source: arduino-1-6-7/trunk/fuentes/arduino-ide-amd64/libraries/WiFi/extras/wifiHD/src/SOFTWARE_FRAMEWORK/SERVICES/LWIP/lwip-1.3.2/src/core/tcp.c @ 46

Last change on this file since 46 was 46, checked in by jrpelegrina, 4 years ago

First release to Xenial

File size: 42.8 KB
Line 
1/* This source file is part of the ATMEL AVR-UC3-SoftwareFramework-1.7.0 Release */
2
3/**
4 * @file
5 * Transmission Control Protocol for IP
6 *
7 * This file contains common functions for the TCP implementation, such as functinos
8 * for manipulating the data structures and the TCP timer functions. TCP functions
9 * related to input and output is found in tcp_in.c and tcp_out.c respectively.
10 *
11 */
12
13/*
14 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
15 * All rights reserved.
16 *
17 * Redistribution and use in source and binary forms, with or without modification,
18 * are permitted provided that the following conditions are met:
19 *
20 * 1. Redistributions of source code must retain the above copyright notice,
21 *    this list of conditions and the following disclaimer.
22 * 2. Redistributions in binary form must reproduce the above copyright notice,
23 *    this list of conditions and the following disclaimer in the documentation
24 *    and/or other materials provided with the distribution.
25 * 3. The name of the author may not be used to endorse or promote products
26 *    derived from this software without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
29 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
30 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
31 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
32 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
33 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
34 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
35 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
36 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
37 * OF SUCH DAMAGE.
38 *
39 * This file is part of the lwIP TCP/IP stack.
40 *
41 * Author: Adam Dunkels <adam@sics.se>
42 *
43 */
44
45#include "lwip/opt.h"
46
47#if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
48
49#include "lwip/def.h"
50#include "lwip/mem.h"
51#include "lwip/memp.h"
52#include "lwip/snmp.h"
53#include "lwip/tcp.h"
54#include "lwip/debug.h"
55#include "lwip/stats.h"
56
57#include <string.h>
58
59const char *tcp_state_str[] = {
60  "CLOSED",     
61  "LISTEN",     
62  "SYN_SENT",   
63  "SYN_RCVD",   
64  "ESTABLISHED", 
65  "FIN_WAIT_1", 
66  "FIN_WAIT_2", 
67  "CLOSE_WAIT", 
68  "CLOSING",     
69  "LAST_ACK",   
70  "TIME_WAIT"   
71};
72
73/* Incremented every coarse grained timer shot (typically every 500 ms). */
74u32_t tcp_ticks;
75const u8_t tcp_backoff[13] =
76    { 1, 2, 3, 4, 5, 6, 7, 7, 7, 7, 7, 7, 7};
77 /* Times per slowtmr hits */
78const u8_t tcp_persist_backoff[7] = { 3, 6, 12, 24, 48, 96, 120 };
79
80/* The TCP PCB lists. */
81
82/** List of all TCP PCBs bound but not yet (connected || listening) */
83struct tcp_pcb *tcp_bound_pcbs; 
84/** List of all TCP PCBs in LISTEN state */
85union tcp_listen_pcbs_t tcp_listen_pcbs;
86/** List of all TCP PCBs that are in a state in which
87 * they accept or send data. */
88struct tcp_pcb *tcp_active_pcbs; 
89/** List of all TCP PCBs in TIME-WAIT state */
90struct tcp_pcb *tcp_tw_pcbs;
91
92struct tcp_pcb *tcp_tmp_pcb;
93
94static u8_t tcp_timer;
95static u16_t tcp_new_port(void);
96
97/**
98 * Called periodically to dispatch TCP timers.
99 *
100 */
101void
102tcp_tmr(void)
103{
104  /* Call tcp_fasttmr() every 250 ms */
105  tcp_fasttmr();
106
107  if (++tcp_timer & 1) {
108    /* Call tcp_tmr() every 500 ms, i.e., every other timer
109       tcp_tmr() is called. */
110    tcp_slowtmr();
111  }
112}
113
114/**
115 * Closes the connection held by the PCB.
116 *
117 * Listening pcbs are freed and may not be referenced any more.
118 * Connection pcbs are freed if not yet connected and may not be referenced
119 * any more. If a connection is established (at least SYN received or in
120 * a closing state), the connection is closed, and put in a closing state.
121 * The pcb is then automatically freed in tcp_slowtmr(). It is therefore
122 * unsafe to reference it.
123 *
124 * @param pcb the tcp_pcb to close
125 * @return ERR_OK if connection has been closed
126 *         another err_t if closing failed and pcb is not freed
127 */
128err_t
129tcp_close(struct tcp_pcb *pcb)
130{
131  err_t err;
132
133#if TCP_DEBUG
134  LWIP_DEBUGF(TCP_DEBUG, ("tcp_close: closing in "));
135  tcp_debug_print_state(pcb->state);
136#endif /* TCP_DEBUG */
137
138  switch (pcb->state) {
139  case CLOSED:
140    /* Closing a pcb in the CLOSED state might seem erroneous,
141     * however, it is in this state once allocated and as yet unused
142     * and the user needs some way to free it should the need arise.
143     * Calling tcp_close() with a pcb that has already been closed, (i.e. twice)
144     * or for a pcb that has been used and then entered the CLOSED state
145     * is erroneous, but this should never happen as the pcb has in those cases
146     * been freed, and so any remaining handles are bogus. */
147    err = ERR_OK;
148    TCP_RMV(&tcp_bound_pcbs, pcb);
149    memp_free(MEMP_TCP_PCB, pcb);
150    pcb = NULL;
151    break;
152  case LISTEN:
153    err = ERR_OK;
154    tcp_pcb_remove((struct tcp_pcb **)&tcp_listen_pcbs.pcbs, pcb);
155    memp_free(MEMP_TCP_PCB_LISTEN, pcb);
156    pcb = NULL;
157    break;
158  case SYN_SENT:
159    err = ERR_OK;
160    tcp_pcb_remove(&tcp_active_pcbs, pcb);
161    memp_free(MEMP_TCP_PCB, pcb);
162    pcb = NULL;
163    snmp_inc_tcpattemptfails();
164    break;
165  case SYN_RCVD:
166    err = tcp_send_ctrl(pcb, TCP_FIN);
167    if (err == ERR_OK) {
168      snmp_inc_tcpattemptfails();
169      pcb->state = FIN_WAIT_1;
170    }
171    break;
172  case ESTABLISHED:
173    err = tcp_send_ctrl(pcb, TCP_FIN);
174    if (err == ERR_OK) {
175      snmp_inc_tcpestabresets();
176      pcb->state = FIN_WAIT_1;
177    }
178    break;
179  case CLOSE_WAIT:
180    err = tcp_send_ctrl(pcb, TCP_FIN);
181    if (err == ERR_OK) {
182      snmp_inc_tcpestabresets();
183      pcb->state = LAST_ACK;
184    }
185    break;
186  default:
187    /* Has already been closed, do nothing. */
188    err = ERR_OK;
189    pcb = NULL;
190    break;
191  }
192
193  if (pcb != NULL && err == ERR_OK) {
194    /* To ensure all data has been sent when tcp_close returns, we have
195       to make sure tcp_output doesn't fail.
196       Since we don't really have to ensure all data has been sent when tcp_close
197       returns (unsent data is sent from tcp timer functions, also), we don't care
198       for the return value of tcp_output for now. */
199    /* @todo: When implementing SO_LINGER, this must be changed somehow:
200       If SOF_LINGER is set, the data should be sent when tcp_close returns. */
201    tcp_output(pcb);
202  }
203  return err;
204}
205
206/**
207 * Abandons a connection and optionally sends a RST to the remote
208 * host.  Deletes the local protocol control block. This is done when
209 * a connection is killed because of shortage of memory.
210 *
211 * @param pcb the tcp_pcb to abort
212 * @param reset boolean to indicate whether a reset should be sent
213 */
214void
215tcp_abandon(struct tcp_pcb *pcb, int reset)
216{
217  u32_t seqno, ackno;
218  u16_t remote_port, local_port;
219  struct ip_addr remote_ip, local_ip;
220#if LWIP_CALLBACK_API 
221  void (* errf)(void *arg, err_t err);
222#endif /* LWIP_CALLBACK_API */
223  void *errf_arg;
224
225 
226  /* Figure out on which TCP PCB list we are, and remove us. If we
227     are in an active state, call the receive function associated with
228     the PCB with a NULL argument, and send an RST to the remote end. */
229  if (pcb->state == TIME_WAIT) {
230    tcp_pcb_remove(&tcp_tw_pcbs, pcb);
231    memp_free(MEMP_TCP_PCB, pcb);
232  } else {
233    seqno = pcb->snd_nxt;
234    ackno = pcb->rcv_nxt;
235    ip_addr_set(&local_ip, &(pcb->local_ip));
236    ip_addr_set(&remote_ip, &(pcb->remote_ip));
237    local_port = pcb->local_port;
238    remote_port = pcb->remote_port;
239#if LWIP_CALLBACK_API
240    errf = pcb->errf;
241#endif /* LWIP_CALLBACK_API */
242    errf_arg = pcb->callback_arg;
243    tcp_pcb_remove(&tcp_active_pcbs, pcb);
244    if (pcb->unacked != NULL) {
245      tcp_segs_free(pcb->unacked);
246    }
247    if (pcb->unsent != NULL) {
248      tcp_segs_free(pcb->unsent);
249    }
250#if TCP_QUEUE_OOSEQ   
251    if (pcb->ooseq != NULL) {
252      tcp_segs_free(pcb->ooseq);
253    }
254#endif /* TCP_QUEUE_OOSEQ */
255    memp_free(MEMP_TCP_PCB, pcb);
256    TCP_EVENT_ERR(errf, errf_arg, ERR_ABRT);
257    if (reset) {
258      LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_abandon: sending RST\n"));
259      tcp_rst(seqno, ackno, &local_ip, &remote_ip, local_port, remote_port);
260    }
261  }
262}
263
264/**
265 * Binds the connection to a local portnumber and IP address. If the
266 * IP address is not given (i.e., ipaddr == NULL), the IP address of
267 * the outgoing network interface is used instead.
268 *
269 * @param pcb the tcp_pcb to bind (no check is done whether this pcb is
270 *        already bound!)
271 * @param ipaddr the local ip address to bind to (use IP_ADDR_ANY to bind
272 *        to any local address
273 * @param port the local port to bind to
274 * @return ERR_USE if the port is already in use
275 *         ERR_OK if bound
276 */
277err_t
278tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
279{
280  struct tcp_pcb *cpcb;
281
282  LWIP_ERROR("tcp_bind: can only bind in state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
283
284  if (port == 0) {
285    port = tcp_new_port();
286  }
287  /* Check if the address already is in use. */
288  /* Check the listen pcbs. */
289  for(cpcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs;
290      cpcb != NULL; cpcb = cpcb->next) {
291    if (cpcb->local_port == port) {
292      if (ip_addr_isany(&(cpcb->local_ip)) ||
293          ip_addr_isany(ipaddr) ||
294          ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
295        return ERR_USE;
296      }
297    }
298  }
299  /* Check the connected pcbs. */
300  for(cpcb = tcp_active_pcbs;
301      cpcb != NULL; cpcb = cpcb->next) {
302    if (cpcb->local_port == port) {
303      if (ip_addr_isany(&(cpcb->local_ip)) ||
304          ip_addr_isany(ipaddr) ||
305          ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
306        return ERR_USE;
307      }
308    }
309  }
310  /* Check the bound, not yet connected pcbs. */
311  for(cpcb = tcp_bound_pcbs; cpcb != NULL; cpcb = cpcb->next) {
312    if (cpcb->local_port == port) {
313      if (ip_addr_isany(&(cpcb->local_ip)) ||
314          ip_addr_isany(ipaddr) ||
315          ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
316        return ERR_USE;
317      }
318    }
319  }
320  /* @todo: until SO_REUSEADDR is implemented (see task #6995 on savannah),
321   * we have to check the pcbs in TIME-WAIT state, also: */
322  for(cpcb = tcp_tw_pcbs; cpcb != NULL; cpcb = cpcb->next) {
323    if (cpcb->local_port == port) {
324      if (ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
325        return ERR_USE;
326      }
327    }
328  }
329
330  if (!ip_addr_isany(ipaddr)) {
331    pcb->local_ip = *ipaddr;
332  }
333  pcb->local_port = port;
334  TCP_REG(&tcp_bound_pcbs, pcb);
335  LWIP_DEBUGF(TCP_DEBUG, ("tcp_bind: bind to port %"U16_F"\n", port));
336  return ERR_OK;
337}
338#if LWIP_CALLBACK_API
339/**
340 * Default accept callback if no accept callback is specified by the user.
341 */
342static err_t
343tcp_accept_null(void *arg, struct tcp_pcb *pcb, err_t err)
344{
345  LWIP_UNUSED_ARG(arg);
346  LWIP_UNUSED_ARG(pcb);
347  LWIP_UNUSED_ARG(err);
348
349  return ERR_ABRT;
350}
351#endif /* LWIP_CALLBACK_API */
352
353/**
354 * Set the state of the connection to be LISTEN, which means that it
355 * is able to accept incoming connections. The protocol control block
356 * is reallocated in order to consume less memory. Setting the
357 * connection to LISTEN is an irreversible process.
358 *
359 * @param pcb the original tcp_pcb
360 * @param backlog the incoming connections queue limit
361 * @return tcp_pcb used for listening, consumes less memory.
362 *
363 * @note The original tcp_pcb is freed. This function therefore has to be
364 *       called like this:
365 *             tpcb = tcp_listen(tpcb);
366 */
367struct tcp_pcb *
368tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog)
369{
370  struct tcp_pcb_listen *lpcb;
371
372  LWIP_UNUSED_ARG(backlog);
373  LWIP_ERROR("tcp_listen: pcb already connected", pcb->state == CLOSED, return NULL);
374
375  /* already listening? */
376  if (pcb->state == LISTEN) {
377    return pcb;
378  }
379  lpcb = memp_malloc(MEMP_TCP_PCB_LISTEN);
380  if (lpcb == NULL) {
381    return NULL;
382  }
383  lpcb->callback_arg = pcb->callback_arg;
384  lpcb->local_port = pcb->local_port;
385  lpcb->state = LISTEN;
386  lpcb->so_options = pcb->so_options;
387  lpcb->so_options |= SOF_ACCEPTCONN;
388  lpcb->ttl = pcb->ttl;
389  lpcb->tos = pcb->tos;
390  ip_addr_set(&lpcb->local_ip, &pcb->local_ip);
391  TCP_RMV(&tcp_bound_pcbs, pcb);
392  memp_free(MEMP_TCP_PCB, pcb);
393#if LWIP_CALLBACK_API
394  lpcb->accept = tcp_accept_null;
395#endif /* LWIP_CALLBACK_API */
396#if TCP_LISTEN_BACKLOG
397  lpcb->accepts_pending = 0;
398  lpcb->backlog = (backlog ? backlog : 1);
399#endif /* TCP_LISTEN_BACKLOG */
400  TCP_REG(&tcp_listen_pcbs.listen_pcbs, lpcb);
401  return (struct tcp_pcb *)lpcb;
402}
403
404/**
405 * Update the state that tracks the available window space to advertise.
406 *
407 * Returns how much extra window would be advertised if we sent an
408 * update now.
409 */
410u32_t tcp_update_rcv_ann_wnd(struct tcp_pcb *pcb)
411{
412  u32_t new_right_edge = pcb->rcv_nxt + pcb->rcv_wnd;
413
414  if (TCP_SEQ_GEQ(new_right_edge, pcb->rcv_ann_right_edge + LWIP_MIN((TCP_WND / 2), pcb->mss))) {
415    /* we can advertise more window */
416    pcb->rcv_ann_wnd = pcb->rcv_wnd;
417    return new_right_edge - pcb->rcv_ann_right_edge;
418  } else {
419    if (TCP_SEQ_GT(pcb->rcv_nxt, pcb->rcv_ann_right_edge)) {
420      /* Can happen due to other end sending out of advertised window,
421       * but within actual available (but not yet advertised) window */
422      pcb->rcv_ann_wnd = 0;
423    } else {
424      /* keep the right edge of window constant */
425      pcb->rcv_ann_wnd = pcb->rcv_ann_right_edge - pcb->rcv_nxt;
426    }
427    return 0;
428  }
429}
430
431/**
432 * This function should be called by the application when it has
433 * processed the data. The purpose is to advertise a larger window
434 * when the data has been processed.
435 *
436 * @param pcb the tcp_pcb for which data is read
437 * @param len the amount of bytes that have been read by the application
438 */
439void
440tcp_recved(struct tcp_pcb *pcb, u16_t len)
441{
442  int wnd_inflation;
443
444  LWIP_ASSERT("tcp_recved: len would wrap rcv_wnd\n",
445              len <= 0xffff - pcb->rcv_wnd );
446
447  pcb->rcv_wnd += len;
448  if (pcb->rcv_wnd > TCP_WND)
449    pcb->rcv_wnd = TCP_WND;
450
451  wnd_inflation = tcp_update_rcv_ann_wnd(pcb);
452
453  /* If the change in the right edge of window is significant (default
454   * watermark is TCP_WND/2), then send an explicit update now.
455   * Otherwise wait for a packet to be sent in the normal course of
456   * events (or more window to be available later) */
457  if (wnd_inflation >= TCP_WND_UPDATE_THRESHOLD) 
458    tcp_ack_now(pcb);
459
460  LWIP_DEBUGF(TCP_DEBUG, ("tcp_recved: recveived %"U16_F" bytes, wnd %"U16_F" (%"U16_F").\n",
461         len, pcb->rcv_wnd, TCP_WND - pcb->rcv_wnd));
462}
463
464/**
465 * A nastly hack featuring 'goto' statements that allocates a
466 * new TCP local port.
467 *
468 * @return a new (free) local TCP port number
469 */
470static u16_t
471tcp_new_port(void)
472{
473  struct tcp_pcb *pcb;
474#ifndef TCP_LOCAL_PORT_RANGE_START
475#define TCP_LOCAL_PORT_RANGE_START 4096
476#define TCP_LOCAL_PORT_RANGE_END   0x7fff
477#endif
478  static u16_t port = TCP_LOCAL_PORT_RANGE_START;
479 
480 again:
481  if (++port > TCP_LOCAL_PORT_RANGE_END) {
482    port = TCP_LOCAL_PORT_RANGE_START;
483  }
484 
485  for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
486    if (pcb->local_port == port) {
487      goto again;
488    }
489  }
490  for(pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
491    if (pcb->local_port == port) {
492      goto again;
493    }
494  }
495  for(pcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs; pcb != NULL; pcb = pcb->next) {
496    if (pcb->local_port == port) {
497      goto again;
498    }
499  }
500  return port;
501}
502
503/**
504 * Connects to another host. The function given as the "connected"
505 * argument will be called when the connection has been established.
506 *
507 * @param pcb the tcp_pcb used to establish the connection
508 * @param ipaddr the remote ip address to connect to
509 * @param port the remote tcp port to connect to
510 * @param connected callback function to call when connected (or on error)
511 * @return ERR_VAL if invalid arguments are given
512 *         ERR_OK if connect request has been sent
513 *         other err_t values if connect request couldn't be sent
514 */
515err_t
516tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
517      err_t (* connected)(void *arg, struct tcp_pcb *tpcb, err_t err))
518{
519  err_t ret;
520  u32_t iss;
521
522  LWIP_ERROR("tcp_connect: can only connected from state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
523
524  LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
525  if (ipaddr != NULL) {
526    pcb->remote_ip = *ipaddr;
527  } else {
528    return ERR_VAL;
529  }
530  pcb->remote_port = port;
531  if (pcb->local_port == 0) {
532    pcb->local_port = tcp_new_port();
533  }
534  iss = tcp_next_iss();
535  pcb->rcv_nxt = 0;
536  pcb->snd_nxt = iss;
537  pcb->lastack = iss - 1;
538  pcb->snd_lbb = iss - 1;
539  pcb->rcv_wnd = TCP_WND;
540  pcb->rcv_ann_wnd = TCP_WND;
541  pcb->rcv_ann_right_edge = pcb->rcv_nxt;
542  pcb->snd_wnd = TCP_WND;
543  /* As initial send MSS, we use TCP_MSS but limit it to 536.
544     The send MSS is updated when an MSS option is received. */
545  pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
546#if TCP_CALCULATE_EFF_SEND_MSS
547  pcb->mss = tcp_eff_send_mss(pcb->mss, ipaddr);
548#endif /* TCP_CALCULATE_EFF_SEND_MSS */
549  pcb->cwnd = 1;
550  pcb->ssthresh = pcb->mss * 10;
551  pcb->state = SYN_SENT;
552#if LWIP_CALLBACK_API 
553  pcb->connected = connected;
554#endif /* LWIP_CALLBACK_API */
555  TCP_RMV(&tcp_bound_pcbs, pcb);
556  TCP_REG(&tcp_active_pcbs, pcb);
557
558  snmp_inc_tcpactiveopens();
559 
560  ret = tcp_enqueue(pcb, NULL, 0, TCP_SYN, 0, TF_SEG_OPTS_MSS
561#if LWIP_TCP_TIMESTAMPS
562                    | TF_SEG_OPTS_TS
563#endif
564                    );
565  if (ret == ERR_OK) { 
566    tcp_output(pcb);
567  }
568  return ret;
569} 
570
571/**
572 * Called every 500 ms and implements the retransmission timer and the timer that
573 * removes PCBs that have been in TIME-WAIT for enough time. It also increments
574 * various timers such as the inactivity timer in each PCB.
575 *
576 * Automatically called from tcp_tmr().
577 */
578void
579tcp_slowtmr(void)
580{
581  struct tcp_pcb *pcb, *pcb2, *prev;
582  u16_t eff_wnd;
583  u8_t pcb_remove;      /* flag if a PCB should be removed */
584  u8_t pcb_reset;       /* flag if a RST should be sent when removing */
585  err_t err;
586
587  err = ERR_OK;
588
589  ++tcp_ticks;
590
591  /* Steps through all of the active PCBs. */
592  prev = NULL;
593  pcb = tcp_active_pcbs;
594  if (pcb == NULL) {
595    LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: no active pcbs\n"));
596  }
597  while (pcb != NULL) {
598    LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: processing active pcb\n"));
599    LWIP_ASSERT("tcp_slowtmr: active pcb->state != CLOSED\n", pcb->state != CLOSED);
600    LWIP_ASSERT("tcp_slowtmr: active pcb->state != LISTEN\n", pcb->state != LISTEN);
601    LWIP_ASSERT("tcp_slowtmr: active pcb->state != TIME-WAIT\n", pcb->state != TIME_WAIT);
602
603    pcb_remove = 0;
604    pcb_reset = 0;
605
606    if (pcb->state == SYN_SENT && pcb->nrtx == TCP_SYNMAXRTX) {
607      ++pcb_remove;
608      LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max SYN retries reached\n"));
609    }
610    else if (pcb->nrtx == TCP_MAXRTX) {
611      ++pcb_remove;
612      LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: max DATA retries reached\n"));
613    } else {
614      if (pcb->persist_backoff > 0) {
615        /* If snd_wnd is zero, use persist timer to send 1 byte probes
616         * instead of using the standard retransmission mechanism. */
617        pcb->persist_cnt++;
618        if (pcb->persist_cnt >= tcp_persist_backoff[pcb->persist_backoff-1]) {
619          pcb->persist_cnt = 0;
620          if (pcb->persist_backoff < sizeof(tcp_persist_backoff)) {
621            pcb->persist_backoff++;
622          }
623          tcp_zero_window_probe(pcb);
624        }
625      } else {
626        /* Increase the retransmission timer if it is running */
627        if(pcb->rtime >= 0)
628          ++pcb->rtime;
629
630        if (pcb->unacked != NULL && pcb->rtime >= pcb->rto) {
631          /* Time for a retransmission. */
632          LWIP_DEBUGF(TCP_RTO_DEBUG, ("tcp_slowtmr: rtime %"S16_F
633                                      " pcb->rto %"S16_F"\n",
634                                      pcb->rtime, pcb->rto));
635
636          /* Double retransmission time-out unless we are trying to
637           * connect to somebody (i.e., we are in SYN_SENT). */
638          if (pcb->state != SYN_SENT) {
639            pcb->rto = ((pcb->sa >> 3) + pcb->sv) << tcp_backoff[pcb->nrtx];
640          }
641
642          /* Reset the retransmission timer. */
643          pcb->rtime = 0;
644
645          /* Reduce congestion window and ssthresh. */
646          eff_wnd = LWIP_MIN(pcb->cwnd, pcb->snd_wnd);
647          pcb->ssthresh = eff_wnd >> 1;
648          if (pcb->ssthresh < pcb->mss) {
649            pcb->ssthresh = pcb->mss * 2;
650          }
651          pcb->cwnd = pcb->mss;
652          LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_slowtmr: cwnd %"U16_F
653                                       " ssthresh %"U16_F"\n",
654                                       pcb->cwnd, pcb->ssthresh));
655 
656          /* The following needs to be called AFTER cwnd is set to one
657             mss - STJ */
658          tcp_rexmit_rto(pcb);
659        }
660      }
661    }
662    /* Check if this PCB has stayed too long in FIN-WAIT-2 */
663    if (pcb->state == FIN_WAIT_2) {
664      if ((u32_t)(tcp_ticks - pcb->tmr) >
665          TCP_FIN_WAIT_TIMEOUT / TCP_SLOW_INTERVAL) {
666        ++pcb_remove;
667        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in FIN-WAIT-2\n"));
668      }
669    }
670
671    /* Check if KEEPALIVE should be sent */
672    if((pcb->so_options & SOF_KEEPALIVE) && 
673       ((pcb->state == ESTABLISHED) || 
674        (pcb->state == CLOSE_WAIT))) {
675#if LWIP_TCP_KEEPALIVE
676      if((u32_t)(tcp_ticks - pcb->tmr) > 
677         (pcb->keep_idle + (pcb->keep_cnt*pcb->keep_intvl))
678         / TCP_SLOW_INTERVAL)
679#else     
680      if((u32_t)(tcp_ticks - pcb->tmr) > 
681         (pcb->keep_idle + TCP_MAXIDLE) / TCP_SLOW_INTERVAL)
682#endif /* LWIP_TCP_KEEPALIVE */
683      {
684        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: KEEPALIVE timeout. Aborting connection to %"U16_F".%"U16_F".%"U16_F".%"U16_F".\n",
685                                ip4_addr1(&pcb->remote_ip), ip4_addr2(&pcb->remote_ip),
686                                ip4_addr3(&pcb->remote_ip), ip4_addr4(&pcb->remote_ip)));
687       
688        ++pcb_remove;
689        ++pcb_reset;
690      }
691#if LWIP_TCP_KEEPALIVE
692      else if((u32_t)(tcp_ticks - pcb->tmr) > 
693              (pcb->keep_idle + pcb->keep_cnt_sent * pcb->keep_intvl)
694              / TCP_SLOW_INTERVAL)
695#else
696      else if((u32_t)(tcp_ticks - pcb->tmr) > 
697              (pcb->keep_idle + pcb->keep_cnt_sent * TCP_KEEPINTVL_DEFAULT) 
698              / TCP_SLOW_INTERVAL)
699#endif /* LWIP_TCP_KEEPALIVE */
700      {
701        tcp_keepalive(pcb);
702        pcb->keep_cnt_sent++;
703      }
704    }
705
706    /* If this PCB has queued out of sequence data, but has been
707       inactive for too long, will drop the data (it will eventually
708       be retransmitted). */
709#if TCP_QUEUE_OOSEQ   
710    if (pcb->ooseq != NULL &&
711        (u32_t)tcp_ticks - pcb->tmr >= pcb->rto * TCP_OOSEQ_TIMEOUT) {
712      tcp_segs_free(pcb->ooseq);
713      pcb->ooseq = NULL;
714      LWIP_DEBUGF(TCP_CWND_DEBUG, ("tcp_slowtmr: dropping OOSEQ queued data\n"));
715    }
716#endif /* TCP_QUEUE_OOSEQ */
717
718    /* Check if this PCB has stayed too long in SYN-RCVD */
719    if (pcb->state == SYN_RCVD) {
720      if ((u32_t)(tcp_ticks - pcb->tmr) >
721          TCP_SYN_RCVD_TIMEOUT / TCP_SLOW_INTERVAL) {
722        ++pcb_remove;
723        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in SYN-RCVD\n"));
724      }
725    }
726
727    /* Check if this PCB has stayed too long in LAST-ACK */
728    if (pcb->state == LAST_ACK) {
729      if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
730        ++pcb_remove;
731        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: removing pcb stuck in LAST-ACK\n"));
732      }
733    }
734
735    /* If the PCB should be removed, do it. */
736    if (pcb_remove) {
737      tcp_pcb_purge(pcb);     
738      /* Remove PCB from tcp_active_pcbs list. */
739      if (prev != NULL) {
740        LWIP_ASSERT("tcp_slowtmr: middle tcp != tcp_active_pcbs", pcb != tcp_active_pcbs);
741        prev->next = pcb->next;
742      } else {
743        /* This PCB was the first. */
744        LWIP_ASSERT("tcp_slowtmr: first pcb == tcp_active_pcbs", tcp_active_pcbs == pcb);
745        tcp_active_pcbs = pcb->next;
746      }
747
748      TCP_EVENT_ERR(pcb->errf, pcb->callback_arg, ERR_ABRT);
749      if (pcb_reset) {
750        tcp_rst(pcb->snd_nxt, pcb->rcv_nxt, &pcb->local_ip, &pcb->remote_ip,
751          pcb->local_port, pcb->remote_port);
752      }
753
754      pcb2 = pcb->next;
755      memp_free(MEMP_TCP_PCB, pcb);
756      pcb = pcb2;
757    } else {
758
759      /* We check if we should poll the connection. */
760      ++pcb->polltmr;
761      if (pcb->polltmr >= pcb->pollinterval) {
762        pcb->polltmr = 0;
763        LWIP_DEBUGF(TCP_DEBUG, ("tcp_slowtmr: polling application\n"));
764        TCP_EVENT_POLL(pcb, err);
765        if (err == ERR_OK) {
766          tcp_output(pcb);
767        }
768      }
769     
770      prev = pcb;
771      pcb = pcb->next;
772    }
773  }
774
775 
776  /* Steps through all of the TIME-WAIT PCBs. */
777  prev = NULL;   
778  pcb = tcp_tw_pcbs;
779  while (pcb != NULL) {
780    LWIP_ASSERT("tcp_slowtmr: TIME-WAIT pcb->state == TIME-WAIT", pcb->state == TIME_WAIT);
781    pcb_remove = 0;
782
783    /* Check if this PCB has stayed long enough in TIME-WAIT */
784    if ((u32_t)(tcp_ticks - pcb->tmr) > 2 * TCP_MSL / TCP_SLOW_INTERVAL) {
785      ++pcb_remove;
786    }
787   
788
789
790    /* If the PCB should be removed, do it. */
791    if (pcb_remove) {
792      tcp_pcb_purge(pcb);     
793      /* Remove PCB from tcp_tw_pcbs list. */
794      if (prev != NULL) {
795        LWIP_ASSERT("tcp_slowtmr: middle tcp != tcp_tw_pcbs", pcb != tcp_tw_pcbs);
796        prev->next = pcb->next;
797      } else {
798        /* This PCB was the first. */
799        LWIP_ASSERT("tcp_slowtmr: first pcb == tcp_tw_pcbs", tcp_tw_pcbs == pcb);
800        tcp_tw_pcbs = pcb->next;
801      }
802      pcb2 = pcb->next;
803      memp_free(MEMP_TCP_PCB, pcb);
804      pcb = pcb2;
805    } else {
806      prev = pcb;
807      pcb = pcb->next;
808    }
809  }
810}
811
812/**
813 * Is called every TCP_FAST_INTERVAL (250 ms) and process data previously
814 * "refused" by upper layer (application) and sends delayed ACKs.
815 *
816 * Automatically called from tcp_tmr().
817 */
818void
819tcp_fasttmr(void)
820{
821  struct tcp_pcb *pcb;
822
823  for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
824    /* If there is data which was previously "refused" by upper layer */
825    if (pcb->refused_data != NULL) {
826      /* Notify again application with data previously received. */
827      err_t err;
828      LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_fasttmr: notify kept packet\n"));
829      TCP_EVENT_RECV(pcb, pcb->refused_data, ERR_OK, err);
830      if (err == ERR_OK) {
831        pcb->refused_data = NULL;
832      }
833    }
834
835    /* send delayed ACKs */ 
836    if (pcb->flags & TF_ACK_DELAY) {
837      LWIP_DEBUGF(TCP_DEBUG, ("tcp_fasttmr: delayed ACK\n"));
838      tcp_ack_now(pcb);
839      pcb->flags &= ~(TF_ACK_DELAY | TF_ACK_NOW);
840    }
841  }
842}
843
844/**
845 * Deallocates a list of TCP segments (tcp_seg structures).
846 *
847 * @param seg tcp_seg list of TCP segments to free
848 * @return the number of pbufs that were deallocated
849 */
850u8_t
851tcp_segs_free(struct tcp_seg *seg)
852{
853  u8_t count = 0;
854  struct tcp_seg *next;
855  while (seg != NULL) {
856    next = seg->next;
857    count += tcp_seg_free(seg);
858    seg = next;
859  }
860  return count;
861}
862
863/**
864 * Frees a TCP segment (tcp_seg structure).
865 *
866 * @param seg single tcp_seg to free
867 * @return the number of pbufs that were deallocated
868 */
869u8_t
870tcp_seg_free(struct tcp_seg *seg)
871{
872  u8_t count = 0;
873 
874  if (seg != NULL) {
875    if (seg->p != NULL) {
876      count = pbuf_free(seg->p);
877#if TCP_DEBUG
878      seg->p = NULL;
879#endif /* TCP_DEBUG */
880    }
881    memp_free(MEMP_TCP_SEG, seg);
882  }
883  return count;
884}
885
886/**
887 * Sets the priority of a connection.
888 *
889 * @param pcb the tcp_pcb to manipulate
890 * @param prio new priority
891 */
892void
893tcp_setprio(struct tcp_pcb *pcb, u8_t prio)
894{
895  pcb->prio = prio;
896}
897#if TCP_QUEUE_OOSEQ
898
899/**
900 * Returns a copy of the given TCP segment.
901 * The pbuf and data are not copied, only the pointers
902 *
903 * @param seg the old tcp_seg
904 * @return a copy of seg
905 */ 
906struct tcp_seg *
907tcp_seg_copy(struct tcp_seg *seg)
908{
909  struct tcp_seg *cseg;
910
911  cseg = memp_malloc(MEMP_TCP_SEG);
912  if (cseg == NULL) {
913    return NULL;
914  }
915  SMEMCPY((u8_t *)cseg, (const u8_t *)seg, sizeof(struct tcp_seg)); 
916  pbuf_ref(cseg->p);
917  return cseg;
918}
919#endif
920
921#if LWIP_CALLBACK_API
922/**
923 * Default receive callback that is called if the user didn't register
924 * a recv callback for the pcb.
925 */
926err_t
927tcp_recv_null(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
928{
929  LWIP_UNUSED_ARG(arg);
930  if (p != NULL) {
931    tcp_recved(pcb, p->tot_len);
932    pbuf_free(p);
933  } else if (err == ERR_OK) {
934    return tcp_close(pcb);
935  }
936  return ERR_OK;
937}
938#endif /* LWIP_CALLBACK_API */
939
940/**
941 * Kills the oldest active connection that has lower priority than prio.
942 *
943 * @param prio minimum priority
944 */
945static void
946tcp_kill_prio(u8_t prio)
947{
948  struct tcp_pcb *pcb, *inactive;
949  u32_t inactivity;
950  u8_t mprio;
951
952
953  mprio = TCP_PRIO_MAX;
954 
955  /* We kill the oldest active connection that has lower priority than prio. */
956  inactivity = 0;
957  inactive = NULL;
958  for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
959    if (pcb->prio <= prio &&
960       pcb->prio <= mprio &&
961       (u32_t)(tcp_ticks - pcb->tmr) >= inactivity) {
962      inactivity = tcp_ticks - pcb->tmr;
963      inactive = pcb;
964      mprio = pcb->prio;
965    }
966  }
967  if (inactive != NULL) {
968    LWIP_DEBUGF(TCP_DEBUG, ("tcp_kill_prio: killing oldest PCB %p (%"S32_F")\n",
969           (void *)inactive, inactivity));
970    tcp_abort(inactive);
971  }     
972}
973
974/**
975 * Kills the oldest connection that is in TIME_WAIT state.
976 * Called from tcp_alloc() if no more connections are available.
977 */
978static void
979tcp_kill_timewait(void)
980{
981  struct tcp_pcb *pcb, *inactive;
982  u32_t inactivity;
983
984  inactivity = 0;
985  inactive = NULL;
986  /* Go through the list of TIME_WAIT pcbs and get the oldest pcb. */
987  for(pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
988    if ((u32_t)(tcp_ticks - pcb->tmr) >= inactivity) {
989      inactivity = tcp_ticks - pcb->tmr;
990      inactive = pcb;
991    }
992  }
993  if (inactive != NULL) {
994    LWIP_DEBUGF(TCP_DEBUG, ("tcp_kill_timewait: killing oldest TIME-WAIT PCB %p (%"S32_F")\n",
995           (void *)inactive, inactivity));
996    tcp_abort(inactive);
997  }     
998}
999
1000/**
1001 * Allocate a new tcp_pcb structure.
1002 *
1003 * @param prio priority for the new pcb
1004 * @return a new tcp_pcb that initially is in state CLOSED
1005 */
1006struct tcp_pcb *
1007tcp_alloc(u8_t prio)
1008{
1009  struct tcp_pcb *pcb;
1010  u32_t iss;
1011 
1012  pcb = memp_malloc(MEMP_TCP_PCB);
1013  if (pcb == NULL) {
1014    /* Try killing oldest connection in TIME-WAIT. */
1015    LWIP_DEBUGF(TCP_DEBUG, ("tcp_alloc: killing off oldest TIME-WAIT connection\n"));
1016    tcp_kill_timewait();
1017    /* Try to allocate a tcp_pcb again. */
1018    pcb = memp_malloc(MEMP_TCP_PCB);
1019    if (pcb == NULL) {
1020      /* Try killing active connections with lower priority than the new one. */
1021      LWIP_DEBUGF(TCP_DEBUG, ("tcp_alloc: killing connection with prio lower than %d\n", prio));
1022      tcp_kill_prio(prio);
1023      /* Try to allocate a tcp_pcb again. */
1024      pcb = memp_malloc(MEMP_TCP_PCB);
1025      if (pcb != NULL) {
1026        /* adjust err stats: memp_malloc failed twice before */
1027        MEMP_STATS_DEC(err, MEMP_TCP_PCB);
1028      }
1029    }
1030    if (pcb != NULL) {
1031      /* adjust err stats: timewait PCB was freed above */
1032      MEMP_STATS_DEC(err, MEMP_TCP_PCB);
1033    }
1034  }
1035  if (pcb != NULL) {
1036    memset(pcb, 0, sizeof(struct tcp_pcb));
1037    pcb->prio = TCP_PRIO_NORMAL;
1038    pcb->snd_buf = TCP_SND_BUF;
1039    pcb->snd_queuelen = 0;
1040    pcb->rcv_wnd = TCP_WND;
1041    pcb->rcv_ann_wnd = TCP_WND;
1042    pcb->tos = 0;
1043    pcb->ttl = TCP_TTL;
1044    /* As initial send MSS, we use TCP_MSS but limit it to 536.
1045       The send MSS is updated when an MSS option is received. */
1046    pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
1047    pcb->rto = 3000 / TCP_SLOW_INTERVAL;
1048    pcb->sa = 0;
1049    pcb->sv = 3000 / TCP_SLOW_INTERVAL;
1050    pcb->rtime = -1;
1051    pcb->cwnd = 1;
1052    iss = tcp_next_iss();
1053    pcb->snd_wl2 = iss;
1054    pcb->snd_nxt = iss;
1055    pcb->lastack = iss;
1056    pcb->snd_lbb = iss;   
1057    pcb->tmr = tcp_ticks;
1058
1059    pcb->polltmr = 0;
1060
1061#if LWIP_CALLBACK_API
1062    pcb->recv = tcp_recv_null;
1063#endif /* LWIP_CALLBACK_API */ 
1064   
1065    /* Init KEEPALIVE timer */
1066    pcb->keep_idle  = TCP_KEEPIDLE_DEFAULT;
1067   
1068#if LWIP_TCP_KEEPALIVE
1069    pcb->keep_intvl = TCP_KEEPINTVL_DEFAULT;
1070    pcb->keep_cnt   = TCP_KEEPCNT_DEFAULT;
1071#endif /* LWIP_TCP_KEEPALIVE */
1072
1073    pcb->keep_cnt_sent = 0;
1074  }
1075  return pcb;
1076}
1077
1078/**
1079 * Creates a new TCP protocol control block but doesn't place it on
1080 * any of the TCP PCB lists.
1081 * The pcb is not put on any list until binding using tcp_bind().
1082 *
1083 * @internal: Maybe there should be a idle TCP PCB list where these
1084 * PCBs are put on. Port reservation using tcp_bind() is implemented but
1085 * allocated pcbs that are not bound can't be killed automatically if wanting
1086 * to allocate a pcb with higher prio (@see tcp_kill_prio())
1087 *
1088 * @return a new tcp_pcb that initially is in state CLOSED
1089 */
1090struct tcp_pcb *
1091tcp_new(void)
1092{
1093  return tcp_alloc(TCP_PRIO_NORMAL);
1094}
1095
1096/**
1097 * Used to specify the argument that should be passed callback
1098 * functions.
1099 *
1100 * @param pcb tcp_pcb to set the callback argument
1101 * @param arg void pointer argument to pass to callback functions
1102 */ 
1103void
1104tcp_arg(struct tcp_pcb *pcb, void *arg)
1105{ 
1106  pcb->callback_arg = arg;
1107}
1108#if LWIP_CALLBACK_API
1109
1110/**
1111 * Used to specify the function that should be called when a TCP
1112 * connection receives data.
1113 *
1114 * @param pcb tcp_pcb to set the recv callback
1115 * @param recv callback function to call for this pcb when data is received
1116 */ 
1117void
1118tcp_recv(struct tcp_pcb *pcb,
1119   err_t (* recv)(void *arg, struct tcp_pcb *tpcb, struct pbuf *p, err_t err))
1120{
1121  pcb->recv = recv;
1122}
1123
1124/**
1125 * Used to specify the function that should be called when TCP data
1126 * has been successfully delivered to the remote host.
1127 *
1128 * @param pcb tcp_pcb to set the sent callback
1129 * @param sent callback function to call for this pcb when data is successfully sent
1130 */ 
1131void
1132tcp_sent(struct tcp_pcb *pcb,
1133   err_t (* sent)(void *arg, struct tcp_pcb *tpcb, u16_t len))
1134{
1135  pcb->sent = sent;
1136}
1137
1138/**
1139 * Used to specify the function that should be called when a fatal error
1140 * has occured on the connection.
1141 *
1142 * @param pcb tcp_pcb to set the err callback
1143 * @param errf callback function to call for this pcb when a fatal error
1144 *        has occured on the connection
1145 */ 
1146void
1147tcp_err(struct tcp_pcb *pcb,
1148   void (* errf)(void *arg, err_t err))
1149{
1150  pcb->errf = errf;
1151}
1152
1153/**
1154 * Used for specifying the function that should be called when a
1155 * LISTENing connection has been connected to another host.
1156 *
1157 * @param pcb tcp_pcb to set the accept callback
1158 * @param accept callback function to call for this pcb when LISTENing
1159 *        connection has been connected to another host
1160 */ 
1161void
1162tcp_accept(struct tcp_pcb *pcb,
1163     err_t (* accept)(void *arg, struct tcp_pcb *newpcb, err_t err))
1164{
1165  pcb->accept = accept;
1166}
1167#endif /* LWIP_CALLBACK_API */
1168
1169
1170/**
1171 * Used to specify the function that should be called periodically
1172 * from TCP. The interval is specified in terms of the TCP coarse
1173 * timer interval, which is called twice a second.
1174 *
1175 */ 
1176void
1177tcp_poll(struct tcp_pcb *pcb,
1178   err_t (* poll)(void *arg, struct tcp_pcb *tpcb), u8_t interval)
1179{
1180#if LWIP_CALLBACK_API
1181  pcb->poll = poll;
1182#endif /* LWIP_CALLBACK_API */ 
1183  pcb->pollinterval = interval;
1184}
1185
1186/**
1187 * Purges a TCP PCB. Removes any buffered data and frees the buffer memory
1188 * (pcb->ooseq, pcb->unsent and pcb->unacked are freed).
1189 *
1190 * @param pcb tcp_pcb to purge. The pcb itself is not deallocated!
1191 */
1192void
1193tcp_pcb_purge(struct tcp_pcb *pcb)
1194{
1195  if (pcb->state != CLOSED &&
1196     pcb->state != TIME_WAIT &&
1197     pcb->state != LISTEN) {
1198
1199    LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge\n"));
1200
1201#if TCP_LISTEN_BACKLOG
1202    if (pcb->state == SYN_RCVD) {
1203      /* Need to find the corresponding listen_pcb and decrease its accepts_pending */
1204      struct tcp_pcb_listen *lpcb;
1205      LWIP_ASSERT("tcp_pcb_purge: pcb->state == SYN_RCVD but tcp_listen_pcbs is NULL",
1206        tcp_listen_pcbs.listen_pcbs != NULL);
1207      for (lpcb = tcp_listen_pcbs.listen_pcbs; lpcb != NULL; lpcb = lpcb->next) {
1208        if ((lpcb->local_port == pcb->local_port) &&
1209            (ip_addr_isany(&lpcb->local_ip) ||
1210             ip_addr_cmp(&pcb->local_ip, &lpcb->local_ip))) {
1211            /* port and address of the listen pcb match the timed-out pcb */
1212            LWIP_ASSERT("tcp_pcb_purge: listen pcb does not have accepts pending",
1213              lpcb->accepts_pending > 0);
1214            lpcb->accepts_pending--;
1215            break;
1216          }
1217      }
1218    }
1219#endif /* TCP_LISTEN_BACKLOG */
1220
1221
1222    if (pcb->refused_data != NULL) {
1223      LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge: data left on ->refused_data\n"));
1224      pbuf_free(pcb->refused_data);
1225      pcb->refused_data = NULL;
1226    }
1227    if (pcb->unsent != NULL) {
1228      LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge: not all data sent\n"));
1229    }
1230    if (pcb->unacked != NULL) {
1231      LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge: data left on ->unacked\n"));
1232    }
1233#if TCP_QUEUE_OOSEQ /* LW */
1234    if (pcb->ooseq != NULL) {
1235      LWIP_DEBUGF(TCP_DEBUG, ("tcp_pcb_purge: data left on ->ooseq\n"));
1236    }
1237
1238    /* Stop the retransmission timer as it will expect data on unacked
1239       queue if it fires */
1240    pcb->rtime = -1;
1241
1242    tcp_segs_free(pcb->ooseq);
1243    pcb->ooseq = NULL;
1244#endif /* TCP_QUEUE_OOSEQ */
1245    tcp_segs_free(pcb->unsent);
1246    tcp_segs_free(pcb->unacked);
1247    pcb->unacked = pcb->unsent = NULL;
1248  }
1249}
1250
1251/**
1252 * Purges the PCB and removes it from a PCB list. Any delayed ACKs are sent first.
1253 *
1254 * @param pcblist PCB list to purge.
1255 * @param pcb tcp_pcb to purge. The pcb itself is NOT deallocated!
1256 */
1257void
1258tcp_pcb_remove(struct tcp_pcb **pcblist, struct tcp_pcb *pcb)
1259{
1260  TCP_RMV(pcblist, pcb);
1261
1262  tcp_pcb_purge(pcb);
1263 
1264  /* if there is an outstanding delayed ACKs, send it */
1265  if (pcb->state != TIME_WAIT &&
1266     pcb->state != LISTEN &&
1267     pcb->flags & TF_ACK_DELAY) {
1268    pcb->flags |= TF_ACK_NOW;
1269    tcp_output(pcb);
1270  }
1271
1272  if (pcb->state != LISTEN) {
1273    LWIP_ASSERT("unsent segments leaking", pcb->unsent == NULL);
1274    LWIP_ASSERT("unacked segments leaking", pcb->unacked == NULL);
1275#if TCP_QUEUE_OOSEQ
1276    LWIP_ASSERT("ooseq segments leaking", pcb->ooseq == NULL);
1277#endif /* TCP_QUEUE_OOSEQ */
1278  }
1279
1280  pcb->state = CLOSED;
1281
1282  LWIP_ASSERT("tcp_pcb_remove: tcp_pcbs_sane()", tcp_pcbs_sane());
1283}
1284
1285/**
1286 * Calculates a new initial sequence number for new connections.
1287 *
1288 * @return u32_t pseudo random sequence number
1289 */
1290u32_t
1291tcp_next_iss(void)
1292{
1293  static u32_t iss = 6510;
1294 
1295  iss += tcp_ticks;       /* XXX */
1296  return iss;
1297}
1298
1299#if TCP_CALCULATE_EFF_SEND_MSS
1300/**
1301 * Calcluates the effective send mss that can be used for a specific IP address
1302 * by using ip_route to determin the netif used to send to the address and
1303 * calculating the minimum of TCP_MSS and that netif's mtu (if set).
1304 */
1305u16_t
1306tcp_eff_send_mss(u16_t sendmss, struct ip_addr *addr)
1307{
1308  u16_t mss_s;
1309  struct netif *outif;
1310
1311  outif = ip_route(addr);
1312  if ((outif != NULL) && (outif->mtu != 0)) {
1313    mss_s = outif->mtu - IP_HLEN - TCP_HLEN;
1314    /* RFC 1122, chap 4.2.2.6:
1315     * Eff.snd.MSS = min(SendMSS+20, MMS_S) - TCPhdrsize - IPoptionsize
1316     * We correct for TCP options in tcp_enqueue(), and don't support
1317     * IP options
1318     */
1319    sendmss = LWIP_MIN(sendmss, mss_s);
1320  }
1321  return sendmss;
1322}
1323#endif /* TCP_CALCULATE_EFF_SEND_MSS */
1324
1325const char*
1326tcp_debug_state_str(enum tcp_state s)
1327{
1328  return tcp_state_str[s];
1329}
1330
1331#if TCP_DEBUG || TCP_INPUT_DEBUG || TCP_OUTPUT_DEBUG
1332/**
1333 * Print a tcp header for debugging purposes.
1334 *
1335 * @param tcphdr pointer to a struct tcp_hdr
1336 */
1337void
1338tcp_debug_print(struct tcp_hdr *tcphdr)
1339{
1340  LWIP_DEBUGF(TCP_DEBUG, ("TCP header:\n"));
1341  LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
1342  LWIP_DEBUGF(TCP_DEBUG, ("|    %5"U16_F"      |    %5"U16_F"      | (src port, dest port)\n",
1343         ntohs(tcphdr->src), ntohs(tcphdr->dest)));
1344  LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
1345  LWIP_DEBUGF(TCP_DEBUG, ("|           %010"U32_F"          | (seq no)\n",
1346          ntohl(tcphdr->seqno)));
1347  LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
1348  LWIP_DEBUGF(TCP_DEBUG, ("|           %010"U32_F"          | (ack no)\n",
1349         ntohl(tcphdr->ackno)));
1350  LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
1351  LWIP_DEBUGF(TCP_DEBUG, ("| %2"U16_F" |   |%"U16_F"%"U16_F"%"U16_F"%"U16_F"%"U16_F"%"U16_F"|     %5"U16_F"     | (hdrlen, flags (",
1352       TCPH_HDRLEN(tcphdr),
1353         TCPH_FLAGS(tcphdr) >> 5 & 1,
1354         TCPH_FLAGS(tcphdr) >> 4 & 1,
1355         TCPH_FLAGS(tcphdr) >> 3 & 1,
1356         TCPH_FLAGS(tcphdr) >> 2 & 1,
1357         TCPH_FLAGS(tcphdr) >> 1 & 1,
1358         TCPH_FLAGS(tcphdr) & 1,
1359         ntohs(tcphdr->wnd)));
1360  tcp_debug_print_flags(TCPH_FLAGS(tcphdr));
1361  LWIP_DEBUGF(TCP_DEBUG, ("), win)\n"));
1362  LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
1363  LWIP_DEBUGF(TCP_DEBUG, ("|    0x%04"X16_F"     |     %5"U16_F"     | (chksum, urgp)\n",
1364         ntohs(tcphdr->chksum), ntohs(tcphdr->urgp)));
1365  LWIP_DEBUGF(TCP_DEBUG, ("+-------------------------------+\n"));
1366}
1367
1368/**
1369 * Print a tcp state for debugging purposes.
1370 *
1371 * @param s enum tcp_state to print
1372 */
1373void
1374tcp_debug_print_state(enum tcp_state s)
1375{
1376  LWIP_DEBUGF(TCP_DEBUG, ("State: %s\n", tcp_state_str[s]));
1377}
1378
1379/**
1380 * Print tcp flags for debugging purposes.
1381 *
1382 * @param flags tcp flags, all active flags are printed
1383 */
1384void
1385tcp_debug_print_flags(u8_t flags)
1386{
1387  if (flags & TCP_FIN) {
1388    LWIP_DEBUGF(TCP_DEBUG, ("FIN "));
1389  }
1390  if (flags & TCP_SYN) {
1391    LWIP_DEBUGF(TCP_DEBUG, ("SYN "));
1392  }
1393  if (flags & TCP_RST) {
1394    LWIP_DEBUGF(TCP_DEBUG, ("RST "));
1395  }
1396  if (flags & TCP_PSH) {
1397    LWIP_DEBUGF(TCP_DEBUG, ("PSH "));
1398  }
1399  if (flags & TCP_ACK) {
1400    LWIP_DEBUGF(TCP_DEBUG, ("ACK "));
1401  }
1402  if (flags & TCP_URG) {
1403    LWIP_DEBUGF(TCP_DEBUG, ("URG "));
1404  }
1405  if (flags & TCP_ECE) {
1406    LWIP_DEBUGF(TCP_DEBUG, ("ECE "));
1407  }
1408  if (flags & TCP_CWR) {
1409    LWIP_DEBUGF(TCP_DEBUG, ("CWR "));
1410  }
1411  LWIP_DEBUGF(TCP_DEBUG, ("\n"));
1412}
1413
1414/**
1415 * Print all tcp_pcbs in every list for debugging purposes.
1416 */
1417void
1418tcp_debug_print_pcbs(void)
1419{
1420  struct tcp_pcb *pcb;
1421  LWIP_DEBUGF(TCP_DEBUG, ("Active PCB states:\n"));
1422  for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
1423    LWIP_DEBUGF(TCP_DEBUG, ("[%p]Local port %"U16_F", foreign port %"U16_F" snd_nxt %"U32_F" rcv_nxt %"U32_F" ",
1424                       pcb, pcb->local_port, pcb->remote_port,
1425                       pcb->snd_nxt, pcb->rcv_nxt));
1426    tcp_debug_print_state(pcb->state);
1427  }   
1428  LWIP_DEBUGF(TCP_DEBUG, ("Listen PCB states:\n"));
1429  for(pcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs; pcb != NULL; pcb = pcb->next) {
1430    LWIP_DEBUGF(TCP_DEBUG, ("[%p]Local port %"U16_F", foreign port %"U16_F" snd_nxt %"U32_F" rcv_nxt %"U32_F" ",
1431                       pcb, pcb->local_port, pcb->remote_port,
1432                       pcb->snd_nxt, pcb->rcv_nxt));
1433    tcp_debug_print_state(pcb->state);
1434  }   
1435  LWIP_DEBUGF(TCP_DEBUG, ("TIME-WAIT PCB states:\n"));
1436  for(pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
1437    LWIP_DEBUGF(TCP_DEBUG, ("[%p]Local port %"U16_F", foreign port %"U16_F" snd_nxt %"U32_F" rcv_nxt %"U32_F" ",
1438                       pcb, pcb->local_port, pcb->remote_port,
1439                       pcb->snd_nxt, pcb->rcv_nxt));
1440    tcp_debug_print_state(pcb->state);
1441  }   
1442}
1443
1444/**
1445 * Check state consistency of the tcp_pcb lists.
1446 */
1447s16_t
1448tcp_pcbs_sane(void)
1449{
1450  struct tcp_pcb *pcb;
1451  for(pcb = tcp_active_pcbs; pcb != NULL; pcb = pcb->next) {
1452    LWIP_ASSERT("tcp_pcbs_sane: active pcb->state != CLOSED", pcb->state != CLOSED);
1453    LWIP_ASSERT("tcp_pcbs_sane: active pcb->state != LISTEN", pcb->state != LISTEN);
1454    LWIP_ASSERT("tcp_pcbs_sane: active pcb->state != TIME-WAIT", pcb->state != TIME_WAIT);
1455  }
1456  for(pcb = tcp_tw_pcbs; pcb != NULL; pcb = pcb->next) {
1457    LWIP_ASSERT("tcp_pcbs_sane: tw pcb->state == TIME-WAIT", pcb->state == TIME_WAIT);
1458  }
1459  return 1;
1460}
1461#endif /* TCP_DEBUG */
1462
1463#endif /* LWIP_TCP */
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