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1 /*
2  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
3  * All rights reserved.
4  *
5  * Redistribution and use in source and binary forms, with or without modification,
6  * are permitted provided that the following conditions are met:
7  *
8  * 1. Redistributions of source code must retain the above copyright notice,
9  *    this list of conditions and the following disclaimer.
10  * 2. Redistributions in binary form must reproduce the above copyright notice,
11  *    this list of conditions and the following disclaimer in the documentation
12  *    and/or other materials provided with the distribution.
13  * 3. The name of the author may not be used to endorse or promote products
14  *    derived from this software without specific prior written permission.
15  *
16  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
17  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
18  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
19  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
20  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
21  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
22  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
23  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
24  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
25  * OF SUCH DAMAGE.
26  *
27  * This file is part of the lwIP TCP/IP stack.
28  *
29  * Author: Adam Dunkels <adam@sics.se>
30  *
31  */
32 #ifndef __LWIP_TCP_IMPL_H__
33 #define __LWIP_TCP_IMPL_H__
34 
35 #include "lwip/opt.h"
36 
37 #if LWIP_TCP /* don't build if not configured for use in lwipopts.h */
38 
39 #include "lwip/tcp.h"
40 #include "lwip/sys.h"
41 #include "lwip/mem.h"
42 #include "lwip/pbuf.h"
43 #include "lwip/ip.h"
44 #include "lwip/icmp.h"
45 #include "lwip/err.h"
46 
47 #ifdef __cplusplus
48 extern "C" {
49 #endif
50 
51 /* Functions for interfacing with TCP: */
52 
53 /* Lower layer interface to TCP: */
54 #define tcp_init() /* Compatibility define, no init needed. */
55 void             tcp_tmr     (void);  /* Must be called every
56                                          TCP_TMR_INTERVAL
57                                          ms. (Typically 250 ms). */
58 /* It is also possible to call these two functions at the right
59    intervals (instead of calling tcp_tmr()). */
60 void             tcp_slowtmr (void);
61 void             tcp_fasttmr (void);
62 
63 
64 /* Only used by IP to pass a TCP segment to TCP: */
65 void             tcp_input   (struct pbuf *p, struct netif *inp);
66 /* Used within the TCP code only: */
67 struct tcp_pcb * tcp_alloc   (u8_t prio);
68 void             tcp_abandon (struct tcp_pcb *pcb, int reset);
69 err_t            tcp_send_empty_ack(struct tcp_pcb *pcb);
70 void             tcp_rexmit  (struct tcp_pcb *pcb);
71 void             tcp_rexmit_rto  (struct tcp_pcb *pcb);
72 void             tcp_rexmit_fast (struct tcp_pcb *pcb);
73 u32_t            tcp_update_rcv_ann_wnd(struct tcp_pcb *pcb);
74 
75 /**
76  * This is the Nagle algorithm: try to combine user data to send as few TCP
77  * segments as possible. Only send if
78  * - no previously transmitted data on the connection remains unacknowledged or
79  * - the TF_NODELAY flag is set (nagle algorithm turned off for this pcb) or
80  * - the only unsent segment is at least pcb->mss bytes long (or there is more
81  *   than one unsent segment - with lwIP, this can happen although unsent->len < mss)
82  * - or if we are in fast-retransmit (TF_INFR)
83  */
84 #define tcp_do_output_nagle(tpcb) ((((tpcb)->unacked == NULL) || \
85                             ((tpcb)->flags & (TF_NODELAY | TF_INFR)) || \
86                             (((tpcb)->unsent != NULL) && (((tpcb)->unsent->next != NULL) || \
87                               ((tpcb)->unsent->len >= (tpcb)->mss))) \
88                             ) ? 1 : 0)
89 #define tcp_output_nagle(tpcb) (tcp_do_output_nagle(tpcb) ? tcp_output(tpcb) : ERR_OK)
90 
91 
92 #define TCP_SEQ_LT(a,b)     ((s32_t)((a)-(b)) < 0)
93 #define TCP_SEQ_LEQ(a,b)    ((s32_t)((a)-(b)) <= 0)
94 #define TCP_SEQ_GT(a,b)     ((s32_t)((a)-(b)) > 0)
95 #define TCP_SEQ_GEQ(a,b)    ((s32_t)((a)-(b)) >= 0)
96 /* is b<=a<=c? */
97 #if 0 /* see bug #10548 */
98 #define TCP_SEQ_BETWEEN(a,b,c) ((c)-(b) >= (a)-(b))
99 #endif
100 #define TCP_SEQ_BETWEEN(a,b,c) (TCP_SEQ_GEQ(a,b) && TCP_SEQ_LEQ(a,c))
101 #define TCP_FIN 0x01U
102 #define TCP_SYN 0x02U
103 #define TCP_RST 0x04U
104 #define TCP_PSH 0x08U
105 #define TCP_ACK 0x10U
106 #define TCP_URG 0x20U
107 #define TCP_ECE 0x40U
108 #define TCP_CWR 0x80U
109 
110 #define TCP_FLAGS 0x3fU
111 
112 /* Length of the TCP header, excluding options. */
113 #define TCP_HLEN 20
114 
115 #ifndef TCP_TMR_INTERVAL
116 #define TCP_TMR_INTERVAL       250  /* The TCP timer interval in milliseconds. */
117 #endif /* TCP_TMR_INTERVAL */
118 
119 #ifndef TCP_FAST_INTERVAL
120 #define TCP_FAST_INTERVAL      TCP_TMR_INTERVAL /* the fine grained timeout in milliseconds */
121 #endif /* TCP_FAST_INTERVAL */
122 
123 #ifndef TCP_SLOW_INTERVAL
124 #define TCP_SLOW_INTERVAL      (2*TCP_TMR_INTERVAL)  /* the coarse grained timeout in milliseconds */
125 #endif /* TCP_SLOW_INTERVAL */
126 
127 #define TCP_FIN_WAIT_TIMEOUT 20000 /* milliseconds */
128 #define TCP_SYN_RCVD_TIMEOUT 20000 /* milliseconds */
129 
130 #define TCP_OOSEQ_TIMEOUT        6U /* x RTO */
131 
132 #ifndef TCP_MSL
133 #define TCP_MSL 60000UL /* The maximum segment lifetime in milliseconds */
134 #endif
135 
136 /* Keepalive values, compliant with RFC 1122. Don't change this unless you know what you're doing */
137 #ifndef  TCP_KEEPIDLE_DEFAULT
138 #define  TCP_KEEPIDLE_DEFAULT     7200000UL /* Default KEEPALIVE timer in milliseconds */
139 #endif
140 
141 #ifndef  TCP_KEEPINTVL_DEFAULT
142 #define  TCP_KEEPINTVL_DEFAULT    75000UL   /* Default Time between KEEPALIVE probes in milliseconds */
143 #endif
144 
145 #ifndef  TCP_KEEPCNT_DEFAULT
146 #define  TCP_KEEPCNT_DEFAULT      9U        /* Default Counter for KEEPALIVE probes */
147 #endif
148 
149 #define  TCP_MAXIDLE              TCP_KEEPCNT_DEFAULT * TCP_KEEPINTVL_DEFAULT  /* Maximum KEEPALIVE probe time */
150 
151 /* Fields are (of course) in network byte order.
152  * Some fields are converted to host byte order in tcp_input().
153  */
154 #ifdef PACK_STRUCT_USE_INCLUDES
155 #  include "arch/bpstruct.h"
156 #endif
157 PACK_STRUCT_BEGIN
158 struct tcp_hdr {
159   PACK_STRUCT_FIELD(u16_t src);
160   PACK_STRUCT_FIELD(u16_t dest);
161   PACK_STRUCT_FIELD(u32_t seqno);
162   PACK_STRUCT_FIELD(u32_t ackno);
163   PACK_STRUCT_FIELD(u16_t _hdrlen_rsvd_flags);
164   PACK_STRUCT_FIELD(u16_t wnd);
165   PACK_STRUCT_FIELD(u16_t chksum);
166   PACK_STRUCT_FIELD(u16_t urgp);
167 } PACK_STRUCT_STRUCT;
168 PACK_STRUCT_END
169 #ifdef PACK_STRUCT_USE_INCLUDES
170 #  include "arch/epstruct.h"
171 #endif
172 
173 #define TCPH_OFFSET(phdr) (ntohs((phdr)->_hdrlen_rsvd_flags) >> 8)
174 #define TCPH_HDRLEN(phdr) (ntohs((phdr)->_hdrlen_rsvd_flags) >> 12)
175 #define TCPH_FLAGS(phdr)  (ntohs((phdr)->_hdrlen_rsvd_flags) & TCP_FLAGS)
176 
177 #define TCPH_OFFSET_SET(phdr, offset) (phdr)->_hdrlen_rsvd_flags = htons(((offset) << 8) | TCPH_FLAGS(phdr))
178 #define TCPH_HDRLEN_SET(phdr, len) (phdr)->_hdrlen_rsvd_flags = htons(((len) << 12) | TCPH_FLAGS(phdr))
179 #define TCPH_FLAGS_SET(phdr, flags) (phdr)->_hdrlen_rsvd_flags = (((phdr)->_hdrlen_rsvd_flags & PP_HTONS((u16_t)(~(u16_t)(TCP_FLAGS)))) | htons(flags))
180 #define TCPH_HDRLEN_FLAGS_SET(phdr, len, flags) (phdr)->_hdrlen_rsvd_flags = htons(((len) << 12) | (flags))
181 
182 #define TCPH_SET_FLAG(phdr, flags ) (phdr)->_hdrlen_rsvd_flags = ((phdr)->_hdrlen_rsvd_flags | htons(flags))
183 #define TCPH_UNSET_FLAG(phdr, flags) (phdr)->_hdrlen_rsvd_flags = htons(ntohs((phdr)->_hdrlen_rsvd_flags) | (TCPH_FLAGS(phdr) & ~(flags)) )
184 
185 #define TCP_TCPLEN(seg) ((seg)->len + ((TCPH_FLAGS((seg)->tcphdr) & (TCP_FIN | TCP_SYN)) != 0))
186 
187 /** Flags used on input processing, not on pcb->flags
188 */
189 #define TF_RESET     (u8_t)0x08U   /* Connection was reset. */
190 #define TF_CLOSED    (u8_t)0x10U   /* Connection was sucessfully closed. */
191 #define TF_GOT_FIN   (u8_t)0x20U   /* Connection was closed by the remote end. */
192 
193 
194 #if LWIP_EVENT_API
195 
196 #define TCP_EVENT_ACCEPT(pcb,err,ret)    ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
197                 LWIP_EVENT_ACCEPT, NULL, 0, err)
198 #define TCP_EVENT_SENT(pcb,space,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
199                    LWIP_EVENT_SENT, NULL, space, ERR_OK)
200 #define TCP_EVENT_RECV(pcb,p,err,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
201                 LWIP_EVENT_RECV, (p), 0, (err))
202 #define TCP_EVENT_CLOSED(pcb,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
203                 LWIP_EVENT_RECV, NULL, 0, ERR_OK)
204 #define TCP_EVENT_CONNECTED(pcb,err,ret) ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
205                 LWIP_EVENT_CONNECTED, NULL, 0, (err))
206 #define TCP_EVENT_POLL(pcb,ret)       ret = lwip_tcp_event((pcb)->callback_arg, (pcb),\
207                 LWIP_EVENT_POLL, NULL, 0, ERR_OK)
208 #define TCP_EVENT_ERR(errf,arg,err)  lwip_tcp_event((arg), NULL, \
209                 LWIP_EVENT_ERR, NULL, 0, (err))
210 
211 #else /* LWIP_EVENT_API */
212 
213 #define TCP_EVENT_ACCEPT(pcb,err,ret)                          \
214   do {                                                         \
215     if((pcb)->accept != NULL)                                  \
216       (ret) = (pcb)->accept((pcb)->callback_arg,(pcb),(err));  \
217     else (ret) = ERR_ARG;                                      \
218   } while (0)
219 
220 #define TCP_EVENT_SENT(pcb,space,ret)                          \
221   do {                                                         \
222     if((pcb)->sent != NULL)                                    \
223       (ret) = (pcb)->sent((pcb)->callback_arg,(pcb),(space));  \
224     else (ret) = ERR_OK;                                       \
225   } while (0)
226 
227 #define TCP_EVENT_RECV(pcb,p,err,ret)                          \
228   do {                                                         \
229     if((pcb)->recv != NULL) {                                  \
230       (ret) = (pcb)->recv((pcb)->callback_arg,(pcb),(p),(err));\
231     } else {                                                   \
232       (ret) = tcp_recv_null(NULL, (pcb), (p), (err));          \
233     }                                                          \
234   } while (0)
235 
236 #define TCP_EVENT_CLOSED(pcb,ret)                                \
237   do {                                                           \
238     if(((pcb)->recv != NULL)) {                                  \
239       (ret) = (pcb)->recv((pcb)->callback_arg,(pcb),NULL,ERR_OK);\
240     } else {                                                     \
241       (ret) = ERR_OK;                                            \
242     }                                                            \
243   } while (0)
244 
245 #define TCP_EVENT_CONNECTED(pcb,err,ret)                         \
246   do {                                                           \
247     if((pcb)->connected != NULL)                                 \
248       (ret) = (pcb)->connected((pcb)->callback_arg,(pcb),(err)); \
249     else (ret) = ERR_OK;                                         \
250   } while (0)
251 
252 #define TCP_EVENT_POLL(pcb,ret)                                \
253   do {                                                         \
254     if((pcb)->poll != NULL)                                    \
255       (ret) = (pcb)->poll((pcb)->callback_arg,(pcb));          \
256     else (ret) = ERR_OK;                                       \
257   } while (0)
258 
259 #define TCP_EVENT_ERR(errf,arg,err)                            \
260   do {                                                         \
261     if((errf) != NULL)                                         \
262       (errf)((arg),(err));                                     \
263   } while (0)
264 
265 #endif /* LWIP_EVENT_API */
266 
267 /** Enabled extra-check for TCP_OVERSIZE if LWIP_DEBUG is enabled */
268 #if TCP_OVERSIZE && defined(LWIP_DEBUG)
269 #define TCP_OVERSIZE_DBGCHECK 1
270 #else
271 #define TCP_OVERSIZE_DBGCHECK 0
272 #endif
273 
274 /** Don't generate checksum on copy if CHECKSUM_GEN_TCP is disabled */
275 #define TCP_CHECKSUM_ON_COPY  (LWIP_CHECKSUM_ON_COPY && CHECKSUM_GEN_TCP)
276 
277 /* This structure represents a TCP segment on the unsent, unacked and ooseq queues */
278 struct tcp_seg {
279   struct tcp_seg *next;    /* used when putting segements on a queue */
280   struct pbuf *p;          /* buffer containing data + TCP header */
281   u16_t len;               /* the TCP length of this segment */
282 #if TCP_OVERSIZE_DBGCHECK
283   u16_t oversize_left;     /* Extra bytes available at the end of the last
284                               pbuf in unsent (used for asserting vs.
285                               tcp_pcb.unsent_oversized only) */
286 #endif /* TCP_OVERSIZE_DBGCHECK */
287 #if TCP_CHECKSUM_ON_COPY
288   u16_t chksum;
289   u8_t  chksum_swapped;
290 #endif /* TCP_CHECKSUM_ON_COPY */
291   u8_t  flags;
292 #define TF_SEG_OPTS_MSS         (u8_t)0x01U /* Include MSS option. */
293 #define TF_SEG_OPTS_TS          (u8_t)0x02U /* Include timestamp option. */
294 #define TF_SEG_DATA_CHECKSUMMED (u8_t)0x04U /* ALL data (not the header) is
295                                                checksummed into 'chksum' */
296   struct tcp_hdr *tcphdr;  /* the TCP header */
297 };
298 
299 #define LWIP_TCP_OPT_LENGTH(flags)              \
300   (flags & TF_SEG_OPTS_MSS ? 4  : 0) +          \
301   (flags & TF_SEG_OPTS_TS  ? 12 : 0)
302 
303 /** This returns a TCP header option for MSS in an u32_t */
304 #define TCP_BUILD_MSS_OPTION(x) (x) = PP_HTONL(((u32_t)2 << 24) |          \
305                                                ((u32_t)4 << 16) |          \
306                                                (((u32_t)TCP_MSS / 256) << 8) | \
307                                                (TCP_MSS & 255))
308 
309 /* Global variables: */
310 extern struct tcp_pcb *tcp_input_pcb;
311 extern u32_t tcp_ticks;
312 
313 /* The TCP PCB lists. */
314 union tcp_listen_pcbs_t { /* List of all TCP PCBs in LISTEN state. */
315   struct tcp_pcb_listen *listen_pcbs;
316   struct tcp_pcb *pcbs;
317 };
318 extern struct tcp_pcb *tcp_bound_pcbs;
319 extern union tcp_listen_pcbs_t tcp_listen_pcbs;
320 extern struct tcp_pcb *tcp_active_pcbs;  /* List of all TCP PCBs that are in a
321               state in which they accept or send
322               data. */
323 extern struct tcp_pcb *tcp_tw_pcbs;      /* List of all TCP PCBs in TIME-WAIT. */
324 
325 extern struct tcp_pcb *tcp_tmp_pcb;      /* Only used for temporary storage. */
326 
327 /* Axioms about the above lists:
328    1) Every TCP PCB that is not CLOSED is in one of the lists.
329    2) A PCB is only in one of the lists.
330    3) All PCBs in the tcp_listen_pcbs list is in LISTEN state.
331    4) All PCBs in the tcp_tw_pcbs list is in TIME-WAIT state.
332 */
333 /* Define two macros, TCP_REG and TCP_RMV that registers a TCP PCB
334    with a PCB list or removes a PCB from a list, respectively. */
335 #ifndef TCP_DEBUG_PCB_LISTS
336 #define TCP_DEBUG_PCB_LISTS 0
337 #endif
338 #if TCP_DEBUG_PCB_LISTS
339 #define TCP_REG(pcbs, npcb) do {\
340                             LWIP_DEBUGF(TCP_DEBUG, ("TCP_REG %p local port %d\n", (npcb), (npcb)->local_port)); \
341                             for(tcp_tmp_pcb = *(pcbs); \
342           tcp_tmp_pcb != NULL; \
343         tcp_tmp_pcb = tcp_tmp_pcb->next) { \
344                                 LWIP_ASSERT("TCP_REG: already registered\n", tcp_tmp_pcb != (npcb)); \
345                             } \
346                             LWIP_ASSERT("TCP_REG: pcb->state != CLOSED", ((pcbs) == &tcp_bound_pcbs) || ((npcb)->state != CLOSED)); \
347                             (npcb)->next = *(pcbs); \
348                             LWIP_ASSERT("TCP_REG: npcb->next != npcb", (npcb)->next != (npcb)); \
349                             *(pcbs) = (npcb); \
350                             LWIP_ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
351               tcp_timer_needed(); \
352                             } while(0)
353 #define TCP_RMV(pcbs, npcb) do { \
354                             LWIP_ASSERT("TCP_RMV: pcbs != NULL", *(pcbs) != NULL); \
355                             LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removing %p from %p\n", (npcb), *(pcbs))); \
356                             if(*(pcbs) == (npcb)) { \
357                                *(pcbs) = (*pcbs)->next; \
358                             } else for(tcp_tmp_pcb = *(pcbs); tcp_tmp_pcb != NULL; tcp_tmp_pcb = tcp_tmp_pcb->next) { \
359                                if(tcp_tmp_pcb->next == (npcb)) { \
360                                   tcp_tmp_pcb->next = (npcb)->next; \
361                                   break; \
362                                } \
363                             } \
364                             (npcb)->next = NULL; \
365                             LWIP_ASSERT("TCP_RMV: tcp_pcbs sane", tcp_pcbs_sane()); \
366                             LWIP_DEBUGF(TCP_DEBUG, ("TCP_RMV: removed %p from %p\n", (npcb), *(pcbs))); \
367                             } while(0)
368 
369 #else /* LWIP_DEBUG */
370 
371 #define TCP_REG(pcbs, npcb)                        \
372   do {                                             \
373     (npcb)->next = *pcbs;                          \
374     *(pcbs) = (npcb);                              \
375     tcp_timer_needed();                            \
376   } while (0)
377 
378 #define TCP_RMV(pcbs, npcb)                        \
379   do {                                             \
380     if(*(pcbs) == (npcb)) {                        \
381       (*(pcbs)) = (*pcbs)->next;                   \
382     }                                              \
383     else {                                         \
384       for(tcp_tmp_pcb = *pcbs;                     \
385           tcp_tmp_pcb != NULL;                     \
386           tcp_tmp_pcb = tcp_tmp_pcb->next) {       \
387         if(tcp_tmp_pcb->next == (npcb)) {          \
388           tcp_tmp_pcb->next = (npcb)->next;        \
389           break;                                   \
390         }                                          \
391       }                                            \
392     }                                              \
393     (npcb)->next = NULL;                           \
394   } while(0)
395 
396 #endif /* LWIP_DEBUG */
397 
398 
399 /* Internal functions: */
400 struct tcp_pcb *tcp_pcb_copy(struct tcp_pcb *pcb);
401 void tcp_pcb_purge(struct tcp_pcb *pcb);
402 void tcp_pcb_remove(struct tcp_pcb **pcblist, struct tcp_pcb *pcb);
403 
404 void tcp_segs_free(struct tcp_seg *seg);
405 void tcp_seg_free(struct tcp_seg *seg);
406 struct tcp_seg *tcp_seg_copy(struct tcp_seg *seg);
407 
408 #define tcp_ack(pcb)                               \
409   do {                                             \
410     if((pcb)->flags & TF_ACK_DELAY) {              \
411       (pcb)->flags &= ~TF_ACK_DELAY;               \
412       (pcb)->flags |= TF_ACK_NOW;                  \
413     }                                              \
414     else {                                         \
415       (pcb)->flags |= TF_ACK_DELAY;                \
416     }                                              \
417   } while (0)
418 
419 #define tcp_ack_now(pcb)                           \
420   do {                                             \
421     (pcb)->flags |= TF_ACK_NOW;                    \
422   } while (0)
423 
424 err_t tcp_send_fin(struct tcp_pcb *pcb);
425 err_t tcp_enqueue_flags(struct tcp_pcb *pcb, u8_t flags);
426 
427 void tcp_rexmit_seg(struct tcp_pcb *pcb, struct tcp_seg *seg);
428 
429 void tcp_rst(u32_t seqno, u32_t ackno,
430        ip_addr_t *local_ip, ip_addr_t *remote_ip,
431        u16_t local_port, u16_t remote_port);
432 
433 u32_t tcp_next_iss(void);
434 
435 void tcp_keepalive(struct tcp_pcb *pcb);
436 void tcp_zero_window_probe(struct tcp_pcb *pcb);
437 
438 #if TCP_CALCULATE_EFF_SEND_MSS
439 u16_t tcp_eff_send_mss(u16_t sendmss, ip_addr_t *addr);
440 #endif /* TCP_CALCULATE_EFF_SEND_MSS */
441 
442 #if LWIP_CALLBACK_API
443 err_t tcp_recv_null(void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err);
444 #endif /* LWIP_CALLBACK_API */
445 
446 #if TCP_DEBUG || TCP_INPUT_DEBUG || TCP_OUTPUT_DEBUG
447 void tcp_debug_print(struct tcp_hdr *tcphdr);
448 void tcp_debug_print_flags(u8_t flags);
449 void tcp_debug_print_state(enum tcp_state s);
450 void tcp_debug_print_pcbs(void);
451 s16_t tcp_pcbs_sane(void);
452 #else
453 #  define tcp_debug_print(tcphdr)
454 #  define tcp_debug_print_flags(flags)
455 #  define tcp_debug_print_state(s)
456 #  define tcp_debug_print_pcbs()
457 #  define tcp_pcbs_sane() 1
458 #endif /* TCP_DEBUG */
459 
460 /** External function (implemented in timers.c), called when TCP detects
461  * that a timer is needed (i.e. active- or time-wait-pcb found). */
462 void tcp_timer_needed(void);
463 
464 
465 #ifdef __cplusplus
466 }
467 #endif
468 
469 #endif /* LWIP_TCP */
470 
471 #endif /* __LWIP_TCP_H__ */
472