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.h"
00075 #endif
00076 
00077 #include <string.h>
00078 
00079 #define SIZEOF_STRUCT_PBUF        LWIP_MEM_ALIGN_SIZE(sizeof(struct pbuf))
00080 /* Since the pool is created in memp, PBUF_POOL_BUFSIZE will be automatically
00081    aligned there. Therefore, PBUF_POOL_BUFSIZE_ALIGNED can be used here. */
00082 #define PBUF_POOL_BUFSIZE_ALIGNED LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE)
00083 
00084 #if TCP_QUEUE_OOSEQ
00085 #define ALLOC_POOL_PBUF(p) do { (p) = alloc_pool_pbuf(); } while (0)
00086 #else
00087 #define ALLOC_POOL_PBUF(p) do { (p) = memp_malloc(MEMP_PBUF_POOL); } while (0)
00088 #endif
00089 
00090 
00091 #if TCP_QUEUE_OOSEQ
00092 /**
00093  * Attempt to reclaim some memory from queued out-of-sequence TCP segments
00094  * if we run out of pool pbufs. It's better to give priority to new packets
00095  * if we're running out.
00096  *
00097  * @return the allocated pbuf.
00098  */
00099 static struct pbuf *
00100 alloc_pool_pbuf(void)
00101 {
00102   struct tcp_pcb *pcb;
00103   struct pbuf *p;
00104 
00105 retry:
00106   p = (struct pbuf *)memp_malloc(MEMP_PBUF_POOL);
00107   if (NULL == p) {
00108     for (pcb=tcp_active_pcbs; NULL != pcb; pcb = pcb->next) {
00109       if (NULL != pcb->ooseq) {
00110         tcp_segs_free(pcb->ooseq);
00111         pcb->ooseq = NULL;
00112         goto retry;
00113       }
00114     }
00115   }
00116   return p;
00117 }
00118 #endif /* TCP_QUEUE_OOSEQ */
00119 
00120 /**
00121  * Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).
00122  *
00123  * The actual memory allocated for the pbuf is determined by the
00124  * layer at which the pbuf is allocated and the requested size
00125  * (from the size parameter).
00126  *
00127  * @param layer flag to define header size
00128  * @param length size of the pbuf's payload
00129  * @param type this parameter decides how and where the pbuf
00130  * should be allocated as follows:
00131  *
00132  * - PBUF_RAM: buffer memory for pbuf is allocated as one large
00133  *             chunk. This includes protocol headers as well.
00134  * - PBUF_ROM: no buffer memory is allocated for the pbuf, even for
00135  *             protocol headers. Additional headers must be prepended
00136  *             by allocating another pbuf and chain in to the front of
00137  *             the ROM pbuf. It is assumed that the memory used is really
00138  *             similar to ROM in that it is immutable and will not be
00139  *             changed. Memory which is dynamic should generally not
00140  *             be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
00141  * - PBUF_REF: no buffer memory is allocated for the pbuf, even for
00142  *             protocol headers. It is assumed that the pbuf is only
00143  *             being used in a single thread. If the pbuf gets queued,
00144  *             then pbuf_take should be called to copy the buffer.
00145  * - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from
00146  *              the pbuf pool that is allocated during pbuf_init().
00147  *
00148  * @return the allocated pbuf. If multiple pbufs where allocated, this
00149  * is the first pbuf of a pbuf chain.
00150  */
00151 struct pbuf *
00152 pbuf_alloc(pbuf_layer layer, u16_t length, pbuf_type type)
00153 {
00154   struct pbuf *p, *q, *r;
00155   u16_t offset;
00156   s32_t rem_len; /* remaining length */
00157   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F")\n", length));
00158 
00159   /* determine header offset */
00160   offset = 0;
00161   switch (layer) {
00162   case PBUF_TRANSPORT:
00163     /* add room for transport (often TCP) layer header */
00164     offset += PBUF_TRANSPORT_HLEN;
00165     /* FALLTHROUGH */
00166   case PBUF_IP:
00167     /* add room for IP layer header */
00168     offset += PBUF_IP_HLEN;
00169     /* FALLTHROUGH */
00170   case PBUF_LINK:
00171     /* add room for link layer header */
00172     offset += PBUF_LINK_HLEN;
00173     break;
00174   case PBUF_RAW:
00175     break;
00176   default:
00177     LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0);
00178     return NULL;
00179   }
00180 
00181   switch (type) {
00182   case PBUF_POOL:
00183     /* allocate head of pbuf chain into p */
00184     ALLOC_POOL_PBUF(p);
00185     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_alloc: allocated pbuf %p\n", (void *)p));
00186     if (p == NULL) {
00187       return NULL;
00188     }
00189     p->type = type;
00190     p->next = NULL;
00191 
00192     /* make the payload pointer point 'offset' bytes into pbuf data memory */
00193     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + (SIZEOF_STRUCT_PBUF + offset)));
00194     LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
00195             ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00196     /* the total length of the pbuf chain is the requested size */
00197     p->tot_len = length;
00198     /* set the length of the first pbuf in the chain */
00199     p->len = LWIP_MIN(length, PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset));
00200     LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00201                 ((u8_t*)p->payload + p->len <=
00202                  (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00203     LWIP_ASSERT("PBUF_POOL_BUFSIZE must be bigger than MEM_ALIGNMENT", p->len != 0);
00204     /* set reference count (needed here in case we fail) */
00205     p->ref = 1;
00206 
00207     /* now allocate the tail of the pbuf chain */
00208 
00209     /* remember first pbuf for linkage in next iteration */
00210     r = p;
00211     /* remaining length to be allocated */
00212     rem_len = length - p->len;
00213     /* any remaining pbufs to be allocated? */
00214     while (rem_len > 0) {
00215       ALLOC_POOL_PBUF(q);
00216       if (q == NULL) {
00217         /* free chain so far allocated */
00218         pbuf_free(p);
00219         /* bail out unsuccesfully */
00220         return NULL;
00221       }
00222       q->type = type;
00223       q->flags = 0;
00224       q->next = NULL;
00225       /* make previous pbuf point to this pbuf */
00226       r->next = q;
00227       /* set total length of this pbuf and next in chain */
00228       LWIP_ASSERT("rem_len < max_u16_t", rem_len < 0xffff);
00229       q->tot_len = (u16_t)rem_len;
00230       /* this pbuf length is pool size, unless smaller sized tail */
00231       q->len = LWIP_MIN((u16_t)rem_len, PBUF_POOL_BUFSIZE_ALIGNED);
00232       q->payload = (void *)((u8_t *)q + SIZEOF_STRUCT_PBUF);
00233       LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
00234               ((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0);
00235       LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00236                   ((u8_t*)p->payload + p->len <=
00237                    (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00238       q->ref = 1;
00239       /* calculate remaining length to be allocated */
00240       rem_len -= q->len;
00241       /* remember this pbuf for linkage in next iteration */
00242       r = q;
00243     }
00244     /* end of chain */
00245     /*r->next = NULL;*/
00246 
00247     break;
00248   case PBUF_RAM:
00249     /* If pbuf is to be allocated in RAM, allocate memory for it. */
00250     p = (struct pbuf*)mem_malloc(LWIP_MEM_ALIGN_SIZE(SIZEOF_STRUCT_PBUF + offset) + LWIP_MEM_ALIGN_SIZE(length));
00251     if (p == NULL) {
00252       return NULL;
00253     }
00254     /* Set up internal structure of the pbuf. */
00255     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + SIZEOF_STRUCT_PBUF + offset));
00256     p->len = p->tot_len = length;
00257     p->next = NULL;
00258     p->type = type;
00259 
00260     LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
00261            ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00262     break;
00263   /* pbuf references existing (non-volatile static constant) ROM payload? */
00264   case PBUF_ROM:
00265   /* pbuf references existing (externally allocated) RAM payload? */
00266   case PBUF_REF:
00267     /* only allocate memory for the pbuf structure */
00268     p = (struct pbuf *)(memp_malloc(MEMP_PBUF)); // static_cast<struct pbuf *>(x)
00269     if (p == NULL) {
00270       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n",
00271                   (type == PBUF_ROM) ? "ROM" : "REF"));
00272       return NULL;
00273     }
00274     /* caller must set this field properly, afterwards */
00275     p->payload = NULL;
00276     p->len = p->tot_len = length;
00277     p->next = NULL;
00278     p->type = type;
00279     break;
00280   default:
00281     LWIP_ASSERT("pbuf_alloc: erroneous type", 0);
00282     return NULL;
00283   }
00284   /* set reference count */
00285   p->ref = 1;
00286   /* set flags */
00287   p->flags = 0;
00288   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
00289   return p;
00290 }
00291 
00292 
00293 /**
00294  * Shrink a pbuf chain to a desired length.
00295  *
00296  * @param p pbuf to shrink.
00297  * @param new_len desired new length of pbuf chain
00298  *
00299  * Depending on the desired length, the first few pbufs in a chain might
00300  * be skipped and left unchanged. The new last pbuf in the chain will be
00301  * resized, and any remaining pbufs will be freed.
00302  *
00303  * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
00304  * @note May not be called on a packet queue.
00305  *
00306  * @note Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).
00307  */
00308 void
00309 pbuf_realloc(struct pbuf *p, u16_t new_len)
00310 {
00311   struct pbuf *q;
00312   u16_t rem_len; /* remaining length */
00313   s32_t grow;
00314 
00315   LWIP_ASSERT("pbuf_realloc: p != NULL", p != NULL);
00316   LWIP_ASSERT("pbuf_realloc: sane p->type", p->type == PBUF_POOL ||
00317               p->type == PBUF_ROM ||
00318               p->type == PBUF_RAM ||
00319               p->type == PBUF_REF);
00320 
00321   /* desired length larger than current length? */
00322   if (new_len >= p->tot_len) {
00323     /* enlarging not yet supported */
00324     return;
00325   }
00326 
00327   /* the pbuf chain grows by (new_len - p->tot_len) bytes
00328    * (which may be negative in case of shrinking) */
00329   grow = new_len - p->tot_len;
00330 
00331   /* first, step over any pbufs that should remain in the chain */
00332   rem_len = new_len;
00333   q = p;
00334   /* should this pbuf be kept? */
00335   while (rem_len > q->len) {
00336     /* decrease remaining length by pbuf length */
00337     rem_len -= q->len;
00338     /* decrease total length indicator */
00339     LWIP_ASSERT("grow < max_u16_t", grow < 0xffff);
00340     q->tot_len += (u16_t)grow;
00341     /* proceed to next pbuf in chain */
00342     q = q->next;
00343     LWIP_ASSERT("pbuf_realloc: q != NULL", q != NULL);
00344   }
00345   /* we have now reached the new last pbuf (in q) */
00346   /* rem_len == desired length for pbuf q */
00347 
00348   /* shrink allocated memory for PBUF_RAM */
00349   /* (other types merely adjust their length fields */
00350   if ((q->type == PBUF_RAM) && (rem_len != q->len)) {
00351     /* reallocate and adjust the length of the pbuf that will be split */
00352     q = (struct pbuf *)(mem_realloc(q, (u8_t *)q->payload - (u8_t *)q + rem_len)); // static_cast<struct pbuf *>(x)
00353     LWIP_ASSERT("mem_realloc give q == NULL", q != NULL);
00354   }
00355   /* adjust length fields for new last pbuf */
00356   q->len = rem_len;
00357   q->tot_len = q->len;
00358 
00359   /* any remaining pbufs in chain? */
00360   if (q->next != NULL) {
00361     /* free remaining pbufs in chain */
00362     pbuf_free(q->next);
00363   }
00364   /* q is last packet in chain */
00365   q->next = NULL;
00366 
00367 }
00368 
00369 /**
00370  * Adjusts the payload pointer to hide or reveal headers in the payload.
00371  *
00372  * Adjusts the ->payload pointer so that space for a header
00373  * (dis)appears in the pbuf payload.
00374  *
00375  * The ->payload, ->tot_len and ->len fields are adjusted.
00376  *
00377  * @param p pbuf to change the header size.
00378  * @param header_size_increment Number of bytes to increment header size which
00379  * increases the size of the pbuf. New space is on the front.
00380  * (Using a negative value decreases the header size.)
00381  * If hdr_size_inc is 0, this function does nothing and returns succesful.
00382  *
00383  * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
00384  * the call will fail. A check is made that the increase in header size does
00385  * not move the payload pointer in front of the start of the buffer.
00386  * @return non-zero on failure, zero on success.
00387  *
00388  */
00389 u8_t
00390 pbuf_header(struct pbuf *p, s16_t header_size_increment)
00391 {
00392   u16_t type;
00393   void *payload;
00394   u16_t increment_magnitude;
00395 
00396   LWIP_ASSERT("p != NULL", p != NULL);
00397   if ((header_size_increment == 0) || (p == NULL))
00398     return 0;
00399  
00400   if (header_size_increment < 0){
00401     increment_magnitude = -header_size_increment;
00402     /* Check that we aren't going to move off the end of the pbuf */
00403     LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);
00404   } else {
00405     increment_magnitude = header_size_increment;
00406 #if 0
00407     /* Can't assert these as some callers speculatively call
00408          pbuf_header() to see if it's OK.  Will return 1 below instead. */
00409     /* Check that we've got the correct type of pbuf to work with */
00410     LWIP_ASSERT("p->type == PBUF_RAM || p->type == PBUF_POOL", 
00411                 p->type == PBUF_RAM || p->type == PBUF_POOL);
00412     /* Check that we aren't going to move off the beginning of the pbuf */
00413     LWIP_ASSERT("p->payload - increment_magnitude >= p + SIZEOF_STRUCT_PBUF",
00414                 (u8_t *)p->payload - increment_magnitude >= (u8_t *)p + SIZEOF_STRUCT_PBUF);
00415 #endif
00416   }
00417 
00418   type = p->type;
00419   /* remember current payload pointer */
00420   payload = p->payload;
00421 
00422   /* pbuf types containing payloads? */
00423   if (type == PBUF_RAM || type == PBUF_POOL) {
00424     /* set new payload pointer */
00425     p->payload = (u8_t *)p->payload - header_size_increment;
00426     /* boundary check fails? */
00427     if ((u8_t *)p->payload < (u8_t *)p + SIZEOF_STRUCT_PBUF) {
00428       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
00429         (void *)p->payload,
00430         (void *)(p + 1)));\
00431       /* restore old payload pointer */
00432       p->payload = payload;
00433       /* bail out unsuccesfully */
00434       return 1;
00435     }
00436   /* pbuf types refering to external payloads? */
00437   } else if (type == PBUF_REF || type == PBUF_ROM) {
00438     /* hide a header in the payload? */
00439     if ((header_size_increment < 0) && (increment_magnitude <= p->len)) {
00440       /* increase payload pointer */
00441       p->payload = (u8_t *)p->payload - header_size_increment;
00442     } else {
00443       /* cannot expand payload to front (yet!)
00444        * bail out unsuccesfully */
00445       return 1;
00446     }
00447   }
00448   else {
00449     /* Unknown type */
00450     LWIP_ASSERT("bad pbuf type", 0);
00451     return 1;
00452   }
00453   /* modify pbuf length fields */
00454   p->len += header_size_increment;
00455   p->tot_len += header_size_increment;
00456 
00457   LWIP_DEBUGF(PBUF_DEBUG, ("pbuf_header: old %p new %p (%"S16_F")\n",
00458     (void *)payload, (void *)p->payload, header_size_increment));
00459 
00460   return 0;
00461 }
00462 
00463 /**
00464  * Dereference a pbuf chain or queue and deallocate any no-longer-used
00465  * pbufs at the head of this chain or queue.
00466  *
00467  * Decrements the pbuf reference count. If it reaches zero, the pbuf is
00468  * deallocated.
00469  *
00470  * For a pbuf chain, this is repeated for each pbuf in the chain,
00471  * up to the first pbuf which has a non-zero reference count after
00472  * decrementing. So, when all reference counts are one, the whole
00473  * chain is free'd.
00474  *
00475  * @param p The pbuf (chain) to be dereferenced.
00476  *
00477  * @return the number of pbufs that were de-allocated
00478  * from the head of the chain.
00479  *
00480  * @note MUST NOT be called on a packet queue (Not verified to work yet).
00481  * @note the reference counter of a pbuf equals the number of pointers
00482  * that refer to the pbuf (or into the pbuf).
00483  *
00484  * @internal examples:
00485  *
00486  * Assuming existing chains a->b->c with the following reference
00487  * counts, calling pbuf_free(a) results in:
00488  * 
00489  * 1->2->3 becomes ...1->3
00490  * 3->3->3 becomes 2->3->3
00491  * 1->1->2 becomes ......1
00492  * 2->1->1 becomes 1->1->1
00493  * 1->1->1 becomes .......
00494  *
00495  */
00496 u8_t
00497 pbuf_free(struct pbuf *p)
00498 {
00499   u16_t type;
00500   struct pbuf *q;
00501   u8_t count;
00502 
00503   if (p == NULL) {
00504     LWIP_ASSERT("p != NULL", p != NULL);
00505     /* if assertions are disabled, proceed with debug output */
00506     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n"));
00507     return 0;
00508   }
00509   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_free(%p)\n", (void *)p));
00510 
00511   PERF_START;
00512 
00513   LWIP_ASSERT("pbuf_free: sane type",
00514     p->type == PBUF_RAM || p->type == PBUF_ROM ||
00515     p->type == PBUF_REF || p->type == PBUF_POOL);
00516 
00517   count = 0;
00518   /* de-allocate all consecutive pbufs from the head of the chain that
00519    * obtain a zero reference count after decrementing*/
00520   while (p != NULL) {
00521     u16_t ref;
00522     SYS_ARCH_DECL_PROTECT(old_level);
00523     /* Since decrementing ref cannot be guaranteed to be a single machine operation
00524      * we must protect it. We put the new ref into a local variable to prevent
00525      * further protection. */
00526     SYS_ARCH_PROTECT(old_level);
00527     /* all pbufs in a chain are referenced at least once */
00528     LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
00529     /* decrease reference count (number of pointers to pbuf) */
00530     ref = --(p->ref);
00531     SYS_ARCH_UNPROTECT(old_level);
00532     /* this pbuf is no longer referenced to? */
00533     if (ref == 0) {
00534       /* remember next pbuf in chain for next iteration */
00535       q = p->next;
00536       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: deallocating %p\n", (void *)p));
00537       type = p->type;
00538       /* is this a pbuf from the pool? */
00539       if (type == PBUF_POOL) {
00540         memp_free(MEMP_PBUF_POOL, p);
00541       /* is this a ROM or RAM referencing pbuf? */
00542       } else if (type == PBUF_ROM || type == PBUF_REF) {
00543         memp_free(MEMP_PBUF, p);
00544       /* type == PBUF_RAM */
00545       } else {
00546         mem_free(p);
00547       }
00548       count++;
00549       /* proceed to next pbuf */
00550       p = q;
00551     /* p->ref > 0, this pbuf is still referenced to */
00552     /* (and so the remaining pbufs in chain as well) */
00553     } else {
00554       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, ref));
00555       /* stop walking through the chain */
00556       p = NULL;
00557     }
00558   }
00559   PERF_STOP("pbuf_free");
00560   /* return number of de-allocated pbufs */
00561   return count;
00562 }
00563 
00564 /**
00565  * Count number of pbufs in a chain
00566  *
00567  * @param p first pbuf of chain
00568  * @return the number of pbufs in a chain
00569  */
00570 
00571 u8_t
00572 pbuf_clen(struct pbuf *p)
00573 {
00574   u8_t len;
00575 
00576   len = 0;
00577   while (p != NULL) {
00578     ++len;
00579     p = p->next;
00580   }
00581   return len;
00582 }
00583 
00584 /**
00585  * Increment the reference count of the pbuf.
00586  *
00587  * @param p pbuf to increase reference counter of
00588  *
00589  */
00590 void
00591 pbuf_ref(struct pbuf *p)
00592 {
00593   SYS_ARCH_DECL_PROTECT(old_level);
00594   /* pbuf given? */
00595   if (p != NULL) {
00596     SYS_ARCH_PROTECT(old_level);
00597     ++(p->ref);
00598     SYS_ARCH_UNPROTECT(old_level);
00599   }
00600 }
00601 
00602 /**
00603  * Concatenate two pbufs (each may be a pbuf chain) and take over
00604  * the caller's reference of the tail pbuf.
00605  * 
00606  * @note The caller MAY NOT reference the tail pbuf afterwards.
00607  * Use pbuf_chain() for that purpose.
00608  * 
00609  * @see pbuf_chain()
00610  */
00611 
00612 void
00613 pbuf_cat(struct pbuf *h, struct pbuf *t)
00614 {
00615   struct pbuf *p;
00616 
00617   LWIP_ERROR("(h != NULL) && (t != NULL) (programmer violates API)",
00618              ((h != NULL) && (t != NULL)), return;);
00619 
00620   /* proceed to last pbuf of chain */
00621   for (p = h; p->next != NULL; p = p->next) {
00622     /* add total length of second chain to all totals of first chain */
00623     p->tot_len += t->tot_len;
00624   }
00625   /* { p is last pbuf of first h chain, p->next == NULL } */
00626   LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
00627   LWIP_ASSERT("p->next == NULL", p->next == NULL);
00628   /* add total length of second chain to last pbuf total of first chain */
00629   p->tot_len += t->tot_len;
00630   /* chain last pbuf of head (p) with first of tail (t) */
00631   p->next = t;
00632   /* p->next now references t, but the caller will drop its reference to t,
00633    * so netto there is no change to the reference count of t.
00634    */
00635 }
00636 
00637 /**
00638  * Chain two pbufs (or pbuf chains) together.
00639  * 
00640  * The caller MUST call pbuf_free(t) once it has stopped
00641  * using it. Use pbuf_cat() instead if you no longer use t.
00642  * 
00643  * @param h head pbuf (chain)
00644  * @param t tail pbuf (chain)
00645  * @note The pbufs MUST belong to the same packet.
00646  * @note MAY NOT be called on a packet queue.
00647  *
00648  * The ->tot_len fields of all pbufs of the head chain are adjusted.
00649  * The ->next field of the last pbuf of the head chain is adjusted.
00650  * The ->ref field of the first pbuf of the tail chain is adjusted.
00651  *
00652  */
00653 void
00654 pbuf_chain(struct pbuf *h, struct pbuf *t)
00655 {
00656   pbuf_cat(h, t);
00657   /* t is now referenced by h */
00658   pbuf_ref(t);
00659   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
00660 }
00661 
00662 /**
00663  * Dechains the first pbuf from its succeeding pbufs in the chain.
00664  *
00665  * Makes p->tot_len field equal to p->len.
00666  * @param p pbuf to dechain
00667  * @return remainder of the pbuf chain, or NULL if it was de-allocated.
00668  * @note May not be called on a packet queue.
00669  */
00670 struct pbuf *
00671 pbuf_dechain(struct pbuf *p)
00672 {
00673   struct pbuf *q;
00674   u8_t tail_gone = 1;
00675   /* tail */
00676   q = p->next;
00677   /* pbuf has successor in chain? */
00678   if (q != NULL) {
00679     /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00680     LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
00681     /* enforce invariant if assertion is disabled */
00682     q->tot_len = p->tot_len - p->len;
00683     /* decouple pbuf from remainder */
00684     p->next = NULL;
00685     /* total length of pbuf p is its own length only */
00686     p->tot_len = p->len;
00687     /* q is no longer referenced by p, free it */
00688     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
00689     tail_gone = pbuf_free(q);
00690     if (tail_gone > 0) {
00691       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_STATE,
00692                   ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
00693     }
00694     /* return remaining tail or NULL if deallocated */
00695   }
00696   /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00697   LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
00698   return ((tail_gone > 0) ? NULL : q);
00699 }
00700 
00701 /**
00702  *
00703  * Create PBUF_RAM copies of pbufs.
00704  *
00705  * Used to queue packets on behalf of the lwIP stack, such as
00706  * ARP based queueing.
00707  *
00708  * @note You MUST explicitly use p = pbuf_take(p);
00709  *
00710  * @note Only one packet is copied, no packet queue!
00711  *
00712  * @param p_to pbuf destination of the copy
00713  * @param p_from pbuf source of the copy
00714  *
00715  * @return ERR_OK if pbuf was copied
00716  *         ERR_ARG if one of the pbufs is NULL or p_to is not big
00717  *                 enough to hold p_from
00718  */
00719 err_t
00720 pbuf_copy(struct pbuf *p_to, struct pbuf *p_from)
00721 {
00722   u16_t offset_to=0, offset_from=0, len;
00723 
00724   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_copy(%p, %p)\n",
00725     (void*)p_to, (void*)p_from));
00726 
00727   /* is the target big enough to hold the source? */
00728   LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
00729              (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);
00730 
00731   /* iterate through pbuf chain */
00732   do
00733   {
00734     LWIP_ASSERT("p_to != NULL", p_to != NULL);
00735     /* copy one part of the original chain */
00736     if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
00737       /* complete current p_from fits into current p_to */
00738       len = p_from->len - offset_from;
00739     } else {
00740       /* current p_from does not fit into current p_to */
00741       len = p_to->len - offset_to;
00742     }
00743     MEMCPY((u8_t*)p_to->payload + offset_to, (u8_t*)p_from->payload + offset_from, len);
00744     offset_to += len;
00745     offset_from += len;
00746     LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
00747     if (offset_to == p_to->len) {
00748       /* on to next p_to (if any) */
00749       offset_to = 0;
00750       p_to = p_to->next;
00751     }
00752     LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
00753     if (offset_from >= p_from->len) {
00754       /* on to next p_from (if any) */
00755       offset_from = 0;
00756       p_from = p_from->next;
00757     }
00758 
00759     if((p_from != NULL) && (p_from->len == p_from->tot_len)) {
00760       /* don't copy more than one packet! */
00761       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00762                  (p_from->next == NULL), return ERR_VAL;);
00763     }
00764     if((p_to != NULL) && (p_to->len == p_to->tot_len)) {
00765       /* don't copy more than one packet! */
00766       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00767                   (p_to->next == NULL), return ERR_VAL;);
00768     }
00769   } while (p_from);
00770   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 1, ("pbuf_copy: end of chain reached.\n"));
00771   return ERR_OK;
00772 }
00773 
00774 /**
00775  * Copy (part of) the contents of a packet buffer
00776  * to an application supplied buffer.
00777  *
00778  * @param buf the pbuf from which to copy data
00779  * @param dataptr the application supplied buffer
00780  * @param len length of data to copy (dataptr must be big enough). No more 
00781  * than buf->tot_len will be copied, irrespective of len
00782  * @param offset offset into the packet buffer from where to begin copying len bytes
00783  * @return the number of bytes copied, or 0 on failure
00784  */
00785 u16_t
00786 pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
00787 {
00788   struct pbuf *p;
00789   u16_t left;
00790   u16_t buf_copy_len;
00791   u16_t copied_total = 0;
00792 
00793   LWIP_ERROR("netbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
00794   LWIP_ERROR("netbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
00795 
00796   left = 0;
00797 
00798   if((buf == NULL) || (dataptr == NULL)) {
00799     return 0;
00800   }
00801 
00802   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00803   for(p = buf; len != 0 && p != NULL; p = p->next) {
00804     if ((offset != 0) && (offset >= p->len)) {
00805       /* don't copy from this buffer -> on to the next */
00806       offset -= p->len;
00807     } else {
00808       /* copy from this buffer. maybe only partially. */
00809       buf_copy_len = p->len - offset;
00810       if (buf_copy_len > len)
00811           buf_copy_len = len;
00812       /* copy the necessary parts of the buffer */
00813       MEMCPY(&((char*)dataptr)[left], &((char*)p->payload)[offset], buf_copy_len);
00814       copied_total += buf_copy_len;
00815       left += buf_copy_len;
00816       len -= buf_copy_len;
00817       offset = 0;
00818     }
00819   }
00820   return copied_total;
00821 }