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[/] [openrisc/] [trunk/] [rtos/] [freertos-6.1.1/] [Demo/] [Common/] [ethernet/] [lwIP/] [core/] [pbuf.c] - Rev 867
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/** * @file * Packet buffer management * * Packets are built from the pbuf data structure. It supports dynamic * memory allocation for packet contents or can reference externally * managed packet contents both in RAM and ROM. Quick allocation for * incoming packets is provided through pools with fixed sized pbufs. * * A packet may span over multiple pbufs, chained as a singly linked * list. This is called a "pbuf chain". * * Multiple packets may be queued, also using this singly linked list. * This is called a "packet queue". * * So, a packet queue consists of one or more pbuf chains, each of * which consist of one or more pbufs. Currently, queues are only * supported in a limited section of lwIP, this is the etharp queueing * code. Outside of this section no packet queues are supported yet. * * The differences between a pbuf chain and a packet queue are very * precise but subtle. * * The last pbuf of a packet has a ->tot_len field that equals the * ->len field. It can be found by traversing the list. If the last * pbuf of a packet has a ->next field other than NULL, more packets * are on the queue. * * Therefore, looping through a pbuf of a single packet, has an * loop end condition (tot_len == p->len), NOT (next == NULL). */ /* * Copyright (c) 2001-2004 Swedish Institute of Computer Science. * All rights reserved. * * Redistribution and use in source and binary forms, with or without modification, * are permitted provided that the following conditions are met: * * 1. Redistributions of source code must retain the above copyright notice, * this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright notice, * this list of conditions and the following disclaimer in the documentation * and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote products * derived from this software without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT * SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING * IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY * OF SUCH DAMAGE. * * This file is part of the lwIP TCP/IP stack. * * Author: Adam Dunkels <adam@sics.se> * */ #include <string.h> #include "lwip/opt.h" #include "lwip/stats.h" #include "lwip/def.h" #include "lwip/mem.h" #include "lwip/memp.h" #include "lwip/pbuf.h" #include "lwip/sys.h" #include "arch/perf.h" static u8_t pbuf_pool_memory[MEM_ALIGNMENT - 1 + PBUF_POOL_SIZE * MEM_ALIGN_SIZE(PBUF_POOL_BUFSIZE + sizeof(struct pbuf))]; #if !SYS_LIGHTWEIGHT_PROT static volatile u8_t pbuf_pool_free_lock, pbuf_pool_alloc_lock; static sys_sem_t pbuf_pool_free_sem; #endif static struct pbuf *pbuf_pool = NULL; /** * Initializes the pbuf module. * * A large part of memory is allocated for holding the pool of pbufs. * The size of the individual pbufs in the pool is given by the size * parameter, and the number of pbufs in the pool by the num parameter. * * After the memory has been allocated, the pbufs are set up. The * ->next pointer in each pbuf is set up to point to the next pbuf in * the pool. * */ void pbuf_init(void) { struct pbuf *p, *q = NULL; u16_t i; pbuf_pool = (struct pbuf *)MEM_ALIGN(pbuf_pool_memory); #if PBUF_STATS lwip_stats.pbuf.avail = PBUF_POOL_SIZE; #endif /* PBUF_STATS */ /* Set up ->next pointers to link the pbufs of the pool together */ p = pbuf_pool; for(i = 0; i < PBUF_POOL_SIZE; ++i) { p->next = (struct pbuf *)((u8_t *)p + PBUF_POOL_BUFSIZE + sizeof(struct pbuf)); p->len = p->tot_len = PBUF_POOL_BUFSIZE; p->payload = MEM_ALIGN((void *)((u8_t *)p + sizeof(struct pbuf))); p->flags = PBUF_FLAG_POOL; q = p; p = p->next; } /* The ->next pointer of last pbuf is NULL to indicate that there are no more pbufs in the pool */ q->next = NULL; #if !SYS_LIGHTWEIGHT_PROT pbuf_pool_alloc_lock = 0; pbuf_pool_free_lock = 0; pbuf_pool_free_sem = sys_sem_new(1); #endif } /** * @internal only called from pbuf_alloc() */ static struct pbuf * pbuf_pool_alloc(void) { struct pbuf *p = NULL; SYS_ARCH_DECL_PROTECT(old_level); SYS_ARCH_PROTECT(old_level); #if !SYS_LIGHTWEIGHT_PROT /* Next, check the actual pbuf pool, but if the pool is locked, we pretend to be out of buffers and return NULL. */ if (pbuf_pool_free_lock) { #if PBUF_STATS ++lwip_stats.pbuf.alloc_locked; #endif /* PBUF_STATS */ return NULL; } pbuf_pool_alloc_lock = 1; if (!pbuf_pool_free_lock) { #endif /* SYS_LIGHTWEIGHT_PROT */ p = pbuf_pool; if (p) { pbuf_pool = p->next; } #if !SYS_LIGHTWEIGHT_PROT #if PBUF_STATS } else { ++lwip_stats.pbuf.alloc_locked; #endif /* PBUF_STATS */ } pbuf_pool_alloc_lock = 0; #endif /* SYS_LIGHTWEIGHT_PROT */ #if PBUF_STATS if (p != NULL) { ++lwip_stats.pbuf.used; if (lwip_stats.pbuf.used > lwip_stats.pbuf.max) { lwip_stats.pbuf.max = lwip_stats.pbuf.used; } } #endif /* PBUF_STATS */ SYS_ARCH_UNPROTECT(old_level); return p; } /** * Allocates a pbuf of the given type (possibly a chain for PBUF_POOL type). * * The actual memory allocated for the pbuf is determined by the * layer at which the pbuf is allocated and the requested size * (from the size parameter). * * @param flag this parameter decides how and where the pbuf * should be allocated as follows: * * - PBUF_RAM: buffer memory for pbuf is allocated as one large * chunk. This includes protocol headers as well. * - PBUF_ROM: no buffer memory is allocated for the pbuf, even for * protocol headers. Additional headers must be prepended * by allocating another pbuf and chain in to the front of * the ROM pbuf. It is assumed that the memory used is really * similar to ROM in that it is immutable and will not be * changed. Memory which is dynamic should generally not * be attached to PBUF_ROM pbufs. Use PBUF_REF instead. * - PBUF_REF: no buffer memory is allocated for the pbuf, even for * protocol headers. It is assumed that the pbuf is only * being used in a single thread. If the pbuf gets queued, * then pbuf_take should be called to copy the buffer. * - PBUF_POOL: the pbuf is allocated as a pbuf chain, with pbufs from * the pbuf pool that is allocated during pbuf_init(). * * @return the allocated pbuf. If multiple pbufs where allocated, this * is the first pbuf of a pbuf chain. */ struct pbuf * pbuf_alloc(pbuf_layer l, u16_t length, pbuf_flag flag) { struct pbuf *p, *q, *r; u16_t offset; s32_t rem_len; /* remaining length */ LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F")\n", length)); /* determine header offset */ offset = 0; switch (l) { case PBUF_TRANSPORT: /* add room for transport (often TCP) layer header */ offset += PBUF_TRANSPORT_HLEN; /* FALLTHROUGH */ case PBUF_IP: /* add room for IP layer header */ offset += PBUF_IP_HLEN; /* FALLTHROUGH */ case PBUF_LINK: /* add room for link layer header */ offset += PBUF_LINK_HLEN; break; case PBUF_RAW: break; default: LWIP_ASSERT("pbuf_alloc: bad pbuf layer", 0); return NULL; } switch (flag) { case PBUF_POOL: /* allocate head of pbuf chain into p */ p = pbuf_pool_alloc(); LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc: allocated pbuf %p\n", (void *)p)); if (p == NULL) { #if PBUF_STATS ++lwip_stats.pbuf.err; #endif /* PBUF_STATS */ return NULL; } p->next = NULL; /* make the payload pointer point 'offset' bytes into pbuf data memory */ p->payload = MEM_ALIGN((void *)((u8_t *)p + (sizeof(struct pbuf) + offset))); LWIP_ASSERT("pbuf_alloc: pbuf p->payload properly aligned", ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0); /* the total length of the pbuf chain is the requested size */ p->tot_len = length; /* set the length of the first pbuf in the chain */ p->len = length > PBUF_POOL_BUFSIZE - offset? PBUF_POOL_BUFSIZE - offset: length; /* set reference count (needed here in case we fail) */ p->ref = 1; /* now allocate the tail of the pbuf chain */ /* remember first pbuf for linkage in next iteration */ r = p; /* remaining length to be allocated */ rem_len = length - p->len; /* any remaining pbufs to be allocated? */ while (rem_len > 0) { q = pbuf_pool_alloc(); if (q == NULL) { LWIP_DEBUGF(PBUF_DEBUG | 2, ("pbuf_alloc: Out of pbufs in pool.\n")); #if PBUF_STATS ++lwip_stats.pbuf.err; #endif /* PBUF_STATS */ /* free chain so far allocated */ pbuf_free(p); /* bail out unsuccesfully */ return NULL; } q->next = NULL; /* make previous pbuf point to this pbuf */ r->next = q; /* set total length of this pbuf and next in chain */ q->tot_len = rem_len; /* this pbuf length is pool size, unless smaller sized tail */ q->len = rem_len > PBUF_POOL_BUFSIZE? PBUF_POOL_BUFSIZE: rem_len; q->payload = (void *)((u8_t *)q + sizeof(struct pbuf)); LWIP_ASSERT("pbuf_alloc: pbuf q->payload properly aligned", ((mem_ptr_t)q->payload % MEM_ALIGNMENT) == 0); q->ref = 1; /* calculate remaining length to be allocated */ rem_len -= q->len; /* remember this pbuf for linkage in next iteration */ r = q; } /* end of chain */ /*r->next = NULL;*/ break; case PBUF_RAM: /* If pbuf is to be allocated in RAM, allocate memory for it. */ p = mem_malloc(MEM_ALIGN_SIZE(sizeof(struct pbuf) + offset) + MEM_ALIGN_SIZE(length)); if (p == NULL) { return NULL; } /* Set up internal structure of the pbuf. */ p->payload = MEM_ALIGN((void *)((u8_t *)p + sizeof(struct pbuf) + offset)); p->len = p->tot_len = length; p->next = NULL; p->flags = PBUF_FLAG_RAM; LWIP_ASSERT("pbuf_alloc: pbuf->payload properly aligned", ((mem_ptr_t)p->payload % MEM_ALIGNMENT) == 0); break; /* pbuf references existing (non-volatile static constant) ROM payload? */ case PBUF_ROM: /* pbuf references existing (externally allocated) RAM payload? */ case PBUF_REF: /* only allocate memory for the pbuf structure */ p = memp_malloc(MEMP_PBUF); if (p == NULL) { LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_alloc: Could not allocate MEMP_PBUF for PBUF_%s.\n", flag == PBUF_ROM?"ROM":"REF")); return NULL; } /* caller must set this field properly, afterwards */ p->payload = NULL; p->len = p->tot_len = length; p->next = NULL; p->flags = (flag == PBUF_ROM? PBUF_FLAG_ROM: PBUF_FLAG_REF); break; default: LWIP_ASSERT("pbuf_alloc: erroneous flag", 0); return NULL; } /* set reference count */ p->ref = 1; LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_alloc(length=%"U16_F") == %p\n", length, (void *)p)); return p; } #if PBUF_STATS #define DEC_PBUF_STATS do { --lwip_stats.pbuf.used; } while (0) #else /* PBUF_STATS */ #define DEC_PBUF_STATS #endif /* PBUF_STATS */ #define PBUF_POOL_FAST_FREE(p) do { \ p->next = pbuf_pool; \ pbuf_pool = p; \ DEC_PBUF_STATS; \ } while (0) #if SYS_LIGHTWEIGHT_PROT #define PBUF_POOL_FREE(p) do { \ SYS_ARCH_DECL_PROTECT(old_level); \ SYS_ARCH_PROTECT(old_level); \ PBUF_POOL_FAST_FREE(p); \ SYS_ARCH_UNPROTECT(old_level); \ } while (0) #else /* SYS_LIGHTWEIGHT_PROT */ #define PBUF_POOL_FREE(p) do { \ sys_sem_wait(pbuf_pool_free_sem); \ PBUF_POOL_FAST_FREE(p); \ sys_sem_signal(pbuf_pool_free_sem); \ } while (0) #endif /* SYS_LIGHTWEIGHT_PROT */ /** * Shrink a pbuf chain to a desired length. * * @param p pbuf to shrink. * @param new_len desired new length of pbuf chain * * Depending on the desired length, the first few pbufs in a chain might * be skipped and left unchanged. The new last pbuf in the chain will be * resized, and any remaining pbufs will be freed. * * @note If the pbuf is ROM/REF, only the ->tot_len and ->len fields are adjusted. * @note May not be called on a packet queue. * * @bug Cannot grow the size of a pbuf (chain) (yet). */ void pbuf_realloc(struct pbuf *p, u16_t new_len) { struct pbuf *q; u16_t rem_len; /* remaining length */ s16_t grow; LWIP_ASSERT("pbuf_realloc: sane p->flags", p->flags == PBUF_FLAG_POOL || p->flags == PBUF_FLAG_ROM || p->flags == PBUF_FLAG_RAM || p->flags == PBUF_FLAG_REF); /* desired length larger than current length? */ if (new_len >= p->tot_len) { /* enlarging not yet supported */ return; } /* the pbuf chain grows by (new_len - p->tot_len) bytes * (which may be negative in case of shrinking) */ grow = new_len - p->tot_len; /* first, step over any pbufs that should remain in the chain */ rem_len = new_len; q = p; /* should this pbuf be kept? */ while (rem_len > q->len) { /* decrease remaining length by pbuf length */ rem_len -= q->len; /* decrease total length indicator */ q->tot_len += grow; /* proceed to next pbuf in chain */ q = q->next; } /* we have now reached the new last pbuf (in q) */ /* rem_len == desired length for pbuf q */ /* shrink allocated memory for PBUF_RAM */ /* (other types merely adjust their length fields */ if ((q->flags == PBUF_FLAG_RAM) && (rem_len != q->len)) { /* reallocate and adjust the length of the pbuf that will be split */ mem_realloc(q, (u8_t *)q->payload - (u8_t *)q + rem_len); } /* adjust length fields for new last pbuf */ q->len = rem_len; q->tot_len = q->len; /* any remaining pbufs in chain? */ if (q->next != NULL) { /* free remaining pbufs in chain */ pbuf_free(q->next); } /* q is last packet in chain */ q->next = NULL; } /** * Adjusts the payload pointer to hide or reveal headers in the payload. * * Adjusts the ->payload pointer so that space for a header * (dis)appears in the pbuf payload. * * The ->payload, ->tot_len and ->len fields are adjusted. * * @param hdr_size_inc Number of bytes to increment header size which * increases the size of the pbuf. New space is on the front. * (Using a negative value decreases the header size.) * If hdr_size_inc is 0, this function does nothing and returns succesful. * * PBUF_ROM and PBUF_REF type buffers cannot have their sizes increased, so * the call will fail. A check is made that the increase in header size does * not move the payload pointer in front of the start of the buffer. * @return non-zero on failure, zero on success. * */ u8_t pbuf_header(struct pbuf *p, s16_t header_size_increment) { u16_t flags; void *payload; LWIP_ASSERT("p != NULL", p != NULL); if ((header_size_increment == 0) || (p == NULL)) return 0; flags = p->flags; /* remember current payload pointer */ payload = p->payload; /* pbuf types containing payloads? */ if (flags == PBUF_FLAG_RAM || flags == PBUF_FLAG_POOL) { /* set new payload pointer */ p->payload = (u8_t *)p->payload - header_size_increment; /* boundary check fails? */ if ((u8_t *)p->payload < (u8_t *)p + sizeof(struct pbuf)) { LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p (not enough space for new header size)\n", (void *)p->payload, (void *)(p + 1)));\ /* restore old payload pointer */ p->payload = payload; /* bail out unsuccesfully */ return 1; } /* pbuf types refering to external payloads? */ } else if (flags == PBUF_FLAG_REF || flags == PBUF_FLAG_ROM) { /* hide a header in the payload? */ if ((header_size_increment < 0) && (header_size_increment - p->len <= 0)) { /* increase payload pointer */ p->payload = (u8_t *)p->payload - header_size_increment; } else { /* cannot expand payload to front (yet!) * bail out unsuccesfully */ return 1; } } /* modify pbuf length fields */ p->len += header_size_increment; p->tot_len += header_size_increment; LWIP_DEBUGF( PBUF_DEBUG, ("pbuf_header: old %p new %p (%"S16_F")\n", (void *)payload, (void *)p->payload, header_size_increment)); return 0; } /** * Dereference a pbuf chain or queue and deallocate any no-longer-used * pbufs at the head of this chain or queue. * * Decrements the pbuf reference count. If it reaches zero, the pbuf is * deallocated. * * For a pbuf chain, this is repeated for each pbuf in the chain, * up to the first pbuf which has a non-zero reference count after * decrementing. So, when all reference counts are one, the whole * chain is free'd. * * @param pbuf The pbuf (chain) to be dereferenced. * * @return the number of pbufs that were de-allocated * from the head of the chain. * * @note MUST NOT be called on a packet queue (Not verified to work yet). * @note the reference counter of a pbuf equals the number of pointers * that refer to the pbuf (or into the pbuf). * * @internal examples: * * Assuming existing chains a->b->c with the following reference * counts, calling pbuf_free(a) results in: * * 1->2->3 becomes ...1->3 * 3->3->3 becomes 2->3->3 * 1->1->2 becomes ......1 * 2->1->1 becomes 1->1->1 * 1->1->1 becomes ....... * */ u8_t pbuf_free(struct pbuf *p) { u16_t flags; struct pbuf *q; u8_t count; SYS_ARCH_DECL_PROTECT(old_level); LWIP_ASSERT("p != NULL", p != NULL); /* if assertions are disabled, proceed with debug output */ if (p == NULL) { LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n")); return 0; } LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_free(%p)\n", (void *)p)); PERF_START; LWIP_ASSERT("pbuf_free: sane flags", p->flags == PBUF_FLAG_RAM || p->flags == PBUF_FLAG_ROM || p->flags == PBUF_FLAG_REF || p->flags == PBUF_FLAG_POOL); count = 0; /* Since decrementing ref cannot be guaranteed to be a single machine operation * we must protect it. Also, the later test of ref must be protected. */ SYS_ARCH_PROTECT(old_level); /* de-allocate all consecutive pbufs from the head of the chain that * obtain a zero reference count after decrementing*/ while (p != NULL) { /* all pbufs in a chain are referenced at least once */ LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0); /* decrease reference count (number of pointers to pbuf) */ p->ref--; /* this pbuf is no longer referenced to? */ if (p->ref == 0) { /* remember next pbuf in chain for next iteration */ q = p->next; LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: deallocating %p\n", (void *)p)); flags = p->flags; /* is this a pbuf from the pool? */ if (flags == PBUF_FLAG_POOL) { p->len = p->tot_len = PBUF_POOL_BUFSIZE; p->payload = (void *)((u8_t *)p + sizeof(struct pbuf)); PBUF_POOL_FREE(p); /* is this a ROM or RAM referencing pbuf? */ } else if (flags == PBUF_FLAG_ROM || flags == PBUF_FLAG_REF) { memp_free(MEMP_PBUF, p); /* flags == PBUF_FLAG_RAM */ } else { mem_free(p); } count++; /* proceed to next pbuf */ p = q; /* p->ref > 0, this pbuf is still referenced to */ /* (and so the remaining pbufs in chain as well) */ } else { LWIP_DEBUGF( PBUF_DEBUG | 2, ("pbuf_free: %p has ref %"U16_F", ending here.\n", (void *)p, (u16_t)p->ref)); /* stop walking through the chain */ p = NULL; } } SYS_ARCH_UNPROTECT(old_level); PERF_STOP("pbuf_free"); /* return number of de-allocated pbufs */ return count; } /** * Count number of pbufs in a chain * * @param p first pbuf of chain * @return the number of pbufs in a chain */ u8_t pbuf_clen(struct pbuf *p) { u8_t len; len = 0; while (p != NULL) { ++len; p = p->next; } return len; } /** * Increment the reference count of the pbuf. * * @param p pbuf to increase reference counter of * */ void pbuf_ref(struct pbuf *p) { SYS_ARCH_DECL_PROTECT(old_level); /* pbuf given? */ if (p != NULL) { SYS_ARCH_PROTECT(old_level); ++(p->ref); SYS_ARCH_UNPROTECT(old_level); } } /** * Concatenate two pbufs (each may be a pbuf chain) and take over * the caller's reference of the tail pbuf. * * @note The caller MAY NOT reference the tail pbuf afterwards. * Use pbuf_chain() for that purpose. * * @see pbuf_chain() */ void pbuf_cat(struct pbuf *h, struct pbuf *t) { struct pbuf *p; LWIP_ASSERT("h != NULL (programmer violates API)", h != NULL); LWIP_ASSERT("t != NULL (programmer violates API)", t != NULL); if ((h == NULL) || (t == NULL)) return; /* proceed to last pbuf of chain */ for (p = h; p->next != NULL; p = p->next) { /* add total length of second chain to all totals of first chain */ p->tot_len += t->tot_len; } /* { p is last pbuf of first h chain, p->next == NULL } */ LWIP_ASSERT("p->tot_len == p->len (of last pbuf in chain)", p->tot_len == p->len); LWIP_ASSERT("p->next == NULL", p->next == NULL); /* add total length of second chain to last pbuf total of first chain */ p->tot_len += t->tot_len; /* chain last pbuf of head (p) with first of tail (t) */ p->next = t; /* p->next now references t, but the caller will drop its reference to t, * so netto there is no change to the reference count of t. */ } /** * Chain two pbufs (or pbuf chains) together. * * The caller MUST call pbuf_free(t) once it has stopped * using it. Use pbuf_cat() instead if you no longer use t. * * @param h head pbuf (chain) * @param t tail pbuf (chain) * @note The pbufs MUST belong to the same packet. * @note MAY NOT be called on a packet queue. * * The ->tot_len fields of all pbufs of the head chain are adjusted. * The ->next field of the last pbuf of the head chain is adjusted. * The ->ref field of the first pbuf of the tail chain is adjusted. * */ void pbuf_chain(struct pbuf *h, struct pbuf *t) { pbuf_cat(h, t); /* t is now referenced by h */ pbuf_ref(t); LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: %p references %p\n", (void *)h, (void *)t)); } /* For packet queueing. Note that queued packets MUST be dequeued first * using pbuf_dequeue() before calling other pbuf_() functions. */ #if ARP_QUEUEING /** * Add a packet to the end of a queue. * * @param q pointer to first packet on the queue * @param n packet to be queued * * Both packets MUST be given, and must be different. */ void pbuf_queue(struct pbuf *p, struct pbuf *n) { #if PBUF_DEBUG /* remember head of queue */ struct pbuf *q = p; #endif /* programmer stupidity checks */ LWIP_ASSERT("p == NULL in pbuf_queue: this indicates a programmer error\n", p != NULL); LWIP_ASSERT("n == NULL in pbuf_queue: this indicates a programmer error\n", n != NULL); LWIP_ASSERT("p == n in pbuf_queue: this indicates a programmer error\n", p != n); if ((p == NULL) || (n == NULL) || (p == n)){ LWIP_DEBUGF(PBUF_DEBUG | DBG_HALT | 3, ("pbuf_queue: programmer argument error\n")); return; } /* iterate through all packets on queue */ while (p->next != NULL) { /* be very picky about pbuf chain correctness */ #if PBUF_DEBUG /* iterate through all pbufs in packet */ while (p->tot_len != p->len) { /* make sure invariant condition holds */ LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len); /* make sure each packet is complete */ LWIP_ASSERT("p->next != NULL", p->next != NULL); p = p->next; /* { p->tot_len == p->len => p is last pbuf of a packet } */ } /* { p is last pbuf of a packet } */ /* proceed to next packet on queue */ #endif /* proceed to next pbuf */ if (p->next != NULL) p = p->next; } /* { p->tot_len == p->len and p->next == NULL } ==> * { p is last pbuf of last packet on queue } */ /* chain last pbuf of queue with n */ p->next = n; /* n is now referenced to by the (packet p in the) queue */ pbuf_ref(n); #if PBUF_DEBUG LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_queue: newly queued packet %p sits after packet %p in queue %p\n", (void *)n, (void *)p, (void *)q)); #endif } /** * Remove a packet from the head of a queue. * * The caller MUST reference the remainder of the queue (as returned). The * caller MUST NOT call pbuf_ref() as it implicitly takes over the reference * from p. * * @param p pointer to first packet on the queue which will be dequeued. * @return first packet on the remaining queue (NULL if no further packets). * */ struct pbuf * pbuf_dequeue(struct pbuf *p) { struct pbuf *q; LWIP_ASSERT("p != NULL", p != NULL); /* iterate through all pbufs in packet p */ while (p->tot_len != p->len) { /* make sure invariant condition holds */ LWIP_ASSERT("p->len < p->tot_len", p->len < p->tot_len); /* make sure each packet is complete */ LWIP_ASSERT("p->next != NULL", p->next != NULL); p = p->next; } /* { p->tot_len == p->len } => p is the last pbuf of the first packet */ /* remember next packet on queue in q */ q = p->next; /* dequeue packet p from queue */ p->next = NULL; /* any next packet on queue? */ if (q != NULL) { /* although q is no longer referenced by p, it MUST be referenced by * the caller, who is maintaining this packet queue. So, we do not call * pbuf_free(q) here, resulting in an implicit pbuf_ref(q) for the caller. */ LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: first remaining packet on queue is %p\n", (void *)q)); } else { LWIP_DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_dequeue: no further packets on queue\n")); } return q; } #endif /** * * Create PBUF_POOL (or PBUF_RAM) copies of PBUF_REF pbufs. * * Used to queue packets on behalf of the lwIP stack, such as * ARP based queueing. * * Go through a pbuf chain and replace any PBUF_REF buffers * with PBUF_POOL (or PBUF_RAM) pbufs, each taking a copy of * the referenced data. * * @note You MUST explicitly use p = pbuf_take(p); * The pbuf you give as argument, may have been replaced * by a (differently located) copy through pbuf_take()! * * @note Any replaced pbufs will be freed through pbuf_free(). * This may deallocate them if they become no longer referenced. * * @param p Head of pbuf chain to process * * @return Pointer to head of pbuf chain */ struct pbuf * pbuf_take(struct pbuf *p) { struct pbuf *q , *prev, *head; LWIP_ASSERT("pbuf_take: p != NULL\n", p != NULL); LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 3, ("pbuf_take(%p)\n", (void*)p)); prev = NULL; head = p; /* iterate through pbuf chain */ do { /* pbuf is of type PBUF_REF? */ if (p->flags == PBUF_FLAG_REF) { LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE, ("pbuf_take: encountered PBUF_REF %p\n", (void *)p)); /* allocate a pbuf (w/ payload) fully in RAM */ /* PBUF_POOL buffers are faster if we can use them */ if (p->len <= PBUF_POOL_BUFSIZE) { q = pbuf_alloc(PBUF_RAW, p->len, PBUF_POOL); if (q == NULL) { LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_POOL\n")); } } else { /* no replacement pbuf yet */ q = NULL; LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: PBUF_POOL too small to replace PBUF_REF\n")); } /* no (large enough) PBUF_POOL was available? retry with PBUF_RAM */ if (q == NULL) { q = pbuf_alloc(PBUF_RAW, p->len, PBUF_RAM); if (q == NULL) { LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_RAM\n")); } } /* replacement pbuf could be allocated? */ if (q != NULL) { /* copy p to q */ /* copy successor */ q->next = p->next; /* remove linkage from original pbuf */ p->next = NULL; /* remove linkage to original pbuf */ if (prev != NULL) { /* prev->next == p at this point */ LWIP_ASSERT("prev->next == p", prev->next == p); /* break chain and insert new pbuf instead */ prev->next = q; /* prev == NULL, so we replaced the head pbuf of the chain */ } else { head = q; } /* copy pbuf payload */ memcpy(q->payload, p->payload, p->len); q->tot_len = p->tot_len; q->len = p->len; /* in case p was the first pbuf, it is no longer refered to by * our caller, as the caller MUST do p = pbuf_take(p); * in case p was not the first pbuf, it is no longer refered to * by prev. we can safely free the pbuf here. * (note that we have set p->next to NULL already so that * we will not free the rest of the chain by accident.) */ pbuf_free(p); /* do not copy ref, since someone else might be using the old buffer */ LWIP_DEBUGF(PBUF_DEBUG, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p, (void *)q)); p = q; } else { /* deallocate chain */ pbuf_free(head); LWIP_DEBUGF(PBUF_DEBUG | 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p)); return NULL; } /* p->flags != PBUF_FLAG_REF */ } else { LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: skipping pbuf not of type PBUF_REF\n")); } /* remember this pbuf */ prev = p; /* proceed to next pbuf in original chain */ p = p->next; } while (p); LWIP_DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: end of chain reached.\n")); return head; } /** * Dechains the first pbuf from its succeeding pbufs in the chain. * * Makes p->tot_len field equal to p->len. * @param p pbuf to dechain * @return remainder of the pbuf chain, or NULL if it was de-allocated. * @note May not be called on a packet queue. */ struct pbuf * pbuf_dechain(struct pbuf *p) { struct pbuf *q; u8_t tail_gone = 1; /* tail */ q = p->next; /* pbuf has successor in chain? */ if (q != NULL) { /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */ LWIP_ASSERT("p->tot_len == p->len + q->tot_len", q->tot_len == p->tot_len - p->len); /* enforce invariant if assertion is disabled */ q->tot_len = p->tot_len - p->len; /* decouple pbuf from remainder */ p->next = NULL; /* total length of pbuf p is its own length only */ p->tot_len = p->len; /* q is no longer referenced by p, free it */ LWIP_DEBUGF(PBUF_DEBUG | DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *)q)); tail_gone = pbuf_free(q); if (tail_gone > 0) { LWIP_DEBUGF(PBUF_DEBUG | DBG_STATE, ("pbuf_dechain: deallocated %p (as it is no longer referenced)\n", (void *)q)); } /* return remaining tail or NULL if deallocated */ } /* assert tot_len invariant: (p->tot_len == p->len + (p->next? p->next->tot_len: 0) */ LWIP_ASSERT("p->tot_len == p->len", p->tot_len == p->len); return (tail_gone > 0? NULL: q); }
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