pbuf.c

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