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lwip/src/core/pbuf.c

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/**
* @file
* Packet buffer management
*
* Packets are built from the pbuf data structure. It supports dynamic
* memory allocation for packet contents or can reference externally
* managed packet contents both in RAM and ROM. Quick allocation for
* incoming packets is provided through pools with fixed sized pbufs.
*
* A packet may span over multiple pbufs, chained as a singly linked
* list. This is called a "pbuf chain".
*
* Multiple packets may be queued, also using this singly linked list.
* This is called a "packet queue".
*
* So, a packet queue consists of one or more pbuf chains, each of
* which consist of one or more pbufs. Currently, queues are only
* supported in a limited section of lwIP, this is the etharp queueing
* code. Outside of this section no packet queues are supported yet.
*
* The differences between a pbuf chain and a packet queue are very
* precise but subtle.
*
* The last pbuf of a packet has a ->tot_len field that equals the
* ->len field. It can be found by traversing the list. If the last
* pbuf of a packet has a ->next field other than NULL, more packets
* are on the queue.
*
* Therefore, looping through a pbuf of a single packet, has an
* loop end condition (tot_len == p->len), NOT (next == NULL).
*/
/*
* Copyright (c) 2001-2004 Swedish Institute of Computer Science.
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without modification,
* are permitted provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright notice,
* this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright notice,
* this list of conditions and the following disclaimer in the documentation
* and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
* SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
* IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
* OF SUCH DAMAGE.
*
* This file is part of the lwIP TCP/IP stack.
*
* Author: Adam Dunkels <adam@sics.se>
*
*/
#include <string.h>
#include "lwip/opt.h"
#include "lwip/stats.h"
#include "lwip/def.h"
#include "lwip/mem.h"
#include "lwip/memp.h"
#include "lwip/pbuf.h"
#include "lwip/sys.h"
#include "arch/perf.h"
static u8_t pbuf_pool_memory[MEM_ALIGNMENT - 1 + PBUF_POOL_SIZE * MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE + sizeof(struct pbuf))];
#if !SYS_LIGHTWEIGHT_PROT
static volatile u8_t pbuf_pool_free_lock, pbuf_pool_alloc_lock;
static sys_sem_t pbuf_pool_free_sem;
#endif
static struct pbuf *pbuf_pool = NULL;
/**
* Initializes the pbuf module.
*
* A large part of memory is allocated for holding the pool of pbufs.
* The size of the individual pbufs in the pool is given by the size
* parameter, and the number of pbufs in the pool by the num parameter.
*
* After the memory has been allocated, the pbufs are set up. The
* ->next pointer in each pbuf is set up to point to the next pbuf in
* the pool.
*
*/
void
pbuf_init(void)
{
struct pbuf *p, *q = NULL;
u16_t i;
pbuf_pool = (struct pbuf *)MEM_ALIGN(pbuf_pool_memory);
#if PBUF_STATS
lwip_stats.pbuf.avail = PBUF_POOL_SIZE;
#endif /* PBUF_STATS */
/* Set up ->next pointers to link the pbufs of the pool together */
p = pbuf_pool;
for(i = 0; i < PBUF_POOL_SIZE; ++i) {
p->next = (struct pbuf *)((u8_t *)p + PBUF_POOL_BUFSIZE + sizeof(struct pbuf));
p->len = p->tot_len = PBUF_POOL_BUFSIZE;
p->payload = MEM_ALIGN((void *)((u8_t *)p + sizeof(struct pbuf)));
p->flags = PBUF_FLAG_POOL;
q = p;
p = p->next;
}
/* The ->next pointer of last pbuf is NULL to indicate that there
are no more pbufs in the pool */
q->next = NULL;
#if !SYS_LIGHTWEIGHT_PROT
pbuf_pool_alloc_lock = 0;
pbuf_pool_free_lock = 0;
pbuf_pool_free_sem = sys_sem_new(1);
#endif
}
/**
* @internal only called from pbuf_alloc()
*/
static struct pbuf *
pbuf_pool_alloc(void)
{
struct pbuf *p = NULL;
SYS_ARCH_DECL_PROTECT(old_level);
SYS_ARCH_PROTECT(old_level);
#if !SYS_LIGHTWEIGHT_PROT
/* Next, check the actual pbuf pool, but if the pool is locked, we
pretend to be out of buffers and return NULL. */
if (pbuf_pool_free_lock) {
#if PBUF_STATS
++lwip_stats.pbuf.alloc_locked;
#endif /* PBUF_STATS */
return NULL;
}
pbuf_pool_alloc_lock = 1;
if (!pbuf_pool_free_lock) {
#endif /* SYS_LIGHTWEIGHT_PROT */
p = pbuf_pool;
if (p) {
pbuf_pool = p->next;
}
#if !SYS_LIGHTWEIGHT_PROT
#if PBUF_STATS
} else {
++lwip_stats.pbuf.alloc_locked;
#endif /* PBUF_STATS */
}
pbuf_pool_alloc_lock = 0;
#endif /* SYS_LIGHTWEIGHT_PROT */
#if PBUF_STATS
if (p != NULL) {
++lwip_stats.pbuf.used;
if (lwip_stats.pbuf.used > lwip_stats.pbuf.max) {
lwip_stats.pbuf.max = lwip_stats.pbuf.used;
}
}
#endif /* PBUF_STATS */
SYS_ARCH_UNPROTECT(old_level);
return p;
}
/**
* Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).
*
* The actual memory allocated for the pbuf is determined by the
* layer at which the pbuf is allocated and the requested size
* (from the size parameter).
*
* @param flag this parameter decides how and where the pbuf
* should be allocated as follows:
*
* - PBUF_RAM: buffer memory for pbuf is allocated as one large
* chunk. This includes protocol headers as well.
* - PBUF_ROM: no buffer memory is allocated for the pbuf, even for
* protocol headers. Additional headers must be prepended
* by allocating another pbuf and chain in to the front of
* the ROM pbuf. It is assumed that the memory used is really
* similar to ROM in that it is immutable and will not be
* changed. Memory which is dynamic should generally not
* be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
* - PBUF_REF: no buffer memory is allocated for the pbuf, even for
* protocol headers. It is assumed that the pbuf is only
* being used in a single thread. If the pbuf gets queued,
* then pbuf_take should be called to copy the buffer.
* - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from
* the pbuf pool that is allocated during pbuf_init().
*
* @return the allocated pbuf. If multiple pbufs where allocated, this
* is the first pbuf of a pbuf chain.
*/
struct pbuf *
pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag)
{
struct pbuf *p, *q, *r;
u16_t offset;
s32_t rem_len; /* remaining length */
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F")\n", length));
/* determine header offset */
offset = 0;
switch (l) {
case PBUF_TRANSPORT:
/* add room for transport (often TCP) layer header */
offset += PBUF_TRANSPORT_HLEN;
/* FALLTHROUGH */
case PBUF_IP:
/* add room for IP layer header */
offset += PBUF_IP_HLEN;
/* FALLTHROUGH */
case PBUF_LINK:
/* add room for link layer header */
offset += PBUF_LINK_HLEN;
break;
case PBUF_RAW:
break;
default:
LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0);
return NULL;
}
switch (flag) {
case PBUF_POOL:
/* allocate head of pbuf chain into p */
p = pbuf_pool_alloc();
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc: allocated pbuf %p\n", (void *)p));
if (p == NULL) {
#if PBUF_STATS
++lwip_stats.pbuf.err;
#endif /* PBUF_STATS */
return NULL;
}
p->next = NULL;
/* make the payload pointer point 'offset' bytes into pbuf data memory */
p->payload = MEM_ALIGN((void *)((u8_t *)p + (sizeof(struct pbuf) + offset)));
LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
/* the total length of the pbuf chain is the requested size */
p->tot_len = length;
/* set the length of the first pbuf in the chain */
p->len = length > PBUF_POOL_BUFSIZE - offset? PBUF_POOL_BUFSIZE - offset: length;
/* set reference count (needed here in case we fail) */
p->ref = 1;
/* now allocate the tail of the pbuf chain */
/* remember first pbuf for linkage in next iteration */
r = p;
/* remaining length to be allocated */
rem_len = length - p->len;
/* any remaining pbufs to be allocated? */
while (rem_len > 0) {
q = pbuf_pool_alloc();
if (q == NULL) {
LWIP_DEBUGF(PBUF_DEBUG | 2, ("pbuf_alloc: Out of pbufs in pool.\n"));
#if PBUF_STATS
++lwip_stats.pbuf.err;
#endif /* PBUF_STATS */
/* free chain so far allocated */
pbuf_free(p);
/* bail out unsuccesfully */
return NULL;
}
q->next = NULL;
/* make previous pbuf point to this pbuf */
r->next = q;
/* set total length of this pbuf and next in chain */
q->tot_len = rem_len;
/* this pbuf length is pool size, unless smaller sized tail */
q->len = rem_len > PBUF_POOL_BUFSIZE? PBUF_POOL_BUFSIZE: rem_len;
q->payload = (void *)((u8_t *)q + sizeof(struct pbuf));
LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0);
q->ref = 1;
/* calculate remaining length to be allocated */
rem_len -= q->len;
/* remember this pbuf for linkage in next iteration */
r = q;
}
/* end of chain */
/*r->next = NULL;*/
break;
case PBUF_RAM:
/* If pbuf is to be allocated in RAM, allocate memory for it. */
p = mem_malloc(MEM_ALIGN_SIZE(sizeof(struct pbuf) + offset) + MEM_ALIGN_SIZE(length));
if (p == NULL) {
return NULL;
}
/* Set up internal structure of the pbuf. */
p->payload = MEM_ALIGN((void *)((u8_t *)p + sizeof(struct pbuf) + offset));
p->len = p->tot_len = length;
p->next = NULL;
p->flags = PBUF_FLAG_RAM;
LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
break;
/* pbuf references existing (non-volatile static constant) ROM payload? */
case PBUF_ROM:
/* pbuf references existing (externally allocated) RAM payload? */
case PBUF_REF:
/* only allocate memory for the pbuf structure */
p = memp_malloc(MEMP_PBUF);
if (p == NULL) {
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n", flag == PBUF_ROM?"ROM":"REF"));
return NULL;
}
/* caller must set this field properly, afterwards */
p->payload = NULL;
p->len = p->tot_len = length;
p->next = NULL;
p->flags = (flag == PBUF_ROM? PBUF_FLAG_ROM: PBUF_FLAG_REF);
break;
default:
LWIP_ASSERT("pbuf_alloc: erroneous flag", 0);
return NULL;
}
/* set reference count */
p->ref = 1;
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
return p;
}
#if PBUF_STATS
#define DEC_PBUF_STATS do { --lwip_stats.pbuf.used; } while (0)
#else /* PBUF_STATS */
#define DEC_PBUF_STATS
#endif /* PBUF_STATS */
#define PBUF_POOL_FAST_FREE(p) do { \
p->next = pbuf_pool; \
pbuf_pool = p; \
DEC_PBUF_STATS; \
} while (0)
#if SYS_LIGHTWEIGHT_PROT
#define PBUF_POOL_FREE(p) do { \
SYS_ARCH_DECL_PROTECT(old_level); \
SYS_ARCH_PROTECT(old_level); \
PBUF_POOL_FAST_FREE(p); \
SYS_ARCH_UNPROTECT(old_level); \
} while (0)
#else /* SYS_LIGHTWEIGHT_PROT */
#define PBUF_POOL_FREE(p) do { \
sys_sem_wait(pbuf_pool_free_sem); \
PBUF_POOL_FAST_FREE(p); \
sys_sem_signal(pbuf_pool_free_sem); \
} while (0)
#endif /* SYS_LIGHTWEIGHT_PROT */
/**
* Shrink a pbuf chain to a desired length.
*
* @param p pbuf to shrink.
* @param new_len desired new length of pbuf chain
*
* Depending on the desired length, the first few pbufs in a chain might
* be skipped and left unchanged. The new last pbuf in the chain will be
* resized, and any remaining pbufs will be freed.
*
* @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
* @note May not be called on a packet queue.
*
* @bug Cannot grow the size of a pbuf (chain) (yet).
*/
void
pbuf_realloc(struct pbuf *p, u16_t new_len)
{
struct pbuf *q;
u16_t rem_len; /* remaining length */
s16_t grow;
LWIP_ASSERT("pbuf_realloc: sane p->flags", p->flags == PBUF_FLAG_POOL ||
p->flags == PBUF_FLAG_ROM ||
p->flags == PBUF_FLAG_RAM ||
p->flags == PBUF_FLAG_REF);
/* desired length larger than current length? */
if (new_len >= p->tot_len) {
/* enlarging not yet supported */
return;
}
/* the pbuf chain grows by (new_len - p->tot_len) bytes
* (which may be negative in case of shrinking) */
grow = new_len - p->tot_len;
/* first, step over any pbufs that should remain in the chain */
rem_len = new_len;
q = p;
/* should this pbuf be kept? */
while (rem_len > q->len) {
/* decrease remaining length by pbuf length */
rem_len -= q->len;
/* decrease total length indicator */
q->tot_len += grow;
/* proceed to next pbuf in chain */
q = q->next;
}
/* we have now reached the new last pbuf (in q) */
/* rem_len == desired length for pbuf q */
/* shrink allocated memory for PBUF_RAM */
/* (other types merely adjust their length fields */
if ((q->flags == PBUF_FLAG_RAM) && (rem_len != q->len)) {
/* reallocate and adjust the length of the pbuf that will be split */
mem_realloc(q, (u8_t *)q->payload - (u8_t *)q + rem_len);
}
/* adjust length fields for new last pbuf */
q->len = rem_len;
q->tot_len = q->len;
/* any remaining pbufs in chain? */
if (q->next != NULL) {
/* free remaining pbufs in chain */
pbuf_free(q->next);
}
/* q is last packet in chain */
q->next = NULL;
}
/**
* Adjusts the payload pointer to hide or reveal headers in the payload.
*
* Adjusts the ->payload pointer so that space for a header
* (dis)appears in the pbuf payload.
*
* The ->payload, ->tot_len and ->len fields are adjusted.
*
* @param hdr_size_inc Number of bytes to increment header size which
* increases the size of the pbuf. New space is on the front.
* (Using a negative value decreases the header size.)
* If hdr_size_inc is 0, this function does nothing and returns succesful.
*
* PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
* the call will fail. A check is made that the increase in header size does
* not move the payload pointer in front of the start of the buffer.
* @return non-zero on failure, zero on success.
*
*/
u8_t
pbuf_header(struct pbuf *p, s16_t header_size_increment)
{
u16_t flags;
void *payload;
LWIP_ASSERT("p != NULL", p != NULL);
if ((header_size_increment == 0) || (p == NULL)) return 0;
flags = p->flags;
/* remember current payload pointer */
payload = p->payload;
/* pbuf types containing payloads? */
if (flags == PBUF_FLAG_RAM || flags == PBUF_FLAG_POOL) {
/* set new payload pointer */
p->payload = (u8_t *)p->payload - header_size_increment;
/* boundary check fails? */
if ((u8_t *)p->payload < (u8_t *)p + sizeof(struct pbuf)) {
LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
(void *)p->payload,
(void *)(p + 1)));\
/* restore old payload pointer */
p->payload = payload;
/* bail out unsuccesfully */
return 1;
}
/* pbuf types refering to external payloads? */
} else if (flags == PBUF_FLAG_REF || flags == PBUF_FLAG_ROM) {
/* hide a header in the payload? */
if ((header_size_increment < 0) && (header_size_increment - p->len <= 0)) {
/* increase payload pointer */
p->payload = (u8_t *)p->payload - header_size_increment;
} else {
/* cannot expand payload to front (yet!)
* bail out unsuccesfully */
return 1;
}
}
/* modify pbuf length fields */
p->len += header_size_increment;
p->tot_len += header_size_increment;
LWIP_DEBUGF( PBUF_DEBUG, ("pbuf_header: old %p new %p (%"S16_F")\n",
(void *)payload, (void *)p->payload, header_size_increment));
return 0;
}
/**
* Dereference a pbuf chain or queue and deallocate any no-longer-used
* pbufs at the head of this chain or queue.
*
* Decrements the pbuf reference count. If it reaches zero, the pbuf is
* deallocated.
*
* For a pbuf chain, this is repeated for each pbuf in the chain,
* up to the first pbuf which has a non-zero reference count after
* decrementing. So, when all reference counts are one, the whole
* chain is free'd.
*
* @param pbuf The pbuf (chain) to be dereferenced.
*
* @return the number of pbufs that were de-allocated
* from the head of the chain.
*
* @note MUST NOT be called on a packet queue (Not verified to work yet).
* @note the reference counter of a pbuf equals the number of pointers
* that refer to the pbuf (or into the pbuf).
*
* @internal examples:
*
* Assuming existing chains a->b->c with the following reference
* counts, calling pbuf_free(a) results in:
*
* 1->2->3 becomes ...1->3
* 3->3->3 becomes 2->3->3
* 1->1->2 becomes ......1
* 2->1->1 becomes 1->1->1
* 1->1->1 becomes .......
*
*/
u8_t
pbuf_free(struct pbuf *p)
{
u16_t flags;
struct pbuf *q;
u8_t count;
SYS_ARCH_DECL_PROTECT(old_level);
LWIP_ASSERT("p != NULL", p != NULL);
/* if assertions are disabled, proceed with debug output */
if (p == NULL) {
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n"));
return 0;
}
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_free(%p)\n", (void *)p));
PERF_START;
LWIP_ASSERT("pbuf_free: sane flags",
p->flags == PBUF_FLAG_RAM || p->flags == PBUF_FLAG_ROM ||
p->flags == PBUF_FLAG_REF || p->flags == PBUF_FLAG_POOL);
count = 0;
/* Since decrementing ref cannot be guaranteed to be a single machine operation
* we must protect it. Also, the later test of ref must be protected.
*/
SYS_ARCH_PROTECT(old_level);
/* de-allocate all consecutive pbufs from the head of the chain that
* obtain a zero reference count after decrementing*/
while (p != NULL) {
/* all pbufs in a chain are referenced at least once */
LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
/* decrease reference count (number of pointers to pbuf) */
p->ref--;
/* this pbuf is no longer referenced to? */
if (p->ref == 0) {
/* remember next pbuf in chain for next iteration */
q = p->next;
LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: deallocating %p\n", (void *)p));
flags = p->flags;
/* is this a pbuf from the pool? */
if (flags == PBUF_FLAG_POOL) {
p->len = p->tot_len = PBUF_POOL_BUFSIZE;
p->payload = (void *)((u8_t *)p + sizeof(struct pbuf));
PBUF_POOL_FREE(p);
/* is this a ROM or RAM referencing pbuf? */
} else if (flags == PBUF_FLAG_ROM || flags == PBUF_FLAG_REF) {
memp_free(MEMP_PBUF, p);
/* flags == PBUF_FLAG_RAM */
} else {
mem_free(p);
}
count++;
/* proceed to next pbuf */
p = q;
/* p->ref > 0, this pbuf is still referenced to */
/* (and so the remaining pbufs in chain as well) */
} else {
LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, (u16_t)p->ref));
/* stop walking through the chain */
p = NULL;
}
}
SYS_ARCH_UNPROTECT(old_level);
PERF_STOP("pbuf_free");
/* return number of de-allocated pbufs */
return count;
}
/**
* Count number of pbufs in a chain
*
* @param p first pbuf of chain
* @return the number of pbufs in a chain
*/
u8_t
pbuf_clen(struct pbuf *p)
{
u8_t len;
len = 0;
while (p != NULL) {
++len;
p = p->next;
}
return len;
}
/**
* Increment the reference count of the pbuf.
*
* @param p pbuf to increase reference counter of
*
*/
void
pbuf_ref(struct pbuf *p)
{
SYS_ARCH_DECL_PROTECT(old_level);
/* pbuf given? */
if (p != NULL) {
SYS_ARCH_PROTECT(old_level);
++(p->ref);
SYS_ARCH_UNPROTECT(old_level);
}
}
/**
* Concatenate two pbufs (each may be a pbuf chain) and take over
* the caller's reference of the tail pbuf.
*
* @note The caller MAY NOT reference the tail pbuf afterwards.
* Use pbuf_chain() for that purpose.
*
* @see pbuf_chain()
*/
void
pbuf_cat(struct pbuf *h, struct pbuf *t)
{
struct pbuf *p;
LWIP_ASSERT("h != NULL (programmer violates API)", h != NULL);
LWIP_ASSERT("t != NULL (programmer violates API)", t != NULL);
if ((h == NULL) || (t == NULL)) return;
/* proceed to last pbuf of chain */
for (p = h; p->next != NULL; p = p->next) {
/* add total length of second chain to all totals of first chain */
p->tot_len += t->tot_len;
}
/* { p is last pbuf of first h chain, p->next == NULL } */
LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
LWIP_ASSERT("p->next == NULL", p->next == NULL);
/* add total length of second chain to last pbuf total of first chain */
p->tot_len += t->tot_len;
/* chain last pbuf of head (p) with first of tail (t) */
p->next = t;
/* p->next now references t, but the caller will drop its reference to t,
* so netto there is no change to the reference count of t.
*/
}
/**
* Chain two pbufs (or pbuf chains) together.
*
* The caller MUST call pbuf_free(t) once it has stopped
* using it. Use pbuf_cat() instead if you no longer use t.
*
* @param h head pbuf (chain)
* @param t tail pbuf (chain)
* @note The pbufs MUST belong to the same packet.
* @note MAY NOT be called on a packet queue.
*
* The ->tot_len fields of all pbufs of the head chain are adjusted.
* The ->next field of the last pbuf of the head chain is adjusted.
* The ->ref field of the first pbuf of the tail chain is adjusted.
*
*/
void
pbuf_chain(struct pbuf *h, struct pbuf *t)
{
pbuf_cat(h, t);
/* t is now referenced by h */
pbuf_ref(t);
LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
}
/* For packet queueing. Note that queued packets MUST be dequeued first
* using pbuf_dequeue() before calling other pbuf_() functions. */
#if ARP_QUEUEING
/**
* Add a packet to the end of a queue.
*
* @param q pointer to first packet on the queue
* @param n packet to be queued
*
* Both packets MUST be given, and must be different.
*/
void
pbuf_queue(struct pbuf *p, struct pbuf *n)
{
#if PBUF_DEBUG /* remember head of queue */
struct pbuf *q = p;
#endif
/* programmer stupidity checks */
LWIP_ASSERT("p == NULL in pbuf_queue: this indicates a programmer error\n", p != NULL);
LWIP_ASSERT("n == NULL in pbuf_queue: this indicates a programmer error\n", n != NULL);
LWIP_ASSERT("p == n in pbuf_queue: this indicates a programmer error\n", p != n);
if ((p == NULL) || (n == NULL) || (p == n)){
LWIP_DEBUGF(PBUF_DEBUG | DBG_HALT | 3, ("pbuf_queue: programmer argument error\n"));
return;
}
/* iterate through all packets on queue */
while (p->next != NULL) {
/* be very picky about pbuf chain correctness */
#if PBUF_DEBUG
/* iterate through all pbufs in packet */
while (p->tot_len != p->len) {
/* make sure invariant condition holds */
LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len);
/* make sure each packet is complete */
LWIP_ASSERT("p->next != NULL", p->next != NULL);
p = p->next;
/* { p->tot_len == p->len => p is last pbuf of a packet } */
}
/* { p is last pbuf of a packet } */
/* proceed to next packet on queue */
#endif
/* proceed to next pbuf */
if (p->next != NULL) p = p->next;
}
/* { p->tot_len == p->len and p->next == NULL } ==>
* { p is last pbuf of last packet on queue } */
/* chain last pbuf of queue with n */
p->next = n;
/* n is now referenced to by the (packet p in the) queue */
pbuf_ref(n);
#if PBUF_DEBUG
LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2,
("pbuf_queue: newly queued packet %p sits after packet %p in queue %p\n",
(void *)n, (void *)p, (void *)q));
#endif
}
/**
* Remove a packet from the head of a queue.
*
* The caller MUST reference the remainder of the queue (as returned). The
* caller MUST NOT call pbuf_ref() as it implicitly takes over the reference
* from p.
*
* @param p pointer to first packet on the queue which will be dequeued.
* @return first packet on the remaining queue (NULL if no further packets).
*
*/
struct pbuf *
pbuf_dequeue(struct pbuf *p)
{
struct pbuf *q;
LWIP_ASSERT("p != NULL", p != NULL);
/* iterate through all pbufs in packet p */
while (p->tot_len != p->len) {
/* make sure invariant condition holds */
LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len);
/* make sure each packet is complete */
LWIP_ASSERT("p->next != NULL", p->next != NULL);
p = p->next;
}
/* { p->tot_len == p->len } => p is the last pbuf of the first packet */
/* remember next packet on queue in q */
q = p->next;
/* dequeue packet p from queue */
p->next = NULL;
/* any next packet on queue? */
if (q != NULL) {
/* although q is no longer referenced by p, it MUST be referenced by
* the caller, who is maintaining this packet queue. So, we do not call
* pbuf_free(q) here, resulting in an implicit pbuf_ref(q) for the caller. */
LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: first remaining packet on queue is %p\n", (void *)q));
} else {
LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: no further packets on queue\n"));
}
return q;
}
#endif
/**
*
* Create PBUF_POOL (or PBUF_RAM) copies of PBUF_REF pbufs.
*
* Used to queue packets on behalf of the lwIP stack, such as
* ARP based queueing.
*
* Go through a pbuf chain and replace any PBUF_REF buffers
* with PBUF_POOL (or PBUF_RAM) pbufs, each taking a copy of
* the referenced data.
*
* @note You MUST explicitly use p = pbuf_take(p);
* The pbuf you give as argument, may have been replaced
* by a (differently located) copy through pbuf_take()!
*
* @note Any replaced pbufs will be freed through pbuf_free().
* This may deallocate them if they become no longer referenced.
*
* @param p Head of pbuf chain to process
*
* @return Pointer to head of pbuf chain
*/
struct pbuf *
pbuf_take(struct pbuf *p)
{
struct pbuf *q , *prev, *head;
LWIP_ASSERT("pbuf_take: p != NULL\n", p != NULL);
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_take(%p)\n", (void*)p));
prev = NULL;
head = p;
/* iterate through pbuf chain */
do
{
/* pbuf is of type PBUF_REF? */
if (p->flags == PBUF_FLAG_REF) {
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE, ("pbuf_take: encountered PBUF_REF %p\n", (void *)p));
/* allocate a pbuf (w/ payload) fully in RAM */
/* PBUF_POOL buffers are faster if we can use them */
if (p->len <= PBUF_POOL_BUFSIZE) {
q = pbuf_alloc(PBUF_RAW, p->len, PBUF_POOL);
if (q == NULL) {
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_POOL\n"));
}
} else {
/* no replacement pbuf yet */
q = NULL;
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: PBUF_POOL too small to replace PBUF_REF\n"));
}
/* no (large enough) PBUF_POOL was available? retry with PBUF_RAM */
if (q == NULL) {
q = pbuf_alloc(PBUF_RAW, p->len, PBUF_RAM);
if (q == NULL) {
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_RAM\n"));
}
}
/* replacement pbuf could be allocated? */
if (q != NULL)
{
/* copy p to q */
/* copy successor */
q->next = p->next;
/* remove linkage from original pbuf */
p->next = NULL;
/* remove linkage to original pbuf */
if (prev != NULL) {
/* prev->next == p at this point */
LWIP_ASSERT("prev->next == p", prev->next == p);
/* break chain and insert new pbuf instead */
prev->next = q;
/* prev == NULL, so we replaced the head pbuf of the chain */
} else {
head = q;
}
/* copy pbuf payload */
memcpy(q->payload, p->payload, p->len);
q->tot_len = p->tot_len;
q->len = p->len;
/* in case p was the first pbuf, it is no longer refered to by
* our caller, as the caller MUST do p = pbuf_take(p);
* in case p was not the first pbuf, it is no longer refered to
* by prev. we can safely free the pbuf here.
* (note that we have set p->next to NULL already so that
* we will not free the rest of the chain by accident.)
*/
pbuf_free(p);
/* do not copy ref, since someone else might be using the old buffer */
LWIP_DEBUGF(PBUF_DEBUG, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p, (void *)q));
p = q;
} else {
/* deallocate chain */
pbuf_free(head);
LWIP_DEBUGF(PBUF_DEBUG | 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p));
return NULL;
}
/* p->flags != PBUF_FLAG_REF */
} else {
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: skipping pbuf not of type PBUF_REF\n"));
}
/* remember this pbuf */
prev = p;
/* proceed to next pbuf in original chain */
p = p->next;
} while (p);
LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: end of chain reached.\n"));
return head;
}
/**
* Dechains the first pbuf from its succeeding pbufs in the chain.
*
* Makes p->tot_len field equal to p->len.
* @param p pbuf to dechain
* @return remainder of the pbuf chain, or NULL if it was de-allocated.
* @note May not be called on a packet queue.
*/
struct pbuf *
pbuf_dechain(struct pbuf *p)
{
struct pbuf *q;
u8_t tail_gone = 1;
/* tail */
q = p->next;
/* pbuf has successor in chain? */
if (q != NULL) {
/* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
/* enforce invariant if assertion is disabled */
q->tot_len = p->tot_len - p->len;
/* decouple pbuf from remainder */
p->next = NULL;
/* total length of pbuf p is its own length only */
p->tot_len = p->len;
/* q is no longer referenced by p, free it */
LWIP_DEBUGF(PBUF_DEBUG | DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
tail_gone = pbuf_free(q);
if (tail_gone > 0) {
LWIP_DEBUGF(PBUF_DEBUG | DBG_STATE,
("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
}
/* return remaining tail or NULL if deallocated */
}
/* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
return (tail_gone > 0? NULL: q);
}
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