3 * Packet buffer management
5 * Packets are built from the pbuf data structure. It supports dynamic
6 * memory allocation for packet contents or can reference externally
7 * managed packet contents both in RAM and ROM. Quick allocation for
8 * incoming packets is provided through pools with fixed sized pbufs.
10 * A packet may span over multiple pbufs, chained as a singly linked
11 * list. This is called a "pbuf chain".
13 * Multiple packets may be queued, also using this singly linked list.
14 * This is called a "packet queue".
16 * So, a packet queue consists of one or more pbuf chains, each of
17 * which consist of one or more pbufs. Currently, queues are only
18 * supported in a limited section of lwIP, this is the etharp queueing
19 * code. Outside of this section no packet queues are supported yet.
21 * The differences between a pbuf chain and a packet queue are very
24 * The last pbuf of a packet has a ->tot_len field that equals the
25 * ->len field. It can be found by traversing the list. If the last
26 * pbuf of a packet has a ->next field other than NULL, more packets
29 * Therefore, looping through a pbuf of a single packet, has an
30 * loop end condition (tot_len == p->len), NOT (next == NULL).
34 * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
35 * All rights reserved.
37 * Redistribution and use in source and binary forms, with or without modification,
38 * are permitted provided that the following conditions are met:
40 * 1. Redistributions of source code must retain the above copyright notice,
41 * this list of conditions and the following disclaimer.
42 * 2. Redistributions in binary form must reproduce the above copyright notice,
43 * this list of conditions and the following disclaimer in the documentation
44 * and/or other materials provided with the distribution.
45 * 3. The name of the author may not be used to endorse or promote products
46 * derived from this software without specific prior written permission.
48 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
49 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
50 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
51 * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
52 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
53 * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
54 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
55 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
56 * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
59 * This file is part of the lwIP TCP/IP stack.
61 * Author: Adam Dunkels <adam@sics.se>
68 #include "lwip/stats.h"
71 #include "lwip/memp.h"
72 #include "lwip/pbuf.h"
74 #include "arch/perf.h"
76 static u8_t pbuf_pool_memory
[MEM_ALIGNMENT
- 1 + PBUF_POOL_SIZE
* MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE
+ sizeof(struct pbuf
))];
78 #if !SYS_LIGHTWEIGHT_PROT
79 static volatile u8_t pbuf_pool_free_lock
, pbuf_pool_alloc_lock
;
80 static sys_sem pbuf_pool_free_sem
;
83 static struct pbuf
*pbuf_pool
= NULL
;
86 * Initializes the pbuf module.
88 * A large part of memory is allocated for holding the pool of pbufs.
89 * The size of the individual pbufs in the pool is given by the size
90 * parameter, and the number of pbufs in the pool by the num parameter.
92 * After the memory has been allocated, the pbufs are set up. The
93 * ->next pointer in each pbuf is set up to point to the next pbuf in
100 struct pbuf
*p
, *q
= NULL
;
103 pbuf_pool
= (struct pbuf
*)MEM_ALIGN(pbuf_pool_memory
);
106 lwip_stats
.pbuf
.avail
= PBUF_POOL_SIZE
;
107 #endif /* PBUF_STATS */
109 /* Set up ->next pointers to link the pbufs of the pool together */
112 for(i
= 0; i
< PBUF_POOL_SIZE
; ++i
) {
113 p
->next
= (struct pbuf
*)((u8_t
*)p
+ PBUF_POOL_BUFSIZE
+ sizeof(struct pbuf
));
114 p
->len
= p
->tot_len
= PBUF_POOL_BUFSIZE
;
115 p
->payload
= MEM_ALIGN((void *)((u8_t
*)p
+ sizeof(struct pbuf
)));
116 p
->flags
= PBUF_FLAG_POOL
;
121 /* The ->next pointer of last pbuf is NULL to indicate that there
122 are no more pbufs in the pool */
125 #if !SYS_LIGHTWEIGHT_PROT
126 pbuf_pool_alloc_lock
= 0;
127 pbuf_pool_free_lock
= 0;
128 LWP_SemInit(&pbuf_pool_free_sem
,1,1);
133 * @internal only called from pbuf_alloc()
136 pbuf_pool_alloc(void)
138 struct pbuf
*p
= NULL
;
140 SYS_ARCH_DECL_PROTECT(old_level
);
141 SYS_ARCH_PROTECT(old_level
);
143 #if !SYS_LIGHTWEIGHT_PROT
144 /* Next, check the actual pbuf pool, but if the pool is locked, we
145 pretend to be out of buffers and return NULL. */
146 if (pbuf_pool_free_lock
) {
148 ++lwip_stats
.pbuf
.alloc_locked
;
149 #endif /* PBUF_STATS */
152 pbuf_pool_alloc_lock
= 1;
153 if (!pbuf_pool_free_lock
) {
154 #endif /* SYS_LIGHTWEIGHT_PROT */
159 #if !SYS_LIGHTWEIGHT_PROT
162 ++lwip_stats
.pbuf
.alloc_locked
;
163 #endif /* PBUF_STATS */
165 pbuf_pool_alloc_lock
= 0;
166 #endif /* SYS_LIGHTWEIGHT_PROT */
170 ++lwip_stats
.pbuf
.used
;
171 if (lwip_stats
.pbuf
.used
> lwip_stats
.pbuf
.max
) {
172 lwip_stats
.pbuf
.max
= lwip_stats
.pbuf
.used
;
175 #endif /* PBUF_STATS */
177 SYS_ARCH_UNPROTECT(old_level
);
183 * Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).
185 * The actual memory allocated for the pbuf is determined by the
186 * layer at which the pbuf is allocated and the requested size
187 * (from the size parameter).
189 * @param flag this parameter decides how and where the pbuf
190 * should be allocated as follows:
192 * - PBUF_RAM: buffer memory for pbuf is allocated as one large
193 * chunk. This includes protocol headers as well.
194 * - PBUF_ROM: no buffer memory is allocated for the pbuf, even for
195 * protocol headers. Additional headers must be prepended
196 * by allocating another pbuf and chain in to the front of
197 * the ROM pbuf. It is assumed that the memory used is really
198 * similar to ROM in that it is immutable and will not be
199 * changed. Memory which is dynamic should generally not
200 * be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
201 * - PBUF_REF: no buffer memory is allocated for the pbuf, even for
202 * protocol headers. It is assumed that the pbuf is only
203 * being used in a single thread. If the pbuf gets queued,
204 * then pbuf_take should be called to copy the buffer.
205 * - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from
206 * the pbuf pool that is allocated during pbuf_init().
208 * @return the allocated pbuf. If multiple pbufs where allocated, this
209 * is the first pbuf of a pbuf chain.
212 pbuf_alloc(pbuf_layer l
, u16_t length
, pbuf_flag flag
)
214 struct pbuf
*p
, *q
, *r
;
216 s32_t rem_len
; /* remaining length */
217 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 3, ("pbuf_alloc(length=%"U16_F
")\n", length
));
219 /* determine header offset */
223 /* add room for transport (often TCP) layer header */
224 offset
+= PBUF_TRANSPORT_HLEN
;
227 /* add room for IP layer header */
228 offset
+= PBUF_IP_HLEN
;
231 /* add room for link layer header */
232 offset
+= PBUF_LINK_HLEN
;
237 LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0);
243 /* allocate head of pbuf chain into p */
244 p
= pbuf_pool_alloc();
245 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 3, ("pbuf_alloc: allocated pbuf %p\n", (void *)p
));
248 ++lwip_stats
.pbuf
.err
;
249 #endif /* PBUF_STATS */
254 /* make the payload pointer point 'offset' bytes into pbuf data memory */
255 p
->payload
= MEM_ALIGN((void *)((u8_t
*)p
+ (sizeof(struct pbuf
) + offset
)));
256 LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
257 ((mem_ptr_t
)p
->payload
% MEM_ALIGNMENT
) == 0);
258 /* the total length of the pbuf chain is the requested size */
260 /* set the length of the first pbuf in the chain */
261 p
->len
= length
> PBUF_POOL_BUFSIZE
- offset
? PBUF_POOL_BUFSIZE
- offset
: length
;
262 /* set reference count (needed here in case we fail) */
265 /* now allocate the tail of the pbuf chain */
267 /* remember first pbuf for linkage in next iteration */
269 /* remaining length to be allocated */
270 rem_len
= length
- p
->len
;
271 /* any remaining pbufs to be allocated? */
272 while (rem_len
> 0) {
273 q
= pbuf_pool_alloc();
275 LWIP_DEBUGF(PBUF_DEBUG
| 2, ("pbuf_alloc: Out of pbufs in pool.\n"));
277 ++lwip_stats
.pbuf
.err
;
278 #endif /* PBUF_STATS */
279 /* free chain so far allocated */
281 /* bail out unsuccesfully */
285 /* make previous pbuf point to this pbuf */
287 /* set total length of this pbuf and next in chain */
288 q
->tot_len
= rem_len
;
289 /* this pbuf length is pool size, unless smaller sized tail */
290 q
->len
= rem_len
> PBUF_POOL_BUFSIZE
? PBUF_POOL_BUFSIZE
: rem_len
;
291 q
->payload
= (void *)((u8_t
*)q
+ sizeof(struct pbuf
));
292 LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
293 ((mem_ptr_t
)q
->payload
% MEM_ALIGNMENT
) == 0);
295 /* calculate remaining length to be allocated */
297 /* remember this pbuf for linkage in next iteration */
305 /* If pbuf is to be allocated in RAM, allocate memory for it. */
306 p
= mem_malloc(MEM_ALIGN_SIZE(sizeof(struct pbuf
) + offset
) + MEM_ALIGN_SIZE(length
));
310 /* Set up internal structure of the pbuf. */
311 p
->payload
= MEM_ALIGN((void *)((u8_t
*)p
+ sizeof(struct pbuf
) + offset
));
312 p
->len
= p
->tot_len
= length
;
314 p
->flags
= PBUF_FLAG_RAM
;
316 LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
317 ((mem_ptr_t
)p
->payload
% MEM_ALIGNMENT
) == 0);
319 /* pbuf references existing (non-volatile static constant) ROM payload? */
321 /* pbuf references existing (externally allocated) RAM payload? */
323 /* only allocate memory for the pbuf structure */
324 p
= memp_malloc(MEMP_PBUF
);
326 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n", flag
== PBUF_ROM
?"ROM":"REF"));
329 /* caller must set this field properly, afterwards */
331 p
->len
= p
->tot_len
= length
;
333 p
->flags
= (flag
== PBUF_ROM
? PBUF_FLAG_ROM
: PBUF_FLAG_REF
);
336 LWIP_ASSERT("pbuf_alloc: erroneous flag", 0);
339 /* set reference count */
341 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 3, ("pbuf_alloc(length=%"U16_F
") == %p\n", length
, (void *)p
));
347 #define DEC_PBUF_STATS do { --lwip_stats.pbuf.used; } while (0)
348 #else /* PBUF_STATS */
349 #define DEC_PBUF_STATS
350 #endif /* PBUF_STATS */
352 #define PBUF_POOL_FAST_FREE(p) do { \
353 p->next = pbuf_pool; \
358 #if SYS_LIGHTWEIGHT_PROT
359 #define PBUF_POOL_FREE(p) do { \
360 SYS_ARCH_DECL_PROTECT(old_level); \
361 SYS_ARCH_PROTECT(old_level); \
362 PBUF_POOL_FAST_FREE(p); \
363 SYS_ARCH_UNPROTECT(old_level); \
365 #else /* SYS_LIGHTWEIGHT_PROT */
366 #define PBUF_POOL_FREE(p) do { \
367 LWP_SemWait(pbuf_pool_free_sem); \
368 PBUF_POOL_FAST_FREE(p); \
369 LWP_SemPost(pbuf_pool_free_sem); \
371 #endif /* SYS_LIGHTWEIGHT_PROT */
374 * Shrink a pbuf chain to a desired length.
376 * @param p pbuf to shrink.
377 * @param new_len desired new length of pbuf chain
379 * Depending on the desired length, the first few pbufs in a chain might
380 * be skipped and left unchanged. The new last pbuf in the chain will be
381 * resized, and any remaining pbufs will be freed.
383 * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
384 * @note May not be called on a packet queue.
386 * @bug Cannot grow the size of a pbuf (chain) (yet).
389 pbuf_realloc(struct pbuf
*p
, u16_t new_len
)
392 u16_t rem_len
; /* remaining length */
395 LWIP_ASSERT("pbuf_realloc: sane p->flags", p
->flags
== PBUF_FLAG_POOL
||
396 p
->flags
== PBUF_FLAG_ROM
||
397 p
->flags
== PBUF_FLAG_RAM
||
398 p
->flags
== PBUF_FLAG_REF
);
400 /* desired length larger than current length? */
401 if (new_len
>= p
->tot_len
) {
402 /* enlarging not yet supported */
406 /* the pbuf chain grows by (new_len - p->tot_len) bytes
407 * (which may be negative in case of shrinking) */
408 grow
= new_len
- p
->tot_len
;
410 /* first, step over any pbufs that should remain in the chain */
413 /* should this pbuf be kept? */
414 while (rem_len
> q
->len
) {
415 /* decrease remaining length by pbuf length */
417 /* decrease total length indicator */
419 /* proceed to next pbuf in chain */
422 /* we have now reached the new last pbuf (in q) */
423 /* rem_len == desired length for pbuf q */
425 /* shrink allocated memory for PBUF_RAM */
426 /* (other types merely adjust their length fields */
427 if ((q
->flags
== PBUF_FLAG_RAM
) && (rem_len
!= q
->len
)) {
428 /* reallocate and adjust the length of the pbuf that will be split */
429 mem_realloc(q
, (u8_t
*)q
->payload
- (u8_t
*)q
+ rem_len
);
431 /* adjust length fields for new last pbuf */
435 /* any remaining pbufs in chain? */
436 if (q
->next
!= NULL
) {
437 /* free remaining pbufs in chain */
440 /* q is last packet in chain */
446 * Adjusts the payload pointer to hide or reveal headers in the payload.
448 * Adjusts the ->payload pointer so that space for a header
449 * (dis)appears in the pbuf payload.
451 * The ->payload, ->tot_len and ->len fields are adjusted.
453 * @param hdr_size_inc Number of bytes to increment header size which
454 * increases the size of the pbuf. New space is on the front.
455 * (Using a negative value decreases the header size.)
456 * If hdr_size_inc is 0, this function does nothing and returns succesful.
458 * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
459 * the call will fail. A check is made that the increase in header size does
460 * not move the payload pointer in front of the start of the buffer.
461 * @return non-zero on failure, zero on success.
465 pbuf_header(struct pbuf
*p
, s16_t header_size_increment
)
469 LWIP_ASSERT("p != NULL", p
!= NULL
);
470 if ((header_size_increment
== 0) || (p
== NULL
)) return 0;
472 /* remember current payload pointer */
473 payload
= p
->payload
;
475 /* pbuf types containing payloads? */
476 if (p
->flags
== PBUF_FLAG_RAM
|| p
->flags
== PBUF_FLAG_POOL
) {
477 /* set new payload pointer */
478 p
->payload
= (u8_t
*)p
->payload
- header_size_increment
;
479 /* boundary check fails? */
480 if ((u8_t
*)p
->payload
< (u8_t
*)p
+ sizeof(struct pbuf
)) {
481 LWIP_DEBUGF( PBUF_DEBUG
| 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
484 /* restore old payload pointer */
485 p
->payload
= payload
;
486 /* bail out unsuccesfully */
489 /* pbuf types refering to external payloads? */
490 } else if (p
->flags
== PBUF_FLAG_REF
|| p
->flags
== PBUF_FLAG_ROM
) {
491 /* hide a header in the payload? */
492 if ((header_size_increment
< 0) && (header_size_increment
- p
->len
<= 0)) {
493 /* increase payload pointer */
494 p
->payload
= (u8_t
*)p
->payload
- header_size_increment
;
496 /* cannot expand payload to front (yet!)
497 * bail out unsuccesfully */
501 /* modify pbuf length fields */
502 p
->len
+= header_size_increment
;
503 p
->tot_len
+= header_size_increment
;
505 LWIP_DEBUGF( PBUF_DEBUG
, ("pbuf_header: old %p new %p (%"S16_F
")\n",
506 (void *)payload
, (void *)p
->payload
, header_size_increment
));
512 * Dereference a pbuf chain or queue and deallocate any no-longer-used
513 * pbufs at the head of this chain or queue.
515 * Decrements the pbuf reference count. If it reaches zero, the pbuf is
518 * For a pbuf chain, this is repeated for each pbuf in the chain,
519 * up to the first pbuf which has a non-zero reference count after
520 * decrementing. So, when all reference counts are one, the whole
523 * @param pbuf The pbuf (chain) to be dereferenced.
525 * @return the number of pbufs that were de-allocated
526 * from the head of the chain.
528 * @note MUST NOT be called on a packet queue (Not verified to work yet).
529 * @note the reference counter of a pbuf equals the number of pointers
530 * that refer to the pbuf (or into the pbuf).
532 * @internal examples:
534 * Assuming existing chains a->b->c with the following reference
535 * counts, calling pbuf_free(a) results in:
537 * 1->2->3 becomes ...1->3
538 * 3->3->3 becomes 2->3->3
539 * 1->1->2 becomes ......1
540 * 2->1->1 becomes 1->1->1
541 * 1->1->1 becomes .......
545 pbuf_free(struct pbuf
*p
)
549 SYS_ARCH_DECL_PROTECT(old_level
);
551 LWIP_ASSERT("p != NULL", p
!= NULL
);
552 /* if assertions are disabled, proceed with debug output */
554 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 2, ("pbuf_free(p == NULL) was called.\n"));
557 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 3, ("pbuf_free(%p)\n", (void *)p
));
561 LWIP_ASSERT("pbuf_free: sane flags",
562 p
->flags
== PBUF_FLAG_RAM
|| p
->flags
== PBUF_FLAG_ROM
||
563 p
->flags
== PBUF_FLAG_REF
|| p
->flags
== PBUF_FLAG_POOL
);
566 /* Since decrementing ref cannot be guaranteed to be a single machine operation
567 * we must protect it. Also, the later test of ref must be protected.
569 SYS_ARCH_PROTECT(old_level
);
570 /* de-allocate all consecutive pbufs from the head of the chain that
571 * obtain a zero reference count after decrementing*/
573 /* all pbufs in a chain are referenced at least once */
574 LWIP_ASSERT("pbuf_free: p->ref > 0", p
->ref
> 0);
575 /* decrease reference count (number of pointers to pbuf) */
577 /* this pbuf is no longer referenced to? */
579 /* remember next pbuf in chain for next iteration */
581 LWIP_DEBUGF( PBUF_DEBUG
| 2, ("pbuf_free: deallocating %p\n", (void *)p
));
582 /* is this a pbuf from the pool? */
583 if (p
->flags
== PBUF_FLAG_POOL
) {
584 p
->len
= p
->tot_len
= PBUF_POOL_BUFSIZE
;
585 p
->payload
= (void *)((u8_t
*)p
+ sizeof(struct pbuf
));
587 /* is this a ROM or RAM referencing pbuf? */
588 } else if (p
->flags
== PBUF_FLAG_ROM
|| p
->flags
== PBUF_FLAG_REF
) {
589 memp_free(MEMP_PBUF
, p
);
590 /* p->flags == PBUF_FLAG_RAM */
595 /* proceed to next pbuf */
597 /* p->ref > 0, this pbuf is still referenced to */
598 /* (and so the remaining pbufs in chain as well) */
600 LWIP_DEBUGF( PBUF_DEBUG
| 2, ("pbuf_free: %p has ref %"U16_F
", ending here.\n", (void *)p
, (u16_t
)p
->ref
));
601 /* stop walking through the chain */
605 SYS_ARCH_UNPROTECT(old_level
);
606 PERF_STOP("pbuf_free");
607 /* return number of de-allocated pbufs */
612 * Count number of pbufs in a chain
614 * @param p first pbuf of chain
615 * @return the number of pbufs in a chain
619 pbuf_clen(struct pbuf
*p
)
632 * Increment the reference count of the pbuf.
634 * @param p pbuf to increase reference counter of
638 pbuf_ref(struct pbuf
*p
)
640 SYS_ARCH_DECL_PROTECT(old_level
);
643 SYS_ARCH_PROTECT(old_level
);
645 SYS_ARCH_UNPROTECT(old_level
);
650 * Concatenate two pbufs (each may be a pbuf chain) and take over
651 * the caller's reference of the tail pbuf.
653 * @note The caller MAY NOT reference the tail pbuf afterwards.
654 * Use pbuf_chain() for that purpose.
660 pbuf_cat(struct pbuf
*h
, struct pbuf
*t
)
664 LWIP_ASSERT("h != NULL (programmer violates API)", h
!= NULL
);
665 LWIP_ASSERT("t != NULL (programmer violates API)", t
!= NULL
);
666 if ((h
== NULL
) || (t
== NULL
)) return;
668 /* proceed to last pbuf of chain */
669 for (p
= h
; p
->next
!= NULL
; p
= p
->next
) {
670 /* add total length of second chain to all totals of first chain */
671 p
->tot_len
+= t
->tot_len
;
673 /* { p is last pbuf of first h chain, p->next == NULL } */
674 LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p
->tot_len
== p
->len
);
675 LWIP_ASSERT("p->next == NULL", p
->next
== NULL
);
676 /* add total length of second chain to last pbuf total of first chain */
677 p
->tot_len
+= t
->tot_len
;
678 /* chain last pbuf of head (p) with first of tail (t) */
680 /* p->next now references t, but the caller will drop its reference to t,
681 * so netto there is no change to the reference count of t.
686 * Chain two pbufs (or pbuf chains) together.
688 * The caller MUST call pbuf_free(t) once it has stopped
689 * using it. Use pbuf_cat() instead if you no longer use t.
691 * @param h head pbuf (chain)
692 * @param t tail pbuf (chain)
693 * @note The pbufs MUST belong to the same packet.
694 * @note MAY NOT be called on a packet queue.
696 * The ->tot_len fields of all pbufs of the head chain are adjusted.
697 * The ->next field of the last pbuf of the head chain is adjusted.
698 * The ->ref field of the first pbuf of the tail chain is adjusted.
702 pbuf_chain(struct pbuf
*h
, struct pbuf
*t
)
705 /* t is now referenced by h */
707 LWIP_DEBUGF(PBUF_DEBUG
| DBG_FRESH
| 2, ("pbuf_chain: %p references %p\n", (void *)h
, (void *)t
));
710 /* For packet queueing. Note that queued packets MUST be dequeued first
711 * using pbuf_dequeue() before calling other pbuf_() functions. */
714 * Add a packet to the end of a queue.
716 * @param q pointer to first packet on the queue
717 * @param n packet to be queued
719 * Both packets MUST be given, and must be different.
722 pbuf_queue(struct pbuf
*p
, struct pbuf
*n
)
724 #if PBUF_DEBUG /* remember head of queue */
727 /* programmer stupidity checks */
728 LWIP_ASSERT("p == NULL in pbuf_queue: this indicates a programmer error\n", p
!= NULL
);
729 LWIP_ASSERT("n == NULL in pbuf_queue: this indicates a programmer error\n", n
!= NULL
);
730 LWIP_ASSERT("p == n in pbuf_queue: this indicates a programmer error\n", p
!= n
);
731 if ((p
== NULL
) || (n
== NULL
) || (p
== n
)){
732 LWIP_DEBUGF(PBUF_DEBUG
| DBG_HALT
| 3, ("pbuf_queue: programmer argument error\n"));
736 /* iterate through all packets on queue */
737 while (p
->next
!= NULL
) {
738 /* be very picky about pbuf chain correctness */
740 /* iterate through all pbufs in packet */
741 while (p
->tot_len
!= p
->len
) {
742 /* make sure invariant condition holds */
743 LWIP_ASSERT("p->len < p->tot_len", p
->len
< p
->tot_len
);
744 /* make sure each packet is complete */
745 LWIP_ASSERT("p->next != NULL", p
->next
!= NULL
);
747 /* { p->tot_len == p->len => p is last pbuf of a packet } */
749 /* { p is last pbuf of a packet } */
750 /* proceed to next packet on queue */
752 /* proceed to next pbuf */
753 if (p
->next
!= NULL
) p
= p
->next
;
755 /* { p->tot_len == p->len and p->next == NULL } ==>
756 * { p is last pbuf of last packet on queue } */
757 /* chain last pbuf of queue with n */
759 /* n is now referenced to by the (packet p in the) queue */
762 LWIP_DEBUGF(PBUF_DEBUG
| DBG_FRESH
| 2,
763 ("pbuf_queue: newly queued packet %p sits after packet %p in queue %p\n",
764 (void *)n
, (void *)p
, (void *)q
));
769 * Remove a packet from the head of a queue.
771 * The caller MUST reference the remainder of the queue (as returned). The
772 * caller MUST NOT call pbuf_ref() as it implicitly takes over the reference
775 * @param p pointer to first packet on the queue which will be dequeued.
776 * @return first packet on the remaining queue (NULL if no further packets).
780 pbuf_dequeue(struct pbuf
*p
)
783 LWIP_ASSERT("p != NULL", p
!= NULL
);
785 /* iterate through all pbufs in packet p */
786 while (p
->tot_len
!= p
->len
) {
787 /* make sure invariant condition holds */
788 LWIP_ASSERT("p->len < p->tot_len", p
->len
< p
->tot_len
);
789 /* make sure each packet is complete */
790 LWIP_ASSERT("p->next != NULL", p
->next
!= NULL
);
793 /* { p->tot_len == p->len } => p is the last pbuf of the first packet */
794 /* remember next packet on queue in q */
796 /* dequeue packet p from queue */
798 /* any next packet on queue? */
800 /* although q is no longer referenced by p, it MUST be referenced by
801 * the caller, who is maintaining this packet queue. So, we do not call
802 * pbuf_free(q) here, resulting in an implicit pbuf_ref(q) for the caller. */
803 LWIP_DEBUGF(PBUF_DEBUG
| DBG_FRESH
| 2, ("pbuf_dequeue: first remaining packet on queue is %p\n", (void *)q
));
805 LWIP_DEBUGF(PBUF_DEBUG
| DBG_FRESH
| 2, ("pbuf_dequeue: no further packets on queue\n"));
813 * Create PBUF_POOL (or PBUF_RAM) copies of PBUF_REF pbufs.
815 * Used to queue packets on behalf of the lwIP stack, such as
816 * ARP based queueing.
818 * Go through a pbuf chain and replace any PBUF_REF buffers
819 * with PBUF_POOL (or PBUF_RAM) pbufs, each taking a copy of
820 * the referenced data.
822 * @note You MUST explicitly use p = pbuf_take(p);
823 * The pbuf you give as argument, may have been replaced
824 * by a (differently located) copy through pbuf_take()!
826 * @note Any replaced pbufs will be freed through pbuf_free().
827 * This may deallocate them if they become no longer referenced.
829 * @param p Head of pbuf chain to process
831 * @return Pointer to head of pbuf chain
834 pbuf_take(struct pbuf
*p
)
836 struct pbuf
*q
, *prev
, *head
;
837 LWIP_ASSERT("pbuf_take: p != NULL\n", p
!= NULL
);
838 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 3, ("pbuf_take(%p)\n", (void*)p
));
842 /* iterate through pbuf chain */
845 /* pbuf is of type PBUF_REF? */
846 if (p
->flags
== PBUF_FLAG_REF
) {
847 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
, ("pbuf_take: encountered PBUF_REF %p\n", (void *)p
));
848 /* allocate a pbuf (w/ payload) fully in RAM */
849 /* PBUF_POOL buffers are faster if we can use them */
850 if (p
->len
<= PBUF_POOL_BUFSIZE
) {
851 q
= pbuf_alloc(PBUF_RAW
, p
->len
, PBUF_POOL
);
853 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 2, ("pbuf_take: Could not allocate PBUF_POOL\n"));
856 /* no replacement pbuf yet */
858 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 2, ("pbuf_take: PBUF_POOL too small to replace PBUF_REF\n"));
860 /* no (large enough) PBUF_POOL was available? retry with PBUF_RAM */
862 q
= pbuf_alloc(PBUF_RAW
, p
->len
, PBUF_RAM
);
864 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 2, ("pbuf_take: Could not allocate PBUF_RAM\n"));
867 /* replacement pbuf could be allocated? */
873 /* remove linkage from original pbuf */
875 /* remove linkage to original pbuf */
877 /* prev->next == p at this point */
878 LWIP_ASSERT("prev->next == p", prev
->next
== p
);
879 /* break chain and insert new pbuf instead */
881 /* prev == NULL, so we replaced the head pbuf of the chain */
885 /* copy pbuf payload */
886 memcpy(q
->payload
, p
->payload
, p
->len
);
887 q
->tot_len
= p
->tot_len
;
889 /* in case p was the first pbuf, it is no longer refered to by
890 * our caller, as the caller MUST do p = pbuf_take(p);
891 * in case p was not the first pbuf, it is no longer refered to
892 * by prev. we can safely free the pbuf here.
893 * (note that we have set p->next to NULL already so that
894 * we will not free the rest of the chain by accident.)
897 /* do not copy ref, since someone else might be using the old buffer */
898 LWIP_DEBUGF(PBUF_DEBUG
, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p
, (void *)q
));
901 /* deallocate chain */
903 LWIP_DEBUGF(PBUF_DEBUG
| 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p
));
906 /* p->flags != PBUF_FLAG_REF */
908 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 1, ("pbuf_take: skipping pbuf not of type PBUF_REF\n"));
910 /* remember this pbuf */
912 /* proceed to next pbuf in original chain */
915 LWIP_DEBUGF(PBUF_DEBUG
| DBG_TRACE
| 1, ("pbuf_take: end of chain reached.\n"));
921 * Dechains the first pbuf from its succeeding pbufs in the chain.
923 * Makes p->tot_len field equal to p->len.
924 * @param p pbuf to dechain
925 * @return remainder of the pbuf chain, or NULL if it was de-allocated.
926 * @note May not be called on a packet queue.
929 pbuf_dechain(struct pbuf
*p
)
935 /* pbuf has successor in chain? */
937 /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
938 LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q
->tot_len
== p
->tot_len
- p
->len
);
939 /* enforce invariant if assertion is disabled */
940 q
->tot_len
= p
->tot_len
- p
->len
;
941 /* decouple pbuf from remainder */
943 /* total length of pbuf p is its own length only */
945 /* q is no longer referenced by p, free it */
946 LWIP_DEBUGF(PBUF_DEBUG
| DBG_STATE
, ("pbuf_dechain: unreferencing %p\n", (void *)q
));
947 tail_gone
= pbuf_free(q
);
949 LWIP_DEBUGF(PBUF_DEBUG
| DBG_STATE
,
950 ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q
));
952 /* return remaining tail or NULL if deallocated */
954 /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
955 LWIP_ASSERT("p->tot_len == p->len", p
->tot_len
== p
->len
);
956 return (tail_gone
> 0? NULL
: q
);