pbuf.c

最新rtlinux内核源码

 *
 * @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;  
  /* this pbuf should 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;

  pbuf_refresh();
}

/**
 * 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 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.)
 *
 * 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 1 on failure, 0 on success.
 */
u8_t
pbuf_header(struct pbuf *p, s16_t header_size)
{
  void *payload;

  /* remember current payload pointer */
  payload = p->payload;

  /* pbuf types containing payloads? */
  if (p->flags == PBUF_FLAG_RAM || p->flags == PBUF_FLAG_POOL) {
    /* set new payload pointer */
    p->payload = (u8_t *)p->payload - header_size;
    /* boundary check fails? */
    if ((u8_t *)p->payload < (u8_t *)p + sizeof(struct pbuf)) {
      DEBUGF( PBUF_DEBUG | 2, ("pbuf_header: failed as %p < %p\n",
        (u8_t *)p->payload,
        (u8_t *)p + sizeof(struct pbuf)) );\
      /* restore old payload pointer */
      p->payload = payload;
      /* bail out unsuccesfully */
      return 1;
    }
  /* pbuf types refering to payloads? */
  } else if (p->flags == PBUF_FLAG_REF || p->flags == PBUF_FLAG_ROM) {
    /* hide a header in the payload? */
    if ((header_size < 0) && (header_size - p->len <= 0)) {
      /* increase payload pointer */
      p->payload = (u8_t *)p->payload - header_size;
    } else {
      /* cannot expand payload to front (yet!)
       * bail out unsuccesfully */
      return 1;
    }
  }
  DEBUGF( PBUF_DEBUG, ("pbuf_header: old %p new %p (%d)\n", payload, p->payload, header_size) );
  /* modify pbuf length fields */
  p->len += header_size;
  p->tot_len += header_size;

  return 0;
}

/**
 * Free a pbuf (chain) from usage, de-allocate non-used head of chain.
 *
 * 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, until
 * a non-zero reference count is encountered, or the end of the chain is
 * reached. 
 *
 * @param pbuf pbuf (chain) to be freed from one user.
 *
 * @return the number of unreferenced pbufs that were de-allocated 
 * from the head of the chain.
 *
 * @note the reference counter of a pbuf equals the number of pointers
 * that refer to the pbuf (or into the pbuf).
 *
 * @internal examples:
 *
 * 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)
{
  struct pbuf *q;
  u8_t count;
  unsigned int state;

  if (p == NULL) {
    DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_free(p == NULL) was called.\n"));
    return 0;
  }

//  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_stop_interrupts(&state);
  /* de-allocate all consecutive pbufs from the head of the chain that
   * obtain a zero reference count */
  while (p != NULL) {
    /* all pbufs in a chain are referenced at least once */
    LWIP_ASSERT("pbuf_free: p->ref > 0", p->ref > 0);
    p->ref--;
    /* this pbuf is no longer referenced to? */
    if (p->ref == 0) {
      /* remember next pbuf in chain for next iteration */
      q = p->next;
      /* is this a pbuf from the pool? */
      if (p->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);
      /* a RAM/ROM referencing pbuf */
      } else if (p->flags == PBUF_FLAG_ROM || p->flags == PBUF_FLAG_REF) {
        memp_freep(MEMP_PBUF, p);
      /* pbuf with data */
      } else {
        mem_free(p);
      }
      count++;
      /* proceed to next pbuf */
      p = q;
    /* p->ref > 0, this pbuf is still referenced to */
    /* (so the remaining pbufs in chain as well)    */
    } else {
      /* stop walking through chain */
      p = NULL;
    }
  }
  sys_allow_interrupts(&state);
  pbuf_refresh();
//  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)
{
  unsigned int state;
  /* pbuf given? */  
  if (p != NULL) {
    sys_stop_interrupts(&state);
    ++(p->ref);
    sys_allow_interrupts(&state);
  }
}

/**
 *
 * Increment the reference count of all pbufs in a chain.
 *
 * @param p first pbuf of chain
 *
 */
void
pbuf_ref_chain(struct pbuf *p)
{
  unsigned int state;
  sys_stop_interrupts(&state);
    
  while (p != NULL) {
    ++p->ref;
    p = p->next;
  }
  sys_allow_interrupts(&state);
}


/**
 *
 * Link two pbufs (or chains) together.
 *
 * @param h head pbuf (chain)
 * @param t tail pbuf (chain)
 * 
 * The ->tot_len field of the first pbuf (h) is adjusted.
 */
void
pbuf_chain(struct pbuf *h, struct pbuf *t)
{
  struct pbuf *p;

  LWIP_ASSERT("h != NULL", h != NULL);
  LWIP_ASSERT("t != NULL", t != NULL);
  
  /* 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 */
  /* add total length of second chain to last pbuf total of first chain */
  p->tot_len += t->tot_len;
  /* chain last pbuf of h chain (p) with first of tail (t) */
  p->next = t;
  /* t is now referenced to one more time */
  pbuf_ref(t);
  DEBUGF(PBUF_DEBUG | DBG_FRESH | 2, ("pbuf_chain: referencing tail %p\n", (void *) t));
}

/**
 * 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.
 */
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 */
    DEBUGF(PBUF_DEBUG | DBG_STATE, ("pbuf_dechain: unreferencing %p\n", (void *) q));
    tail_gone = pbuf_free(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);
}

/**
 *
 * Create PBUF_POOL (or PBUF_RAM) copies of PBUF_REF pbufs.
 *
 * 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 pbuf_take()!
 *
 * @note Any replaced pbufs will be freed through pbuf_free().
 *
 * Used to queue packets on behalf of the lwIP stack, such as
 * ARP based queueing.
 *
 * @param p Head of pbuf chain to process
 *
 * @return Pointer to new 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);
  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) {
      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) DEBUGF(PBUF_DEBUG | DBG_TRACE | 2, ("pbuf_take: Could not allocate PBUF_POOL\n"));
      } else {
      	/* no replacement pbuf yet */
        q = NULL;
        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) 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 */
        DEBUGF(PBUF_DEBUG, ("pbuf_take: replaced PBUF_REF %p with %p\n", (void *)p, (void *)q));
        p = q;
      } else {
        /* deallocate chain */
        pbuf_free(head);
        DEBUGF(PBUF_DEBUG | 2, ("pbuf_take: failed to allocate replacement pbuf for %p\n", (void *)p));
        return NULL;
      }
    /* p->flags != PBUF_FLAG_REF */
    } else {
      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);
  DEBUGF(PBUF_DEBUG | DBG_TRACE | 1, ("pbuf_take: end of chain reached.\n"));
  
  return head;
}