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 
00074 #include <string.h>
00075 
00076 #define SIZEOF_STRUCT_PBUF        LWIP_MEM_ALIGN_SIZE(sizeof(struct pbuf))
00077 /* Since the pool is created in memp, PBUF_POOL_BUFSIZE will be automatically
00078    aligned there. Therefore, PBUF_POOL_BUFSIZE_ALIGNED can be used here. */
00079 #define PBUF_POOL_BUFSIZE_ALIGNED LWIP_MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE)
00080 
00081 /**
00082  * Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type).
00083  *
00084  * The actual memory allocated for the pbuf is determined by the
00085  * layer at which the pbuf is allocated and the requested size
00086  * (from the size parameter).
00087  *
00088  * @param layer flag to define header size
00089  * @param length size of the pbuf's payload
00090  * @param type this parameter decides how and where the pbuf
00091  * should be allocated as follows:
00092  *
00093  * - PBUF_RAM: buffer memory for pbuf is allocated as one large
00094  *             chunk. This includes protocol headers as well.
00095  * - PBUF_ROM: no buffer memory is allocated for the pbuf, even for
00096  *             protocol headers. Additional headers must be prepended
00097  *             by allocating another pbuf and chain in to the front of
00098  *             the ROM pbuf. It is assumed that the memory used is really
00099  *             similar to ROM in that it is immutable and will not be
00100  *             changed. Memory which is dynamic should generally not
00101  *             be attached to PBUF_ROM pbufs. Use PBUF_REF instead.
00102  * - PBUF_REF: no buffer memory is allocated for the pbuf, even for
00103  *             protocol headers. It is assumed that the pbuf is only
00104  *             being used in a single thread. If the pbuf gets queued,
00105  *             then pbuf_take should be called to copy the buffer.
00106  * - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from
00107  *              the pbuf pool that is allocated during pbuf_init().
00108  *
00109  * @return the allocated pbuf. If multiple pbufs where allocated, this
00110  * is the first pbuf of a pbuf chain.
00111  */
00112 struct pbuf *
00113 pbuf_alloc(pbuf_layer layer, u16_t length, pbuf_type type)
00114 {
00115   struct pbuf *p, *q, *r;
00116   u16_t offset;
00117   s32_t rem_len; /* remaining length */
00118   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F")\n", length));
00119 
00120   /* determine header offset */
00121   offset = 0;
00122   switch (layer) {
00123   case PBUF_TRANSPORT:
00124     /* add room for transport (often TCP) layer header */
00125     offset += PBUF_TRANSPORT_HLEN;
00126     /* FALLTHROUGH */
00127   case PBUF_IP:
00128     /* add room for IP layer header */
00129     offset += PBUF_IP_HLEN;
00130     /* FALLTHROUGH */
00131   case PBUF_LINK:
00132     /* add room for link layer header */
00133     offset += PBUF_LINK_HLEN;
00134     break;
00135   case PBUF_RAW:
00136     break;
00137   default:
00138     LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0);
00139     return NULL;
00140   }
00141 
00142   switch (type) {
00143   case PBUF_POOL:
00144     /* allocate head of pbuf chain into p */
00145       p = (struct pbuf *)(memp_malloc(MEMP_PBUF_POOL)); // static_cast<struct pbuf *>(memp_malloc(MEMP_PBUF_POOL));
00146     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_alloc: allocated pbuf %p\n", (void *)p));
00147     if (p == NULL) {
00148       return NULL;
00149     }
00150     p->type = type;
00151     p->next = NULL;
00152 
00153     /* make the payload pointer point 'offset' bytes into pbuf data memory */
00154     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + (SIZEOF_STRUCT_PBUF + offset)));
00155     LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned",
00156             ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00157     /* the total length of the pbuf chain is the requested size */
00158     p->tot_len = length;
00159     /* set the length of the first pbuf in the chain */
00160     p->len = LWIP_MIN(length, PBUF_POOL_BUFSIZE_ALIGNED - LWIP_MEM_ALIGN_SIZE(offset));
00161     LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00162                 ((u8_t*)p->payload + p->len <=
00163                  (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00164     /* set reference count (needed here in case we fail) */
00165     p->ref = 1;
00166 
00167     /* now allocate the tail of the pbuf chain */
00168 
00169     /* remember first pbuf for linkage in next iteration */
00170     r = p;
00171     /* remaining length to be allocated */
00172     rem_len = length - p->len;
00173     /* any remaining pbufs to be allocated? */
00174     while (rem_len > 0) {
00175       q = (struct pbuf *)(memp_malloc(MEMP_PBUF_POOL)); // static_cast<struct pbuf *>(x)
00176       if (q == NULL) {
00177         /* free chain so far allocated */
00178         pbuf_free(p);
00179         /* bail out unsuccesfully */
00180         return NULL;
00181       }
00182       q->type = type;
00183       q->flags = 0;
00184       q->next = NULL;
00185       /* make previous pbuf point to this pbuf */
00186       r->next = q;
00187       /* set total length of this pbuf and next in chain */
00188       LWIP_ASSERT("rem_len < max_u16_t", rem_len < 0xffff);
00189       q->tot_len = (u16_t)rem_len;
00190       /* this pbuf length is pool size, unless smaller sized tail */
00191       q->len = LWIP_MIN((u16_t)rem_len, PBUF_POOL_BUFSIZE_ALIGNED);
00192       q->payload = (void *)((u8_t *)q + SIZEOF_STRUCT_PBUF);
00193       LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned",
00194               ((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0);
00195       LWIP_ASSERT("check p->payload + p->len does not overflow pbuf",
00196                   ((u8_t*)p->payload + p->len <=
00197                    (u8_t*)p + SIZEOF_STRUCT_PBUF + PBUF_POOL_BUFSIZE_ALIGNED));
00198       q->ref = 1;
00199       /* calculate remaining length to be allocated */
00200       rem_len -= q->len;
00201       /* remember this pbuf for linkage in next iteration */
00202       r = q;
00203     }
00204     /* end of chain */
00205     /*r->next = NULL;*/
00206 
00207     break;
00208   case PBUF_RAM:
00209     /* If pbuf is to be allocated in RAM, allocate memory for it. */
00210     p = (struct pbuf*)mem_malloc(LWIP_MEM_ALIGN_SIZE(SIZEOF_STRUCT_PBUF + offset) + LWIP_MEM_ALIGN_SIZE(length));
00211     if (p == NULL) {
00212       return NULL;
00213     }
00214     /* Set up internal structure of the pbuf. */
00215     p->payload = LWIP_MEM_ALIGN((void *)((u8_t *)p + SIZEOF_STRUCT_PBUF + offset));
00216     p->len = p->tot_len = length;
00217     p->next = NULL;
00218     p->type = type;
00219 
00220     LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned",
00221            ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0);
00222     break;
00223   /* pbuf references existing (non-volatile static constant) ROM payload? */
00224   case PBUF_ROM:
00225   /* pbuf references existing (externally allocated) RAM payload? */
00226   case PBUF_REF:
00227     /* only allocate memory for the pbuf structure */
00228     p = static_cast<struct pbuf *>(memp_malloc(MEMP_PBUF));
00229     if (p == NULL) {
00230       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n",
00231                   (type == PBUF_ROM) ? "ROM" : "REF"));
00232       return NULL;
00233     }
00234     /* caller must set this field properly, afterwards */
00235     p->payload = NULL;
00236     p->len = p->tot_len = length;
00237     p->next = NULL;
00238     p->type = type;
00239     break;
00240   default:
00241     LWIP_ASSERT("pbuf_alloc: erroneous type", 0);
00242     return NULL;
00243   }
00244   /* set reference count */
00245   p->ref = 1;
00246   /* set flags */
00247   p->flags = 0;
00248   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p));
00249   return p;
00250 }
00251 
00252 
00253 /**
00254  * Shrink a pbuf chain to a desired length.
00255  *
00256  * @param p pbuf to shrink.
00257  * @param new_len desired new length of pbuf chain
00258  *
00259  * Depending on the desired length, the first few pbufs in a chain might
00260  * be skipped and left unchanged. The new last pbuf in the chain will be
00261  * resized, and any remaining pbufs will be freed.
00262  *
00263  * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted.
00264  * @note May not be called on a packet queue.
00265  *
00266  * @note Despite its name, pbuf_realloc cannot grow the size of a pbuf (chain).
00267  */
00268 void
00269 pbuf_realloc(struct pbuf *p, u16_t new_len)
00270 {
00271   struct pbuf *q;
00272   u16_t rem_len; /* remaining length */
00273   s32_t grow;
00274 
00275   LWIP_ASSERT("pbuf_realloc: sane p->type", p->type == PBUF_POOL ||
00276               p->type == PBUF_ROM ||
00277               p->type == PBUF_RAM ||
00278               p->type == PBUF_REF);
00279 
00280   /* desired length larger than current length? */
00281   if (new_len >= p->tot_len) {
00282     /* enlarging not yet supported */
00283     return;
00284   }
00285 
00286   /* the pbuf chain grows by (new_len - p->tot_len) bytes
00287    * (which may be negative in case of shrinking) */
00288   grow = new_len - p->tot_len;
00289 
00290   /* first, step over any pbufs that should remain in the chain */
00291   rem_len = new_len;
00292   q = p;
00293   /* should this pbuf be kept? */
00294   while (rem_len > q->len) {
00295     /* decrease remaining length by pbuf length */
00296     rem_len -= q->len;
00297     /* decrease total length indicator */
00298     LWIP_ASSERT("grow < max_u16_t", grow < 0xffff);
00299     q->tot_len += (u16_t)grow;
00300     /* proceed to next pbuf in chain */
00301     q = q->next;
00302   }
00303   /* we have now reached the new last pbuf (in q) */
00304   /* rem_len == desired length for pbuf q */
00305 
00306   /* shrink allocated memory for PBUF_RAM */
00307   /* (other types merely adjust their length fields */
00308   if ((q->type == PBUF_RAM) && (rem_len != q->len)) {
00309     /* reallocate and adjust the length of the pbuf that will be split */
00310     q = static_cast<struct pbuf *>(mem_realloc(q, (u8_t *)q->payload - (u8_t *)q + rem_len));
00311     LWIP_ASSERT("mem_realloc give q == NULL", q != NULL);
00312   }
00313   /* adjust length fields for new last pbuf */
00314   q->len = rem_len;
00315   q->tot_len = q->len;
00316 
00317   /* any remaining pbufs in chain? */
00318   if (q->next != NULL) {
00319     /* free remaining pbufs in chain */
00320     pbuf_free(q->next);
00321   }
00322   /* q is last packet in chain */
00323   q->next = NULL;
00324 
00325 }
00326 
00327 /**
00328  * Adjusts the payload pointer to hide or reveal headers in the payload.
00329  *
00330  * Adjusts the ->payload pointer so that space for a header
00331  * (dis)appears in the pbuf payload.
00332  *
00333  * The ->payload, ->tot_len and ->len fields are adjusted.
00334  *
00335  * @param p pbuf to change the header size.
00336  * @param header_size_increment Number of bytes to increment header size which
00337  * increases the size of the pbuf. New space is on the front.
00338  * (Using a negative value decreases the header size.)
00339  * If hdr_size_inc is 0, this function does nothing and returns succesful.
00340  *
00341  * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so
00342  * the call will fail. A check is made that the increase in header size does
00343  * not move the payload pointer in front of the start of the buffer.
00344  * @return non-zero on failure, zero on success.
00345  *
00346  */
00347 u8_t
00348 pbuf_header(struct pbuf *p, s16_t header_size_increment)
00349 {
00350   u16_t type;
00351   void *payload;
00352   u16_t increment_magnitude;
00353 
00354   LWIP_ASSERT("p != NULL", p != NULL);
00355   if ((header_size_increment == 0) || (p == NULL))
00356     return 0;
00357  
00358   if (header_size_increment < 0){
00359     increment_magnitude = -header_size_increment;
00360     /* Check that we aren't going to move off the end of the pbuf */
00361     LWIP_ERROR("increment_magnitude <= p->len", (increment_magnitude <= p->len), return 1;);
00362   } else {
00363     increment_magnitude = header_size_increment;
00364 #if 0
00365     /* Can't assert these as some callers speculatively call
00366          pbuf_header() to see if it's OK.  Will return 1 below instead. */
00367     /* Check that we've got the correct type of pbuf to work with */
00368     LWIP_ASSERT("p->type == PBUF_RAM || p->type == PBUF_POOL", 
00369                 p->type == PBUF_RAM || p->type == PBUF_POOL);
00370     /* Check that we aren't going to move off the beginning of the pbuf */
00371     LWIP_ASSERT("p->payload - increment_magnitude >= p + SIZEOF_STRUCT_PBUF",
00372                 (u8_t *)p->payload - increment_magnitude >= (u8_t *)p + SIZEOF_STRUCT_PBUF);
00373 #endif
00374   }
00375 
00376   type = p->type;
00377   /* remember current payload pointer */
00378   payload = p->payload;
00379 
00380   /* pbuf types containing payloads? */
00381   if (type == PBUF_RAM || type == PBUF_POOL) {
00382     /* set new payload pointer */
00383     p->payload = (u8_t *)p->payload - header_size_increment;
00384     /* boundary check fails? */
00385     if ((u8_t *)p->payload < (u8_t *)p + SIZEOF_STRUCT_PBUF) {
00386       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n",
00387         (void *)p->payload,
00388         (void *)(p + 1)));\
00389       /* restore old payload pointer */
00390       p->payload = payload;
00391       /* bail out unsuccesfully */
00392       return 1;
00393     }
00394   /* pbuf types refering to external payloads? */
00395   } else if (type == PBUF_REF || type == PBUF_ROM) {
00396     /* hide a header in the payload? */
00397     if ((header_size_increment < 0) && (increment_magnitude <= p->len)) {
00398       /* increase payload pointer */
00399       p->payload = (u8_t *)p->payload - header_size_increment;
00400     } else {
00401       /* cannot expand payload to front (yet!)
00402        * bail out unsuccesfully */
00403       return 1;
00404     }
00405   }
00406   else {
00407     /* Unknown type */
00408     LWIP_ASSERT("bad pbuf type", 0);
00409     return 1;
00410   }
00411   /* modify pbuf length fields */
00412   p->len += header_size_increment;
00413   p->tot_len += header_size_increment;
00414 
00415   LWIP_DEBUGF(PBUF_DEBUG, ("pbuf_header: old %p new %p (%"S16_F")\n",
00416     (void *)payload, (void *)p->payload, header_size_increment));
00417 
00418   return 0;
00419 }
00420 
00421 /**
00422  * Dereference a pbuf chain or queue and deallocate any no-longer-used
00423  * pbufs at the head of this chain or queue.
00424  *
00425  * Decrements the pbuf reference count. If it reaches zero, the pbuf is
00426  * deallocated.
00427  *
00428  * For a pbuf chain, this is repeated for each pbuf in the chain,
00429  * up to the first pbuf which has a non-zero reference count after
00430  * decrementing. So, when all reference counts are one, the whole
00431  * chain is free'd.
00432  *
00433  * @param p The pbuf (chain) to be dereferenced.
00434  *
00435  * @return the number of pbufs that were de-allocated
00436  * from the head of the chain.
00437  *
00438  * @note MUST NOT be called on a packet queue (Not verified to work yet).
00439  * @note the reference counter of a pbuf equals the number of pointers
00440  * that refer to the pbuf (or into the pbuf).
00441  *
00442  * @internal examples:
00443  *
00444  * Assuming existing chains a->b->c with the following reference
00445  * counts, calling pbuf_free(a) results in:
00446  * 
00447  * 1->2->3 becomes ...1->3
00448  * 3->3->3 becomes 2->3->3
00449  * 1->1->2 becomes ......1
00450  * 2->1->1 becomes 1->1->1
00451  * 1->1->1 becomes .......
00452  *
00453  */
00454 u8_t
00455 pbuf_free(struct pbuf *p)
00456 {
00457   u16_t type;
00458   struct pbuf *q;
00459   u8_t count;
00460 
00461   if (p == NULL) {
00462     LWIP_ASSERT("p != NULL", p != NULL);
00463     /* if assertions are disabled, proceed with debug output */
00464     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n"));
00465     return 0;
00466   }
00467   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_free(%p)\n", (void *)p));
00468 
00469   PERF_START;
00470 
00471   LWIP_ASSERT("pbuf_free: sane type",
00472     p->type == PBUF_RAM || p->type == PBUF_ROM ||
00473     p->type == PBUF_REF || p->type == PBUF_POOL);
00474 
00475   count = 0;
00476   /* de-allocate all consecutive pbufs from the head of the chain that
00477    * obtain a zero reference count after decrementing*/
00478   while (p != NULL) {
00479     u16_t ref;
00480     SYS_ARCH_DECL_PROTECT(old_level);
00481     /* Since decrementing ref cannot be guaranteed to be a single machine operation
00482      * we must protect it. We put the new ref into a local variable to prevent
00483      * further protection. */
00484     SYS_ARCH_PROTECT(old_level);
00485     /* all pbufs in a chain are referenced at least once */
00486     LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
00487     /* decrease reference count (number of pointers to pbuf) */
00488     ref = --(p->ref);
00489     SYS_ARCH_UNPROTECT(old_level);
00490     /* this pbuf is no longer referenced to? */
00491     if (ref == 0) {
00492       /* remember next pbuf in chain for next iteration */
00493       q = p->next;
00494       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: deallocating %p\n", (void *)p));
00495       type = p->type;
00496       /* is this a pbuf from the pool? */
00497       if (type == PBUF_POOL) {
00498         memp_free(MEMP_PBUF_POOL, p);
00499       /* is this a ROM or RAM referencing pbuf? */
00500       } else if (type == PBUF_ROM || type == PBUF_REF) {
00501         memp_free(MEMP_PBUF, p);
00502       /* type == PBUF_RAM */
00503       } else {
00504         mem_free(p);
00505       }
00506       count++;
00507       /* proceed to next pbuf */
00508       p = q;
00509     /* p->ref > 0, this pbuf is still referenced to */
00510     /* (and so the remaining pbufs in chain as well) */
00511     } else {
00512       LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, ref));
00513       /* stop walking through the chain */
00514       p = NULL;
00515     }
00516   }
00517   PERF_STOP("pbuf_free");
00518   /* return number of de-allocated pbufs */
00519   return count;
00520 }
00521 
00522 /**
00523  * Count number of pbufs in a chain
00524  *
00525  * @param p first pbuf of chain
00526  * @return the number of pbufs in a chain
00527  */
00528 
00529 u8_t
00530 pbuf_clen(struct pbuf *p)
00531 {
00532   u8_t len;
00533 
00534   len = 0;
00535   while (p != NULL) {
00536     ++len;
00537     p = p->next;
00538   }
00539   return len;
00540 }
00541 
00542 /**
00543  * Increment the reference count of the pbuf.
00544  *
00545  * @param p pbuf to increase reference counter of
00546  *
00547  */
00548 void
00549 pbuf_ref(struct pbuf *p)
00550 {
00551   SYS_ARCH_DECL_PROTECT(old_level);
00552   /* pbuf given? */
00553   if (p != NULL) {
00554     SYS_ARCH_PROTECT(old_level);
00555     ++(p->ref);
00556     SYS_ARCH_UNPROTECT(old_level);
00557   }
00558 }
00559 
00560 /**
00561  * Concatenate two pbufs (each may be a pbuf chain) and take over
00562  * the caller's reference of the tail pbuf.
00563  * 
00564  * @note The caller MAY NOT reference the tail pbuf afterwards.
00565  * Use pbuf_chain() for that purpose.
00566  * 
00567  * @see pbuf_chain()
00568  */
00569 
00570 void
00571 pbuf_cat(struct pbuf *h, struct pbuf *t)
00572 {
00573   struct pbuf *p;
00574 
00575   LWIP_ERROR("(h != NULL) && (t != NULL) (programmer violates API)",
00576              ((h != NULL) && (t != NULL)), return;);
00577 
00578   /* proceed to last pbuf of chain */
00579   for (p = h; p->next != NULL; p = p->next) {
00580     /* add total length of second chain to all totals of first chain */
00581     p->tot_len += t->tot_len;
00582   }
00583   /* { p is last pbuf of first h chain, p->next == NULL } */
00584   LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len);
00585   LWIP_ASSERT("p->next == NULL", p->next == NULL);
00586   /* add total length of second chain to last pbuf total of first chain */
00587   p->tot_len += t->tot_len;
00588   /* chain last pbuf of head (p) with first of tail (t) */
00589   p->next = t;
00590   /* p->next now references t, but the caller will drop its reference to t,
00591    * so netto there is no change to the reference count of t.
00592    */
00593 }
00594 
00595 /**
00596  * Chain two pbufs (or pbuf chains) together.
00597  * 
00598  * The caller MUST call pbuf_free(t) once it has stopped
00599  * using it. Use pbuf_cat() instead if you no longer use t.
00600  * 
00601  * @param h head pbuf (chain)
00602  * @param t tail pbuf (chain)
00603  * @note The pbufs MUST belong to the same packet.
00604  * @note MAY NOT be called on a packet queue.
00605  *
00606  * The ->tot_len fields of all pbufs of the head chain are adjusted.
00607  * The ->next field of the last pbuf of the head chain is adjusted.
00608  * The ->ref field of the first pbuf of the tail chain is adjusted.
00609  *
00610  */
00611 void
00612 pbuf_chain(struct pbuf *h, struct pbuf *t)
00613 {
00614   pbuf_cat(h, t);
00615   /* t is now referenced by h */
00616   pbuf_ref(t);
00617   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t));
00618 }
00619 
00620 /**
00621  * Dechains the first pbuf from its succeeding pbufs in the chain.
00622  *
00623  * Makes p->tot_len field equal to p->len.
00624  * @param p pbuf to dechain
00625  * @return remainder of the pbuf chain, or NULL if it was de-allocated.
00626  * @note May not be called on a packet queue.
00627  */
00628 struct pbuf *
00629 pbuf_dechain(struct pbuf *p)
00630 {
00631   struct pbuf *q;
00632   u8_t tail_gone = 1;
00633   /* tail */
00634   q = p->next;
00635   /* pbuf has successor in chain? */
00636   if (q != NULL) {
00637     /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00638     LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len);
00639     /* enforce invariant if assertion is disabled */
00640     q->tot_len = p->tot_len - p->len;
00641     /* decouple pbuf from remainder */
00642     p->next = NULL;
00643     /* total length of pbuf p is its own length only */
00644     p->tot_len = p->len;
00645     /* q is no longer referenced by p, free it */
00646     LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *)q));
00647     tail_gone = pbuf_free(q);
00648     if (tail_gone > 0) {
00649       LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_STATE,
00650                   ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q));
00651     }
00652     /* return remaining tail or NULL if deallocated */
00653   }
00654   /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */
00655   LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len);
00656   return ((tail_gone > 0) ? NULL : q);
00657 }
00658 
00659 /**
00660  *
00661  * Create PBUF_RAM copies of pbufs.
00662  *
00663  * Used to queue packets on behalf of the lwIP stack, such as
00664  * ARP based queueing.
00665  *
00666  * @note You MUST explicitly use p = pbuf_take(p);
00667  *
00668  * @note Only one packet is copied, no packet queue!
00669  *
00670  * @param p_to pbuf source of the copy
00671  * @param p_from pbuf destination of the copy
00672  *
00673  * @return ERR_OK if pbuf was copied
00674  *         ERR_ARG if one of the pbufs is NULL or p_to is not big
00675  *                 enough to hold p_from
00676  */
00677 err_t
00678 pbuf_copy(struct pbuf *p_to, struct pbuf *p_from)
00679 {
00680   u16_t offset_to=0, offset_from=0, len;
00681 
00682   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 3, ("pbuf_copy(%p, %p)\n",
00683     (void*)p_to, (void*)p_from));
00684 
00685   /* is the target big enough to hold the source? */
00686   LWIP_ERROR("pbuf_copy: target not big enough to hold source", ((p_to != NULL) &&
00687              (p_from != NULL) && (p_to->tot_len >= p_from->tot_len)), return ERR_ARG;);
00688 
00689   /* iterate through pbuf chain */
00690   do
00691   {
00692     LWIP_ASSERT("p_to != NULL", p_to != NULL);
00693     /* copy one part of the original chain */
00694     if ((p_to->len - offset_to) >= (p_from->len - offset_from)) {
00695       /* complete current p_from fits into current p_to */
00696       len = p_from->len - offset_from;
00697     } else {
00698       /* current p_from does not fit into current p_to */
00699       len = p_to->len - offset_to;
00700     }
00701     MEMCPY((u8_t*)p_to->payload + offset_to, (u8_t*)p_from->payload + offset_from, len);
00702     offset_to += len;
00703     offset_from += len;
00704     LWIP_ASSERT("offset_to <= p_to->len", offset_to <= p_to->len);
00705     if (offset_to == p_to->len) {
00706       /* on to next p_to (if any) */
00707       offset_to = 0;
00708       p_to = p_to->next;
00709     }
00710     LWIP_ASSERT("offset_from <= p_from->len", offset_from <= p_from->len);
00711     if (offset_from >= p_from->len) {
00712       /* on to next p_from (if any) */
00713       offset_from = 0;
00714       p_from = p_from->next;
00715     }
00716 
00717     if((p_from != NULL) && (p_from->len == p_from->tot_len)) {
00718       /* don't copy more than one packet! */
00719       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00720                  (p_from->next == NULL), return ERR_VAL;);
00721     }
00722     if((p_to != NULL) && (p_to->len == p_to->tot_len)) {
00723       /* don't copy more than one packet! */
00724       LWIP_ERROR("pbuf_copy() does not allow packet queues!\n",
00725                   (p_to->next == NULL), return ERR_VAL;);
00726     }
00727   } while (p_from);
00728   LWIP_DEBUGF(PBUF_DEBUG | LWIP_DBG_TRACE | 1, ("pbuf_copy: end of chain reached.\n"));
00729   return ERR_OK;
00730 }
00731 
00732 /**
00733  * Copy (part of) the contents of a packet buffer
00734  * to an application supplied buffer.
00735  *
00736  * @param buf the pbuf from which to copy data
00737  * @param dataptr the application supplied buffer
00738  * @param len length of data to copy (dataptr must be big enough)
00739  * @param offset offset into the packet buffer from where to begin copying len bytes
00740  */
00741 u16_t
00742 pbuf_copy_partial(struct pbuf *buf, void *dataptr, u16_t len, u16_t offset)
00743 {
00744   struct pbuf *p;
00745   u16_t left;
00746   u16_t buf_copy_len;
00747   u16_t copied_total = 0;
00748 
00749   LWIP_ERROR("netbuf_copy_partial: invalid buf", (buf != NULL), return 0;);
00750   LWIP_ERROR("netbuf_copy_partial: invalid dataptr", (dataptr != NULL), return 0;);
00751 
00752   left = 0;
00753 
00754   if((buf == NULL) || (dataptr == NULL)) {
00755     return 0;
00756   }
00757 
00758   /* Note some systems use byte copy if dataptr or one of the pbuf payload pointers are unaligned. */
00759   for(p = buf; len != 0 && p != NULL; p = p->next) {
00760     if ((offset != 0) && (offset >= p->len)) {
00761       /* don't copy from this buffer -> on to the next */
00762       offset -= p->len;
00763     } else {
00764       /* copy from this buffer. maybe only partially. */
00765       buf_copy_len = p->len - offset;
00766       if (buf_copy_len > len)
00767           buf_copy_len = len;
00768       /* copy the necessary parts of the buffer */
00769       MEMCPY(&((char*)dataptr)[left], &((char*)p->payload)[offset], buf_copy_len);
00770       copied_total += buf_copy_len;
00771       left += buf_copy_len;
00772       len -= buf_copy_len;
00773       offset = 0;
00774     }
00775   }
00776   return copied_total;
00777 }