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",
00204       (PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset)) > 0 );
00205     /* set reference count (needed here in case we fail) */
00206     p->ref = 1;
00207 
00208     /* now allocate the tail of the pbuf chain */
00209 
00210     /* remember first pbuf for linkage in next iteration */
00211     r = p;
00212     /* remaining length to be allocated */
00213     rem_len = length - p->len;
00214     /* any remaining pbufs to be allocated? */
00215     while (rem_len > 0) {
00216       ALLOC_POOL_PBUF(q);
00217       if (q == NULL) {
00218         /* free chain so far allocated */
00219         pbuf_free(p);
00220         /* bail out unsuccesfully */
00221         return NULL;
00222       }
00223       q->type = type;
00224       q->flags = 0;
00225       q->next = NULL;
00226       /* make previous pbuf point to this pbuf */
00227       r->next = q;
00228       /* set total length of this pbuf and next in chain */
00229       LWIP_ASSERT("rem_len < max_u16_t", rem_len < 0xffff);
00230       q->tot_len = (u16_t)rem_len;
00231       /* this pbuf length is pool size, unless smaller sized tail */
00232       q->len = LWIP_MIN((u16_t)rem_len, PBUF_POOL_BUFSIZE_ALIGNED);
00233       q->payload = (void *)((u8_t *)q + SIZEOF_STRUCT_PBUF);
00234       LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
00235               ((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0);
00236       LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00237                   ((u8_t*)p->payload + p->len <=
00238                    (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00239       q->ref = 1;
00240       /* calculate remaining length to be allocated */
00241       rem_len -= q->len;
00242       /* remember this pbuf for linkage in next iteration */
00243       r = q;
00244     }
00245     /* end of chain */
00246     /*r->next = NULL;*/
00247 
00248     break;
00249   case PBUF_RAM:
00250     /* If pbuf is to be allocated in RAM, allocate memory for it. */
00251     p = (struct pbuf*)mem_malloc(LWIP_MEM_ALIGN_SIZE(SIZEOF_STRUCT_PBUF + offset) + LWIP_MEM_ALIGN_SIZE(length));
00252     if (p == NULL) {
00253       return NULL;
00254     }
00255     /* Set up internal structure of the pbuf. */
00256     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + SIZEOF_STRUCT_PBUF + offset));
00257     p->len = p->tot_len = length;
00258     p->next = NULL;
00259     p->type = type;
00260 
00261     LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
00262            ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00263     break;
00264   /* pbuf references existing (non-volatile static constant) ROM payload? */
00265   case PBUF_ROM:
00266   /* pbuf references existing (externally allocated) RAM payload? */
00267   case PBUF_REF:
00268     /* only allocate memory for the pbuf structure */
00269     p = (struct pbuf *)memp_malloc(MEMP_PBUF);
00270     if (p == NULL) {
00271       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n",
00272                   (type == PBUF_ROM) ? "ROM" : "REF"));
00273       return NULL;
00274     }
00275     /* caller must set this field properly, afterwards */
00276     p->payload = NULL;
00277     p->len = p->tot_len = length;
00278     p->next = NULL;
00279     p->type = type;
00280     break;
00281   default:
00282     LWIP_ASSERT("pbuf_alloc: erroneous type", 0);
00283     return NULL;
00284   }
00285   /* set reference count */
00286   p->ref = 1;
00287   /* set flags */
00288   p->flags = 0;
00289   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
00290   return p;
00291 }
00292 
00293 
00294 /**
00295  * Shrink a pbuf chain to a desired length.
00296  *
00297  * @param p pbuf to shrink.
00298  * @param new_len desired new length of pbuf chain
00299  *
00300  * Depending on the desired length, the first few pbufs in a chain might
00301  * be skipped and left unchanged. The new last pbuf in the chain will be
00302  * resized, and any remaining pbufs will be freed.
00303  *
00304  * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
00305  * @note May not be called on a packet queue.
00306  *
00307  * @note Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).
00308  */
00309 void
00310 pbuf_realloc(struct pbuf *p, u16_t new_len)
00311 {
00312   struct pbuf *q;
00313   u16_t rem_len; /* remaining length */
00314   s32_t grow;
00315 
00316   LWIP_ASSERT("pbuf_realloc: p != NULL", p != NULL);
00317   LWIP_ASSERT("pbuf_realloc: sane p->type", p->type == PBUF_POOL ||
00318               p->type == PBUF_ROM ||
00319               p->type == PBUF_RAM ||
00320               p->type == PBUF_REF);
00321 
00322   /* desired length larger than current length? */
00323   if (new_len >= p->tot_len) {
00324     /* enlarging not yet supported */
00325     return;
00326   }
00327 
00328   /* the pbuf chain grows by (new_len - p->tot_len) bytes
00329    * (which may be negative in case of shrinking) */
00330   grow = new_len - p->tot_len;
00331 
00332   /* first, step over any pbufs that should remain in the chain */
00333   rem_len = new_len;
00334   q = p;
00335   /* should this pbuf be kept? */
00336   while (rem_len > q->len) {
00337     /* decrease remaining length by pbuf length */
00338     rem_len -= q->len;
00339     /* decrease total length indicator */
00340     LWIP_ASSERT("grow < max_u16_t", grow < 0xffff);
00341     q->tot_len += (u16_t)grow;
00342     /* proceed to next pbuf in chain */
00343     q = q->next;
00344     LWIP_ASSERT("pbuf_realloc: q != NULL", q != NULL);
00345   }
00346   /* we have now reached the new last pbuf (in q) */
00347   /* rem_len == desired length for pbuf q */
00348 
00349   /* shrink allocated memory for PBUF_RAM */
00350   /* (other types merely adjust their length fields */
00351   if ((q->type == PBUF_RAM) && (rem_len != q->len)) {
00352     /* reallocate and adjust the length of the pbuf that will be split */
00353     q = (struct pbuf *)mem_realloc(q, (u8_t *)q->payload - (u8_t *)q + rem_len);
00354     LWIP_ASSERT("mem_realloc give q == NULL", q != NULL);
00355   }
00356   /* adjust length fields for new last pbuf */
00357   q->len = rem_len;
00358   q->tot_len = q->len;
00359 
00360   /* any remaining pbufs in chain? */
00361   if (q->next != NULL) {
00362     /* free remaining pbufs in chain */
00363     pbuf_free(q->next);
00364   }
00365   /* q is last packet in chain */
00366   q->next = NULL;
00367 
00368 }
00369 
00370 /**
00371  * Adjusts the payload pointer to hide or reveal headers in the payload.
00372  *
00373  * Adjusts the ->payload pointer so that space for a header
00374  * (dis)appears in the pbuf payload.
00375  *
00376  * The ->payload, ->tot_len and ->len fields are adjusted.
00377  *
00378  * @param p pbuf to change the header size.
00379  * @param header_size_increment Number of bytes to increment header size which
00380  * increases the size of the pbuf. New space is on the front.
00381  * (Using a negative value decreases the header size.)
00382  * If hdr_size_inc is 0, this function does nothing and returns succesful.
00383  *
00384  * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
00385  * the call will fail. A check is made that the increase in header size does
00386  * not move the payload pointer in front of the start of the buffer.
00387  * @return non-zero on failure, zero on success.
00388  *
00389  */
00390 u8_t
00391 pbuf_header(struct pbuf *p, s16_t header_size_increment)
00392 {
00393   u16_t type;
00394   void *payload;
00395   u16_t increment_magnitude;
00396 
00397   LWIP_ASSERT("p != NULL", p != NULL);
00398   if ((header_size_increment == 0) || (p == NULL))
00399     return 0;
00400  
00401   if (header_size_increment < 0){
00402     increment_magnitude = -header_size_increment;
00403     /* Check that we aren't going to move off the end of the pbuf */
00404     LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);
00405   } else {
00406     increment_magnitude = header_size_increment;
00407 #if 0
00408     /* Can't assert these as some callers speculatively call
00409          pbuf_header() to see if it's OK.  Will return 1 below instead. */
00410     /* Check that we've got the correct type of pbuf to work with */
00411     LWIP_ASSERT("p->type == PBUF_RAM || p->type == PBUF_POOL", 
00412                 p->type == PBUF_RAM || p->type == PBUF_POOL);
00413     /* Check that we aren't going to move off the beginning of the pbuf */
00414     LWIP_ASSERT("p->payload - increment_magnitude >= p + SIZEOF_STRUCT_PBUF",
00415                 (u8_t *)p->payload - increment_magnitude >= (u8_t *)p + SIZEOF_STRUCT_PBUF);
00416 #endif
00417   }
00418 
00419   type = p->type;
00420   /* remember current payload pointer */
00421   payload = p->payload;
00422 
00423   /* pbuf types containing payloads? */
00424   if (type == PBUF_RAM || type == PBUF_POOL) {
00425     /* set new payload pointer */
00426     p->payload = (u8_t *)p->payload - header_size_increment;
00427     /* boundary check fails? */
00428     if ((u8_t *)p->payload < (u8_t *)p + SIZEOF_STRUCT_PBUF) {
00429       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
00430         (void *)p->payload,
00431         (void *)(p + 1)));\
00432       /* restore old payload pointer */
00433       p->payload = payload;
00434       /* bail out unsuccesfully */
00435       return 1;
00436     }
00437   /* pbuf types refering to external payloads? */
00438   } else if (type == PBUF_REF || type == PBUF_ROM) {
00439     /* hide a header in the payload? */
00440     if ((header_size_increment < 0) && (increment_magnitude <= p->len)) {
00441       /* increase payload pointer */
00442       p->payload = (u8_t *)p->payload - header_size_increment;
00443     } else {
00444       /* cannot expand payload to front (yet!)
00445        * bail out unsuccesfully */
00446       return 1;
00447     }
00448   }
00449   else {
00450     /* Unknown type */
00451     LWIP_ASSERT("bad pbuf type", 0);
00452     return 1;
00453   }
00454   /* modify pbuf length fields */
00455   p->len += header_size_increment;
00456   p->tot_len += header_size_increment;
00457 
00458   LWIP_DEBUGF(PBUF_DEBUG, ("pbuf_header: old %p new %p (%"S16_F")\n",
00459     (void *)payload, (void *)p->payload, header_size_increment));
00460 
00461   return 0;
00462 }
00463 
00464 /**
00465  * Dereference a pbuf chain or queue and deallocate any no-longer-used
00466  * pbufs at the head of this chain or queue.
00467  *
00468  * Decrements the pbuf reference count. If it reaches zero, the pbuf is
00469  * deallocated.
00470  *
00471  * For a pbuf chain, this is repeated for each pbuf in the chain,
00472  * up to the first pbuf which has a non-zero reference count after
00473  * decrementing. So, when all reference counts are one, the whole
00474  * chain is free'd.
00475  *
00476  * @param p The pbuf (chain) to be dereferenced.
00477  *
00478  * @return the number of pbufs that were de-allocated
00479  * from the head of the chain.
00480  *
00481  * @note MUST NOT be called on a packet queue (Not verified to work yet).
00482  * @note the reference counter of a pbuf equals the number of pointers
00483  * that refer to the pbuf (or into the pbuf).
00484  *
00485  * @internal examples:
00486  *
00487  * Assuming existing chains a->b->c with the following reference
00488  * counts, calling pbuf_free(a) results in:
00489  * 
00490  * 1->2->3 becomes ...1->3
00491  * 3->3->3 becomes 2->3->3
00492  * 1->1->2 becomes ......1
00493  * 2->1->1 becomes 1->1->1
00494  * 1->1->1 becomes .......
00495  *
00496  */
00497 u8_t
00498 pbuf_free(struct pbuf *p)
00499 {
00500   u16_t type;
00501   struct pbuf *q;
00502   u8_t count;
00503 
00504   if (p == NULL) {
00505     LWIP_ASSERT("p != NULL", p != NULL);
00506     /* if assertions are disabled, proceed with debug output */
00507     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n"));
00508     return 0;
00509   }
00510   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_free(%p)\n", (void *)p));
00511 
00512   PERF_START;
00513 
00514   LWIP_ASSERT("pbuf_free: sane type",
00515     p->type == PBUF_RAM || p->type == PBUF_ROM ||
00516     p->type == PBUF_REF || p->type == PBUF_POOL);
00517 
00518   count = 0;
00519   /* de-allocate all consecutive pbufs from the head of the chain that
00520    * obtain a zero reference count after decrementing*/
00521   while (p != NULL) {
00522     u16_t ref;
00523     SYS_ARCH_DECL_PROTECT(old_level);
00524     /* Since decrementing ref cannot be guaranteed to be a single machine operation
00525      * we must protect it. We put the new ref into a local variable to prevent
00526      * further protection. */
00527     SYS_ARCH_PROTECT(old_level);
00528     /* all pbufs in a chain are referenced at least once */
00529     LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
00530     /* decrease reference count (number of pointers to pbuf) */
00531     ref = --(p->ref);
00532     SYS_ARCH_UNPROTECT(old_level);
00533     /* this pbuf is no longer referenced to? */
00534     if (ref == 0) {
00535       /* remember next pbuf in chain for next iteration */
00536       q = p->next;
00537       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: deallocating %p\n", (void *)p));
00538       type = p->type;
00539       /* is this a pbuf from the pool? */
00540       if (type == PBUF_POOL) {
00541         memp_free(MEMP_PBUF_POOL, p);
00542       /* is this a ROM or RAM referencing pbuf? */
00543       } else if (type == PBUF_ROM || type == PBUF_REF) {
00544         memp_free(MEMP_PBUF, p);
00545       /* type == PBUF_RAM */
00546       } else {
00547         mem_free(p);
00548       }
00549       count++;
00550       /* proceed to next pbuf */
00551       p = q;
00552     /* p->ref > 0, this pbuf is still referenced to */
00553     /* (and so the remaining pbufs in chain as well) */
00554     } else {
00555       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, ref));
00556       /* stop walking through the chain */
00557       p = NULL;
00558     }
00559   }
00560   PERF_STOP("pbuf_free");
00561   /* return number of de-allocated pbufs */
00562   return count;
00563 }
00564 
00565 /**
00566  * Count number of pbufs in a chain
00567  *
00568  * @param p first pbuf of chain
00569  * @return the number of pbufs in a chain
00570  */
00571 
00572 u8_t
00573 pbuf_clen(struct pbuf *p)
00574 {
00575   u8_t len;
00576 
00577   len = 0;
00578   while (p != NULL) {
00579     ++len;
00580     p = p->next;
00581   }
00582   return len;
00583 }
00584 
00585 /**
00586  * Increment the reference count of the pbuf.
00587  *
00588  * @param p pbuf to increase reference counter of
00589  *
00590  */
00591 void
00592 pbuf_ref(struct pbuf *p)
00593 {
00594   SYS_ARCH_DECL_PROTECT(old_level);
00595   /* pbuf given? */
00596   if (p != NULL) {
00597     SYS_ARCH_PROTECT(old_level);
00598     ++(p->ref);
00599     SYS_ARCH_UNPROTECT(old_level);
00600   }
00601 }
00602 
00603 /**
00604  * Concatenate two pbufs (each may be a pbuf chain) and take over
00605  * the caller's reference of the tail pbuf.
00606  * 
00607  * @note The caller MAY NOT reference the tail pbuf afterwards.
00608  * Use pbuf_chain() for that purpose.
00609  * 
00610  * @see pbuf_chain()
00611  */
00612 
00613 void
00614 pbuf_cat(struct pbuf *h, struct pbuf *t)
00615 {
00616   struct pbuf *p;
00617 
00618   LWIP_ERROR("(h != NULL) && (t != NULL) (programmer violates API)",
00619              ((h != NULL) && (t != NULL)), return;);
00620 
00621   /* proceed to last pbuf of chain */
00622   for (p = h; p->next != NULL; p = p->next) {
00623     /* add total length of second chain to all totals of first chain */
00624     p->tot_len += t->tot_len;
00625   }
00626   /* { p is last pbuf of first h chain, p->next == NULL } */
00627   LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
00628   LWIP_ASSERT("p->next == NULL", p->next == NULL);
00629   /* add total length of second chain to last pbuf total of first chain */
00630   p->tot_len += t->tot_len;
00631   /* chain last pbuf of head (p) with first of tail (t) */
00632   p->next = t;
00633   /* p->next now references t, but the caller will drop its reference to t,
00634    * so netto there is no change to the reference count of t.
00635    */
00636 }
00637 
00638 /**
00639  * Chain two pbufs (or pbuf chains) together.
00640  * 
00641  * The caller MUST call pbuf_free(t) once it has stopped
00642  * using it. Use pbuf_cat() instead if you no longer use t.
00643  * 
00644  * @param h head pbuf (chain)
00645  * @param t tail pbuf (chain)
00646  * @note The pbufs MUST belong to the same packet.
00647  * @note MAY NOT be called on a packet queue.
00648  *
00649  * The ->tot_len fields of all pbufs of the head chain are adjusted.
00650  * The ->next field of the last pbuf of the head chain is adjusted.
00651  * The ->ref field of the first pbuf of the tail chain is adjusted.
00652  *
00653  */
00654 void
00655 pbuf_chain(struct pbuf *h, struct pbuf *t)
00656 {
00657   pbuf_cat(h, t);
00658   /* t is now referenced by h */
00659   pbuf_ref(t);
00660   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
00661 }
00662 
00663 /**
00664  * Dechains the first pbuf from its succeeding pbufs in the chain.
00665  *
00666  * Makes p->tot_len field equal to p->len.
00667  * @param p pbuf to dechain
00668  * @return remainder of the pbuf chain, or NULL if it was de-allocated.
00669  * @note May not be called on a packet queue.
00670  */
00671 struct pbuf *
00672 pbuf_dechain(struct pbuf *p)
00673 {
00674   struct pbuf *q;
00675   u8_t tail_gone = 1;
00676   /* tail */
00677   q = p->next;
00678   /* pbuf has successor in chain? */
00679   if (q != NULL) {
00680     /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00681     LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
00682     /* enforce invariant if assertion is disabled */
00683     q->tot_len = p->tot_len - p->len;
00684     /* decouple pbuf from remainder */
00685     p->next = NULL;
00686     /* total length of pbuf p is its own length only */
00687     p->tot_len = p->len;
00688     /* q is no longer referenced by p, free it */
00689     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
00690     tail_gone = pbuf_free(q);
00691     if (tail_gone > 0) {
00692       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_STATE,
00693                   ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
00694     }
00695     /* return remaining tail or NULL if deallocated */
00696   }
00697   /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00698   LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
00699   return ((tail_gone > 0) ? NULL : q);
00700 }
00701 
00702 /**
00703  *
00704  * Create PBUF_RAM copies of pbufs.
00705  *
00706  * Used to queue packets on behalf of the lwIP stack, such as
00707  * ARP based queueing.
00708  *
00709  * @note You MUST explicitly use p = pbuf_take(p);
00710  *
00711  * @note Only one packet is copied, no packet queue!
00712  *
00713  * @param p_to pbuf destination of the copy
00714  * @param p_from pbuf source of the copy
00715  *
00716  * @return ERR_OK if pbuf was copied
00717  *         ERR_ARG if one of the pbufs is NULL or p_to is not big
00718  *                 enough to hold p_from
00719  */
00720 err_t
00721 pbuf_copy(struct pbuf *p_to, struct pbuf *p_from)
00722 {
00723   u16_t offset_to=0, offset_from=0, len;
00724 
00725   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_copy(%p, %p)\n",
00726     (void*)p_to, (void*)p_from));
00727 
00728   /* is the target big enough to hold the source? */
00729   LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
00730              (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);
00731 
00732   /* iterate through pbuf chain */
00733   do
00734   {
00735     LWIP_ASSERT("p_to != NULL", p_to != NULL);
00736     /* copy one part of the original chain */
00737     if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
00738       /* complete current p_from fits into current p_to */
00739       len = p_from->len - offset_from;
00740     } else {
00741       /* current p_from does not fit into current p_to */
00742       len = p_to->len - offset_to;
00743     }
00744     MEMCPY((u8_t*)p_to->payload + offset_to, (u8_t*)p_from->payload + offset_from, len);
00745     offset_to += len;
00746     offset_from += len;
00747     LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
00748     if (offset_to == p_to->len) {
00749       /* on to next p_to (if any) */
00750       offset_to = 0;
00751       p_to = p_to->next;
00752     }
00753     LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
00754     if (offset_from >= p_from->len) {
00755       /* on to next p_from (if any) */
00756       offset_from = 0;
00757       p_from = p_from->next;
00758     }
00759 
00760     if((p_from != NULL) && (p_from->len == p_from->tot_len)) {
00761       /* don't copy more than one packet! */
00762       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00763                  (p_from->next == NULL), return ERR_VAL;);
00764     }
00765     if((p_to != NULL) && (p_to->len == p_to->tot_len)) {
00766       /* don't copy more than one packet! */
00767       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00768                   (p_to->next == NULL), return ERR_VAL;);
00769     }
00770   } while (p_from);
00771   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 1, ("pbuf_copy: end of chain reached.\n"));
00772   return ERR_OK;
00773 }
00774 
00775 /**
00776  * Copy (part of) the contents of a packet buffer
00777  * to an application supplied buffer.
00778  *
00779  * @param buf the pbuf from which to copy data
00780  * @param dataptr the application supplied buffer
00781  * @param len length of data to copy (dataptr must be big enough). No more 
00782  * than buf->tot_len will be copied, irrespective of len
00783  * @param offset offset into the packet buffer from where to begin copying len bytes
00784  * @return the number of bytes copied, or 0 on failure
00785  */
00786 u16_t
00787 pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
00788 {
00789   struct pbuf *p;
00790   u16_t left;
00791   u16_t buf_copy_len;
00792   u16_t copied_total = 0;
00793 
00794   LWIP_ERROR("pbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
00795   LWIP_ERROR("pbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
00796 
00797   left = 0;
00798 
00799   if((buf == NULL) || (dataptr == NULL)) {
00800     return 0;
00801   }
00802 
00803   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00804   for(p = buf; len != 0 && p != NULL; p = p->next) {
00805     if ((offset != 0) && (offset >= p->len)) {
00806       /* don't copy from this buffer -> on to the next */
00807       offset -= p->len;
00808     } else {
00809       /* copy from this buffer. maybe only partially. */
00810       buf_copy_len = p->len - offset;
00811       if (buf_copy_len > len)
00812           buf_copy_len = len;
00813       /* copy the necessary parts of the buffer */
00814       MEMCPY(&((char*)dataptr)[left], &((char*)p->payload)[offset], buf_copy_len);
00815       copied_total += buf_copy_len;
00816       left += buf_copy_len;
00817       len -= buf_copy_len;
00818       offset = 0;
00819     }
00820   }
00821   return copied_total;
00822 }
00823 
00824 /**
00825  * Copy application supplied data into a pbuf.
00826  * This function can only be used to copy the equivalent of buf->tot_len data.
00827  *
00828  * @param buf pbuf to fill with data
00829  * @param dataptr application supplied data buffer
00830  * @param len length of the application supplied data buffer
00831  *
00832  * @return ERR_OK if successful, ERR_MEM if the pbuf is not big enough
00833  */
00834 err_t
00835 pbuf_take(struct pbuf *buf, const void *dataptr, u16_t len)
00836 {
00837   struct pbuf *p;
00838   u16_t buf_copy_len;
00839   u16_t total_copy_len = len;
00840   u16_t copied_total = 0;
00841 
00842   LWIP_ERROR("pbuf_take: invalid buf", (buf != NULL), return 0;);
00843   LWIP_ERROR("pbuf_take: invalid dataptr", (dataptr != NULL), return 0;);
00844 
00845   if ((buf == NULL) || (dataptr == NULL) || (buf->tot_len < len)) {
00846     return ERR_ARG;
00847   }
00848 
00849   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00850   for(p = buf; total_copy_len != 0; p = p->next) {
00851     LWIP_ASSERT("pbuf_take: invalid pbuf", p != NULL);
00852     buf_copy_len = total_copy_len;
00853     if (buf_copy_len > p->len) {
00854       /* this pbuf cannot hold all remaining data */
00855       buf_copy_len = p->len;
00856     }
00857     /* copy the necessary parts of the buffer */
00858     MEMCPY(p->payload, &((char*)dataptr)[copied_total], buf_copy_len);
00859     total_copy_len -= buf_copy_len;
00860     copied_total += buf_copy_len;
00861   }
00862   LWIP_ASSERT("did not copy all data", total_copy_len == 0 && copied_total == len);
00863   return ERR_OK;
00864 }
00865 
00866 /**
00867  * Creates a single pbuf out of a queue of pbufs.
00868  *
00869  * @remark: The source pbuf 'p' is not freed by this function because that can
00870  *          be illegal in some places!
00871  *
00872  * @param p the source pbuf
00873  * @param layer pbuf_layer of the new pbuf
00874  *
00875  * @return a new, single pbuf (p->next is NULL)
00876  *         or the old pbuf if allocation fails
00877  */
00878 struct pbuf*
00879 pbuf_coalesce(struct pbuf *p, pbuf_layer layer)
00880 {
00881   struct pbuf *q;
00882   err_t err;
00883   if (p->next == NULL) {
00884     return p;
00885   }
00886   q = pbuf_alloc(layer, p->tot_len, PBUF_RAM);
00887   if (q == NULL) {
00888     /* @todo: what do we do now? */
00889     return p;
00890   }
00891   err = pbuf_copy(q, p);
00892   LWIP_ASSERT("pbuf_copy failed", err == ERR_OK);
00893   pbuf_free(p);
00894   return q;
00895 }