tor-browser

user_mbuf.c (38732B)

---

/*-
* 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(_MSC_VER)
#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);
}