/src/usrsctp/usrsctplib/user_mbuf.c

Source
/*-
 * Copyright (c) 1982, 1986, 1988, 1993
 *      The Regents of the University of California.
 * 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. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``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 REGENTS OR CONTRIBUTORS 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.
 *
 */

/*
 *  __Userspace__ version of /usr/src/sys/kern/kern_mbuf.c
 *  We are initializing two zones for Mbufs and Clusters.
 *
 */

#if defined(_WIN32) && defined(__MINGW32__)
#include <minmax.h>
#endif

#include <stdio.h>
#include <string.h>
/* #include <sys/param.h> This defines MSIZE 256 */
#if !defined(SCTP_SIMPLE_ALLOCATOR)
#include "umem.h"
#endif
#include "user_mbuf.h"
#include "user_environment.h"
#include "user_atomic.h"
#include "netinet/sctp_pcb.h"

#define KIPC_MAX_LINKHDR        4       /* int: max length of link header (see sys/sysclt.h) */
#define KIPC_MAX_PROTOHDR 5 /* int: max length of network header (see sys/sysclt.h)*/
int max_linkhdr = KIPC_MAX_LINKHDR;
int max_protohdr = KIPC_MAX_PROTOHDR; /* Size of largest protocol layer header. */

/*
 * Zones from which we allocate.
 */
sctp_zone_t zone_mbuf;
sctp_zone_t zone_clust;
sctp_zone_t zone_ext_refcnt;

/* __Userspace__ clust_mb_args will be passed as callback data to mb_ctor_clust
 * and mb_dtor_clust.
 * Note: I had to use struct clust_args as an encapsulation for an mbuf pointer.
 * struct mbuf * clust_mb_args; does not work.
 */
struct clust_args clust_mb_args;


/* __Userspace__
 * Local prototypes.
 */
static int  mb_ctor_mbuf(void *, void *, int);
static int      mb_ctor_clust(void *, void *, int);
static void mb_dtor_mbuf(void *,  void *);
static void mb_dtor_clust(void *, void *);


/***************** Functions taken from user_mbuf.h *************/

static int mbuf_constructor_dup(struct mbuf *m, int pkthdr, short type)
{
  int flags = pkthdr;

  m->m_next = NULL;
  m->m_nextpkt = NULL;
  m->m_len = 0;
  m->m_flags = flags;
  m->m_type = type;
  if (flags & M_PKTHDR) {
    m->m_data = m->m_pktdat;
    m->m_pkthdr.rcvif = NULL;
    m->m_pkthdr.len = 0;
    m->m_pkthdr.header = NULL;
    m->m_pkthdr.csum_flags = 0;
    m->m_pkthdr.csum_data = 0;
    m->m_pkthdr.tso_segsz = 0;
    m->m_pkthdr.ether_vtag = 0;
    SLIST_INIT(&m->m_pkthdr.tags);
  } else
    m->m_data = m->m_dat;

  return (0);
}

/* __Userspace__ */
struct mbuf *
m_get(int how, short type)
{
  struct mbuf *mret;
#if defined(SCTP_SIMPLE_ALLOCATOR)
  struct mb_args mbuf_mb_args;

  /* The following setter function is not yet being enclosed within
   * #if USING_MBUF_CONSTRUCTOR - #endif, until I have thoroughly tested
   * mb_dtor_mbuf. See comment there
   */
  mbuf_mb_args.flags = 0;
  mbuf_mb_args.type = type;
#endif
  /* Mbuf master zone, zone_mbuf, has already been
   * created in mbuf_initialize() */
  mret = SCTP_ZONE_GET(zone_mbuf, struct mbuf);
#if defined(SCTP_SIMPLE_ALLOCATOR)
  mb_ctor_mbuf(mret, &mbuf_mb_args, 0);
#endif
  /*mret =  ((struct mbuf *)umem_cache_alloc(zone_mbuf, UMEM_DEFAULT));*/

  /* There are cases when an object available in the current CPU's
   * loaded magazine and in those cases the object's constructor is not applied.
   * If that is the case, then we are duplicating constructor initialization here,
   * so that the mbuf is properly constructed before returning it.
   */
  if (mret) {
#if USING_MBUF_CONSTRUCTOR
    if (! (mret->m_type == type) ) {
      mbuf_constructor_dup(mret, 0, type);
    }
#else
    mbuf_constructor_dup(mret, 0, type);
#endif

  }
  return mret;
}


/* __Userspace__ */
struct mbuf *
m_gethdr(int how, short type)
{
  struct mbuf *mret;
#if defined(SCTP_SIMPLE_ALLOCATOR)
  struct mb_args mbuf_mb_args;

  /* The following setter function is not yet being enclosed within
   * #if USING_MBUF_CONSTRUCTOR - #endif, until I have thoroughly tested
   * mb_dtor_mbuf. See comment there
   */
  mbuf_mb_args.flags = M_PKTHDR;
  mbuf_mb_args.type = type;
#endif
  mret = SCTP_ZONE_GET(zone_mbuf, struct mbuf);
#if defined(SCTP_SIMPLE_ALLOCATOR)
  mb_ctor_mbuf(mret, &mbuf_mb_args, 0);
#endif
  /*mret = ((struct mbuf *)umem_cache_alloc(zone_mbuf, UMEM_DEFAULT));*/
  /* There are cases when an object available in the current CPU's
   * loaded magazine and in those cases the object's constructor is not applied.
   * If that is the case, then we are duplicating constructor initialization here,
   * so that the mbuf is properly constructed before returning it.
   */
  if (mret) {
#if USING_MBUF_CONSTRUCTOR
    if (! ((mret->m_flags & M_PKTHDR) && (mret->m_type == type)) ) {
      mbuf_constructor_dup(mret, M_PKTHDR, type);
    }
#else
    mbuf_constructor_dup(mret, M_PKTHDR, type);
#endif
  }
  return mret;
}

/* __Userspace__ */
struct mbuf *
m_free(struct mbuf *m)
{

  struct mbuf *n = m->m_next;

  if (m->m_flags & M_EXT)
    mb_free_ext(m);
  else if ((m->m_flags & M_NOFREE) == 0) {
#if defined(SCTP_SIMPLE_ALLOCATOR)
    mb_dtor_mbuf(m, NULL);
#endif
    SCTP_ZONE_FREE(zone_mbuf, m);
  }
    /*umem_cache_free(zone_mbuf, m);*/
  return (n);
}


static void
clust_constructor_dup(caddr_t m_clust, struct mbuf* m)
{
  u_int *refcnt;
  int type, size;

  if (m == NULL) {
    return;
  }
  /* Assigning cluster of MCLBYTES. TODO: Add jumbo frame functionality */
  type = EXT_CLUSTER;
  size = MCLBYTES;

  refcnt = SCTP_ZONE_GET(zone_ext_refcnt, u_int);
  /*refcnt = (u_int *)umem_cache_alloc(zone_ext_refcnt, UMEM_DEFAULT);*/
#if !defined(SCTP_SIMPLE_ALLOCATOR)
  if (refcnt == NULL) {
    umem_reap();
    refcnt = SCTP_ZONE_GET(zone_ext_refcnt, u_int);
    /*refcnt = (u_int *)umem_cache_alloc(zone_ext_refcnt, UMEM_DEFAULT);*/
  }
#endif
  *refcnt = 1;
  m->m_ext.ext_buf = (caddr_t)m_clust;
  m->m_data = m->m_ext.ext_buf;
  m->m_flags |= M_EXT;
  m->m_ext.ext_free = NULL;
  m->m_ext.ext_args = NULL;
  m->m_ext.ext_size = size;
  m->m_ext.ext_type = type;
  m->m_ext.ref_cnt = refcnt;
  return;
}


/* __Userspace__ */
void
m_clget(struct mbuf *m, int how)
{
  caddr_t mclust_ret;
#if defined(SCTP_SIMPLE_ALLOCATOR)
  struct clust_args clust_mb_args_l;
#endif
  if (m->m_flags & M_EXT) {
    SCTPDBG(SCTP_DEBUG_USR, "%s: %p mbuf already has cluster\n", __func__, (void *)m);
  }
  m->m_ext.ext_buf = (char *)NULL;
#if defined(SCTP_SIMPLE_ALLOCATOR)
  clust_mb_args_l.parent_mbuf = m;
#endif
  mclust_ret = SCTP_ZONE_GET(zone_clust, char);
#if defined(SCTP_SIMPLE_ALLOCATOR)
  mb_ctor_clust(mclust_ret, &clust_mb_args_l, 0);
#endif
  /*mclust_ret = umem_cache_alloc(zone_clust, UMEM_DEFAULT);*/
  /*
   On a cluster allocation failure, call umem_reap() and retry.
   */

  if (mclust_ret == NULL) {
#if !defined(SCTP_SIMPLE_ALLOCATOR)
  /*  mclust_ret = SCTP_ZONE_GET(zone_clust, char);
    mb_ctor_clust(mclust_ret, &clust_mb_args, 0);
#else*/
    umem_reap();
    mclust_ret = SCTP_ZONE_GET(zone_clust, char);
#endif
    /*mclust_ret = umem_cache_alloc(zone_clust, UMEM_DEFAULT);*/
    /* if (NULL == mclust_ret) { */
    SCTPDBG(SCTP_DEBUG_USR, "Memory allocation failure in %s\n", __func__);
    /* } */
  }

#if USING_MBUF_CONSTRUCTOR
  if ((m->m_ext.ext_buf == NULL)) {
    clust_constructor_dup(mclust_ret, m);
  }
#else
  clust_constructor_dup(mclust_ret, m);
#endif
}

struct mbuf *
m_getm2(struct mbuf *m, int len, int how, short type, int flags, int allonebuf)
{
  struct mbuf *mb, *nm = NULL, *mtail = NULL;
  int size, mbuf_threshold, space_needed = len;

  KASSERT(len >= 0, ("%s: len is < 0", __func__));

  /* Validate flags. */
  flags &= (M_PKTHDR | M_EOR);

  /* Packet header mbuf must be first in chain. */
  if ((flags & M_PKTHDR) && m != NULL) {
    flags &= ~M_PKTHDR;
  }

  if (allonebuf == 0)
    mbuf_threshold = SCTP_BASE_SYSCTL(sctp_mbuf_threshold_count);
  else
    mbuf_threshold = 1;

  /* Loop and append maximum sized mbufs to the chain tail. */
  while (len > 0) {
    if ((!allonebuf && len >= MCLBYTES) || (len > (int)(((mbuf_threshold - 1) * MLEN) + MHLEN))) {
      mb = m_gethdr(how, type);
      MCLGET(mb, how);
      size = MCLBYTES;
      /* SCTP_BUF_LEN(mb) = MCLBYTES; */
    } else if (flags & M_PKTHDR) {
      mb = m_gethdr(how, type);
      if (len < MHLEN) {
        size = len;
      } else {
        size = MHLEN;
      }
    } else {
      mb = m_get(how, type);
      if (len < MLEN) {
        size = len;
      } else {
        size = MLEN;
      }
    }

    /* Fail the whole operation if one mbuf can't be allocated. */
    if (mb == NULL) {
      if (nm != NULL)
        m_freem(nm);
      return (NULL);
    }

    if (allonebuf != 0 && size < space_needed) {
      m_freem(mb);
      return (NULL);
    }

    /* Book keeping. */
    len -= size;
    if (mtail != NULL)
      mtail->m_next = mb;
    else
      nm = mb;
    mtail = mb;
    flags &= ~M_PKTHDR;     /* Only valid on the first mbuf. */
  }
  if (flags & M_EOR) {
    mtail->m_flags |= M_EOR;  /* Only valid on the last mbuf. */
  }

  /* If mbuf was supplied, append new chain to the end of it. */
  if (m != NULL) {
    for (mtail = m; mtail->m_next != NULL; mtail = mtail->m_next);
    mtail->m_next = nm;
    mtail->m_flags &= ~M_EOR;
  } else {
    m = nm;
  }

  return (m);
}

/*
 * Copy the contents of uio into a properly sized mbuf chain.
 */
struct mbuf *
m_uiotombuf(struct uio *uio, int how, int len, int align, int flags)
{
  struct mbuf *m, *mb;
  int error, length;
  ssize_t total;
  int progress = 0;

  /*
   * len can be zero or an arbitrary large value bound by
   * the total data supplied by the uio.
   */
  if (len > 0)
    total = min(uio->uio_resid, len);
  else
    total = uio->uio_resid;
  /*
   * The smallest unit returned by m_getm2() is a single mbuf
   * with pkthdr.  We can't align past it.
   */
  if (align >= MHLEN)
    return (NULL);
  /*
   * Give us the full allocation or nothing.
   * If len is zero return the smallest empty mbuf.
   */
  m = m_getm2(NULL, (int)max(total + align, 1), how, MT_DATA, flags, 0);
  if (m == NULL)
    return (NULL);
  m->m_data += align;

  /* Fill all mbufs with uio data and update header information. */
  for (mb = m; mb != NULL; mb = mb->m_next) {
    length = (int)min(M_TRAILINGSPACE(mb), total - progress);
    error = uiomove(mtod(mb, void *), length, uio);
    if (error) {
      m_freem(m);
      return (NULL);
    }

    mb->m_len = length;
    progress += length;
    if (flags & M_PKTHDR)
      m->m_pkthdr.len += length;
  }
  KASSERT(progress == total, ("%s: progress != total", __func__));

  return (m);
}

u_int
m_length(struct mbuf *m0, struct mbuf **last)
{
  struct mbuf *m;
  u_int len;

  len = 0;
  for (m = m0; m != NULL; m = m->m_next) {
    len += m->m_len;
    if (m->m_next == NULL)
      break;
  }
  if (last != NULL)
  *last = m;
  return (len);
}

struct mbuf *
m_last(struct mbuf *m)
{
  while (m->m_next) {
    m = m->m_next;
  }
  return (m);
}

/*
 * Unlink a tag from the list of tags associated with an mbuf.
 */
static __inline void
m_tag_unlink(struct mbuf *m, struct m_tag *t)
{

  SLIST_REMOVE(&m->m_pkthdr.tags, t, m_tag, m_tag_link);
}

/*
 * Reclaim resources associated with a tag.
 */
static __inline void
m_tag_free(struct m_tag *t)
{

  (*t->m_tag_free)(t);
}

/*
 * Set up the contents of a tag.  Note that this does not fill in the free
 * method; the caller is expected to do that.
 *
 * XXX probably should be called m_tag_init, but that was already taken.
 */
static __inline void
m_tag_setup(struct m_tag *t, uint32_t cookie, int type, int len)
{

  t->m_tag_id = type;
  t->m_tag_len = len;
  t->m_tag_cookie = cookie;
}

/************ End functions from user_mbuf.h  ******************/



/************ End functions to substitute umem_cache_alloc and umem_cache_free **************/

void
mbuf_initialize(void *dummy)
{

  /*
   * __Userspace__Configure UMA zones for Mbufs and Clusters.
   * (TODO: m_getcl() - using packet secondary zone).
   * There is no provision for trash_init and trash_fini in umem.
   *
   */
 /* zone_mbuf = umem_cache_create(MBUF_MEM_NAME, MSIZE, 0,
        mb_ctor_mbuf, mb_dtor_mbuf, NULL,
        &mbuf_mb_args,
        NULL, 0);
  zone_mbuf = umem_cache_create(MBUF_MEM_NAME, MSIZE, 0, NULL, NULL, NULL, NULL, NULL, 0);*/
#if defined(SCTP_SIMPLE_ALLOCATOR)
  SCTP_ZONE_INIT(zone_mbuf, MBUF_MEM_NAME, MSIZE, 0);
#else
  zone_mbuf = umem_cache_create(MBUF_MEM_NAME, MSIZE, 0,
                                mb_ctor_mbuf, mb_dtor_mbuf, NULL,
                                NULL,
                                NULL, 0);
#endif
  /*zone_ext_refcnt = umem_cache_create(MBUF_EXTREFCNT_MEM_NAME, sizeof(u_int), 0,
        NULL, NULL, NULL,
        NULL,
        NULL, 0);*/
  SCTP_ZONE_INIT(zone_ext_refcnt, MBUF_EXTREFCNT_MEM_NAME, sizeof(u_int), 0);

  /*zone_clust = umem_cache_create(MBUF_CLUSTER_MEM_NAME, MCLBYTES, 0,
         mb_ctor_clust, mb_dtor_clust, NULL,
         &clust_mb_args,
         NULL, 0);
  zone_clust = umem_cache_create(MBUF_CLUSTER_MEM_NAME, MCLBYTES, 0, NULL, NULL, NULL, NULL, NULL,0);*/
#if defined(SCTP_SIMPLE_ALLOCATOR)
  SCTP_ZONE_INIT(zone_clust, MBUF_CLUSTER_MEM_NAME, MCLBYTES, 0);
#else
  zone_clust = umem_cache_create(MBUF_CLUSTER_MEM_NAME, MCLBYTES, 0,
                   mb_ctor_clust, mb_dtor_clust, NULL,
                   &clust_mb_args,
                   NULL, 0);
#endif

  /* uma_prealloc() goes here... */

  /* __Userspace__ Add umem_reap here for low memory situation?
   *
   */

}



/*
 * __Userspace__
 *
 * Constructor for Mbuf master zone. We have a different constructor
 * for allocating the cluster.
 *
 * The 'arg' pointer points to a mb_args structure which
 * contains call-specific information required to support the
 * mbuf allocation API.  See user_mbuf.h.
 *
 * The flgs parameter below can be UMEM_DEFAULT or UMEM_NOFAIL depending on what
 * was passed when umem_cache_alloc was called.
 * TODO: Use UMEM_NOFAIL in umem_cache_alloc and also define a failure handler
 * and call umem_nofail_callback(my_failure_handler) in the stack initialization routines
 * The advantage of using UMEM_NOFAIL is that we don't have to check if umem_cache_alloc
 * was successful or not. The failure handler would take care of it, if we use the UMEM_NOFAIL
 * flag.
 *
 * NOTE Ref: http://docs.sun.com/app/docs/doc/819-2243/6n4i099p2?l=en&a=view&q=umem_zalloc)
 * The umem_nofail_callback() function sets the **process-wide** UMEM_NOFAIL callback.
 * It also mentions that umem_nofail_callback is Evolving.
 *
 */
static int
mb_ctor_mbuf(void *mem, void *arg, int flgs)
{
#if USING_MBUF_CONSTRUCTOR
  struct mbuf *m;
  struct mb_args *args;

  int flags;
  short type;

  m = (struct mbuf *)mem;
  args = (struct mb_args *)arg;
  flags = args->flags;
  type = args->type;

  m->m_next = NULL;
  m->m_nextpkt = NULL;
  m->m_len = 0;
  m->m_flags = flags;
  m->m_type = type;
  if (flags & M_PKTHDR) {
    m->m_data = m->m_pktdat;
    m->m_pkthdr.rcvif = NULL;
    m->m_pkthdr.len = 0;
    m->m_pkthdr.header = NULL;
    m->m_pkthdr.csum_flags = 0;
    m->m_pkthdr.csum_data = 0;
    m->m_pkthdr.tso_segsz = 0;
    m->m_pkthdr.ether_vtag = 0;
    SLIST_INIT(&m->m_pkthdr.tags);
  } else
    m->m_data = m->m_dat;
#endif
  return (0);
}


/*
 * __Userspace__
 * The Mbuf master zone destructor.
 * This would be called in response to umem_cache_destroy
 * TODO: Recheck if this is what we want to do in this destructor.
 * (Note: the number of times mb_dtor_mbuf is called is equal to the
 * number of individual mbufs allocated from zone_mbuf.
 */
static void
mb_dtor_mbuf(void *mem, void *arg)
{
  struct mbuf *m;

  m = (struct mbuf *)mem;
  if ((m->m_flags & M_PKTHDR) != 0) {
    m_tag_delete_chain(m, NULL);
  }
}


/* __Userspace__
 * The Cluster zone constructor.
 *
 * Here the 'arg' pointer points to the Mbuf which we
 * are configuring cluster storage for.  If 'arg' is
 * empty we allocate just the cluster without setting
 * the mbuf to it.  See mbuf.h.
 */
static int
mb_ctor_clust(void *mem, void *arg, int flgs)
{

#if USING_MBUF_CONSTRUCTOR
  struct mbuf *m;
  struct clust_args * cla;
  u_int *refcnt;
  int type, size;
  sctp_zone_t zone;

  /* Assigning cluster of MCLBYTES. TODO: Add jumbo frame functionality */
  type = EXT_CLUSTER;
  zone = zone_clust;
  size = MCLBYTES;

  cla = (struct clust_args *)arg;
  m = cla->parent_mbuf;

  refcnt = SCTP_ZONE_GET(zone_ext_refcnt, u_int);
  /*refcnt = (u_int *)umem_cache_alloc(zone_ext_refcnt, UMEM_DEFAULT);*/
  *refcnt = 1;

  if (m != NULL) {
    m->m_ext.ext_buf = (caddr_t)mem;
    m->m_data = m->m_ext.ext_buf;
    m->m_flags |= M_EXT;
    m->m_ext.ext_free = NULL;
    m->m_ext.ext_args = NULL;
    m->m_ext.ext_size = size;
    m->m_ext.ext_type = type;
    m->m_ext.ref_cnt = refcnt;
  }
#endif
  return (0);
}

/* __Userspace__ */
static void
mb_dtor_clust(void *mem, void *arg)
{

  /* mem is of type caddr_t.  In sys/types.h we have typedef char * caddr_t;  */
  /* mb_dtor_clust is called at time of umem_cache_destroy() (the number of times
   * mb_dtor_clust is called is equal to the number of individual mbufs allocated
   * from zone_clust. Similarly for mb_dtor_mbuf).
   * At this point the following:
   *  struct mbuf *m;
   *   m = (struct mbuf *)arg;
   *  assert (*(m->m_ext.ref_cnt) == 0); is not meaningful since  m->m_ext.ref_cnt = NULL;
   *  has been done in mb_free_ext().
   */

}




/* Unlink and free a packet tag. */
void
m_tag_delete(struct mbuf *m, struct m_tag *t)
{
  KASSERT(m && t, ("m_tag_delete: null argument, m %p t %p", (void *)m, (void *)t));
  m_tag_unlink(m, t);
  m_tag_free(t);
}


/* Unlink and free a packet tag chain, starting from given tag. */
void
m_tag_delete_chain(struct mbuf *m, struct m_tag *t)
{

  struct m_tag *p, *q;

  KASSERT(m, ("m_tag_delete_chain: null mbuf"));
  if (t != NULL)
    p = t;
  else
    p = SLIST_FIRST(&m->m_pkthdr.tags);
  if (p == NULL)
    return;
  while ((q = SLIST_NEXT(p, m_tag_link)) != NULL)
    m_tag_delete(m, q);
  m_tag_delete(m, p);
}

#if 0
static void
sctp_print_mbuf_chain(struct mbuf *m)
{
  SCTP_DEBUG_USR(SCTP_DEBUG_USR, "Printing mbuf chain %p.\n", (void *)m);
  for(; m; m=m->m_next) {
    SCTP_DEBUG_USR(SCTP_DEBUG_USR, "%p: m_len = %ld, m_type = %x, m_next = %p.\n", (void *)m, m->m_len, m->m_type, (void *)m->m_next);
    if (m->m_flags & M_EXT)
      SCTP_DEBUG_USR(SCTP_DEBUG_USR, "%p: extend_size = %d, extend_buffer = %p, ref_cnt = %d.\n", (void *)m, m->m_ext.ext_size, (void *)m->m_ext.ext_buf, *(m->m_ext.ref_cnt));
  }
}
#endif

/*
 * Free an entire chain of mbufs and associated external buffers, if
 * applicable.
 */
void
m_freem(struct mbuf *mb)
{
  while (mb != NULL)
    mb = m_free(mb);
}

/*
 * __Userspace__
 * clean mbufs with M_EXT storage attached to them
 * if the reference count hits 1.
 */
void
mb_free_ext(struct mbuf *m)
{

  int skipmbuf;

  KASSERT((m->m_flags & M_EXT) == M_EXT, ("%s: M_EXT not set", __func__));
  KASSERT(m->m_ext.ref_cnt != NULL, ("%s: ref_cnt not set", __func__));

  /*
   * check if the header is embedded in the cluster
   */
  skipmbuf = (m->m_flags & M_NOFREE);

  /* Free the external attached storage if this
   * mbuf is the only reference to it.
   *__Userspace__ TODO: jumbo frames
   *
  */
  /* NOTE: We had the same code that SCTP_DECREMENT_AND_CHECK_REFCOUNT
           reduces to here before but the IPHONE malloc commit had changed
           this to compare to 0 instead of 1 (see next line).  Why?
          . .. this caused a huge memory leak in Linux.
  */
#ifdef IPHONE
  if (atomic_fetchadd_int(m->m_ext.ref_cnt, -1) == 0)
#else
  if (SCTP_DECREMENT_AND_CHECK_REFCOUNT(m->m_ext.ref_cnt))
#endif
  {
    if (m->m_ext.ext_type == EXT_CLUSTER){
#if defined(SCTP_SIMPLE_ALLOCATOR)
      mb_dtor_clust(m->m_ext.ext_buf, &clust_mb_args);
#endif
      SCTP_ZONE_FREE(zone_clust, m->m_ext.ext_buf);
      SCTP_ZONE_FREE(zone_ext_refcnt, (u_int*)m->m_ext.ref_cnt);
      m->m_ext.ref_cnt = NULL;
    }
  }

  if (skipmbuf)
    return;


  /* __Userspace__ Also freeing the storage for ref_cnt
   * Free this mbuf back to the mbuf zone with all m_ext
   * information purged.
   */
  m->m_ext.ext_buf = NULL;
  m->m_ext.ext_free = NULL;
  m->m_ext.ext_args = NULL;
  m->m_ext.ref_cnt = NULL;
  m->m_ext.ext_size = 0;
  m->m_ext.ext_type = 0;
  m->m_flags &= ~M_EXT;
#if defined(SCTP_SIMPLE_ALLOCATOR)
  mb_dtor_mbuf(m, NULL);
#endif
  SCTP_ZONE_FREE(zone_mbuf, m);

  /*umem_cache_free(zone_mbuf, m);*/
}

/*
 * "Move" mbuf pkthdr from "from" to "to".
 * "from" must have M_PKTHDR set, and "to" must be empty.
 */
void
m_move_pkthdr(struct mbuf *to, struct mbuf *from)
{

  to->m_flags = (from->m_flags & M_COPYFLAGS) | (to->m_flags & M_EXT);
  if ((to->m_flags & M_EXT) == 0)
    to->m_data = to->m_pktdat;
  to->m_pkthdr = from->m_pkthdr;   /* especially tags */
  SLIST_INIT(&from->m_pkthdr.tags); /* purge tags from src */
  from->m_flags &= ~M_PKTHDR;
}


/*
 * Rearange an mbuf chain so that len bytes are contiguous
 * and in the data area of an mbuf (so that mtod and dtom
 * will work for a structure of size len).  Returns the resulting
 * mbuf chain on success, frees it and returns null on failure.
 * If there is room, it will add up to max_protohdr-len extra bytes to the
 * contiguous region in an attempt to avoid being called next time.
 */
struct mbuf *
m_pullup(struct mbuf *n, int len)
{
  struct mbuf *m;
  int count;
  int space;

  /*
   * If first mbuf has no cluster, and has room for len bytes
   * without shifting current data, pullup into it,
   * otherwise allocate a new mbuf to prepend to the chain.
   */
  if ((n->m_flags & M_EXT) == 0 &&
      n->m_data + len < &n->m_dat[MLEN] && n->m_next) {
    if (n->m_len >= len)
      return (n);
    m = n;
    n = n->m_next;
    len -= m->m_len;
  } else {
    if (len > MHLEN)
      goto bad;
    MGET(m, M_NOWAIT, n->m_type);
    if (m == NULL)
      goto bad;
    m->m_len = 0;
    if (n->m_flags & M_PKTHDR)
      M_MOVE_PKTHDR(m, n);
  }
  space = (int)(&m->m_dat[MLEN] - (m->m_data + m->m_len));
  do {
    count = min(min(max(len, max_protohdr), space), n->m_len);
    memcpy(mtod(m, caddr_t) + m->m_len,mtod(n, caddr_t), (u_int)count);
    len -= count;
    m->m_len += count;
    n->m_len -= count;
    space -= count;
    if (n->m_len)
      n->m_data += count;
    else
      n = m_free(n);
  } while (len > 0 && n);
  if (len > 0) {
    (void) m_free(m);
    goto bad;
  }
  m->m_next = n;
  return (m);
bad:
  m_freem(n);
  return (NULL);
}


static struct mbuf *
m_dup1(struct mbuf *m, int off, int len, int wait)
{
  struct mbuf *n = NULL;
  int copyhdr;

  if (len > MCLBYTES)
    return NULL;
  if (off == 0 && (m->m_flags & M_PKTHDR) != 0)
    copyhdr = 1;
  else
    copyhdr = 0;
  if (len >= MINCLSIZE) {
    if (copyhdr == 1) {
      m_clget(n, wait); /* TODO: include code for copying the header */
      m_dup_pkthdr(n, m, wait);
    } else
      m_clget(n, wait);
  } else {
    if (copyhdr == 1)
      n = m_gethdr(wait, m->m_type);
    else
      n = m_get(wait, m->m_type);
  }
  if (!n)
    return NULL; /* ENOBUFS */

  if (copyhdr && !m_dup_pkthdr(n, m, wait)) {
    m_free(n);
    return NULL;
  }
  m_copydata(m, off, len, mtod(n, caddr_t));
  n->m_len = len;
  return n;
}


/* Taken from sys/kern/uipc_mbuf2.c */
struct mbuf *
m_pulldown(struct mbuf *m, int off, int len, int *offp)
{
  struct mbuf *n, *o;
  int hlen, tlen, olen;
  int writable;

  /* check invalid arguments. */
  KASSERT(m, ("m == NULL in m_pulldown()"));
  if (len > MCLBYTES) {
    m_freem(m);
    return NULL;    /* impossible */
  }

#ifdef PULLDOWN_DEBUG
  {
    struct mbuf *t;
    SCTP_DEBUG_USR(SCTP_DEBUG_USR, "before:");
    for (t = m; t; t = t->m_next)
      SCTP_DEBUG_USR(SCTP_DEBUG_USR, " %d", t->m_len);
    SCTP_DEBUG_USR(SCTP_DEBUG_USR, "\n");
  }
#endif
  n = m;
  while (n != NULL && off > 0) {
    if (n->m_len > off)
      break;
    off -= n->m_len;
    n = n->m_next;
  }
  /* be sure to point non-empty mbuf */
  while (n != NULL && n->m_len == 0)
    n = n->m_next;
  if (!n) {
    m_freem(m);
    return NULL;    /* mbuf chain too short */
  }

  writable = 0;
  if ((n->m_flags & M_EXT) == 0 ||
      (n->m_ext.ext_type == EXT_CLUSTER && M_WRITABLE(n)))
    writable = 1;

  /*
   * the target data is on <n, off>.
   * if we got enough data on the mbuf "n", we're done.
   */
  if ((off == 0 || offp) && len <= n->m_len - off && writable)
    goto ok;

  /*
   * when len <= n->m_len - off and off != 0, it is a special case.
   * len bytes from <n, off> sits in single mbuf, but the caller does
   * not like the starting position (off).
   * chop the current mbuf into two pieces, set off to 0.
   */
  if (len <= n->m_len - off) {
    o = m_dup1(n, off, n->m_len - off, M_NOWAIT);
    if (o == NULL) {
      m_freem(m);
    return NULL;    /* ENOBUFS */
    }
    n->m_len = off;
    o->m_next = n->m_next;
    n->m_next = o;
    n = n->m_next;
    off = 0;
    goto ok;
  }
  /*
   * we need to take hlen from <n, off> and tlen from <n->m_next, 0>,
   * and construct contiguous mbuf with m_len == len.
   * note that hlen + tlen == len, and tlen > 0.
   */
  hlen = n->m_len - off;
  tlen = len - hlen;

  /*
   * ensure that we have enough trailing data on mbuf chain.
   * if not, we can do nothing about the chain.
   */
  olen = 0;
  for (o = n->m_next; o != NULL; o = o->m_next)
    olen += o->m_len;
  if (hlen + olen < len) {
    m_freem(m);
    return NULL;    /* mbuf chain too short */
  }

  /*
   * easy cases first.
   * we need to use m_copydata() to get data from <n->m_next, 0>.
   */
  if ((off == 0 || offp) && (M_TRAILINGSPACE(n) >= tlen) && writable) {
    m_copydata(n->m_next, 0, tlen, mtod(n, caddr_t) + n->m_len);
    n->m_len += tlen;
    m_adj(n->m_next, tlen);
    goto ok;
  }

  if ((off == 0 || offp) && (M_LEADINGSPACE(n->m_next) >= hlen) && writable) {
    n->m_next->m_data -= hlen;
    n->m_next->m_len += hlen;
    memcpy( mtod(n->m_next, caddr_t), mtod(n, caddr_t) + off,hlen);
    n->m_len -= hlen;
    n = n->m_next;
    off = 0;
    goto ok;
  }

  /*
   * now, we need to do the hard way.  don't m_copy as there's no room
   * on both end.
   */
  if (len > MLEN)
    m_clget(o, M_NOWAIT);
    /* o = m_getcl(M_NOWAIT, m->m_type, 0);*/
  else
    o = m_get(M_NOWAIT, m->m_type);
  if (!o) {
    m_freem(m);
    return NULL;    /* ENOBUFS */
  }
  /* get hlen from <n, off> into <o, 0> */
  o->m_len = hlen;
  memcpy(mtod(o, caddr_t), mtod(n, caddr_t) + off, hlen);
  n->m_len -= hlen;
  /* get tlen from <n->m_next, 0> into <o, hlen> */
  m_copydata(n->m_next, 0, tlen, mtod(o, caddr_t) + o->m_len);
  o->m_len += tlen;
  m_adj(n->m_next, tlen);
  o->m_next = n->m_next;
  n->m_next = o;
  n = o;
  off = 0;
ok:
#ifdef PULLDOWN_DEBUG
  {
    struct mbuf *t;
    SCTP_DEBUG_USR(SCTP_DEBUG_USR, "after:");
    for (t = m; t; t = t->m_next)
      SCTP_DEBUG_USR(SCTP_DEBUG_USR, "%c%d", t == n ? '*' : ' ', t->m_len);
    SCTP_DEBUG_USR(SCTP_DEBUG_USR, " (off=%d)\n", off);
  }
#endif
  if (offp)
    *offp = off;
  return n;
}

/*
 * Attach the the cluster from *m to *n, set up m_ext in *n
 * and bump the refcount of the cluster.
 */
static void
mb_dupcl(struct mbuf *n, struct mbuf *m)
{
  KASSERT((m->m_flags & M_EXT) == M_EXT, ("%s: M_EXT not set", __func__));
  KASSERT(m->m_ext.ref_cnt != NULL, ("%s: ref_cnt not set", __func__));
  KASSERT((n->m_flags & M_EXT) == 0, ("%s: M_EXT set", __func__));

  if (*(m->m_ext.ref_cnt) == 1)
    *(m->m_ext.ref_cnt) += 1;
  else
    atomic_add_int(m->m_ext.ref_cnt, 1);
  n->m_ext.ext_buf = m->m_ext.ext_buf;
  n->m_ext.ext_free = m->m_ext.ext_free;
  n->m_ext.ext_args = m->m_ext.ext_args;
  n->m_ext.ext_size = m->m_ext.ext_size;
  n->m_ext.ref_cnt = m->m_ext.ref_cnt;
  n->m_ext.ext_type = m->m_ext.ext_type;
  n->m_flags |= M_EXT;
}


/*
 * Make a copy of an mbuf chain starting "off0" bytes from the beginning,
 * continuing for "len" bytes.  If len is M_COPYALL, copy to end of mbuf.
 * The wait parameter is a choice of M_TRYWAIT/M_NOWAIT from caller.
 * Note that the copy is read-only, because clusters are not copied,
 * only their reference counts are incremented.
 */

struct mbuf *
m_copym(struct mbuf *m, int off0, int len, int wait)
{
  struct mbuf *n, **np;
  int off = off0;
  struct mbuf *top;
  int copyhdr = 0;

  KASSERT(off >= 0, ("m_copym, negative off %d", off));
  KASSERT(len >= 0, ("m_copym, negative len %d", len));
  KASSERT(m != NULL, ("m_copym, m is NULL"));

#if !defined(INVARIANTS)
  if (m == NULL) {
    return (NULL);
  }
#endif
  if (off == 0 && m->m_flags & M_PKTHDR)
    copyhdr = 1;
  while (off > 0) {
    KASSERT(m != NULL, ("m_copym, offset > size of mbuf chain"));
    if (off < m->m_len)
      break;
    off -= m->m_len;
    m = m->m_next;
  }
  np = &top;
  top = 0;
  while (len > 0) {
    if (m == NULL) {
      KASSERT(len == M_COPYALL, ("m_copym, length > size of mbuf chain"));
      break;
    }
    if (copyhdr)
      MGETHDR(n, wait, m->m_type);
    else
      MGET(n, wait, m->m_type);
    *np = n;
    if (n == NULL)
      goto nospace;
    if (copyhdr) {
      if (!m_dup_pkthdr(n, m, wait))
        goto nospace;
      if (len == M_COPYALL)
        n->m_pkthdr.len -= off0;
      else
        n->m_pkthdr.len = len;
      copyhdr = 0;
    }
    n->m_len = min(len, m->m_len - off);
    if (m->m_flags & M_EXT) {
      n->m_data = m->m_data + off;
      mb_dupcl(n, m);
    } else
      memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off, (u_int)n->m_len);
    if (len != M_COPYALL)
      len -= n->m_len;
    off = 0;
    m = m->m_next;
    np = &n->m_next;
  }

  return (top);
nospace:
  m_freem(top);
  return (NULL);
}


int
m_tag_copy_chain(struct mbuf *to, struct mbuf *from, int how)
{
  struct m_tag *p, *t, *tprev = NULL;

  KASSERT(to && from, ("m_tag_copy_chain: null argument, to %p from %p", (void *)to, (void *)from));
  m_tag_delete_chain(to, NULL);
  SLIST_FOREACH(p, &from->m_pkthdr.tags, m_tag_link) {
    t = m_tag_copy(p, how);
    if (t == NULL) {
      m_tag_delete_chain(to, NULL);
      return 0;
    }
    if (tprev == NULL)
      SLIST_INSERT_HEAD(&to->m_pkthdr.tags, t, m_tag_link);
    else
      SLIST_INSERT_AFTER(tprev, t, m_tag_link);
    tprev = t;
  }
  return 1;
}

/*
 * Duplicate "from"'s mbuf pkthdr in "to".
 * "from" must have M_PKTHDR set, and "to" must be empty.
 * In particular, this does a deep copy of the packet tags.
 */
int
m_dup_pkthdr(struct mbuf *to, struct mbuf *from, int how)
{

  KASSERT(to, ("m_dup_pkthdr: to is NULL"));
  KASSERT(from, ("m_dup_pkthdr: from is NULL"));
  to->m_flags = (from->m_flags & M_COPYFLAGS) | (to->m_flags & M_EXT);
  if ((to->m_flags & M_EXT) == 0)
    to->m_data = to->m_pktdat;
  to->m_pkthdr = from->m_pkthdr;
  SLIST_INIT(&to->m_pkthdr.tags);
  return (m_tag_copy_chain(to, from, MBTOM(how)));
}

/* Copy a single tag. */
struct m_tag *
m_tag_copy(struct m_tag *t, int how)
{
  struct m_tag *p;

  KASSERT(t, ("m_tag_copy: null tag"));
  p = m_tag_alloc(t->m_tag_cookie, t->m_tag_id, t->m_tag_len, how);
  if (p == NULL)
    return (NULL);
  memcpy(p + 1, t + 1, t->m_tag_len); /* Copy the data */
  return p;
}

/* Get a packet tag structure along with specified data following. */
struct m_tag *
m_tag_alloc(uint32_t cookie, int type, int len, int wait)
{
  struct m_tag *t;

  if (len < 0)
    return NULL;
  t = malloc(len + sizeof(struct m_tag));
  if (t == NULL)
    return NULL;
  m_tag_setup(t, cookie, type, len);
  t->m_tag_free = m_tag_free_default;
  return t;
}

/* Free a packet tag. */
void
m_tag_free_default(struct m_tag *t)
{
  free(t);
}

/*
 * Copy data from a buffer back into the indicated mbuf chain,
 * starting "off" bytes from the beginning, extending the mbuf
 * chain if necessary.
 */
void
m_copyback(struct mbuf *m0, int off, int len, caddr_t cp)
{
  int mlen;
  struct mbuf *m = m0, *n;
  int totlen = 0;

  if (m0 == NULL)
    return;
  while (off > (mlen = m->m_len)) {
    off -= mlen;
    totlen += mlen;
    if (m->m_next == NULL) {
      n = m_get(M_NOWAIT, m->m_type);
      if (n == NULL)
        goto out;
      memset(mtod(n, caddr_t), 0, MLEN);
      n->m_len = min(MLEN, len + off);
      m->m_next = n;
    }
    m = m->m_next;
  }
  while (len > 0) {
    mlen = min (m->m_len - off, len);
    memcpy(off + mtod(m, caddr_t), cp, (u_int)mlen);
    cp += mlen;
    len -= mlen;
    mlen += off;
    off = 0;
    totlen += mlen;
    if (len == 0)
      break;
    if (m->m_next == NULL) {
      n = m_get(M_NOWAIT, m->m_type);
      if (n == NULL)
        break;
      n->m_len = min(MLEN, len);
      m->m_next = n;
    }
    m = m->m_next;
  }
out:  if (((m = m0)->m_flags & M_PKTHDR) && (m->m_pkthdr.len < totlen))
    m->m_pkthdr.len = totlen;
}

/*
 * Apply function f to the data in an mbuf chain starting "off" bytes from
 * the beginning, continuing for "len" bytes.
 */
int
m_apply(struct mbuf *m, int off, int len,
        int (*f)(void *, void *, u_int), void *arg)
{
  u_int count;
  int rval;

  KASSERT(off >= 0, ("m_apply, negative off %d", off));
  KASSERT(len >= 0, ("m_apply, negative len %d", len));
  while (off > 0) {
    KASSERT(m != NULL, ("m_apply, offset > size of mbuf chain"));
    if (off < m->m_len)
      break;
    off -= m->m_len;
    m = m->m_next;
  }
  while (len > 0) {
    KASSERT(m != NULL, ("m_apply, offset > size of mbuf chain"));
    count = min(m->m_len - off, len);
    rval = (*f)(arg, mtod(m, caddr_t) + off, count);
    if (rval)
      return (rval);
    len -= count;
    off = 0;
    m = m->m_next;
  }
  return (0);
}

/*
 * Lesser-used path for M_PREPEND:
 * allocate new mbuf to prepend to chain,
 * copy junk along.
 */
struct mbuf *
m_prepend(struct mbuf *m, int len, int how)
{
  struct mbuf *mn;

  if (m->m_flags & M_PKTHDR)
    MGETHDR(mn, how, m->m_type);
  else
    MGET(mn, how, m->m_type);
  if (mn == NULL) {
    m_freem(m);
    return (NULL);
  }
  if (m->m_flags & M_PKTHDR)
    M_MOVE_PKTHDR(mn, m);
  mn->m_next = m;
  m = mn;
  if (m->m_flags & M_PKTHDR) {
    if (len < MHLEN)
      MH_ALIGN(m, len);
  } else {
    if (len < MLEN)
      M_ALIGN(m, len);
  }
  m->m_len = len;
  return (m);
}

/*
 * Copy data from an mbuf chain starting "off" bytes from the beginning,
 * continuing for "len" bytes, into the indicated buffer.
 */
void
m_copydata(const struct mbuf *m, int off, int len, caddr_t cp)
{
  u_int count;

  KASSERT(off >= 0, ("m_copydata, negative off %d", off));
  KASSERT(len >= 0, ("m_copydata, negative len %d", len));
  while (off > 0) {
    KASSERT(m != NULL, ("m_copydata, offset > size of mbuf chain"));
    if (off < m->m_len)
      break;
    off -= m->m_len;
    m = m->m_next;
  }
  while (len > 0) {
    KASSERT(m != NULL, ("m_copydata, length > size of mbuf chain"));
    count = min(m->m_len - off, len);
    memcpy(cp, mtod(m, caddr_t) + off, count);
    len -= count;
    cp += count;
    off = 0;
    m = m->m_next;
  }
}


/*
 * Concatenate mbuf chain n to m.
 * Both chains must be of the same type (e.g. MT_DATA).
 * Any m_pkthdr is not updated.
 */
void
m_cat(struct mbuf *m, struct mbuf *n)
{
  while (m->m_next)
    m = m->m_next;
  while (n) {
    if (m->m_flags & M_EXT ||
        m->m_data + m->m_len + n->m_len >= &m->m_dat[MLEN]) {
      /* just join the two chains */
      m->m_next = n;
      return;
    }
    /* splat the data from one into the other */
    memcpy(mtod(m, caddr_t) + m->m_len, mtod(n, caddr_t), (u_int)n->m_len);
    m->m_len += n->m_len;
    n = m_free(n);
  }
}


void
m_adj(struct mbuf *mp, int req_len)
{
  int len = req_len;
  struct mbuf *m;
  int count;

  if ((m = mp) == NULL)
    return;
  if (len >= 0) {
    /*
     * Trim from head.
     */
    while (m != NULL && len > 0) {
      if (m->m_len <= len) {
        len -= m->m_len;
        m->m_len = 0;
        m = m->m_next;
      } else {
        m->m_len -= len;
        m->m_data += len;
        len = 0;
      }
    }
    m = mp;
    if (mp->m_flags & M_PKTHDR)
      m->m_pkthdr.len -= (req_len - len);
  } else {
    /*
     * Trim from tail.  Scan the mbuf chain,
     * calculating its length and finding the last mbuf.
     * If the adjustment only affects this mbuf, then just
     * adjust and return.  Otherwise, rescan and truncate
     * after the remaining size.
     */
    len = -len;
    count = 0;
    for (;;) {
      count += m->m_len;
      if (m->m_next == (struct mbuf *)0)
        break;
      m = m->m_next;
    }
    if (m->m_len >= len) {
      m->m_len -= len;
      if (mp->m_flags & M_PKTHDR)
        mp->m_pkthdr.len -= len;
      return;
    }
    count -= len;
    if (count < 0)
      count = 0;
    /*
     * Correct length for chain is "count".
     * Find the mbuf with last data, adjust its length,
     * and toss data from remaining mbufs on chain.
     */
    m = mp;
    if (m->m_flags & M_PKTHDR)
      m->m_pkthdr.len = count;
    for (; m; m = m->m_next) {
      if (m->m_len >= count) {
        m->m_len = count;
        if (m->m_next != NULL) {
          m_freem(m->m_next);
          m->m_next = NULL;
        }
        break;
      }
      count -= m->m_len;
    }
  }
}


/* m_split is used within sctp_handle_cookie_echo. */

/*
 * Partition an mbuf chain in two pieces, returning the tail --
 * all but the first len0 bytes.  In case of failure, it returns NULL and
 * attempts to restore the chain to its original state.
 *
 * Note that the resulting mbufs might be read-only, because the new
 * mbuf can end up sharing an mbuf cluster with the original mbuf if
 * the "breaking point" happens to lie within a cluster mbuf. Use the
 * M_WRITABLE() macro to check for this case.
 */
struct mbuf *
m_split(struct mbuf *m0, int len0, int wait)
{
  struct mbuf *m, *n;
  u_int len = len0, remain;

  /* MBUF_CHECKSLEEP(wait); */
  for (m = m0; m && (int)len > m->m_len; m = m->m_next)
    len -= m->m_len;
  if (m == NULL)
    return (NULL);
  remain = m->m_len - len;
  if (m0->m_flags & M_PKTHDR) {
    MGETHDR(n, wait, m0->m_type);
    if (n == NULL)
      return (NULL);
    n->m_pkthdr.rcvif = m0->m_pkthdr.rcvif;
    n->m_pkthdr.len = m0->m_pkthdr.len - len0;
    m0->m_pkthdr.len = len0;
    if (m->m_flags & M_EXT)
      goto extpacket;
    if (remain > MHLEN) {
      /* m can't be the lead packet */
      MH_ALIGN(n, 0);
      n->m_next = m_split(m, len, wait);
      if (n->m_next == NULL) {
        (void) m_free(n);
        return (NULL);
      } else {
        n->m_len = 0;
        return (n);
      }
    } else
      MH_ALIGN(n, remain);
  } else if (remain == 0) {
    n = m->m_next;
    m->m_next = NULL;
    return (n);
  } else {
    MGET(n, wait, m->m_type);
    if (n == NULL)
      return (NULL);
    M_ALIGN(n, remain);
  }
extpacket:
  if (m->m_flags & M_EXT) {
    n->m_data = m->m_data + len;
    mb_dupcl(n, m);
  } else {
    memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + len, remain);
  }
  n->m_len = remain;
  m->m_len = len;
  n->m_next = m->m_next;
  m->m_next = NULL;
  return (n);
}




int
pack_send_buffer(caddr_t buffer, struct mbuf* mb){

  int count_to_copy;
  int total_count_copied = 0;
  int offset = 0;

  do {
    count_to_copy = mb->m_len;
    memcpy(buffer+offset, mtod(mb, caddr_t), count_to_copy);
    offset += count_to_copy;
    total_count_copied += count_to_copy;
    mb = mb->m_next;
  } while(mb);

  return (total_count_copied);
}

Coverage Report

Created: 2025-11-16 06:35