pbuf.c

00001 /**
00002  * @file
00003  * Packet buffer management
00004  *
00005  * Packets are built from the pbuf data structure. It supports dynamic
00006  * memory allocation for packet contents or can reference externally
00007  * managed packet contents both in RAM and ROM. Quick allocation for
00008  * incoming packets is provided through pools with fixed sized pbufs.
00009  *
00010  * A packet may span over multiple pbufs, chained as a singly linked
00011  * list. This is called a "pbuf chain".
00012  *
00013  * Multiple packets may be queued, also using this singly linked list.
00014  * This is called a "packet queue".
00015  * 
00016  * So, a packet queue consists of one or more pbuf chains, each of
00017  * which consist of one or more pbufs. CURRENTLY, PACKET QUEUES ARE
00018  * NOT SUPPORTED!!! Use helper structs to queue multiple packets.
00019  * 
00020  * The differences between a pbuf chain and a packet queue are very
00021  * precise but subtle. 
00022  *
00023  * The last pbuf of a packet has a ->tot_len field that equals the
00024  * ->len field. It can be found by traversing the list. If the last
00025  * pbuf of a packet has a ->next field other than NULL, more packets
00026  * are on the queue.
00027  *
00028  * Therefore, looping through a pbuf of a single packet, has an
00029  * loop end condition (tot_len == p->len), NOT (next == NULL).
00030  */
00031 
00032 /*
00033  * Copyright (c) 2001-2004 Swedish Institute of Computer Science.
00034  * All rights reserved.
00035  *
00036  * Redistribution and use in source and binary forms, with or without modification,
00037  * are permitted provided that the following conditions are met:
00038  *
00039  * 1. Redistributions of source code must retain the above copyright notice,
00040  *    this list of conditions and the following disclaimer.
00041  * 2. Redistributions in binary form must reproduce the above copyright notice,
00042  *    this list of conditions and the following disclaimer in the documentation
00043  *    and/or other materials provided with the distribution.
00044  * 3. The name of the author may not be used to endorse or promote products
00045  *    derived from this software without specific prior written permission.
00046  *
00047  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED
00048  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
00049  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT
00050  * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
00051  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
00052  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
00053  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
00054  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
00055  * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY
00056  * OF SUCH DAMAGE.
00057  *
00058  * This file is part of the lwIP TCP/IP stack.
00059  *
00060  * Author: Adam Dunkels <adam@sics.se>
00061  *
00062  */
00063 
00064 #include "lwip/opt.h"
00065 
00066 #include "lwip/stats.h"
00067 #include "lwip/def.h"
00068 #include "lwip/mem.h"
00069 #include "lwip/memp.h"
00070 #include "lwip/pbuf.h"
00071 #include "lwip/sys.h"
00072 #include "arch/perf.h"
00073 #if TCP_QUEUE_OOSEQ
00074 #include "lwip/tcp_impl.h"
00075 #endif
00076 #if LWIP_CHECKSUM_ON_COPY
00077 #include "lwip/inet_chksum.h"
00078 #endif
00079 
00080 #include <string.h>
00081 
00082 #define SIZEOF_STRUCT_PBUF        LWIP_MEM_ALIGN_SIZE(sizeof(struct pbuf))
00083 /* Since the pool is created in memp, PBUF_POOL_BUFSIZE will be automatically
00084    aligned there. Therefore, PBUF_POOL_BUFSIZE_ALIGNED can be used here. */
00085 #define PBUF_POOL_BUFSIZE_ALIGNED LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE)
00086 
00087 #if !LWIP_TCP || !TCP_QUEUE_OOSEQ || NO_SYS
00088 #define PBUF_POOL_IS_EMPTY()
00089 #else /* !LWIP_TCP || !TCP_QUEUE_OOSEQ || NO_SYS */
00090 /** Define this to 0 to prevent freeing ooseq pbufs when the PBUF_POOL is empty */
00091 #ifndef PBUF_POOL_FREE_OOSEQ
00092 #define PBUF_POOL_FREE_OOSEQ 1
00093 #endif /* PBUF_POOL_FREE_OOSEQ */
00094 
00095 #if PBUF_POOL_FREE_OOSEQ
00096 #include "lwip/tcpip.h"
00097 #define PBUF_POOL_IS_EMPTY() pbuf_pool_is_empty()
00098 static u8_t pbuf_free_ooseq_queued;
00099 /**
00100  * Attempt to reclaim some memory from queued out-of-sequence TCP segments
00101  * if we run out of pool pbufs. It's better to give priority to new packets
00102  * if we're running out.
00103  *
00104  * This must be done in the correct thread context therefore this function
00105  * can only be used with NO_SYS=0 and through tcpip_callback.
00106  */
00107 static void
00108 pbuf_free_ooseq(void* arg)
00109 {
00110   struct tcp_pcb* pcb;
00111   SYS_ARCH_DECL_PROTECT(old_level);
00112   LWIP_UNUSED_ARG(arg);
00113 
00114   SYS_ARCH_PROTECT(old_level);
00115   pbuf_free_ooseq_queued = 0;
00116   SYS_ARCH_UNPROTECT(old_level);
00117 
00118   for (pcb = tcp_active_pcbs; NULL != pcb; pcb = pcb->next) {
00119     if (NULL != pcb->ooseq) {
00120       /** Free the ooseq pbufs of one PCB only */
00121       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free_ooseq: freeing out-of-sequence pbufs\n"));
00122       tcp_segs_free(pcb->ooseq);
00123       pcb->ooseq = NULL;
00124       return;
00125     }
00126   }
00127 }
00128 
00129 /** Queue a call to pbuf_free_ooseq if not already queued. */
00130 static void
00131 pbuf_pool_is_empty(void)
00132 {
00133   u8_t queued;
00134   SYS_ARCH_DECL_PROTECT(old_level);
00135 
00136   SYS_ARCH_PROTECT(old_level);
00137   queued = pbuf_free_ooseq_queued;
00138   pbuf_free_ooseq_queued = 1;
00139   SYS_ARCH_UNPROTECT(old_level);
00140 
00141   if(!queued) {
00142     /* queue a call to pbuf_free_ooseq if not already queued */
00143     if(tcpip_callback_with_block(pbuf_free_ooseq, NULL, 0) != ERR_OK) {
00144       SYS_ARCH_PROTECT(old_level);
00145       pbuf_free_ooseq_queued = 0;
00146       SYS_ARCH_UNPROTECT(old_level);
00147     }
00148   }
00149 }
00150 #endif /* PBUF_POOL_FREE_OOSEQ */
00151 #endif /* !LWIP_TCP || !TCP_QUEUE_OOSEQ || NO_SYS */
00152 
00153 /**
00154  * Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).
00155  *
00156  * The actual memory allocated for the pbuf is determined by the
00157  * layer at which the pbuf is allocated and the requested size
00158  * (from the size parameter).
00159  *
00160  * @param layer flag to define header size
00161  * @param length size of the pbuf's payload
00162  * @param type this parameter decides how and where the pbuf
00163  * should be allocated as follows:
00164  *
00165  * - PBUF_RAM: buffer memory for pbuf is allocated as one large
00166  *             chunk. This includes protocol headers as well.
00167  * - PBUF_ROM: no buffer memory is allocated for the pbuf, even for
00168  *             protocol headers. Additional headers must be prepended
00169  *             by allocating another pbuf and chain in to the front of
00170  *             the ROM pbuf. It is assumed that the memory used is really
00171  *             similar to ROM in that it is immutable and will not be
00172  *             changed. Memory which is dynamic should generally not
00173  *             be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
00174  * - PBUF_REF: no buffer memory is allocated for the pbuf, even for
00175  *             protocol headers. It is assumed that the pbuf is only
00176  *             being used in a single thread. If the pbuf gets queued,
00177  *             then pbuf_take should be called to copy the buffer.
00178  * - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from
00179  *              the pbuf pool that is allocated during pbuf_init().
00180  *
00181  * @return the allocated pbuf. If multiple pbufs where allocated, this
00182  * is the first pbuf of a pbuf chain.
00183  */
00184 struct pbuf *
00185 pbuf_alloc(pbuf_layer layer, u16_t length, pbuf_type type)
00186 {
00187   struct pbuf *p, *q, *r;
00188   u16_t offset;
00189   s32_t rem_len; /* remaining length */
00190   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc(length=%"U16_F")\n", length));
00191 
00192   /* determine header offset */
00193   offset = 0;
00194   switch (layer) {
00195   case PBUF_TRANSPORT:
00196     /* add room for transport (often TCP) layer header */
00197     offset += PBUF_TRANSPORT_HLEN;
00198     /* FALLTHROUGH */
00199   case PBUF_IP:
00200     /* add room for IP layer header */
00201     offset += PBUF_IP_HLEN;
00202     /* FALLTHROUGH */
00203   case PBUF_LINK:
00204     /* add room for link layer header */
00205     offset += PBUF_LINK_HLEN;
00206     break;
00207   case PBUF_RAW:
00208     break;
00209   default:
00210     LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0);
00211     return NULL;
00212   }
00213 
00214   switch (type) {
00215   case PBUF_POOL:
00216     /* allocate head of pbuf chain into p */
00217     p = (struct pbuf *)memp_malloc(MEMP_PBUF_POOL);
00218     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc: allocated pbuf %p\n", (void *)p));
00219     if (p == NULL) {
00220       PBUF_POOL_IS_EMPTY();
00221       return NULL;
00222     }
00223     p->type = type;
00224     p->next = NULL;
00225 
00226     /* make the payload pointer point 'offset' bytes into pbuf data memory */
00227     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + (SIZEOF_STRUCT_PBUF + offset)));
00228     LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
00229             ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00230     /* the total length of the pbuf chain is the requested size */
00231     p->tot_len = length;
00232     /* set the length of the first pbuf in the chain */
00233     p->len = LWIP_MIN(length, PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset));
00234     LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00235                 ((u8_t*)p->payload + p->len <=
00236                  (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00237     LWIP_ASSERT("PBUF_POOL_BUFSIZE must be bigger than MEM_ALIGNMENT",
00238       (PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset)) > 0 );
00239     /* set reference count (needed here in case we fail) */
00240     p->ref = 1;
00241 
00242     /* now allocate the tail of the pbuf chain */
00243 
00244     /* remember first pbuf for linkage in next iteration */
00245     r = p;
00246     /* remaining length to be allocated */
00247     rem_len = length - p->len;
00248     /* any remaining pbufs to be allocated? */
00249     while (rem_len > 0) {
00250       q = (struct pbuf *)memp_malloc(MEMP_PBUF_POOL);
00251       if (q == NULL) {
00252         PBUF_POOL_IS_EMPTY();
00253         /* free chain so far allocated */
00254         pbuf_free(p);
00255         /* bail out unsuccesfully */
00256         return NULL;
00257       }
00258       q->type = type;
00259       q->flags = 0;
00260       q->next = NULL;
00261       /* make previous pbuf point to this pbuf */
00262       r->next = q;
00263       /* set total length of this pbuf and next in chain */
00264       LWIP_ASSERT("rem_len < max_u16_t", rem_len < 0xffff);
00265       q->tot_len = (u16_t)rem_len;
00266       /* this pbuf length is pool size, unless smaller sized tail */
00267       q->len = LWIP_MIN((u16_t)rem_len, PBUF_POOL_BUFSIZE_ALIGNED);
00268       q->payload = (void *)((u8_t *)q + SIZEOF_STRUCT_PBUF);
00269       LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
00270               ((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0);
00271       LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00272                   ((u8_t*)p->payload + p->len <=
00273                    (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00274       q->ref = 1;
00275       /* calculate remaining length to be allocated */
00276       rem_len -= q->len;
00277       /* remember this pbuf for linkage in next iteration */
00278       r = q;
00279     }
00280     /* end of chain */
00281     /*r->next = NULL;*/
00282 
00283     break;
00284   case PBUF_RAM:
00285     /* If pbuf is to be allocated in RAM, allocate memory for it. */
00286     p = (struct pbuf*)mem_malloc(LWIP_MEM_ALIGN_SIZE(SIZEOF_STRUCT_PBUF + offset) + LWIP_MEM_ALIGN_SIZE(length));
00287     if (p == NULL) {
00288       return NULL;
00289     }
00290     /* Set up internal structure of the pbuf. */
00291     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + SIZEOF_STRUCT_PBUF + offset));
00292     p->len = p->tot_len = length;
00293     p->next = NULL;
00294     p->type = type;
00295 
00296     LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
00297            ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00298     break;
00299   /* pbuf references existing (non-volatile static constant) ROM payload? */
00300   case PBUF_ROM:
00301   /* pbuf references existing (externally allocated) RAM payload? */
00302   case PBUF_REF:
00303     /* only allocate memory for the pbuf structure */
00304     p = (struct pbuf *)memp_malloc(MEMP_PBUF);
00305     if (p == NULL) {
00306       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00307                   ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n",
00308                   (type == PBUF_ROM) ? "ROM" : "REF"));
00309       return NULL;
00310     }
00311     /* caller must set this field properly, afterwards */
00312     p->payload = NULL;
00313     p->len = p->tot_len = length;
00314     p->next = NULL;
00315     p->type = type;
00316     break;
00317   default:
00318     LWIP_ASSERT("pbuf_alloc: erroneous type", 0);
00319     return NULL;
00320   }
00321   /* set reference count */
00322   p->ref = 1;
00323   /* set flags */
00324   p->flags = 0;
00325   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
00326   return p;
00327 }
00328 
00329 #if LWIP_SUPPORT_CUSTOM_PBUF
00330 /** Initialize a custom pbuf (already allocated).
00331  *
00332  * @param layer flag to define header size
00333  * @param length size of the pbuf's payload
00334  * @param type type of the pbuf (only used to treat the pbuf accordingly, as
00335  *        this function allocates no memory)
00336  * @param p pointer to the custom pbuf to initialize (already allocated)
00337  * @param payload_mem pointer to the buffer that is used for payload and headers,
00338  *        must be at least big enough to hold 'length' plus the header size,
00339  *        may be NULL if set later
00340  * @param payload_mem_len the size of the 'payload_mem' buffer, must be at least
00341  *        big enough to hold 'length' plus the header size
00342  */
00343 struct pbuf*
00344 pbuf_alloced_custom(pbuf_layer l, u16_t length, pbuf_type type, struct pbuf_custom *p,
00345                     void *payload_mem, u16_t payload_mem_len)
00346 {
00347   u16_t offset;
00348   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloced_custom(length=%"U16_F")\n", length));
00349 
00350   /* determine header offset */
00351   offset = 0;
00352   switch (l) {
00353   case PBUF_TRANSPORT:
00354     /* add room for transport (often TCP) layer header */
00355     offset += PBUF_TRANSPORT_HLEN;
00356     /* FALLTHROUGH */
00357   case PBUF_IP:
00358     /* add room for IP layer header */
00359     offset += PBUF_IP_HLEN;
00360     /* FALLTHROUGH */
00361   case PBUF_LINK:
00362     /* add room for link layer header */
00363     offset += PBUF_LINK_HLEN;
00364     break;
00365   case PBUF_RAW:
00366     break;
00367   default:
00368     LWIP_ASSERT("pbuf_alloced_custom: bad pbuf layer", 0);
00369     return NULL;
00370   }
00371 
00372   if (LWIP_MEM_ALIGN_SIZE(offset) + length < payload_mem_len) {
00373     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_WARNING, ("pbuf_alloced_custom(length=%"U16_F") buffer too short\n", length));
00374     return NULL;
00375   }
00376 
00377   p->pbuf.next = NULL;
00378   if (payload_mem != NULL) {
00379     p->pbuf.payload = (void *)((u8_t *)payload_mem + offset);
00380   } else {
00381     p->pbuf.payload = NULL;
00382   }
00383   p->pbuf.flags = PBUF_FLAG_IS_CUSTOM;
00384   p->pbuf.len = p->pbuf.tot_len = length;
00385   p->pbuf.type = type;
00386   p->pbuf.ref = 1;
00387   return &p->pbuf;
00388 }
00389 #endif /* LWIP_SUPPORT_CUSTOM_PBUF */
00390 
00391 /**
00392  * Shrink a pbuf chain to a desired length.
00393  *
00394  * @param p pbuf to shrink.
00395  * @param new_len desired new length of pbuf chain
00396  *
00397  * Depending on the desired length, the first few pbufs in a chain might
00398  * be skipped and left unchanged. The new last pbuf in the chain will be
00399  * resized, and any remaining pbufs will be freed.
00400  *
00401  * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
00402  * @note May not be called on a packet queue.
00403  *
00404  * @note Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).
00405  */
00406 void
00407 pbuf_realloc(struct pbuf *p, u16_t new_len)
00408 {
00409   struct pbuf *q;
00410   u16_t rem_len; /* remaining length */
00411   s32_t grow;
00412 
00413   LWIP_ASSERT("pbuf_realloc: p != NULL", p != NULL);
00414   LWIP_ASSERT("pbuf_realloc: sane p->type", p->type == PBUF_POOL ||
00415               p->type == PBUF_ROM ||
00416               p->type == PBUF_RAM ||
00417               p->type == PBUF_REF);
00418 
00419   /* desired length larger than current length? */
00420   if (new_len >= p->tot_len) {
00421     /* enlarging not yet supported */
00422     return;
00423   }
00424 
00425   /* the pbuf chain grows by (new_len - p->tot_len) bytes
00426    * (which may be negative in case of shrinking) */
00427   grow = new_len - p->tot_len;
00428 
00429   /* first, step over any pbufs that should remain in the chain */
00430   rem_len = new_len;
00431   q = p;
00432   /* should this pbuf be kept? */
00433   while (rem_len > q->len) {
00434     /* decrease remaining length by pbuf length */
00435     rem_len -= q->len;
00436     /* decrease total length indicator */
00437     LWIP_ASSERT("grow < max_u16_t", grow < 0xffff);
00438     q->tot_len += (u16_t)grow;
00439     /* proceed to next pbuf in chain */
00440     q = q->next;
00441     LWIP_ASSERT("pbuf_realloc: q != NULL", q != NULL);
00442   }
00443   /* we have now reached the new last pbuf (in q) */
00444   /* rem_len == desired length for pbuf q */
00445 
00446   /* shrink allocated memory for PBUF_RAM */
00447   /* (other types merely adjust their length fields */
00448   if ((q->type == PBUF_RAM) && (rem_len != q->len)) {
00449     /* reallocate and adjust the length of the pbuf that will be split */
00450     q = (struct pbuf *)mem_trim(q, (u16_t)((u8_t *)q->payload - (u8_t *)q) + rem_len);
00451     LWIP_ASSERT("mem_trim returned q == NULL", q != NULL);
00452   }
00453   /* adjust length fields for new last pbuf */
00454   q->len = rem_len;
00455   q->tot_len = q->len;
00456 
00457   /* any remaining pbufs in chain? */
00458   if (q->next != NULL) {
00459     /* free remaining pbufs in chain */
00460     pbuf_free(q->next);
00461   }
00462   /* q is last packet in chain */
00463   q->next = NULL;
00464 
00465 }
00466 
00467 /**
00468  * Adjusts the payload pointer to hide or reveal headers in the payload.
00469  *
00470  * Adjusts the ->payload pointer so that space for a header
00471  * (dis)appears in the pbuf payload.
00472  *
00473  * The ->payload, ->tot_len and ->len fields are adjusted.
00474  *
00475  * @param p pbuf to change the header size.
00476  * @param header_size_increment Number of bytes to increment header size which
00477  * increases the size of the pbuf. New space is on the front.
00478  * (Using a negative value decreases the header size.)
00479  * If hdr_size_inc is 0, this function does nothing and returns succesful.
00480  *
00481  * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
00482  * the call will fail. A check is made that the increase in header size does
00483  * not move the payload pointer in front of the start of the buffer.
00484  * @return non-zero on failure, zero on success.
00485  *
00486  */
00487 u8_t
00488 pbuf_header(struct pbuf *p, s16_t header_size_increment)
00489 {
00490   u16_t type;
00491   void *payload;
00492   u16_t increment_magnitude;
00493 
00494   LWIP_ASSERT("p != NULL", p != NULL);
00495   if ((header_size_increment == 0) || (p == NULL)) {
00496     return 0;
00497   }
00498  
00499   if (header_size_increment < 0){
00500     increment_magnitude = -header_size_increment;
00501     /* Check that we aren't going to move off the end of the pbuf */
00502     LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);
00503   } else {
00504     increment_magnitude = header_size_increment;
00505 #if 0
00506     /* Can't assert these as some callers speculatively call
00507          pbuf_header() to see if it's OK.  Will return 1 below instead. */
00508     /* Check that we've got the correct type of pbuf to work with */
00509     LWIP_ASSERT("p->type == PBUF_RAM || p->type == PBUF_POOL", 
00510                 p->type == PBUF_RAM || p->type == PBUF_POOL);
00511     /* Check that we aren't going to move off the beginning of the pbuf */
00512     LWIP_ASSERT("p->payload - increment_magnitude >= p + SIZEOF_STRUCT_PBUF",
00513                 (u8_t *)p->payload - increment_magnitude >= (u8_t *)p + SIZEOF_STRUCT_PBUF);
00514 #endif
00515   }
00516 
00517   type = p->type;
00518   /* remember current payload pointer */
00519   payload = p->payload;
00520 
00521   /* pbuf types containing payloads? */
00522   if (type == PBUF_RAM || type == PBUF_POOL) {
00523     /* set new payload pointer */
00524     p->payload = (u8_t *)p->payload - header_size_increment;
00525     /* boundary check fails? */
00526     if ((u8_t *)p->payload < (u8_t *)p + SIZEOF_STRUCT_PBUF) {
00527       LWIP_DEBUGF( PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00528         ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
00529         (void *)p->payload, (void *)(p + 1)));
00530       /* restore old payload pointer */
00531       p->payload = payload;
00532       /* bail out unsuccesfully */
00533       return 1;
00534     }
00535   /* pbuf types refering to external payloads? */
00536   } else if (type == PBUF_REF || type == PBUF_ROM) {
00537     /* hide a header in the payload? */
00538     if ((header_size_increment < 0) && (increment_magnitude <= p->len)) {
00539       /* increase payload pointer */
00540       p->payload = (u8_t *)p->payload - header_size_increment;
00541     } else {
00542       /* cannot expand payload to front (yet!)
00543        * bail out unsuccesfully */
00544       return 1;
00545     }
00546   } else {
00547     /* Unknown type */
00548     LWIP_ASSERT("bad pbuf type", 0);
00549     return 1;
00550   }
00551   /* modify pbuf length fields */
00552   p->len += header_size_increment;
00553   p->tot_len += header_size_increment;
00554 
00555   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_header: old %p new %p (%"S16_F")\n",
00556     (void *)payload, (void *)p->payload, header_size_increment));
00557 
00558   return 0;
00559 }
00560 
00561 /**
00562  * Dereference a pbuf chain or queue and deallocate any no-longer-used
00563  * pbufs at the head of this chain or queue.
00564  *
00565  * Decrements the pbuf reference count. If it reaches zero, the pbuf is
00566  * deallocated.
00567  *
00568  * For a pbuf chain, this is repeated for each pbuf in the chain,
00569  * up to the first pbuf which has a non-zero reference count after
00570  * decrementing. So, when all reference counts are one, the whole
00571  * chain is free'd.
00572  *
00573  * @param p The pbuf (chain) to be dereferenced.
00574  *
00575  * @return the number of pbufs that were de-allocated
00576  * from the head of the chain.
00577  *
00578  * @note MUST NOT be called on a packet queue (Not verified to work yet).
00579  * @note the reference counter of a pbuf equals the number of pointers
00580  * that refer to the pbuf (or into the pbuf).
00581  *
00582  * @internal examples:
00583  *
00584  * Assuming existing chains a->b->c with the following reference
00585  * counts, calling pbuf_free(a) results in:
00586  * 
00587  * 1->2->3 becomes ...1->3
00588  * 3->3->3 becomes 2->3->3
00589  * 1->1->2 becomes ......1
00590  * 2->1->1 becomes 1->1->1
00591  * 1->1->1 becomes .......
00592  *
00593  */
00594 u8_t
00595 pbuf_free(struct pbuf *p)
00596 {
00597   u16_t type;
00598   struct pbuf *q;
00599   u8_t count;
00600 
00601   if (p == NULL) {
00602     LWIP_ASSERT("p != NULL", p != NULL);
00603     /* if assertions are disabled, proceed with debug output */
00604     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00605       ("pbuf_free(p == NULL) was called.\n"));
00606     return 0;
00607   }
00608   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free(%p)\n", (void *)p));
00609 
00610   PERF_START;
00611 
00612   LWIP_ASSERT("pbuf_free: sane type",
00613     p->type == PBUF_RAM || p->type == PBUF_ROM ||
00614     p->type == PBUF_REF || p->type == PBUF_POOL);
00615 
00616   count = 0;
00617   /* de-allocate all consecutive pbufs from the head of the chain that
00618    * obtain a zero reference count after decrementing*/
00619   while (p != NULL) {
00620     u16_t ref;
00621     SYS_ARCH_DECL_PROTECT(old_level);
00622     /* Since decrementing ref cannot be guaranteed to be a single machine operation
00623      * we must protect it. We put the new ref into a local variable to prevent
00624      * further protection. */
00625     SYS_ARCH_PROTECT(old_level);
00626     /* all pbufs in a chain are referenced at least once */
00627     LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
00628     /* decrease reference count (number of pointers to pbuf) */
00629     ref = --(p->ref);
00630     SYS_ARCH_UNPROTECT(old_level);
00631     /* this pbuf is no longer referenced to? */
00632     if (ref == 0) {
00633       /* remember next pbuf in chain for next iteration */
00634       q = p->next;
00635       LWIP_DEBUGF( PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free: deallocating %p\n", (void *)p));
00636       type = p->type;
00637 #if LWIP_SUPPORT_CUSTOM_PBUF
00638       /* is this a custom pbuf? */
00639       if ((p->flags & PBUF_FLAG_IS_CUSTOM) != 0) {
00640         struct pbuf_custom *pc = (struct pbuf_custom*)p;
00641         LWIP_ASSERT("pc->custom_free_function != NULL", pc->custom_free_function != NULL);
00642         pc->custom_free_function(p);
00643       } else
00644 #endif /* LWIP_SUPPORT_CUSTOM_PBUF */
00645       {
00646         /* is this a pbuf from the pool? */
00647         if (type == PBUF_POOL) {
00648           memp_free(MEMP_PBUF_POOL, p);
00649         /* is this a ROM or RAM referencing pbuf? */
00650         } else if (type == PBUF_ROM || type == PBUF_REF) {
00651           memp_free(MEMP_PBUF, p);
00652         /* type == PBUF_RAM */
00653         } else {
00654           mem_free(p);
00655         }
00656       }
00657       count++;
00658       /* proceed to next pbuf */
00659       p = q;
00660     /* p->ref > 0, this pbuf is still referenced to */
00661     /* (and so the remaining pbufs in chain as well) */
00662     } else {
00663       LWIP_DEBUGF( PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, ref));
00664       /* stop walking through the chain */
00665       p = NULL;
00666     }
00667   }
00668   PERF_STOP("pbuf_free");
00669   /* return number of de-allocated pbufs */
00670   return count;
00671 }
00672 
00673 /**
00674  * Count number of pbufs in a chain
00675  *
00676  * @param p first pbuf of chain
00677  * @return the number of pbufs in a chain
00678  */
00679 
00680 u8_t
00681 pbuf_clen(struct pbuf *p)
00682 {
00683   u8_t len;
00684 
00685   len = 0;
00686   while (p != NULL) {
00687     ++len;
00688     p = p->next;
00689   }
00690   return len;
00691 }
00692 
00693 /**
00694  * Increment the reference count of the pbuf.
00695  *
00696  * @param p pbuf to increase reference counter of
00697  *
00698  */
00699 void
00700 pbuf_ref(struct pbuf *p)
00701 {
00702   SYS_ARCH_DECL_PROTECT(old_level);
00703   /* pbuf given? */
00704   if (p != NULL) {
00705     SYS_ARCH_PROTECT(old_level);
00706     ++(p->ref);
00707     SYS_ARCH_UNPROTECT(old_level);
00708   }
00709 }
00710 
00711 /**
00712  * Concatenate two pbufs (each may be a pbuf chain) and take over
00713  * the caller's reference of the tail pbuf.
00714  * 
00715  * @note The caller MAY NOT reference the tail pbuf afterwards.
00716  * Use pbuf_chain() for that purpose.
00717  * 
00718  * @see pbuf_chain()
00719  */
00720 
00721 void
00722 pbuf_cat(struct pbuf *h, struct pbuf *t)
00723 {
00724   struct pbuf *p;
00725 
00726   LWIP_ERROR("(h != NULL) && (t != NULL) (programmer violates API)",
00727              ((h != NULL) && (t != NULL)), return;);
00728 
00729   /* proceed to last pbuf of chain */
00730   for (p = h; p->next != NULL; p = p->next) {
00731     /* add total length of second chain to all totals of first chain */
00732     p->tot_len += t->tot_len;
00733   }
00734   /* { p is last pbuf of first h chain, p->next == NULL } */
00735   LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
00736   LWIP_ASSERT("p->next == NULL", p->next == NULL);
00737   /* add total length of second chain to last pbuf total of first chain */
00738   p->tot_len += t->tot_len;
00739   /* chain last pbuf of head (p) with first of tail (t) */
00740   p->next = t;
00741   /* p->next now references t, but the caller will drop its reference to t,
00742    * so netto there is no change to the reference count of t.
00743    */
00744 }
00745 
00746 /**
00747  * Chain two pbufs (or pbuf chains) together.
00748  * 
00749  * The caller MUST call pbuf_free(t) once it has stopped
00750  * using it. Use pbuf_cat() instead if you no longer use t.
00751  * 
00752  * @param h head pbuf (chain)
00753  * @param t tail pbuf (chain)
00754  * @note The pbufs MUST belong to the same packet.
00755  * @note MAY NOT be called on a packet queue.
00756  *
00757  * The ->tot_len fields of all pbufs of the head chain are adjusted.
00758  * The ->next field of the last pbuf of the head chain is adjusted.
00759  * The ->ref field of the first pbuf of the tail chain is adjusted.
00760  *
00761  */
00762 void
00763 pbuf_chain(struct pbuf *h, struct pbuf *t)
00764 {
00765   pbuf_cat(h, t);
00766   /* t is now referenced by h */
00767   pbuf_ref(t);
00768   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
00769 }
00770 
00771 /**
00772  * Dechains the first pbuf from its succeeding pbufs in the chain.
00773  *
00774  * Makes p->tot_len field equal to p->len.
00775  * @param p pbuf to dechain
00776  * @return remainder of the pbuf chain, or NULL if it was de-allocated.
00777  * @note May not be called on a packet queue.
00778  */
00779 struct pbuf *
00780 pbuf_dechain(struct pbuf *p)
00781 {
00782   struct pbuf *q;
00783   u8_t tail_gone = 1;
00784   /* tail */
00785   q = p->next;
00786   /* pbuf has successor in chain? */
00787   if (q != NULL) {
00788     /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00789     LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
00790     /* enforce invariant if assertion is disabled */
00791     q->tot_len = p->tot_len - p->len;
00792     /* decouple pbuf from remainder */
00793     p->next = NULL;
00794     /* total length of pbuf p is its own length only */
00795     p->tot_len = p->len;
00796     /* q is no longer referenced by p, free it */
00797     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
00798     tail_gone = pbuf_free(q);
00799     if (tail_gone > 0) {
00800       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE,
00801                   ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
00802     }
00803     /* return remaining tail or NULL if deallocated */
00804   }
00805   /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00806   LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
00807   return ((tail_gone > 0) ? NULL : q);
00808 }
00809 
00810 /**
00811  *
00812  * Create PBUF_RAM copies of pbufs.
00813  *
00814  * Used to queue packets on behalf of the lwIP stack, such as
00815  * ARP based queueing.
00816  *
00817  * @note You MUST explicitly use p = pbuf_take(p);
00818  *
00819  * @note Only one packet is copied, no packet queue!
00820  *
00821  * @param p_to pbuf destination of the copy
00822  * @param p_from pbuf source of the copy
00823  *
00824  * @return ERR_OK if pbuf was copied
00825  *         ERR_ARG if one of the pbufs is NULL or p_to is not big
00826  *                 enough to hold p_from
00827  */
00828 err_t
00829 pbuf_copy(struct pbuf *p_to, struct pbuf *p_from)
00830 {
00831   u16_t offset_to=0, offset_from=0, len;
00832 
00833   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy(%p, %p)\n",
00834     (void*)p_to, (void*)p_from));
00835 
00836   /* is the target big enough to hold the source? */
00837   LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
00838              (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);
00839 
00840   /* iterate through pbuf chain */
00841   do
00842   {
00843     LWIP_ASSERT("p_to != NULL", p_to != NULL);
00844     /* copy one part of the original chain */
00845     if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
00846       /* complete current p_from fits into current p_to */
00847       len = p_from->len - offset_from;
00848     } else {
00849       /* current p_from does not fit into current p_to */
00850       len = p_to->len - offset_to;
00851     }
00852     MEMCPY((u8_t*)p_to->payload + offset_to, (u8_t*)p_from->payload + offset_from, len);
00853     offset_to += len;
00854     offset_from += len;
00855     LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
00856     if (offset_to == p_to->len) {
00857       /* on to next p_to (if any) */
00858       offset_to = 0;
00859       p_to = p_to->next;
00860     }
00861     LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
00862     if (offset_from >= p_from->len) {
00863       /* on to next p_from (if any) */
00864       offset_from = 0;
00865       p_from = p_from->next;
00866     }
00867 
00868     if((p_from != NULL) && (p_from->len == p_from->tot_len)) {
00869       /* don't copy more than one packet! */
00870       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00871                  (p_from->next == NULL), return ERR_VAL;);
00872     }
00873     if((p_to != NULL) && (p_to->len == p_to->tot_len)) {
00874       /* don't copy more than one packet! */
00875       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00876                   (p_to->next == NULL), return ERR_VAL;);
00877     }
00878   } while (p_from);
00879   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy: end of chain reached.\n"));
00880   return ERR_OK;
00881 }
00882 
00883 /**
00884  * Copy (part of) the contents of a packet buffer
00885  * to an application supplied buffer.
00886  *
00887  * @param buf the pbuf from which to copy data
00888  * @param dataptr the application supplied buffer
00889  * @param len length of data to copy (dataptr must be big enough). No more 
00890  * than buf->tot_len will be copied, irrespective of len
00891  * @param offset offset into the packet buffer from where to begin copying len bytes
00892  * @return the number of bytes copied, or 0 on failure
00893  */
00894 u16_t
00895 pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
00896 {
00897   struct pbuf *p;
00898   u16_t left;
00899   u16_t buf_copy_len;
00900   u16_t copied_total = 0;
00901 
00902   LWIP_ERROR("pbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
00903   LWIP_ERROR("pbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
00904 
00905   left = 0;
00906 
00907   if((buf == NULL) || (dataptr == NULL)) {
00908     return 0;
00909   }
00910 
00911   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00912   for(p = buf; len != 0 && p != NULL; p = p->next) {
00913     if ((offset != 0) && (offset >= p->len)) {
00914       /* don't copy from this buffer -> on to the next */
00915       offset -= p->len;
00916     } else {
00917       /* copy from this buffer. maybe only partially. */
00918       buf_copy_len = p->len - offset;
00919       if (buf_copy_len > len)
00920           buf_copy_len = len;
00921       /* copy the necessary parts of the buffer */
00922       MEMCPY(&((char*)dataptr)[left], &((char*)p->payload)[offset], buf_copy_len);
00923       copied_total += buf_copy_len;
00924       left += buf_copy_len;
00925       len -= buf_copy_len;
00926       offset = 0;
00927     }
00928   }
00929   return copied_total;
00930 }
00931 
00932 /**
00933  * Copy application supplied data into a pbuf.
00934  * This function can only be used to copy the equivalent of buf->tot_len data.
00935  *
00936  * @param buf pbuf to fill with data
00937  * @param dataptr application supplied data buffer
00938  * @param len length of the application supplied data buffer
00939  *
00940  * @return ERR_OK if successful, ERR_MEM if the pbuf is not big enough
00941  */
00942 err_t
00943 pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len)
00944 {
00945   struct pbuf *p;
00946   u16_t buf_copy_len;
00947   u16_t total_copy_len = len;
00948   u16_t copied_total = 0;
00949 
00950   LWIP_ERROR("pbuf_take: invalid buf", (buf != NULL), return 0;);
00951   LWIP_ERROR("pbuf_take: invalid dataptr", (dataptr != NULL), return 0;);
00952 
00953   if ((buf == NULL) || (dataptr == NULL) || (buf->tot_len < len)) {
00954     return ERR_ARG;
00955   }
00956 
00957   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00958   for(p = buf; total_copy_len != 0; p = p->next) {
00959     LWIP_ASSERT("pbuf_take: invalid pbuf", p != NULL);
00960     buf_copy_len = total_copy_len;
00961     if (buf_copy_len > p->len) {
00962       /* this pbuf cannot hold all remaining data */
00963       buf_copy_len = p->len;
00964     }
00965     /* copy the necessary parts of the buffer */
00966     MEMCPY(p->payload, &((char*)dataptr)[copied_total], buf_copy_len);
00967     total_copy_len -= buf_copy_len;
00968     copied_total += buf_copy_len;
00969   }
00970   LWIP_ASSERT("did not copy all data", total_copy_len == 0 && copied_total == len);
00971   return ERR_OK;
00972 }
00973 
00974 /**
00975  * Creates a single pbuf out of a queue of pbufs.
00976  *
00977  * @remark: Either the source pbuf 'p' is freed by this function or the original
00978  *          pbuf 'p' is returned, therefore the caller has to check the result!
00979  *
00980  * @param p the source pbuf
00981  * @param layer pbuf_layer of the new pbuf
00982  *
00983  * @return a new, single pbuf (p->next is NULL)
00984  *         or the old pbuf if allocation fails
00985  */
00986 struct pbuf*
00987 pbuf_coalesce(struct pbuf *p, pbuf_layer layer)
00988 {
00989   struct pbuf *q;
00990   err_t err;
00991   if (p->next == NULL) {
00992     return p;
00993   }
00994   q = pbuf_alloc(layer, p->tot_len, PBUF_RAM);
00995   if (q == NULL) {
00996     /* @todo: what do we do now? */
00997     return p;
00998   }
00999   err = pbuf_copy(q, p);
01000   LWIP_ASSERT("pbuf_copy failed", err == ERR_OK);
01001   /* next line references err variable even if LWIP_ASSERT is ignored. */
01002   (void)err;
01003   pbuf_free(p);
01004   return q;
01005 }
01006 
01007 #if LWIP_CHECKSUM_ON_COPY
01008 /**
01009  * Copies data into a single pbuf (*not* into a pbuf queue!) and updates
01010  * the checksum while copying
01011  *
01012  * @param p the pbuf to copy data into
01013  * @param start_offset offset of p->payload where to copy the data to
01014  * @param dataptr data to copy into the pbuf
01015  * @param len length of data to copy into the pbuf
01016  * @param chksum pointer to the checksum which is updated
01017  * @return ERR_OK if successful, another error if the data does not fit
01018  *         within the (first) pbuf (no pbuf queues!)
01019  */
01020 err_t
01021 pbuf_fill_chksum(struct pbuf *p, u16_t start_offset, const void *dataptr,
01022                  u16_t len, u16_t *chksum)
01023 {
01024   u32_t acc;
01025   u16_t copy_chksum;
01026   char *dst_ptr;
01027   LWIP_ASSERT("p != NULL", p != NULL);
01028   LWIP_ASSERT("dataptr != NULL", dataptr != NULL);
01029   LWIP_ASSERT("chksum != NULL", chksum != NULL);
01030   LWIP_ASSERT("len != 0", len != 0);
01031 
01032   if ((start_offset >= p->len) || (start_offset + len > p->len)) {
01033     return ERR_ARG;
01034   }
01035 
01036   dst_ptr = ((char*)p->payload) + start_offset;
01037   copy_chksum = LWIP_CHKSUM_COPY(dst_ptr, dataptr, len);
01038   if ((start_offset & 1) != 0) {
01039     copy_chksum = SWAP_BYTES_IN_WORD(copy_chksum);
01040   }
01041   acc = *chksum;
01042   acc += copy_chksum;
01043   *chksum = FOLD_U32T(acc);
01044   return ERR_OK;
01045 }
01046 #endif /* LWIP_CHECKSUM_ON_COPY */
01047 
01048  /** Get one byte from the specified position in a pbuf
01049  * WARNING: returns zero for offset >= p->tot_len
01050  *
01051  * @param p pbuf to parse
01052  * @param offset offset into p of the byte to return
01053  * @return byte at an offset into p OR ZERO IF 'offset' >= p->tot_len
01054  */
01055 u8_t
01056 pbuf_get_at(struct pbuf* p, u16_t offset)
01057 {
01058   u16_t copy_from = offset;
01059   struct pbuf* q = p;
01060 
01061   /* get the correct pbuf */
01062   while ((q != NULL) && (q->len <= copy_from)) {
01063     copy_from -= q->len;
01064     q = q->next;
01065   }
01066   /* return requested data if pbuf is OK */
01067   if ((q != NULL) && (q->len > copy_from)) {
01068     return ((u8_t*)q->payload)[copy_from];
01069   }
01070   return 0;
01071 }
01072 
01073 /** Compare pbuf contents at specified offset with memory s2, both of length n
01074  *
01075  * @param p pbuf to compare
01076  * @param offset offset into p at wich to start comparing
01077  * @param s2 buffer to compare
01078  * @param n length of buffer to compare
01079  * @return zero if equal, nonzero otherwise
01080  *         (0xffff if p is too short, diffoffset+1 otherwise)
01081  */
01082 u16_t
01083 pbuf_memcmp(struct pbuf* p, u16_t offset, const void* s2, u16_t n)
01084 {
01085   u16_t start = offset;
01086   struct pbuf* q = p;
01087 
01088   /* get the correct pbuf */
01089   while ((q != NULL) && (q->len <= start)) {
01090     start -= q->len;
01091     q = q->next;
01092   }
01093   /* return requested data if pbuf is OK */
01094   if ((q != NULL) && (q->len > start)) {
01095     u16_t i;
01096     for(i = 0; i < n; i++) {
01097       u8_t a = pbuf_get_at(q, start + i);
01098       u8_t b = ((u8_t*)s2)[i];
01099       if (a != b) {
01100         return i+1;
01101       }
01102     }
01103     return 0;
01104   }
01105   return 0xffff;
01106 }
01107 
01108 /** Find occurrence of mem (with length mem_len) in pbuf p, starting at offset
01109  * start_offset.
01110  *
01111  * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
01112  *        return value 'not found'
01113  * @param mem search for the contents of this buffer
01114  * @param mem_len length of 'mem'
01115  * @param start_offset offset into p at which to start searching
01116  * @return 0xFFFF if substr was not found in p or the index where it was found
01117  */
01118 u16_t
01119 pbuf_memfind(struct pbuf* p, const void* mem, u16_t mem_len, u16_t start_offset)
01120 {
01121   u16_t i;
01122   u16_t max = p->tot_len - mem_len;
01123   if (p->tot_len >= mem_len + start_offset) {
01124     for(i = start_offset; i <= max; ) {
01125       u16_t plus = pbuf_memcmp(p, i, mem, mem_len);
01126       if (plus == 0) {
01127         return i;
01128       } else {
01129         i += plus;
01130       }
01131     }
01132   }
01133   return 0xFFFF;
01134 }
01135 
01136 /** Find occurrence of substr with length substr_len in pbuf p, start at offset
01137  * start_offset
01138  * WARNING: in contrast to strstr(), this one does not stop at the first \0 in
01139  * the pbuf/source string!
01140  *
01141  * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
01142  *        return value 'not found'
01143  * @param substr string to search for in p, maximum length is 0xFFFE
01144  * @return 0xFFFF if substr was not found in p or the index where it was found
01145  */
01146 u16_t
01147 pbuf_strstr(struct pbuf* p, const char* substr)
01148 {
01149   size_t substr_len;
01150   if ((substr == NULL) || (substr[0] == 0) || (p->tot_len == 0xFFFF)) {
01151     return 0xFFFF;
01152   }
01153   substr_len = strlen(substr);
01154   if (substr_len >= 0xFFFF) {
01155     return 0xFFFF;
01156   }
01157   return pbuf_memfind(p, substr, (u16_t)substr_len, 0);
01158 }