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 LWIP_TCP && 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 || !PBUF_POOL_FREE_OOSEQ
00088 #define PBUF_POOL_IS_EMPTY()
00089 #else /* !LWIP_TCP || !TCP_QUEUE_OOSEQ || !PBUF_POOL_FREE_OOSEQ */
00090 
00091 #if !NO_SYS
00092 #ifndef PBUF_POOL_FREE_OOSEQ_QUEUE_CALL
00093 #include "lwip/tcpip.h"
00094 #define PBUF_POOL_FREE_OOSEQ_QUEUE_CALL()  do { \
00095   if(tcpip_callback_with_block(pbuf_free_ooseq_callback, NULL, 0) != ERR_OK) { \
00096       SYS_ARCH_PROTECT(old_level); \
00097       pbuf_free_ooseq_pending = 0; \
00098       SYS_ARCH_UNPROTECT(old_level); \
00099   } } while(0)
00100 #endif /* PBUF_POOL_FREE_OOSEQ_QUEUE_CALL */
00101 #endif /* !NO_SYS */
00102 
00103 volatile u8_t pbuf_free_ooseq_pending;
00104 #define PBUF_POOL_IS_EMPTY() pbuf_pool_is_empty()
00105 
00106 /**
00107  * Attempt to reclaim some memory from queued out-of-sequence TCP segments
00108  * if we run out of pool pbufs. It's better to give priority to new packets
00109  * if we're running out.
00110  *
00111  * This must be done in the correct thread context therefore this function
00112  * can only be used with NO_SYS=0 and through tcpip_callback.
00113  */
00114 #if !NO_SYS
00115 static
00116 #endif /* !NO_SYS */
00117 void
00118 pbuf_free_ooseq(void)
00119 {
00120   struct tcp_pcb* pcb;
00121   SYS_ARCH_DECL_PROTECT(old_level);
00122 
00123   SYS_ARCH_PROTECT(old_level);
00124   pbuf_free_ooseq_pending = 0;
00125   SYS_ARCH_UNPROTECT(old_level);
00126 
00127   for (pcb = tcp_active_pcbs; NULL != pcb; pcb = pcb->next) {
00128     if (NULL != pcb->ooseq) {
00129       /** Free the ooseq pbufs of one PCB only */
00130       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free_ooseq: freeing out-of-sequence pbufs\n"));
00131       tcp_segs_free(pcb->ooseq);
00132       pcb->ooseq = NULL;
00133       return;
00134     }
00135   }
00136 }
00137 
00138 #if !NO_SYS
00139 /**
00140  * Just a callback function for tcpip_timeout() that calls pbuf_free_ooseq().
00141  */
00142 static void
00143 pbuf_free_ooseq_callback(void *arg)
00144 {
00145   LWIP_UNUSED_ARG(arg);
00146   pbuf_free_ooseq();
00147 }
00148 #endif /* !NO_SYS */
00149 
00150 /** Queue a call to pbuf_free_ooseq if not already queued. */
00151 static void
00152 pbuf_pool_is_empty(void)
00153 {
00154 #ifndef PBUF_POOL_FREE_OOSEQ_QUEUE_CALL
00155   SYS_ARCH_DECL_PROTECT(old_level);
00156   SYS_ARCH_PROTECT(old_level);
00157   pbuf_free_ooseq_pending = 1;
00158   SYS_ARCH_UNPROTECT(old_level);
00159 #else /* PBUF_POOL_FREE_OOSEQ_QUEUE_CALL */
00160   u8_t queued;
00161   SYS_ARCH_DECL_PROTECT(old_level);
00162   SYS_ARCH_PROTECT(old_level);
00163   queued = pbuf_free_ooseq_pending;
00164   pbuf_free_ooseq_pending = 1;
00165   SYS_ARCH_UNPROTECT(old_level);
00166 
00167   if(!queued) {
00168     /* queue a call to pbuf_free_ooseq if not already queued */
00169     PBUF_POOL_FREE_OOSEQ_QUEUE_CALL();
00170   }
00171 #endif /* PBUF_POOL_FREE_OOSEQ_QUEUE_CALL */
00172 }
00173 #endif /* !LWIP_TCP || !TCP_QUEUE_OOSEQ || !PBUF_POOL_FREE_OOSEQ */
00174 
00175 /**
00176  * Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).
00177  *
00178  * The actual memory allocated for the pbuf is determined by the
00179  * layer at which the pbuf is allocated and the requested size
00180  * (from the size parameter).
00181  *
00182  * @param layer flag to define header size
00183  * @param length size of the pbuf's payload
00184  * @param type this parameter decides how and where the pbuf
00185  * should be allocated as follows:
00186  *
00187  * - PBUF_RAM: buffer memory for pbuf is allocated as one large
00188  *             chunk. This includes protocol headers as well.
00189  * - PBUF_ROM: no buffer memory is allocated for the pbuf, even for
00190  *             protocol headers. Additional headers must be prepended
00191  *             by allocating another pbuf and chain in to the front of
00192  *             the ROM pbuf. It is assumed that the memory used is really
00193  *             similar to ROM in that it is immutable and will not be
00194  *             changed. Memory which is dynamic should generally not
00195  *             be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
00196  * - PBUF_REF: no buffer memory is allocated for the pbuf, even for
00197  *             protocol headers. It is assumed that the pbuf is only
00198  *             being used in a single thread. If the pbuf gets queued,
00199  *             then pbuf_take should be called to copy the buffer.
00200  * - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from
00201  *              the pbuf pool that is allocated during pbuf_init().
00202  *
00203  * @return the allocated pbuf. If multiple pbufs where allocated, this
00204  * is the first pbuf of a pbuf chain.
00205  */
00206 struct pbuf *
00207 pbuf_alloc(pbuf_layer layer, u16_t length, pbuf_type type)
00208 {
00209   struct pbuf *p, *q, *r;
00210   u16_t offset;
00211   s32_t rem_len; /* remaining length */
00212   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc(length=%"U16_F")\n", length));
00213 
00214   /* determine header offset */
00215   switch (layer) {
00216   case PBUF_TRANSPORT:
00217     /* add room for transport (often TCP) layer header */
00218     offset = PBUF_LINK_HLEN + PBUF_IP_HLEN + PBUF_TRANSPORT_HLEN;
00219     break;
00220   case PBUF_IP:
00221     /* add room for IP layer header */
00222     offset = PBUF_LINK_HLEN + PBUF_IP_HLEN;
00223     break;
00224   case PBUF_LINK:
00225     /* add room for link layer header */
00226     offset = PBUF_LINK_HLEN;
00227     break;
00228   case PBUF_RAW:
00229     offset = 0;
00230     break;
00231   default:
00232     LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0);
00233     return NULL;
00234   }
00235 
00236   switch (type) {
00237   case PBUF_POOL:
00238     /* allocate head of pbuf chain into p */
00239     p = (struct pbuf *)memp_malloc(MEMP_PBUF_POOL);
00240     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc: allocated pbuf %p\n", (void *)p));
00241     if (p == NULL) {
00242       PBUF_POOL_IS_EMPTY();
00243       return NULL;
00244     }
00245     p->type = type;
00246     p->next = NULL;
00247 
00248     /* make the payload pointer point 'offset' bytes into pbuf data memory */
00249     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + (SIZEOF_STRUCT_PBUF + offset)));
00250     LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
00251             ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00252     /* the total length of the pbuf chain is the requested size */
00253     p->tot_len = length;
00254     /* set the length of the first pbuf in the chain */
00255     p->len = LWIP_MIN(length, PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset));
00256     LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00257                 ((u8_t*)p->payload + p->len <=
00258                  (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00259     LWIP_ASSERT("PBUF_POOL_BUFSIZE must be bigger than MEM_ALIGNMENT",
00260       (PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset)) > 0 );
00261     /* set reference count (needed here in case we fail) */
00262     p->ref = 1;
00263 
00264     /* now allocate the tail of the pbuf chain */
00265 
00266     /* remember first pbuf for linkage in next iteration */
00267     r = p;
00268     /* remaining length to be allocated */
00269     rem_len = length - p->len;
00270     /* any remaining pbufs to be allocated? */
00271     while (rem_len > 0) {
00272       q = (struct pbuf *)memp_malloc(MEMP_PBUF_POOL);
00273       if (q == NULL) {
00274         PBUF_POOL_IS_EMPTY();
00275         /* free chain so far allocated */
00276         pbuf_free(p);
00277         /* bail out unsuccesfully */
00278         return NULL;
00279       }
00280       q->type = type;
00281       q->flags = 0;
00282       q->next = NULL;
00283       /* make previous pbuf point to this pbuf */
00284       r->next = q;
00285       /* set total length of this pbuf and next in chain */
00286       LWIP_ASSERT("rem_len < max_u16_t", rem_len < 0xffff);
00287       q->tot_len = (u16_t)rem_len;
00288       /* this pbuf length is pool size, unless smaller sized tail */
00289       q->len = LWIP_MIN((u16_t)rem_len, PBUF_POOL_BUFSIZE_ALIGNED);
00290       q->payload = (void *)((u8_t *)q + SIZEOF_STRUCT_PBUF);
00291       LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
00292               ((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0);
00293       LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00294                   ((u8_t*)p->payload + p->len <=
00295                    (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00296       q->ref = 1;
00297       /* calculate remaining length to be allocated */
00298       rem_len -= q->len;
00299       /* remember this pbuf for linkage in next iteration */
00300       r = q;
00301     }
00302     /* end of chain */
00303     /*r->next = NULL;*/
00304 
00305     break;
00306   case PBUF_RAM:
00307     /* If pbuf is to be allocated in RAM, allocate memory for it. */
00308     p = (struct pbuf*)mem_malloc(LWIP_MEM_ALIGN_SIZE(SIZEOF_STRUCT_PBUF + offset) + LWIP_MEM_ALIGN_SIZE(length));
00309     if (p == NULL) {
00310       return NULL;
00311     }
00312     /* Set up internal structure of the pbuf. */
00313     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + SIZEOF_STRUCT_PBUF + offset));
00314     p->len = p->tot_len = length;
00315     p->next = NULL;
00316     p->type = type;
00317 
00318     LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
00319            ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00320     break;
00321   /* pbuf references existing (non-volatile static constant) ROM payload? */
00322   case PBUF_ROM:
00323   /* pbuf references existing (externally allocated) RAM payload? */
00324   case PBUF_REF:
00325     /* only allocate memory for the pbuf structure */
00326     p = (struct pbuf *)memp_malloc(MEMP_PBUF);
00327     if (p == NULL) {
00328       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00329                   ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n",
00330                   (type == PBUF_ROM) ? "ROM" : "REF"));
00331       return NULL;
00332     }
00333     /* caller must set this field properly, afterwards */
00334     p->payload = NULL;
00335     p->len = p->tot_len = length;
00336     p->next = NULL;
00337     p->type = type;
00338     break;
00339   default:
00340     LWIP_ASSERT("pbuf_alloc: erroneous type", 0);
00341     return NULL;
00342   }
00343   /* set reference count */
00344   p->ref = 1;
00345   /* set flags */
00346   p->flags = 0;
00347   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
00348   return p;
00349 }
00350 
00351 #if LWIP_SUPPORT_CUSTOM_PBUF
00352 /** Initialize a custom pbuf (already allocated).
00353  *
00354  * @param layer flag to define header size
00355  * @param length size of the pbuf's payload
00356  * @param type type of the pbuf (only used to treat the pbuf accordingly, as
00357  *        this function allocates no memory)
00358  * @param p pointer to the custom pbuf to initialize (already allocated)
00359  * @param payload_mem pointer to the buffer that is used for payload and headers,
00360  *        must be at least big enough to hold 'length' plus the header size,
00361  *        may be NULL if set later.
00362  *        ATTENTION: The caller is responsible for correct alignment of this buffer!!
00363  * @param payload_mem_len the size of the 'payload_mem' buffer, must be at least
00364  *        big enough to hold 'length' plus the header size
00365  */
00366 struct pbuf*
00367 pbuf_alloced_custom(pbuf_layer l, u16_t length, pbuf_type type, struct pbuf_custom *p,
00368                     void *payload_mem, u16_t payload_mem_len)
00369 {
00370   u16_t offset;
00371   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_alloced_custom(length=%"U16_F")\n", length));
00372 
00373   /* determine header offset */
00374   switch (l) {
00375   case PBUF_TRANSPORT:
00376     /* add room for transport (often TCP) layer header */
00377     offset = PBUF_LINK_HLEN + PBUF_IP_HLEN + PBUF_TRANSPORT_HLEN;
00378     break;
00379   case PBUF_IP:
00380     /* add room for IP layer header */
00381     offset = PBUF_LINK_HLEN + PBUF_IP_HLEN;
00382     break;
00383   case PBUF_LINK:
00384     /* add room for link layer header */
00385     offset = PBUF_LINK_HLEN;
00386     break;
00387   case PBUF_RAW:
00388     offset = 0;
00389     break;
00390   default:
00391     LWIP_ASSERT("pbuf_alloced_custom: bad pbuf layer", 0);
00392     return NULL;
00393   }
00394 
00395   if (LWIP_MEM_ALIGN_SIZE(offset) + length > payload_mem_len) {
00396     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_WARNING, ("pbuf_alloced_custom(length=%"U16_F") buffer too short\n", length));
00397     return NULL;
00398   }
00399 
00400   p->pbuf.next = NULL;
00401   if (payload_mem != NULL) {
00402     p->pbuf.payload = (u8_t *)payload_mem + LWIP_MEM_ALIGN_SIZE(offset);
00403   } else {
00404     p->pbuf.payload = NULL;
00405   }
00406   p->pbuf.flags = PBUF_FLAG_IS_CUSTOM;
00407   p->pbuf.len = p->pbuf.tot_len = length;
00408   p->pbuf.type = type;
00409   p->pbuf.ref = 1;
00410   return &p->pbuf;
00411 }
00412 #endif /* LWIP_SUPPORT_CUSTOM_PBUF */
00413 
00414 /**
00415  * Shrink a pbuf chain to a desired length.
00416  *
00417  * @param p pbuf to shrink.
00418  * @param new_len desired new length of pbuf chain
00419  *
00420  * Depending on the desired length, the first few pbufs in a chain might
00421  * be skipped and left unchanged. The new last pbuf in the chain will be
00422  * resized, and any remaining pbufs will be freed.
00423  *
00424  * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
00425  * @note May not be called on a packet queue.
00426  *
00427  * @note Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).
00428  */
00429 void
00430 pbuf_realloc(struct pbuf *p, u16_t new_len)
00431 {
00432   struct pbuf *q;
00433   u16_t rem_len; /* remaining length */
00434   s32_t grow;
00435 
00436   LWIP_ASSERT("pbuf_realloc: p != NULL", p != NULL);
00437   LWIP_ASSERT("pbuf_realloc: sane p->type", p->type == PBUF_POOL ||
00438               p->type == PBUF_ROM ||
00439               p->type == PBUF_RAM ||
00440               p->type == PBUF_REF);
00441 
00442   /* desired length larger than current length? */
00443   if (new_len >= p->tot_len) {
00444     /* enlarging not yet supported */
00445     return;
00446   }
00447 
00448   /* the pbuf chain grows by (new_len - p->tot_len) bytes
00449    * (which may be negative in case of shrinking) */
00450   grow = new_len - p->tot_len;
00451 
00452   /* first, step over any pbufs that should remain in the chain */
00453   rem_len = new_len;
00454   q = p;
00455   /* should this pbuf be kept? */
00456   while (rem_len > q->len) {
00457     /* decrease remaining length by pbuf length */
00458     rem_len -= q->len;
00459     /* decrease total length indicator */
00460     LWIP_ASSERT("grow < max_u16_t", grow < 0xffff);
00461     q->tot_len += (u16_t)grow;
00462     /* proceed to next pbuf in chain */
00463     q = q->next;
00464     LWIP_ASSERT("pbuf_realloc: q != NULL", q != NULL);
00465   }
00466   /* we have now reached the new last pbuf (in q) */
00467   /* rem_len == desired length for pbuf q */
00468 
00469   /* shrink allocated memory for PBUF_RAM */
00470   /* (other types merely adjust their length fields */
00471   if ((q->type == PBUF_RAM) && (rem_len != q->len)) {
00472     /* reallocate and adjust the length of the pbuf that will be split */
00473     q = (struct pbuf *)mem_trim(q, (u16_t)((u8_t *)q->payload - (u8_t *)q) + rem_len);
00474     LWIP_ASSERT("mem_trim returned q == NULL", q != NULL);
00475   }
00476   /* adjust length fields for new last pbuf */
00477   q->len = rem_len;
00478   q->tot_len = q->len;
00479 
00480   /* any remaining pbufs in chain? */
00481   if (q->next != NULL) {
00482     /* free remaining pbufs in chain */
00483     pbuf_free(q->next);
00484   }
00485   /* q is last packet in chain */
00486   q->next = NULL;
00487 
00488 }
00489 
00490 /**
00491  * Adjusts the payload pointer to hide or reveal headers in the payload.
00492  *
00493  * Adjusts the ->payload pointer so that space for a header
00494  * (dis)appears in the pbuf payload.
00495  *
00496  * The ->payload, ->tot_len and ->len fields are adjusted.
00497  *
00498  * @param p pbuf to change the header size.
00499  * @param header_size_increment Number of bytes to increment header size which
00500  * increases the size of the pbuf. New space is on the front.
00501  * (Using a negative value decreases the header size.)
00502  * If hdr_size_inc is 0, this function does nothing and returns succesful.
00503  *
00504  * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
00505  * the call will fail. A check is made that the increase in header size does
00506  * not move the payload pointer in front of the start of the buffer.
00507  * @return non-zero on failure, zero on success.
00508  *
00509  */
00510 u8_t
00511 pbuf_header(struct pbuf *p, s16_t header_size_increment)
00512 {
00513   u16_t type;
00514   void *payload;
00515   u16_t increment_magnitude;
00516 
00517   LWIP_ASSERT("p != NULL", p != NULL);
00518   if ((header_size_increment == 0) || (p == NULL)) {
00519     return 0;
00520   }
00521  
00522   if (header_size_increment < 0){
00523     increment_magnitude = -header_size_increment;
00524     /* Check that we aren't going to move off the end of the pbuf */
00525     LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);
00526   } else {
00527     increment_magnitude = header_size_increment;
00528 #if 0
00529     /* Can't assert these as some callers speculatively call
00530          pbuf_header() to see if it's OK.  Will return 1 below instead. */
00531     /* Check that we've got the correct type of pbuf to work with */
00532     LWIP_ASSERT("p->type == PBUF_RAM || p->type == PBUF_POOL", 
00533                 p->type == PBUF_RAM || p->type == PBUF_POOL);
00534     /* Check that we aren't going to move off the beginning of the pbuf */
00535     LWIP_ASSERT("p->payload - increment_magnitude >= p + SIZEOF_STRUCT_PBUF",
00536                 (u8_t *)p->payload - increment_magnitude >= (u8_t *)p + SIZEOF_STRUCT_PBUF);
00537 #endif
00538   }
00539 
00540   type = p->type;
00541   /* remember current payload pointer */
00542   payload = p->payload;
00543 
00544   /* pbuf types containing payloads? */
00545   if (type == PBUF_RAM || type == PBUF_POOL) {
00546     /* set new payload pointer */
00547     p->payload = (u8_t *)p->payload - header_size_increment;
00548     /* boundary check fails? */
00549     if ((u8_t *)p->payload < (u8_t *)p + SIZEOF_STRUCT_PBUF) {
00550       LWIP_DEBUGF( PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00551         ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
00552         (void *)p->payload, (void *)(p + 1)));
00553       /* restore old payload pointer */
00554       p->payload = payload;
00555       /* bail out unsuccesfully */
00556       return 1;
00557     }
00558   /* pbuf types refering to external payloads? */
00559   } else if (type == PBUF_REF || type == PBUF_ROM) {
00560     /* hide a header in the payload? */
00561     if ((header_size_increment < 0) && (increment_magnitude <= p->len)) {
00562       /* increase payload pointer */
00563       p->payload = (u8_t *)p->payload - header_size_increment;
00564     } else {
00565       /* cannot expand payload to front (yet!)
00566        * bail out unsuccesfully */
00567       return 1;
00568     }
00569   } else {
00570     /* Unknown type */
00571     LWIP_ASSERT("bad pbuf type", 0);
00572     return 1;
00573   }
00574   /* modify pbuf length fields */
00575   p->len += header_size_increment;
00576   p->tot_len += header_size_increment;
00577 
00578   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_header: old %p new %p (%"S16_F")\n",
00579     (void *)payload, (void *)p->payload, header_size_increment));
00580 
00581   return 0;
00582 }
00583 
00584 /**
00585  * Dereference a pbuf chain or queue and deallocate any no-longer-used
00586  * pbufs at the head of this chain or queue.
00587  *
00588  * Decrements the pbuf reference count. If it reaches zero, the pbuf is
00589  * deallocated.
00590  *
00591  * For a pbuf chain, this is repeated for each pbuf in the chain,
00592  * up to the first pbuf which has a non-zero reference count after
00593  * decrementing. So, when all reference counts are one, the whole
00594  * chain is free'd.
00595  *
00596  * @param p The pbuf (chain) to be dereferenced.
00597  *
00598  * @return the number of pbufs that were de-allocated
00599  * from the head of the chain.
00600  *
00601  * @note MUST NOT be called on a packet queue (Not verified to work yet).
00602  * @note the reference counter of a pbuf equals the number of pointers
00603  * that refer to the pbuf (or into the pbuf).
00604  *
00605  * @internal examples:
00606  *
00607  * Assuming existing chains a->b->c with the following reference
00608  * counts, calling pbuf_free(a) results in:
00609  * 
00610  * 1->2->3 becomes ...1->3
00611  * 3->3->3 becomes 2->3->3
00612  * 1->1->2 becomes ......1
00613  * 2->1->1 becomes 1->1->1
00614  * 1->1->1 becomes .......
00615  *
00616  */
00617 u8_t
00618 pbuf_free(struct pbuf *p)
00619 {
00620   u16_t type;
00621   struct pbuf *q;
00622   u8_t count;
00623 
00624   if (p == NULL) {
00625     LWIP_ASSERT("p != NULL", p != NULL);
00626     /* if assertions are disabled, proceed with debug output */
00627     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_LEVEL_SERIOUS,
00628       ("pbuf_free(p == NULL) was called.\n"));
00629     return 0;
00630   }
00631   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free(%p)\n", (void *)p));
00632 
00633   PERF_START;
00634 
00635   LWIP_ASSERT("pbuf_free: sane type",
00636     p->type == PBUF_RAM || p->type == PBUF_ROM ||
00637     p->type == PBUF_REF || p->type == PBUF_POOL);
00638 
00639   count = 0;
00640   /* de-allocate all consecutive pbufs from the head of the chain that
00641    * obtain a zero reference count after decrementing*/
00642   while (p != NULL) {
00643     u16_t ref;
00644     SYS_ARCH_DECL_PROTECT(old_level);
00645     /* Since decrementing ref cannot be guaranteed to be a single machine operation
00646      * we must protect it. We put the new ref into a local variable to prevent
00647      * further protection. */
00648     SYS_ARCH_PROTECT(old_level);
00649     /* all pbufs in a chain are referenced at least once */
00650     LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
00651     /* decrease reference count (number of pointers to pbuf) */
00652     ref = --(p->ref);
00653     SYS_ARCH_UNPROTECT(old_level);
00654     /* this pbuf is no longer referenced to? */
00655     if (ref == 0) {
00656       /* remember next pbuf in chain for next iteration */
00657       q = p->next;
00658       LWIP_DEBUGF( PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free: deallocating %p\n", (void *)p));
00659       type = p->type;
00660 #if LWIP_SUPPORT_CUSTOM_PBUF
00661       /* is this a custom pbuf? */
00662       if ((p->flags & PBUF_FLAG_IS_CUSTOM) != 0) {
00663         struct pbuf_custom *pc = (struct pbuf_custom*)p;
00664         LWIP_ASSERT("pc->custom_free_function != NULL", pc->custom_free_function != NULL);
00665         pc->custom_free_function(p);
00666       } else
00667 #endif /* LWIP_SUPPORT_CUSTOM_PBUF */
00668       {
00669         /* is this a pbuf from the pool? */
00670         if (type == PBUF_POOL) {
00671           memp_free(MEMP_PBUF_POOL, p);
00672         /* is this a ROM or RAM referencing pbuf? */
00673         } else if (type == PBUF_ROM || type == PBUF_REF) {
00674           memp_free(MEMP_PBUF, p);
00675         /* type == PBUF_RAM */
00676         } else {
00677           mem_free(p);
00678         }
00679       }
00680       count++;
00681       /* proceed to next pbuf */
00682       p = q;
00683     /* p->ref > 0, this pbuf is still referenced to */
00684     /* (and so the remaining pbufs in chain as well) */
00685     } else {
00686       LWIP_DEBUGF( PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, ref));
00687       /* stop walking through the chain */
00688       p = NULL;
00689     }
00690   }
00691   PERF_STOP("pbuf_free");
00692   /* return number of de-allocated pbufs */
00693   return count;
00694 }
00695 
00696 /**
00697  * Count number of pbufs in a chain
00698  *
00699  * @param p first pbuf of chain
00700  * @return the number of pbufs in a chain
00701  */
00702 
00703 u8_t
00704 pbuf_clen(struct pbuf *p)
00705 {
00706   u8_t len;
00707 
00708   len = 0;
00709   while (p != NULL) {
00710     ++len;
00711     p = p->next;
00712   }
00713   return len;
00714 }
00715 
00716 /**
00717  * Increment the reference count of the pbuf.
00718  *
00719  * @param p pbuf to increase reference counter of
00720  *
00721  */
00722 void
00723 pbuf_ref(struct pbuf *p)
00724 {
00725   SYS_ARCH_DECL_PROTECT(old_level);
00726   /* pbuf given? */
00727   if (p != NULL) {
00728     SYS_ARCH_PROTECT(old_level);
00729     ++(p->ref);
00730     SYS_ARCH_UNPROTECT(old_level);
00731   }
00732 }
00733 
00734 /**
00735  * Concatenate two pbufs (each may be a pbuf chain) and take over
00736  * the caller's reference of the tail pbuf.
00737  * 
00738  * @note The caller MAY NOT reference the tail pbuf afterwards.
00739  * Use pbuf_chain() for that purpose.
00740  * 
00741  * @see pbuf_chain()
00742  */
00743 
00744 void
00745 pbuf_cat(struct pbuf *h, struct pbuf *t)
00746 {
00747   struct pbuf *p;
00748 
00749   LWIP_ERROR("(h != NULL) && (t != NULL) (programmer violates API)",
00750              ((h != NULL) && (t != NULL)), return;);
00751 
00752   /* proceed to last pbuf of chain */
00753   for (p = h; p->next != NULL; p = p->next) {
00754     /* add total length of second chain to all totals of first chain */
00755     p->tot_len += t->tot_len;
00756   }
00757   /* { p is last pbuf of first h chain, p->next == NULL } */
00758   LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
00759   LWIP_ASSERT("p->next == NULL", p->next == NULL);
00760   /* add total length of second chain to last pbuf total of first chain */
00761   p->tot_len += t->tot_len;
00762   /* chain last pbuf of head (p) with first of tail (t) */
00763   p->next = t;
00764   /* p->next now references t, but the caller will drop its reference to t,
00765    * so netto there is no change to the reference count of t.
00766    */
00767 }
00768 
00769 /**
00770  * Chain two pbufs (or pbuf chains) together.
00771  * 
00772  * The caller MUST call pbuf_free(t) once it has stopped
00773  * using it. Use pbuf_cat() instead if you no longer use t.
00774  * 
00775  * @param h head pbuf (chain)
00776  * @param t tail pbuf (chain)
00777  * @note The pbufs MUST belong to the same packet.
00778  * @note MAY NOT be called on a packet queue.
00779  *
00780  * The ->tot_len fields of all pbufs of the head chain are adjusted.
00781  * The ->next field of the last pbuf of the head chain is adjusted.
00782  * The ->ref field of the first pbuf of the tail chain is adjusted.
00783  *
00784  */
00785 void
00786 pbuf_chain(struct pbuf *h, struct pbuf *t)
00787 {
00788   pbuf_cat(h, t);
00789   /* t is now referenced by h */
00790   pbuf_ref(t);
00791   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
00792 }
00793 
00794 /**
00795  * Dechains the first pbuf from its succeeding pbufs in the chain.
00796  *
00797  * Makes p->tot_len field equal to p->len.
00798  * @param p pbuf to dechain
00799  * @return remainder of the pbuf chain, or NULL if it was de-allocated.
00800  * @note May not be called on a packet queue.
00801  */
00802 struct pbuf *
00803 pbuf_dechain(struct pbuf *p)
00804 {
00805   struct pbuf *q;
00806   u8_t tail_gone = 1;
00807   /* tail */
00808   q = p->next;
00809   /* pbuf has successor in chain? */
00810   if (q != NULL) {
00811     /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00812     LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
00813     /* enforce invariant if assertion is disabled */
00814     q->tot_len = p->tot_len - p->len;
00815     /* decouple pbuf from remainder */
00816     p->next = NULL;
00817     /* total length of pbuf p is its own length only */
00818     p->tot_len = p->len;
00819     /* q is no longer referenced by p, free it */
00820     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
00821     tail_gone = pbuf_free(q);
00822     if (tail_gone > 0) {
00823       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE,
00824                   ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
00825     }
00826     /* return remaining tail or NULL if deallocated */
00827   }
00828   /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00829   LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
00830   return ((tail_gone > 0) ? NULL : q);
00831 }
00832 
00833 /**
00834  *
00835  * Create PBUF_RAM copies of pbufs.
00836  *
00837  * Used to queue packets on behalf of the lwIP stack, such as
00838  * ARP based queueing.
00839  *
00840  * @note You MUST explicitly use p = pbuf_take(p);
00841  *
00842  * @note Only one packet is copied, no packet queue!
00843  *
00844  * @param p_to pbuf destination of the copy
00845  * @param p_from pbuf source of the copy
00846  *
00847  * @return ERR_OK if pbuf was copied
00848  *         ERR_ARG if one of the pbufs is NULL or p_to is not big
00849  *                 enough to hold p_from
00850  */
00851 err_t
00852 pbuf_copy(struct pbuf *p_to, struct pbuf *p_from)
00853 {
00854   u16_t offset_to=0, offset_from=0, len;
00855 
00856   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy(%p, %p)\n",
00857     (void*)p_to, (void*)p_from));
00858 
00859   /* is the target big enough to hold the source? */
00860   LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
00861              (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);
00862 
00863   /* iterate through pbuf chain */
00864   do
00865   {
00866     /* copy one part of the original chain */
00867     if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
00868       /* complete current p_from fits into current p_to */
00869       len = p_from->len - offset_from;
00870     } else {
00871       /* current p_from does not fit into current p_to */
00872       len = p_to->len - offset_to;
00873     }
00874     MEMCPY((u8_t*)p_to->payload + offset_to, (u8_t*)p_from->payload + offset_from, len);
00875     offset_to += len;
00876     offset_from += len;
00877     LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
00878     LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
00879     if (offset_from >= p_from->len) {
00880       /* on to next p_from (if any) */
00881       offset_from = 0;
00882       p_from = p_from->next;
00883     }
00884     if (offset_to == p_to->len) {
00885       /* on to next p_to (if any) */
00886       offset_to = 0;
00887       p_to = p_to->next;
00888       LWIP_ERROR("p_to != NULL", (p_to != NULL) || (p_from == NULL) , return ERR_ARG;);
00889     }
00890 
00891     if((p_from != NULL) && (p_from->len == p_from->tot_len)) {
00892       /* don't copy more than one packet! */
00893       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00894                  (p_from->next == NULL), return ERR_VAL;);
00895     }
00896     if((p_to != NULL) && (p_to->len == p_to->tot_len)) {
00897       /* don't copy more than one packet! */
00898       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00899                   (p_to->next == NULL), return ERR_VAL;);
00900     }
00901   } while (p_from);
00902   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE, ("pbuf_copy: end of chain reached.\n"));
00903   return ERR_OK;
00904 }
00905 
00906 /**
00907  * Copy (part of) the contents of a packet buffer
00908  * to an application supplied buffer.
00909  *
00910  * @param buf the pbuf from which to copy data
00911  * @param dataptr the application supplied buffer
00912  * @param len length of data to copy (dataptr must be big enough). No more 
00913  * than buf->tot_len will be copied, irrespective of len
00914  * @param offset offset into the packet buffer from where to begin copying len bytes
00915  * @return the number of bytes copied, or 0 on failure
00916  */
00917 u16_t
00918 pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
00919 {
00920   struct pbuf *p;
00921   u16_t left;
00922   u16_t buf_copy_len;
00923   u16_t copied_total = 0;
00924 
00925   LWIP_ERROR("pbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
00926   LWIP_ERROR("pbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
00927 
00928   left = 0;
00929 
00930   if((buf == NULL) || (dataptr == NULL)) {
00931     return 0;
00932   }
00933 
00934   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00935   for(p = buf; len != 0 && p != NULL; p = p->next) {
00936     if ((offset != 0) && (offset >= p->len)) {
00937       /* don't copy from this buffer -> on to the next */
00938       offset -= p->len;
00939     } else {
00940       /* copy from this buffer. maybe only partially. */
00941       buf_copy_len = p->len - offset;
00942       if (buf_copy_len > len)
00943           buf_copy_len = len;
00944       /* copy the necessary parts of the buffer */
00945       MEMCPY(&((char*)dataptr)[left], &((char*)p->payload)[offset], buf_copy_len);
00946       copied_total += buf_copy_len;
00947       left += buf_copy_len;
00948       len -= buf_copy_len;
00949       offset = 0;
00950     }
00951   }
00952   return copied_total;
00953 }
00954 
00955 /**
00956  * Copy application supplied data into a pbuf.
00957  * This function can only be used to copy the equivalent of buf->tot_len data.
00958  *
00959  * @param buf pbuf to fill with data
00960  * @param dataptr application supplied data buffer
00961  * @param len length of the application supplied data buffer
00962  *
00963  * @return ERR_OK if successful, ERR_MEM if the pbuf is not big enough
00964  */
00965 err_t
00966 pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len)
00967 {
00968   struct pbuf *p;
00969   u16_t buf_copy_len;
00970   u16_t total_copy_len = len;
00971   u16_t copied_total = 0;
00972 
00973   LWIP_ERROR("pbuf_take: invalid buf", (buf != NULL), return 0;);
00974   LWIP_ERROR("pbuf_take: invalid dataptr", (dataptr != NULL), return 0;);
00975 
00976   if ((buf == NULL) || (dataptr == NULL) || (buf->tot_len < len)) {
00977     return ERR_ARG;
00978   }
00979 
00980   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00981   for(p = buf; total_copy_len != 0; p = p->next) {
00982     LWIP_ASSERT("pbuf_take: invalid pbuf", p != NULL);
00983     buf_copy_len = total_copy_len;
00984     if (buf_copy_len > p->len) {
00985       /* this pbuf cannot hold all remaining data */
00986       buf_copy_len = p->len;
00987     }
00988     /* copy the necessary parts of the buffer */
00989     MEMCPY(p->payload, &((char*)dataptr)[copied_total], buf_copy_len);
00990     total_copy_len -= buf_copy_len;
00991     copied_total += buf_copy_len;
00992   }
00993   LWIP_ASSERT("did not copy all data", total_copy_len == 0 && copied_total == len);
00994   return ERR_OK;
00995 }
00996 
00997 /**
00998  * Creates a single pbuf out of a queue of pbufs.
00999  *
01000  * @remark: Either the source pbuf 'p' is freed by this function or the original
01001  *          pbuf 'p' is returned, therefore the caller has to check the result!
01002  *
01003  * @param p the source pbuf
01004  * @param layer pbuf_layer of the new pbuf
01005  *
01006  * @return a new, single pbuf (p->next is NULL)
01007  *         or the old pbuf if allocation fails
01008  */
01009 struct pbuf*
01010 pbuf_coalesce(struct pbuf *p, pbuf_layer layer)
01011 {
01012   struct pbuf *q;
01013   err_t err;
01014   if (p->next == NULL) {
01015     return p;
01016   }
01017   q = pbuf_alloc(layer, p->tot_len, PBUF_RAM);
01018   if (q == NULL) {
01019     /* @todo: what do we do now? */
01020     return p;
01021   }
01022   err = pbuf_copy(q, p);
01023   LWIP_ASSERT("pbuf_copy failed", err == ERR_OK);
01024   pbuf_free(p);
01025   return q;
01026 }
01027 
01028 #if LWIP_CHECKSUM_ON_COPY
01029 /**
01030  * Copies data into a single pbuf (*not* into a pbuf queue!) and updates
01031  * the checksum while copying
01032  *
01033  * @param p the pbuf to copy data into
01034  * @param start_offset offset of p->payload where to copy the data to
01035  * @param dataptr data to copy into the pbuf
01036  * @param len length of data to copy into the pbuf
01037  * @param chksum pointer to the checksum which is updated
01038  * @return ERR_OK if successful, another error if the data does not fit
01039  *         within the (first) pbuf (no pbuf queues!)
01040  */
01041 err_t
01042 pbuf_fill_chksum(struct pbuf *p, u16_t start_offset, const void *dataptr,
01043                  u16_t len, u16_t *chksum)
01044 {
01045   u32_t acc;
01046   u16_t copy_chksum;
01047   char *dst_ptr;
01048   LWIP_ASSERT("p != NULL", p != NULL);
01049   LWIP_ASSERT("dataptr != NULL", dataptr != NULL);
01050   LWIP_ASSERT("chksum != NULL", chksum != NULL);
01051   LWIP_ASSERT("len != 0", len != 0);
01052 
01053   if ((start_offset >= p->len) || (start_offset + len > p->len)) {
01054     return ERR_ARG;
01055   }
01056 
01057   dst_ptr = ((char*)p->payload) + start_offset;
01058   copy_chksum = LWIP_CHKSUM_COPY(dst_ptr, dataptr, len);
01059   if ((start_offset & 1) != 0) {
01060     copy_chksum = SWAP_BYTES_IN_WORD(copy_chksum);
01061   }
01062   acc = *chksum;
01063   acc += copy_chksum;
01064   *chksum = FOLD_U32T(acc);
01065   return ERR_OK;
01066 }
01067 #endif /* LWIP_CHECKSUM_ON_COPY */
01068 
01069  /** Get one byte from the specified position in a pbuf
01070  * WARNING: returns zero for offset >= p->tot_len
01071  *
01072  * @param p pbuf to parse
01073  * @param offset offset into p of the byte to return
01074  * @return byte at an offset into p OR ZERO IF 'offset' >= p->tot_len
01075  */
01076 u8_t
01077 pbuf_get_at(struct pbuf* p, u16_t offset)
01078 {
01079   u16_t copy_from = offset;
01080   struct pbuf* q = p;
01081 
01082   /* get the correct pbuf */
01083   while ((q != NULL) && (q->len <= copy_from)) {
01084     copy_from -= q->len;
01085     q = q->next;
01086   }
01087   /* return requested data if pbuf is OK */
01088   if ((q != NULL) && (q->len > copy_from)) {
01089     return ((u8_t*)q->payload)[copy_from];
01090   }
01091   return 0;
01092 }
01093 
01094 /** Compare pbuf contents at specified offset with memory s2, both of length n
01095  *
01096  * @param p pbuf to compare
01097  * @param offset offset into p at wich to start comparing
01098  * @param s2 buffer to compare
01099  * @param n length of buffer to compare
01100  * @return zero if equal, nonzero otherwise
01101  *         (0xffff if p is too short, diffoffset+1 otherwise)
01102  */
01103 u16_t
01104 pbuf_memcmp(struct pbuf* p, u16_t offset, const void* s2, u16_t n)
01105 {
01106   u16_t start = offset;
01107   struct pbuf* q = p;
01108 
01109   /* get the correct pbuf */
01110   while ((q != NULL) && (q->len <= start)) {
01111     start -= q->len;
01112     q = q->next;
01113   }
01114   /* return requested data if pbuf is OK */
01115   if ((q != NULL) && (q->len > start)) {
01116     u16_t i;
01117     for(i = 0; i < n; i++) {
01118       u8_t a = pbuf_get_at(q, start + i);
01119       u8_t b = ((u8_t*)s2)[i];
01120       if (a != b) {
01121         return i+1;
01122       }
01123     }
01124     return 0;
01125   }
01126   return 0xffff;
01127 }
01128 
01129 /** Find occurrence of mem (with length mem_len) in pbuf p, starting at offset
01130  * start_offset.
01131  *
01132  * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
01133  *        return value 'not found'
01134  * @param mem search for the contents of this buffer
01135  * @param mem_len length of 'mem'
01136  * @param start_offset offset into p at which to start searching
01137  * @return 0xFFFF if substr was not found in p or the index where it was found
01138  */
01139 u16_t
01140 pbuf_memfind(struct pbuf* p, const void* mem, u16_t mem_len, u16_t start_offset)
01141 {
01142   u16_t i;
01143   u16_t max = p->tot_len - mem_len;
01144   if (p->tot_len >= mem_len + start_offset) {
01145     for(i = start_offset; i <= max; ) {
01146       u16_t plus = pbuf_memcmp(p, i, mem, mem_len);
01147       if (plus == 0) {
01148         return i;
01149       } else {
01150         i += plus;
01151       }
01152     }
01153   }
01154   return 0xFFFF;
01155 }
01156 
01157 /** Find occurrence of substr with length substr_len in pbuf p, start at offset
01158  * start_offset
01159  * WARNING: in contrast to strstr(), this one does not stop at the first \0 in
01160  * the pbuf/source string!
01161  *
01162  * @param p pbuf to search, maximum length is 0xFFFE since 0xFFFF is used as
01163  *        return value 'not found'
01164  * @param substr string to search for in p, maximum length is 0xFFFE
01165  * @return 0xFFFF if substr was not found in p or the index where it was found
01166  */
01167 u16_t
01168 pbuf_strstr(struct pbuf* p, const char* substr)
01169 {
01170   size_t substr_len;
01171   if ((substr == NULL) || (substr[0] == 0) || (p->tot_len == 0xFFFF)) {
01172     return 0xFFFF;
01173   }
01174   substr_len = strlen(substr);
01175   if (substr_len >= 0xFFFF) {
01176     return 0xFFFF;
01177   }
01178   return pbuf_memfind(p, substr, (u16_t)substr_len, 0);
01179 }