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_t 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 pbuf_pool_free_sem = sys_sem_new(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);
\r
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 */
\r
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 */
\r
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"));
\r
330 /* caller must set this field properly, afterwards */
332 p->len = p->tot_len = length;
334 p->flags = (flag == PBUF_ROM? PBUF_FLAG_ROM: PBUF_FLAG_REF);
337 LWIP_ASSERT("pbuf_alloc: erroneous flag", 0);
\r
340 /* set reference count */
342 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
\r
348 #define DEC_PBUF_STATS do { --lwip_stats.pbuf.used; } while (0)
349 #else /* PBUF_STATS */
350 #define DEC_PBUF_STATS
351 #endif /* PBUF_STATS */
353 #define PBUF_POOL_FAST_FREE(p) do { \
354 p->next = pbuf_pool; \
359 #if SYS_LIGHTWEIGHT_PROT
360 #define PBUF_POOL_FREE(p) do { \
361 SYS_ARCH_DECL_PROTECT(old_level); \
362 SYS_ARCH_PROTECT(old_level); \
363 PBUF_POOL_FAST_FREE(p); \
364 SYS_ARCH_UNPROTECT(old_level); \
366 #else /* SYS_LIGHTWEIGHT_PROT */
367 #define PBUF_POOL_FREE(p) do { \
368 sys_sem_wait(pbuf_pool_free_sem); \
369 PBUF_POOL_FAST_FREE(p); \
370 sys_sem_signal(pbuf_pool_free_sem); \
372 #endif /* SYS_LIGHTWEIGHT_PROT */
375 * Shrink a pbuf chain to a desired length.
377 * @param p pbuf to shrink.
378 * @param new_len desired new length of pbuf chain
380 * Depending on the desired length, the first few pbufs in a chain might
381 * be skipped and left unchanged. The new last pbuf in the chain will be
382 * resized, and any remaining pbufs will be freed.
384 * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
385 * @note May not be called on a packet queue.
387 * @bug Cannot grow the size of a pbuf (chain) (yet).
390 pbuf_realloc(struct pbuf *p, u16_t new_len)
393 u16_t rem_len; /* remaining length */
396 LWIP_ASSERT("pbuf_realloc: sane p->flags", p->flags == PBUF_FLAG_POOL ||
397 p->flags == PBUF_FLAG_ROM ||
398 p->flags == PBUF_FLAG_RAM ||
399 p->flags == PBUF_FLAG_REF);
401 /* desired length larger than current length? */
402 if (new_len >= p->tot_len) {
403 /* enlarging not yet supported */
407 /* the pbuf chain grows by (new_len - p->tot_len) bytes
408 * (which may be negative in case of shrinking) */
409 grow = new_len - p->tot_len;
411 /* first, step over any pbufs that should remain in the chain */
414 /* should this pbuf be kept? */
415 while (rem_len > q->len) {
416 /* decrease remaining length by pbuf length */
418 /* decrease total length indicator */
420 /* proceed to next pbuf in chain */
423 /* we have now reached the new last pbuf (in q) */
424 /* rem_len == desired length for pbuf q */
426 /* shrink allocated memory for PBUF_RAM */
427 /* (other types merely adjust their length fields */
428 if ((q->flags == PBUF_FLAG_RAM) && (rem_len != q->len)) {
429 /* reallocate and adjust the length of the pbuf that will be split */
430 mem_realloc(q, (u8_t *)q->payload - (u8_t *)q + rem_len);
432 /* adjust length fields for new last pbuf */
436 /* any remaining pbufs in chain? */
437 if (q->next != NULL) {
438 /* free remaining pbufs in chain */
441 /* q is last packet in chain */
447 * Adjusts the payload pointer to hide or reveal headers in the payload.
449 * Adjusts the ->payload pointer so that space for a header
450 * (dis)appears in the pbuf payload.
452 * The ->payload, ->tot_len and ->len fields are adjusted.
454 * @param hdr_size_inc Number of bytes to increment header size which
455 * increases the size of the pbuf. New space is on the front.
456 * (Using a negative value decreases the header size.)
457 * If hdr_size_inc is 0, this function does nothing and returns succesful.
459 * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
460 * the call will fail. A check is made that the increase in header size does
461 * not move the payload pointer in front of the start of the buffer.
462 * @return non-zero on failure, zero on success.
466 pbuf_header(struct pbuf *p, s16_t header_size_increment)
471 LWIP_ASSERT("p != NULL", p != NULL);
472 if ((header_size_increment == 0) || (p == NULL)) return 0;
475 /* remember current payload pointer */
476 payload = p->payload;
478 /* pbuf types containing payloads? */
479 if (flags == PBUF_FLAG_RAM || flags == PBUF_FLAG_POOL) {
480 /* set new payload pointer */
481 p->payload = (u8_t *)p->payload - header_size_increment;
482 /* boundary check fails? */
483 if ((u8_t *)p->payload < (u8_t *)p + sizeof(struct pbuf)) {
484 LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
487 /* restore old payload pointer */
488 p->payload = payload;
489 /* bail out unsuccesfully */
492 /* pbuf types refering to external payloads? */
493 } else if (flags == PBUF_FLAG_REF || flags == PBUF_FLAG_ROM) {
494 /* hide a header in the payload? */
495 if ((header_size_increment < 0) && (header_size_increment - p->len <= 0)) {
496 /* increase payload pointer */
497 p->payload = (u8_t *)p->payload - header_size_increment;
499 /* cannot expand payload to front (yet!)
500 * bail out unsuccesfully */
504 /* modify pbuf length fields */
505 p->len += header_size_increment;
506 p->tot_len += header_size_increment;
508 LWIP_DEBUGF( PBUF_DEBUG, ("pbuf_header: old %p new %p (%"S16_F")\n",
509 (void *)payload, (void *)p->payload, header_size_increment));
515 * Dereference a pbuf chain or queue and deallocate any no-longer-used
516 * pbufs at the head of this chain or queue.
518 * Decrements the pbuf reference count. If it reaches zero, the pbuf is
521 * For a pbuf chain, this is repeated for each pbuf in the chain,
522 * up to the first pbuf which has a non-zero reference count after
523 * decrementing. So, when all reference counts are one, the whole
526 * @param pbuf The pbuf (chain) to be dereferenced.
528 * @return the number of pbufs that were de-allocated
529 * from the head of the chain.
531 * @note MUST NOT be called on a packet queue (Not verified to work yet).
532 * @note the reference counter of a pbuf equals the number of pointers
533 * that refer to the pbuf (or into the pbuf).
535 * @internal examples:
537 * Assuming existing chains a->b->c with the following reference
538 * counts, calling pbuf_free(a) results in:
540 * 1->2->3 becomes ...1->3
541 * 3->3->3 becomes 2->3->3
542 * 1->1->2 becomes ......1
543 * 2->1->1 becomes 1->1->1
544 * 1->1->1 becomes .......
548 pbuf_free(struct pbuf *p)
553 SYS_ARCH_DECL_PROTECT(old_level);
555 LWIP_ASSERT("p != NULL", p != NULL);
\r
557 /* if assertions are disabled, proceed with debug output */
559 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n"));
562 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_free(%p)\n", (void *)p));
566 LWIP_ASSERT("pbuf_free: sane flags",
567 p->flags == PBUF_FLAG_RAM || p->flags == PBUF_FLAG_ROM ||
568 p->flags == PBUF_FLAG_REF || p->flags == PBUF_FLAG_POOL);
571 /* Since decrementing ref cannot be guaranteed to be a single machine operation
572 * we must protect it. Also, the later test of ref must be protected.
574 SYS_ARCH_PROTECT(old_level);
575 /* de-allocate all consecutive pbufs from the head of the chain that
576 * obtain a zero reference count after decrementing*/
578 /* all pbufs in a chain are referenced at least once */
579 LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
580 /* decrease reference count (number of pointers to pbuf) */
582 /* this pbuf is no longer referenced to? */
584 /* remember next pbuf in chain for next iteration */
586 LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: deallocating %p\n", (void *)p));
588 /* is this a pbuf from the pool? */
589 if (flags == PBUF_FLAG_POOL) {
590 p->len = p->tot_len = PBUF_POOL_BUFSIZE;
591 p->payload = (void *)((u8_t *)p + sizeof(struct pbuf));
593 /* is this a ROM or RAM referencing pbuf? */
594 } else if (flags == PBUF_FLAG_ROM || flags == PBUF_FLAG_REF) {
595 memp_free(MEMP_PBUF, p);
596 /* flags == PBUF_FLAG_RAM */
601 /* proceed to next pbuf */
603 /* p->ref > 0, this pbuf is still referenced to */
604 /* (and so the remaining pbufs in chain as well) */
606 LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, (u16_t)p->ref));
607 /* stop walking through the chain */
611 SYS_ARCH_UNPROTECT(old_level);
612 PERF_STOP("pbuf_free");
613 /* return number of de-allocated pbufs */
\r
619 * Count number of pbufs in a chain
621 * @param p first pbuf of chain
622 * @return the number of pbufs in a chain
626 pbuf_clen(struct pbuf *p)
639 * Increment the reference count of the pbuf.
641 * @param p pbuf to increase reference counter of
645 pbuf_ref(struct pbuf *p)
647 SYS_ARCH_DECL_PROTECT(old_level);
650 SYS_ARCH_PROTECT(old_level);
652 SYS_ARCH_UNPROTECT(old_level);
657 * Concatenate two pbufs (each may be a pbuf chain) and take over
658 * the caller's reference of the tail pbuf.
660 * @note The caller MAY NOT reference the tail pbuf afterwards.
661 * Use pbuf_chain() for that purpose.
667 pbuf_cat(struct pbuf *h, struct pbuf *t)
671 LWIP_ASSERT("h != NULL (programmer violates API)", h != NULL);
672 LWIP_ASSERT("t != NULL (programmer violates API)", t != NULL);
673 if ((h == NULL) || (t == NULL)) return;
675 /* proceed to last pbuf of chain */
676 for (p = h; p->next != NULL; p = p->next) {
677 /* add total length of second chain to all totals of first chain */
678 p->tot_len += t->tot_len;
680 /* { p is last pbuf of first h chain, p->next == NULL } */
681 LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
682 LWIP_ASSERT("p->next == NULL", p->next == NULL);
683 /* add total length of second chain to last pbuf total of first chain */
684 p->tot_len += t->tot_len;
685 /* chain last pbuf of head (p) with first of tail (t) */
687 /* p->next now references t, but the caller will drop its reference to t,
688 * so netto there is no change to the reference count of t.
693 * Chain two pbufs (or pbuf chains) together.
695 * The caller MUST call pbuf_free(t) once it has stopped
696 * using it. Use pbuf_cat() instead if you no longer use t.
698 * @param h head pbuf (chain)
699 * @param t tail pbuf (chain)
700 * @note The pbufs MUST belong to the same packet.
701 * @note MAY NOT be called on a packet queue.
703 * The ->tot_len fields of all pbufs of the head chain are adjusted.
704 * The ->next field of the last pbuf of the head chain is adjusted.
705 * The ->ref field of the first pbuf of the tail chain is adjusted.
709 pbuf_chain(struct pbuf *h, struct pbuf *t)
712 /* t is now referenced by h */
714 LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
717 /* For packet queueing. Note that queued packets MUST be dequeued first
718 * using pbuf_dequeue() before calling other pbuf_() functions. */
721 * Add a packet to the end of a queue.
723 * @param q pointer to first packet on the queue
724 * @param n packet to be queued
726 * Both packets MUST be given, and must be different.
729 pbuf_queue(struct pbuf *p, struct pbuf *n)
731 #if PBUF_DEBUG /* remember head of queue */
734 /* programmer stupidity checks */
735 LWIP_ASSERT("p == NULL in pbuf_queue: this indicates a programmer error\n", p != NULL);
736 LWIP_ASSERT("n == NULL in pbuf_queue: this indicates a programmer error\n", n != NULL);
737 LWIP_ASSERT("p == n in pbuf_queue: this indicates a programmer error\n", p != n);
738 if ((p == NULL) || (n == NULL) || (p == n)){
739 LWIP_DEBUGF(PBUF_DEBUG | DBG_HALT | 3, ("pbuf_queue: programmer argument error\n"));
743 /* iterate through all packets on queue */
744 while (p->next != NULL) {
745 /* be very picky about pbuf chain correctness */
747 /* iterate through all pbufs in packet */
748 while (p->tot_len != p->len) {
749 /* make sure invariant condition holds */
750 LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len);
751 /* make sure each packet is complete */
752 LWIP_ASSERT("p->next != NULL", p->next != NULL);
754 /* { p->tot_len == p->len => p is last pbuf of a packet } */
756 /* { p is last pbuf of a packet } */
757 /* proceed to next packet on queue */
759 /* proceed to next pbuf */
760 if (p->next != NULL) p = p->next;
762 /* { p->tot_len == p->len and p->next == NULL } ==>
763 * { p is last pbuf of last packet on queue } */
764 /* chain last pbuf of queue with n */
766 /* n is now referenced to by the (packet p in the) queue */
769 LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2,
770 ("pbuf_queue: newly queued packet %p sits after packet %p in queue %p\n",
771 (void *)n, (void *)p, (void *)q));
776 * Remove a packet from the head of a queue.
778 * The caller MUST reference the remainder of the queue (as returned). The
779 * caller MUST NOT call pbuf_ref() as it implicitly takes over the reference
782 * @param p pointer to first packet on the queue which will be dequeued.
783 * @return first packet on the remaining queue (NULL if no further packets).
787 pbuf_dequeue(struct pbuf *p)
790 LWIP_ASSERT("p != NULL", p != NULL);
792 /* iterate through all pbufs in packet p */
793 while (p->tot_len != p->len) {
794 /* make sure invariant condition holds */
795 LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len);
796 /* make sure each packet is complete */
797 LWIP_ASSERT("p->next != NULL", p->next != NULL);
800 /* { p->tot_len == p->len } => p is the last pbuf of the first packet */
801 /* remember next packet on queue in q */
803 /* dequeue packet p from queue */
805 /* any next packet on queue? */
807 /* although q is no longer referenced by p, it MUST be referenced by
808 * the caller, who is maintaining this packet queue. So, we do not call
809 * pbuf_free(q) here, resulting in an implicit pbuf_ref(q) for the caller. */
810 LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: first remaining packet on queue is %p\n", (void *)q));
812 LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: no further packets on queue\n"));
820 * Create PBUF_POOL (or PBUF_RAM) copies of PBUF_REF pbufs.
822 * Used to queue packets on behalf of the lwIP stack, such as
823 * ARP based queueing.
825 * Go through a pbuf chain and replace any PBUF_REF buffers
826 * with PBUF_POOL (or PBUF_RAM) pbufs, each taking a copy of
827 * the referenced data.
829 * @note You MUST explicitly use p = pbuf_take(p);
830 * The pbuf you give as argument, may have been replaced
831 * by a (differently located) copy through pbuf_take()!
833 * @note Any replaced pbufs will be freed through pbuf_free().
834 * This may deallocate them if they become no longer referenced.
836 * @param p Head of pbuf chain to process
838 * @return Pointer to head of pbuf chain
841 pbuf_take(struct pbuf *p)
843 struct pbuf *q , *prev, *head;
844 LWIP_ASSERT("pbuf_take: p != NULL\n", p != NULL);
845 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_take(%p)\n", (void*)p));
849 /* iterate through pbuf chain */
852 /* pbuf is of type PBUF_REF? */
853 if (p->flags == PBUF_FLAG_REF) {
854 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE, ("pbuf_take: encountered PBUF_REF %p\n", (void *)p));
855 /* allocate a pbuf (w/ payload) fully in RAM */
856 /* PBUF_POOL buffers are faster if we can use them */
857 if (p->len <= PBUF_POOL_BUFSIZE) {
858 q = pbuf_alloc(PBUF_RAW, p->len, PBUF_POOL);
860 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_POOL\n"));
863 /* no replacement pbuf yet */
865 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: PBUF_POOL too small to replace PBUF_REF\n"));
867 /* no (large enough) PBUF_POOL was available? retry with PBUF_RAM */
869 q = pbuf_alloc(PBUF_RAW, p->len, PBUF_RAM);
871 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_RAM\n"));
874 /* replacement pbuf could be allocated? */
880 /* remove linkage from original pbuf */
882 /* remove linkage to original pbuf */
884 /* prev->next == p at this point */
885 LWIP_ASSERT("prev->next == p", prev->next == p);
886 /* break chain and insert new pbuf instead */
888 /* prev == NULL, so we replaced the head pbuf of the chain */
892 /* copy pbuf payload */
893 memcpy(q->payload, p->payload, p->len);
894 q->tot_len = p->tot_len;
896 /* in case p was the first pbuf, it is no longer refered to by
897 * our caller, as the caller MUST do p = pbuf_take(p);
898 * in case p was not the first pbuf, it is no longer refered to
899 * by prev. we can safely free the pbuf here.
900 * (note that we have set p->next to NULL already so that
901 * we will not free the rest of the chain by accident.)
904 /* do not copy ref, since someone else might be using the old buffer */
905 LWIP_DEBUGF(PBUF_DEBUG, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p, (void *)q));
908 /* deallocate chain */
910 LWIP_DEBUGF(PBUF_DEBUG | 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p));
913 /* p->flags != PBUF_FLAG_REF */
915 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: skipping pbuf not of type PBUF_REF\n"));
917 /* remember this pbuf */
919 /* proceed to next pbuf in original chain */
922 LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: end of chain reached.\n"));
928 * Dechains the first pbuf from its succeeding pbufs in the chain.
930 * Makes p->tot_len field equal to p->len.
931 * @param p pbuf to dechain
932 * @return remainder of the pbuf chain, or NULL if it was de-allocated.
933 * @note May not be called on a packet queue.
936 pbuf_dechain(struct pbuf *p)
942 /* pbuf has successor in chain? */
944 /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
945 LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
946 /* enforce invariant if assertion is disabled */
947 q->tot_len = p->tot_len - p->len;
948 /* decouple pbuf from remainder */
950 /* total length of pbuf p is its own length only */
952 /* q is no longer referenced by p, free it */
953 LWIP_DEBUGF(PBUF_DEBUG | DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
954 tail_gone = pbuf_free(q);
956 LWIP_DEBUGF(PBUF_DEBUG | DBG_STATE,
957 ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
959 /* return remaining tail or NULL if deallocated */
961 /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
962 LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
963 return (tail_gone > 0? NULL: q);