Diff: lwip/core/pbuf.c

Revision:

1:9d93f4dc2f46

Parent:

0:8b387bed54c2

--- a/lwip/core/pbuf.c	Mon Jan 10 21:03:11 2011 +0000
+++ /dev/null	Thu Jan 01 00:00:00 1970 +0000
@@ -1,1156 +0,0 @@
-/**
- * @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, PACKET QUEUES ARE
- * NOT SUPPORTED!!! Use helper structs to queue multiple packets.
- * 
- * 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 "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"
-#if TCP_QUEUE_OOSEQ
-#include "lwip/tcp_impl.h"
-#endif
-#if LWIP_CHECKSUM_ON_COPY
-#include "lwip/inet_chksum.h"
-#endif
-
-#include <string.h>
-
-#define SIZEOF_STRUCT_PBUF        LWIP_MEM_ALIGN_SIZE(sizeof(struct pbuf))
-/* Since the pool is created in memp, PBUF_POOL_BUFSIZE will be automatically
-   aligned there. Therefore, PBUF_POOL_BUFSIZE_ALIGNED can be used here. */
-#define PBUF_POOL_BUFSIZE_ALIGNED LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE)
-
-#if !LWIP_TCP || !TCP_QUEUE_OOSEQ || NO_SYS
-#define PBUF_POOL_IS_EMPTY()
-#else /* !LWIP_TCP || !TCP_QUEUE_OOSEQ || NO_SYS */
-/** Define this to 0 to prevent freeing ooseq pbufs when the PBUF_POOL is empty */
-#ifndef PBUF_POOL_FREE_OOSEQ
-#define PBUF_POOL_FREE_OOSEQ 1
-#endif /* PBUF_POOL_FREE_OOSEQ */
-
-#if PBUF_POOL_FREE_OOSEQ
-#include "lwip/tcpip.h"
-#define PBUF_POOL_IS_EMPTY() pbuf_pool_is_empty()
-static u8_t pbuf_free_ooseq_queued;
-/**
- * Attempt to reclaim some memory from queued out-of-sequence TCP segments
- * if we run out of pool pbufs. It's better to give priority to new packets
- * if we're running out.
- *
- * This must be done in the correct thread context therefore this function
- * can only be used with NO_SYS=0 and through tcpip_callback.
- */
-static void
-pbuf_free_ooseq(void* arg)
-{
-  struct tcp_pcb* pcb;
-  SYS_ARCH_DECL_PROTECT(old_level);
-  LWIP_UNUSED_ARG(arg);
-
-  SYS_ARCH_PROTECT(old_level);
-  pbuf_free_ooseq_queued = 0;
-  SYS_ARCH_UNPROTECT(old_level);
-
-  for (pcb = tcp_active_pcbs; NULL != pcb; pcb = pcb->next) {
-    if (NULL != pcb->ooseq) {
-      /** Free the ooseq pbufs of one PCB only */
-      LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free_ooseq: freeing out-of-sequence pbufs\n"));
-      tcp_segs_free(pcb->ooseq);
-      pcb->ooseq = NULL;
-      return;
-    }
-  }
-}
-
-/** Queue a call to pbuf_free_ooseq if not already queued. */
-static void
-pbuf_pool_is_empty(void)
-{
-  u8_t queued;
-  SYS_ARCH_DECL_PROTECT(old_level);
-
-  SYS_ARCH_PROTECT(old_level);
-  queued = pbuf_free_ooseq_queued;
-  pbuf_free_ooseq_queued = 1;
-  SYS_ARCH_UNPROTECT(old_level);
-
-  if(!queued) {
-    /* queue a call to pbuf_free_ooseq if not already queued */
-    if(tcpip_callback_with_block(pbuf_free_ooseq, NULL, 0) != ERR_OK) {
-      SYS_ARCH_PROTECT(old_level);
-      pbuf_free_ooseq_queued = 0;
-      SYS_ARCH_UNPROTECT(old_level);
-    }
-  }
-}
-#endif /* PBUF_POOL_FREE_OOSEQ */
-#endif /* !LWIP_TCP || !TCP_QUEUE_OOSEQ || NO_SYS */
-
-/**
- * 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 layer flag to define header size
- * @param length size of the pbuf's payload
- * @param type 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 layer, u16_t length, pbuf_type type)
-{
-  struct pbuf *p, *q, *r;
-  u16_t offset;
-  s32_t rem_len; /* remaining length */
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc(length=%"U16_F")\n", length));
-
-  /* determine header offset */
-  offset = 0;
-  switch (layer) {
-  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 (type) {
-  case PBUF_POOL:
-    /* allocate head of pbuf chain into p */
-    p = (struct pbuf *)memp_malloc(MEMP_PBUF_POOL);
-    LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc: allocated pbuf %p\n", (void *)p));
-    if (p == NULL) {
-      PBUF_POOL_IS_EMPTY();
-      return NULL;
-    }
-    p->type = type;
-    p->next = NULL;
-
-    /* make the payload pointer point 'offset' bytes into pbuf data memory */
-    p->payload = LWIP_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 = LWIP_MIN(length, PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset));
-    LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
-                ((u8_t*)p->payload + p->len <=
-                 (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
-    LWIP_ASSERT("PBUF_POOL_BUFSIZE must be bigger than MEM_ALIGNMENT",
-      (PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset)) > 0 );
-    /* 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 = (struct pbuf *)memp_malloc(MEMP_PBUF_POOL);
-      if (q == NULL) {
-        PBUF_POOL_IS_EMPTY();
-        /* free chain so far allocated */
-        pbuf_free(p);
-        /* bail out unsuccesfully */
-        return NULL;
-      }
-      q->type = type;
-      q->flags = 0;
-      q->next = NULL;
-      /* make previous pbuf point to this pbuf */
-      r->next = q;
-      /* set total length of this pbuf and next in chain */
-      LWIP_ASSERT("rem_len < max_u16_t", rem_len < 0xffff);
-      q->tot_len = (u16_t)rem_len;
-      /* this pbuf length is pool size, unless smaller sized tail */
-      q->len = LWIP_MIN((u16_t)rem_len, PBUF_POOL_BUFSIZE_ALIGNED);
-      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);
-      LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
-                  ((u8_t*)p->payload + p->len <=
-                   (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
-      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 = (struct pbuf*)mem_malloc(LWIP_MEM_ALIGN_SIZE(SIZEOF_STRUCT_PBUF + offset) + LWIP_MEM_ALIGN_SIZE(length));
-    if (p == NULL) {
-      return NULL;
-    }
-    /* Set up internal structure of the pbuf. */
-    p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + SIZEOF_STRUCT_PBUF + offset));
-    p->len = p->tot_len = length;
-    p->next = NULL;
-    p->type = type;
-
-    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 = (struct pbuf *)memp_malloc(MEMP_PBUF);
-    if (p == NULL) {
-      LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
-                  ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n",
-                  (type == 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->type = type;
-    break;
-  default:
-    LWIP_ASSERT("pbuf_alloc: erroneous type", 0);
-    return NULL;
-  }
-  /* set reference count */
-  p->ref = 1;
-  /* set flags */
-  p->flags = 0;
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
-  return p;
-}
-
-#if LWIP_SUPPORT_CUSTOM_PBUF
-/** Initialize a custom pbuf (already allocated).
- *
- * @param layer flag to define header size
- * @param length size of the pbuf's payload
- * @param type type of the pbuf (only used to treat the pbuf accordingly, as
- *        this function allocates no memory)
- * @param p pointer to the custom pbuf to initialize (already allocated)
- * @param payload_mem pointer to the buffer that is used for payload and headers,
- *        must be at least big enough to hold 'length' plus the header size,
- *        may be NULL if set later
- * @param payload_mem_len the size of the 'payload_mem' buffer, must be at least
- *        big enough to hold 'length' plus the header size
- */
-struct pbuf*
-pbuf_alloced_custom(pbuf_layer l, u16_t length, pbuf_type type, struct pbuf_custom *p,
-                    void *payload_mem, u16_t payload_mem_len)
-{
-  u16_t offset;
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloced_custom(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_alloced_custom: bad pbuf layer", 0);
-    return NULL;
-  }
-
-  if (LWIP_MEM_ALIGN_SIZE(offset) + length < payload_mem_len) {
-    LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_WARNING, ("pbuf_alloced_custom(length=%"U16_F") buffer too short\n", length));
-    return NULL;
-  }
-
-  p->pbuf.next = NULL;
-  if (payload_mem != NULL) {
-    p->pbuf.payload = LWIP_MEM_ALIGN((void *)((u8_t *)payload_mem + offset));
-  } else {
-    p->pbuf.payload = NULL;
-  }
-  p->pbuf.flags = PBUF_FLAG_IS_CUSTOM;
-  p->pbuf.len = p->pbuf.tot_len = length;
-  p->pbuf.type = type;
-  p->pbuf.ref = 1;
-  return &p->pbuf;
-}
-#endif /* LWIP_SUPPORT_CUSTOM_PBUF */
-
-/**
- * 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.
- *
- * @note Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).
- */
-void
-pbuf_realloc(struct pbuf *p, u16_t new_len)
-{
-  struct pbuf *q;
-  u16_t rem_len; /* remaining length */
-  s32_t grow;
-
-  LWIP_ASSERT("pbuf_realloc: p != NULL", p != NULL);
-  LWIP_ASSERT("pbuf_realloc: sane p->type", p->type == PBUF_POOL ||
-              p->type == PBUF_ROM ||
-              p->type == PBUF_RAM ||
-              p->type == PBUF_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 */
-    LWIP_ASSERT("grow < max_u16_t", grow < 0xffff);
-    q->tot_len += (u16_t)grow;
-    /* proceed to next pbuf in chain */
-    q = q->next;
-    LWIP_ASSERT("pbuf_realloc: q != NULL", q != NULL);
-  }
-  /* 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->type == PBUF_RAM) && (rem_len != q->len)) {
-    /* reallocate and adjust the length of the pbuf that will be split */
-    q = (struct pbuf *)mem_trim(q, (u16_t)((u8_t *)q->payload - (u8_t *)q) + rem_len);
-    LWIP_ASSERT("mem_trim returned q == NULL", q != NULL);
-  }
-  /* 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 p pbuf to change the header size.
- * @param header_size_increment 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 type;
-  void *payload;
-  u16_t increment_magnitude;
-
-  LWIP_ASSERT("p != NULL", p != NULL);
-  if ((header_size_increment == 0) || (p == NULL)) {
-    return 0;
-  }
- 
-  if (header_size_increment < 0){
-    increment_magnitude = -header_size_increment;
-    /* Check that we aren't going to move off the end of the pbuf */
-    LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);
-  } else {
-    increment_magnitude = header_size_increment;
-#if 0
-    /* Can't assert these as some callers speculatively call
-         pbuf_header() to see if it's OK.  Will return 1 below instead. */
-    /* Check that we've got the correct type of pbuf to work with */
-    LWIP_ASSERT("p->type == PBUF_RAM || p->type == PBUF_POOL", 
-                p->type == PBUF_RAM || p->type == PBUF_POOL);
-    /* Check that we aren't going to move off the beginning of the pbuf */
-    LWIP_ASSERT("p->payload - increment_magnitude >= p + SIZEOF_STRUCT_PBUF",
-                (u8_t *)p->payload - increment_magnitude >= (u8_t *)p + SIZEOF_STRUCT_PBUF);
-#endif
-  }
-
-  type = p->type;
-  /* remember current payload pointer */
-  payload = p->payload;
-
-  /* pbuf types containing payloads? */
-  if (type == PBUF_RAM || type == PBUF_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 | LWIP_DBG_LEVEL_SERIOUS,
-        ("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 (type == PBUF_REF || type == PBUF_ROM) {
-    /* hide a header in the payload? */
-    if ((header_size_increment < 0) && (increment_magnitude <= p->len)) {
-      /* increase payload pointer */
-      p->payload = (u8_t *)p->payload - header_size_increment;
-    } else {
-      /* cannot expand payload to front (yet!)
-       * bail out unsuccesfully */
-      return 1;
-    }
-  } else {
-    /* Unknown type */
-    LWIP_ASSERT("bad pbuf type", 0);
-    return 1;
-  }
-  /* modify pbuf length fields */
-  p->len += header_size_increment;
-  p->tot_len += header_size_increment;
-
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("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 p 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 type;
-  struct pbuf *q;
-  u8_t count;
-
-  if (p == NULL) {
-    LWIP_ASSERT("p != NULL", p != NULL);
-    /* if assertions are disabled, proceed with debug output */
-    LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
-      ("pbuf_free(p == NULL) was called.\n"));
-    return 0;
-  }
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free(%p)\n", (void *)p));
-
-  PERF_START;
-
-  LWIP_ASSERT("pbuf_free: sane type",
-    p->type == PBUF_RAM || p->type == PBUF_ROM ||
-    p->type == PBUF_REF || p->type == PBUF_POOL);
-
-  count = 0;
-  /* de-allocate all consecutive pbufs from the head of the chain that
-   * obtain a zero reference count after decrementing*/
-  while (p != NULL) {
-    u16_t ref;
-    SYS_ARCH_DECL_PROTECT(old_level);
-    /* Since decrementing ref cannot be guaranteed to be a single machine operation
-     * we must protect it. We put the new ref into a local variable to prevent
-     * further protection. */
-    SYS_ARCH_PROTECT(old_level);
-    /* 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) */
-    ref = --(p->ref);
-    SYS_ARCH_UNPROTECT(old_level);
-    /* this pbuf is no longer referenced to? */
-    if (ref == 0) {
-      /* remember next pbuf in chain for next iteration */
-      q = p->next;
-      LWIP_DEBUGF( PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free: deallocating %p\n", (void *)p));
-      type = p->type;
-#if LWIP_SUPPORT_CUSTOM_PBUF
-      /* is this a custom pbuf? */
-      if ((p->flags & PBUF_FLAG_IS_CUSTOM) != 0) {
-        struct pbuf_custom *pc = (struct pbuf_custom*)p;
-        LWIP_ASSERT("pc->custom_free_function != NULL", pc->custom_free_function != NULL);
-        pc->custom_free_function(p);
-      } else
-#endif /* LWIP_SUPPORT_CUSTOM_PBUF */
-      {
-        /* is this a pbuf from the pool? */
-        if (type == PBUF_POOL) {
-          memp_free(MEMP_PBUF_POOL, p);
-        /* is this a ROM or RAM referencing pbuf? */
-        } else if (type == PBUF_ROM || type == PBUF_REF) {
-          memp_free(MEMP_PBUF, p);
-        /* type == PBUF_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 | LWIP_DBG_TRACE, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, ref));
-      /* stop walking through the chain */
-      p = NULL;
-    }
-  }
-  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_ERROR("(h != NULL) && (t != NULL) (programmer violates API)",
-             ((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 | LWIP_DBG_TRACE, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
-}
-
-/**
- * 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 | LWIP_DBG_TRACE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
-    tail_gone = pbuf_free(q);
-    if (tail_gone > 0) {
-      LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE,
-                  ("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);
-}
-
-/**
- *
- * Create PBUF_RAM copies of pbufs.
- *
- * Used to queue packets on behalf of the lwIP stack, such as
- * ARP based queueing.
- *
- * @note You MUST explicitly use p = pbuf_take(p);
- *
- * @note Only one packet is copied, no packet queue!
- *
- * @param p_to pbuf destination of the copy
- * @param p_from pbuf source of the copy
- *
- * @return ERR_OK if pbuf was copied
- *         ERR_ARG if one of the pbufs is NULL or p_to is not big
- *                 enough to hold p_from
- */
-err_t
-pbuf_copy(struct pbuf *p_to, struct pbuf *p_from)
-{
-  u16_t offset_to=0, offset_from=0, len;
-
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy(%p, %p)\n",
-    (void*)p_to, (void*)p_from));
-
-  /* is the target big enough to hold the source? */
-  LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
-             (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);
-
-  /* iterate through pbuf chain */
-  do
-  {
-    LWIP_ASSERT("p_to != NULL", p_to != NULL);
-    /* copy one part of the original chain */
-    if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
-      /* complete current p_from fits into current p_to */
-      len = p_from->len - offset_from;
-    } else {
-      /* current p_from does not fit into current p_to */
-      len = p_to->len - offset_to;
-    }
-    MEMCPY((u8_t*)p_to->payload + offset_to, (u8_t*)p_from->payload + offset_from, len);
-    offset_to += len;
-    offset_from += len;
-    LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
-    if (offset_to == p_to->len) {
-      /* on to next p_to (if any) */
-      offset_to = 0;
-      p_to = p_to->next;
-    }
-    LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
-    if (offset_from >= p_from->len) {
-      /* on to next p_from (if any) */
-      offset_from = 0;
-      p_from = p_from->next;
-    }
-
-    if((p_from != NULL) && (p_from->len == p_from->tot_len)) {
-      /* don't copy more than one packet! */
-      LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
-                 (p_from->next == NULL), return ERR_VAL;);
-    }
-    if((p_to != NULL) && (p_to->len == p_to->tot_len)) {
-      /* don't copy more than one packet! */
-      LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
-                  (p_to->next == NULL), return ERR_VAL;);
-    }
-  } while (p_from);
-  LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy: end of chain reached.\n"));
-  return ERR_OK;
-}
-
-/**
- * Copy (part of) the contents of a packet buffer
- * to an application supplied buffer.
- *
- * @param buf the pbuf from which to copy data
- * @param dataptr the application supplied buffer
- * @param len length of data to copy (dataptr must be big enough). No more 
- * than buf->tot_len will be copied, irrespective of len
- * @param offset offset into the packet buffer from where to begin copying len bytes
- * @return the number of bytes copied, or 0 on failure
- */
-u16_t
-pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
-{
-  struct pbuf *p;
-  u16_t left;
-  u16_t buf_copy_len;
-  u16_t copied_total = 0;
-
-  LWIP_ERROR("pbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
-  LWIP_ERROR("pbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
-
-  left = 0;
-
-  if((buf == NULL) || (dataptr == NULL)) {
-    return 0;
-  }
-
-  /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
-  for(p = buf; len != 0 && p != NULL; p = p->next) {
-    if ((offset != 0) && (offset >= p->len)) {
-      /* don't copy from this buffer -> on to the next */
-      offset -= p->len;
-    } else {
-      /* copy from this buffer. maybe only partially. */
-      buf_copy_len = p->len - offset;
-      if (buf_copy_len > len)
-          buf_copy_len = len;
-      /* copy the necessary parts of the buffer */
-      MEMCPY(&((char*)dataptr)[left], &((char*)p->payload)[offset], buf_copy_len);
-      copied_total += buf_copy_len;
-      left += buf_copy_len;
-      len -= buf_copy_len;
-      offset = 0;
-    }
-  }
-  return copied_total;
-}
-
-/**
- * Copy application supplied data into a pbuf.
- * This function can only be used to copy the equivalent of buf->tot_len data.
- *
- * @param buf pbuf to fill with data
- * @param dataptr application supplied data buffer
- * @param len length of the application supplied data buffer
- *
- * @return ERR_OK if successful, ERR_MEM if the pbuf is not big enough
- */
-err_t
-pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len)
-{
-  struct pbuf *p;
-  u16_t buf_copy_len;
-  u16_t total_copy_len = len;
-  u16_t copied_total = 0;
-
-  LWIP_ERROR("pbuf_take: invalid buf", (buf != NULL), return 0;);
-  LWIP_ERROR("pbuf_take: invalid dataptr", (dataptr != NULL), return 0;);
-
-  if ((buf == NULL) || (dataptr == NULL) || (buf->tot_len < len)) {
-    return ERR_ARG;
-  }
-
-  /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
-  for(p = buf; total_copy_len != 0; p = p->next) {
-    LWIP_ASSERT("pbuf_take: invalid pbuf", p != NULL);
-    buf_copy_len = total_copy_len;
-    if (buf_copy_len > p->len) {
-      /* this pbuf cannot hold all remaining data */
-      buf_copy_len = p->len;
-    }
-    /* copy the necessary parts of the buffer */
-    MEMCPY(p->payload, &((char*)dataptr)[copied_total], buf_copy_len);
-    total_copy_len -= buf_copy_len;
-    copied_total += buf_copy_len;
-  }
-  LWIP_ASSERT("did not copy all data", total_copy_len == 0 && copied_total == len);
-  return ERR_OK;
-}
-
-/**
- * Creates a single pbuf out of a queue of pbufs.
- *
- * @remark: Either the source pbuf 'p' is freed by this function or the original
- *          pbuf 'p' is returned, therefore the caller has to check the result!
- *
- * @param p the source pbuf
- * @param layer pbuf_layer of the new pbuf
- *
- * @return a new, single pbuf (p->next is NULL)
- *         or the old pbuf if allocation fails
- */
-struct pbuf*
-pbuf_coalesce(struct pbuf *p, pbuf_layer layer)
-{
-  struct pbuf *q;
-  err_t err;
-  if (p->next == NULL) {
-    return p;
-  }
-  q = pbuf_alloc(layer, p->tot_len, PBUF_RAM);
-  if (q == NULL) {
-    /* @todo: what do we do now? */
-    return p;
-  }
-  err = pbuf_copy(q, p);
-  LWIP_ASSERT("pbuf_copy failed", err == ERR_OK);
-  pbuf_free(p);
-  return q;
-}
-
-#if LWIP_CHECKSUM_ON_COPY
-/**
- * Copies data into a single pbuf (*not* into a pbuf queue!) and updates
- * the checksum while copying
- *
- * @param p the pbuf to copy data into
- * @param start_offset offset of p->payload where to copy the data to
- * @param dataptr data to copy into the pbuf
- * @param len length of data to copy into the pbuf
- * @param chksum pointer to the checksum which is updated
- * @return ERR_OK if successful, another error if the data does not fit
- *         within the (first) pbuf (no pbuf queues!)
- */
-err_t
-pbuf_fill_chksum(struct pbuf *p, u16_t start_offset, const void *dataptr,
-                 u16_t len, u16_t *chksum)
-{
-  u32_t acc;
-  u16_t copy_chksum;
-  char *dst_ptr;
-  LWIP_ASSERT("p != NULL", p != NULL);
-  LWIP_ASSERT("dataptr != NULL", dataptr != NULL);
-  LWIP_ASSERT("chksum != NULL", chksum != NULL);
-  LWIP_ASSERT("len != 0", len != 0);
-
-  if ((start_offset >= p->len) || (start_offset + len > p->len)) {
-    return ERR_ARG;
-  }
-
-  dst_ptr = ((char*)p->payload) + start_offset;
-  copy_chksum = LWIP_CHKSUM_COPY(dst_ptr, dataptr, len);
-  if ((start_offset & 1) != 0) {
-    copy_chksum = SWAP_BYTES_IN_WORD(copy_chksum);
-  }
-  acc = *chksum;
-  acc += copy_chksum;
-  *chksum = FOLD_U32T(acc);
-  return ERR_OK;
-}
-#endif /* LWIP_CHECKSUM_ON_COPY */
-
- /** Get one byte from the specified position in a pbuf
- * WARNING: returns zero for offset >= p->tot_len
- *
- * @param p pbuf to parse
- * @param offset offset into p of the byte to return
- * @return byte at an offset into p OR ZERO IF 'offset' >= p->tot_len
- */
-u8_t
-pbuf_get_at(struct pbuf* p, u16_t offset)
-{
-  u16_t copy_from = offset;
-  struct pbuf* q = p;
-
-  /* get the correct pbuf */
-  while ((q != NULL) && (q->len <= copy_from)) {
-    copy_from -= q->len;
-    q = q->next;
-  }
-  /* return requested data if pbuf is OK */
-  if ((q != NULL) && (q->len > copy_from)) {
-    return ((u8_t*)q->payload)[copy_from];
-  }
-  return 0;
-}
-
-/** Compare pbuf contents at specified offset with memory s2, both of length n
- *
- * @param p pbuf to compare
- * @param offset offset into p at wich to start comparing
- * @param s2 buffer to compare
- * @param n length of buffer to compare
- * @return zero if equal, nonzero otherwise
- *         (0xffff if p is too short, diffoffset+1 otherwise)
- */
-u16_t
-pbuf_memcmp(struct pbuf* p, u16_t offset, const void* s2, u16_t n)
-{
-  u16_t start = offset;
-  struct pbuf* q = p;
-
-  /* get the correct pbuf */
-  while ((q != NULL) && (q->len <= start)) {
-    start -= q->len;
-    q = q->next;
-  }
-  /* return requested data if pbuf is OK */
-  if ((q != NULL) && (q->len > start)) {
-    u16_t i;
-    for(i = 0; i < n; i++) {
-      u8_t a = pbuf_get_at(q, start + i);
-      u8_t b = ((u8_t*)s2)[i];
-      if (a != b) {
-        return i+1;
-      }
-    }
-    return 0;
-  }
-  return 0xffff;
-}
-
-/** Find occurrence of mem (with length mem_len) in pbuf p, starting at offset
- * start_offset.
- *
- * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
- *        return value 'not found'
- * @param mem search for the contents of this buffer
- * @param mem_len length of 'mem'
- * @param start_offset offset into p at which to start searching
- * @return 0xFFFF if substr was not found in p or the index where it was found
- */
-u16_t
-pbuf_memfind(struct pbuf* p, const void* mem, u16_t mem_len, u16_t start_offset)
-{
-  u16_t i;
-  u16_t max = p->tot_len - mem_len;
-  if (p->tot_len >= mem_len + start_offset) {
-    for(i = start_offset; i <= max; ) {
-      u16_t plus = pbuf_memcmp(p, i, mem, mem_len);
-      if (plus == 0) {
-        return i;
-      } else {
-        i += plus;
-      }
-    }
-  }
-  return 0xFFFF;
-}
-
-/** Find occurrence of substr with length substr_len in pbuf p, start at offset
- * start_offset
- * WARNING: in contrast to strstr(), this one does not stop at the first \0 in
- * the pbuf/source string!
- *
- * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
- *        return value 'not found'
- * @param substr string to search for in p, maximum length is 0xFFFE
- * @return 0xFFFF if substr was not found in p or the index where it was found
- */
-u16_t
-pbuf_strstr(struct pbuf* p, const char* substr)
-{
-  size_t substr_len;
-  if ((substr == NULL) || (substr[0] == 0) || (p->tot_len == 0xFFFF)) {
-    return 0xFFFF;
-  }
-  substr_len = strlen(substr);
-  if (substr_len >= 0xFFFF) {
-    return 0xFFFF;
-  }
-  return pbuf_memfind(p, substr, (u16_t)substr_len, 0);
-}