 #else
 #define tcp_pcbs_sane() 1
 #endif /* TCP_DEBUG */


 /* The TCP PCB lists. */
 extern struct tcp_pcb_listen *tcp_listen_pcbs;  /* List of all TCP PCBs in LISTEN state. */
 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. */

 /* Axoims 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 {\
                             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) { \
                                 ASSERT("TCP_REG: already registered\n", tcp_tmp_pcb != npcb); \
                             } \
                             ASSERT("TCP_REG: pcb->state != CLOSED", npcb->state != CLOSED); \
                             npcb->next = *pcbs; \
                             ASSERT("TCP_REG: npcb->next != npcb", npcb->next != npcb); \
                             *(pcbs) = npcb; \
                             ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
                             } while(0)
 #define TCP_RMV(pcbs, npcb) do { \
                             ASSERT("TCP_RMV: pcbs != NULL", *pcbs != NULL); \
                             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 != NULL && tcp_tmp_pcb->next == npcb) { \
                                   tcp_tmp_pcb->next = npcb->next; \
                                   break; \
                                } \
                             } \
                             npcb->next = NULL; \
                             ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
                             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; \
                             } 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 != NULL && tcp_tmp_pcb->next == npcb) { \
                                   tcp_tmp_pcb->next = npcb->next; \
                                   break; \
                                } \
                             } \
                             npcb->next = NULL; \
                             } while(0)
 #endif /* LWIP_DEBUG */
 #endif /* __LWIP_TCP_H__ */
	/*
	* Copyright (c) 2001, 2002 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/sys.h"
	#include "lwip/mem.h"

	#include "lwip/pbuf.h"
	#include "lwip/opt.h"
	#include "lwip/ip.h"
	#include "lwip/icmp.h"

	#include "lwip/sys.h"

	#include "lwip/err.h"

	#include "lwip/event.h"

	struct tcp_pcb;

	/* Functions for interfacing with TCP: */

	/* Lower layer interface to TCP: */
	void tcp_init (void); /* Must be called first to
	initialize TCP. */
	void tcp_tmr (void); /* Must be called every
	TCP_TMR_INTERVAL
	ms. (Typically 100 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)

	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 (struct tcp_pcb *pcb);
	void tcp_abort (struct tcp_pcb *pcb);
	err_t tcp_close (struct tcp_pcb *pcb);
	err_t tcp_write (struct tcp_pcb pcb, const void dataptr, u16_t len,
	u8_t copy);

	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_output (struct tcp_pcb *pcb);
	void tcp_rexmit (struct tcp_pcb *pcb);



	#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)

	#define TCP_FIN 0x01
	#define TCP_SYN 0x02
	#define TCP_RST 0x04
	#define TCP_PSH 0x08
	#define TCP_ACK 0x10
	#define TCP_URG 0x20

	#define TCP_FLAGS 0x3f

	/* Length of the TCP header, excluding options. */
	#define TCP_HLEN 20

	#define TCP_TMR_INTERVAL 100 /* The TCP timer interval in
	milliseconds. */

	#define TCP_FAST_INTERVAL 200 /* the fine grained timeout in
	milliseconds */
	#define TCP_SLOW_INTERVAL 500 /* the coarse grained timeout in
	milliseconds */
	#define TCP_FIN_WAIT_TIMEOUT 20000 /* milliseconds */
	#define TCP_SYN_RCVD_TIMEOUT 20000 /* milliseconds */

	#define TCP_OOSEQ_TIMEOUT 6 /* x RTO */

	#define TCP_MSL 60000 /* The maximum segment lifetime in microseconds */

	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 _offset_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

	#define TCPH_OFFSET(hdr) (NTOHS((hdr)->_offset_flags) >> 8)
	#define TCPH_FLAGS(hdr) (NTOHS((hdr)->_offset_flags) & 0xff)

	#define TCPH_OFFSET_SET(hdr, offset) (hdr)->_offset_flags = HTONS(((offset) << 8) \| TCPH_FLAGS(hdr))
	#define TCPH_FLAGS_SET(hdr, flags) (hdr)->_offset_flags = HTONS((TCPH_OFFSET(hdr) << 8) \| (flags))

	#define TCP_TCPLEN(seg) ((seg)->len + ((TCPH_FLAGS((seg)->tcphdr) & TCP_FIN \|\| \
	TCPH_FLAGS((seg)->tcphdr) & TCP_SYN)? 1: 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
	};


	/* the TCP protocol control block */
	struct tcp_pcb {
	struct tcp_pcb next; / for the linked list */
	u8_t prio;
	void *callback_arg;

	struct ip_addr local_ip;
	u16_t local_port;

	struct ip_addr remote_ip;
	u16_t remote_port;

	/* receiver varables */
	u32_t rcv_nxt; /* next seqno expected */
	u16_t rcv_wnd; /* receiver window */

	enum tcp_state state; /* TCP state */

	/* Timers */
	u16_t tmr;
	u8_t polltmr, pollinterval;

	/* Retransmission timer. */
	u8_t rtime;

	u16_t mss; /* maximum segment size */

	u8_t flags;
	#define TF_ACK_DELAY 0x01U /* Delayed ACK. */
	#define TF_ACK_NOW 0x02U /* Immediate ACK. */
	#define TF_INFR 0x04U /* In fast recovery. */
	#define TF_RESET 0x08U /* Connection was reset. */
	#define TF_CLOSED 0x10U /* Connection was sucessfully closed. */
	#define TF_GOT_FIN 0x20U /* Connection was closed by the remote end. */

	/* RTT estimation variables. */
	u16_t rttest; /* RTT estimate in 500ms ticks */
	u32_t rtseq; /* sequence number being timed */
	s16_t sa, sv;

	u16_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 seqno to be sent */
	snd_max, /* Highest seqno sent. */
	snd_wnd, /* sender window */
	snd_wl1, snd_wl2, /* Sequence and acknowledgement numbers of last
	window update. */
	snd_lbb; /* Sequence number of next byte to be buffered. */

	u16_t acked;

	u16_t snd_buf; /* Avaliable buffer space for sending (in bytes). */
	u8_t snd_queuelen; /* Avaliable 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 */

	#if LWIP_CALLBACK_API
	/* Function to be called when more send buffer space is avaliable. */
	err_t (* sent)(void arg, struct tcp_pcb pcb, u16_t space);

	/* Function to be called when (in-sequence) data has arrived. */
	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. */
	err_t (* connected)(void arg, struct tcp_pcb pcb, err_t err);

	/* Function to call when a listener has been connected. */
	err_t (* accept)(void arg, struct tcp_pcb newpcb, err_t err);

	/* Function which is called periodically. */
	err_t (* poll)(void arg, struct tcp_pcb pcb);

	/* Function to be called whenever a fatal error occurs. */
	void (* errf)(void *arg, err_t err);
	#endif /* LWIP_CALLBACK_API */
	};

	struct tcp_pcb_listen {
	struct tcp_pcb_listen next; / for the linked list */
	u8_t prio;
	void *callback_arg;

	struct ip_addr local_ip;
	u16_t local_port;

	#if LWIP_CALLBACK_API
	/* Function to call when a listener has been connected. */
	err_t (* accept)(void arg, struct tcp_pcb newpcb, err_t err);
	#endif /* LWIP_CALLBACK_API */
	};

	#if LWIP_EVENT_API
	#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) \
	if((pcb)->accept != NULL) \
	(ret = (pcb)->accept((pcb)->callback_arg,(pcb),(err)))
	#define TCP_EVENT_SENT(pcb,space,ret) \
	if((pcb)->sent != NULL) \
	(ret = (pcb)->sent((pcb)->callback_arg,(pcb),(space)))
	#define TCP_EVENT_RECV(pcb,p,err,ret) \
	if((pcb)->recv != NULL) \
	(ret = (pcb)->recv((pcb)->callback_arg,(pcb),(p),(err)))
	#define TCP_EVENT_CONNECTED(pcb,err,ret) \
	if((pcb)->connected != NULL) \
	(ret = (pcb)->connected((pcb)->callback_arg,(pcb),(err)))
	#define TCP_EVENT_POLL(pcb,ret) \
	if((pcb)->poll != NULL) \
	(ret = (pcb)->poll((pcb)->callback_arg,(pcb)))
	#define TCP_EVENT_ERR(errf,arg,err) \
	if((errf) != NULL) \
	(errf)((arg),(err))
	#endif /* LWIP_EVENT_API */

	/* This structure is used to repressent TCP segments when queued. */
	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 */
	struct tcp_hdr tcphdr; / the TCP header */
	};

	/* 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) 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; \
	}

	#define tcp_ack_now(pcb) (pcb)->flags \|= TF_ACK_NOW; \
	tcp_output(pcb)

	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 copy,
	u8_t *optdata, u8_t optlen);

	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);

	extern struct tcp_pcb *tcp_input_pcb;
	extern u32_t tcp_ticks;

	#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);
	int tcp_pcbs_sane(void);
	#else
	#define tcp_pcbs_sane() 1
	#endif /* TCP_DEBUG */


	/* The TCP PCB lists. */
	extern struct tcp_pcb_listen tcp_listen_pcbs; / List of all TCP PCBs in LISTEN state. */
	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. */

	/* Axoims 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 {\
	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) { \
	ASSERT("TCP_REG: already registered\n", tcp_tmp_pcb != npcb); \
	} \
	ASSERT("TCP_REG: pcb->state != CLOSED", npcb->state != CLOSED); \
	npcb->next = *pcbs; \
	ASSERT("TCP_REG: npcb->next != npcb", npcb->next != npcb); \
	*(pcbs) = npcb; \
	ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
	} while(0)
	#define TCP_RMV(pcbs, npcb) do { \
	ASSERT("TCP_RMV: pcbs != NULL", *pcbs != NULL); \
	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 != NULL && tcp_tmp_pcb->next == npcb) { \
	tcp_tmp_pcb->next = npcb->next; \
	break; \
	} \
	} \
	npcb->next = NULL; \
	ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
	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; \
	} 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 != NULL && tcp_tmp_pcb->next == npcb) { \
	tcp_tmp_pcb->next = npcb->next; \
	break; \
	} \
	} \
	npcb->next = NULL; \
	} while(0)
	#endif /* LWIP_DEBUG */
	#endif /* __LWIP_TCP_H__ */