uipc_mbuf.c

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/*-
 * Copyright (c) 1982, 1986, 1988, 1991, 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.
 * 4. 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.
 *
 *      @(#)uipc_mbuf.c 8.2 (Berkeley) 1/4/94
 */

#include <sys/cdefs.h>
__FBSDID("$BSDSUniX$");

#include "opt_param.h"
#include "opt_mbuf_stress_test.h"
#include "opt_mbuf_profiling.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/limits.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/sysctl.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/uio.h>

int     max_linkhdr;
int     max_protohdr;
int     max_hdr;
int     max_datalen;
#ifdef MBUF_STRESS_TEST
int     m_defragpackets;
int     m_defragbytes;
int     m_defraguseless;
int     m_defragfailure;
int     m_defragrandomfailures;
#endif

/*
 * sysctl(8) exported objects
 */
SYSCTL_INT(_kern_ipc, KIPC_MAX_LINKHDR, max_linkhdr, CTLFLAG_RD,
           &max_linkhdr, 0, "Size of largest link layer header");
SYSCTL_INT(_kern_ipc, KIPC_MAX_PROTOHDR, max_protohdr, CTLFLAG_RD,
           &max_protohdr, 0, "Size of largest protocol layer header");
SYSCTL_INT(_kern_ipc, KIPC_MAX_HDR, max_hdr, CTLFLAG_RD,
           &max_hdr, 0, "Size of largest link plus protocol header");
SYSCTL_INT(_kern_ipc, KIPC_MAX_DATALEN, max_datalen, CTLFLAG_RD,
           &max_datalen, 0, "Minimum space left in mbuf after max_hdr");
#ifdef MBUF_STRESS_TEST
SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragpackets, CTLFLAG_RD,
           &m_defragpackets, 0, "");
SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragbytes, CTLFLAG_RD,
           &m_defragbytes, 0, "");
SYSCTL_INT(_kern_ipc, OID_AUTO, m_defraguseless, CTLFLAG_RD,
           &m_defraguseless, 0, "");
SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragfailure, CTLFLAG_RD,
           &m_defragfailure, 0, "");
SYSCTL_INT(_kern_ipc, OID_AUTO, m_defragrandomfailures, CTLFLAG_RW,
           &m_defragrandomfailures, 0, "");
#endif

/*
 * Allocate a given length worth of mbufs and/or clusters (whatever fits
 * best) and return a pointer to the top of the allocated chain.  If an
 * existing mbuf chain is provided, then we will append the new chain
 * to the existing one but still return the top of the newly allocated
 * chain.
 */
struct mbuf *
m_getm2(struct mbuf *m, int len, int how, short type, int flags)
{
        struct mbuf *mb, *nm = NULL, *mtail = NULL;

        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;

        /* Loop and append maximum sized mbufs to the chain tail. */
        while (len > 0) {
                if (len > MCLBYTES)
                        mb = m_getjcl(how, type, (flags & M_PKTHDR),
                            MJUMPAGESIZE);
                else if (len >= MINCLSIZE)
                        mb = m_getcl(how, type, (flags & M_PKTHDR));
                else if (flags & M_PKTHDR)
                        mb = m_gethdr(how, type);
                else
                        mb = m_get(how, type);

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

                /* Book keeping. */
                len -= (mb->m_flags & M_EXT) ? mb->m_ext.ext_size :
                        ((mb->m_flags & M_PKTHDR) ? MHLEN : MLEN);
                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);
}

/*
 * 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);
}

/*-
 * Configure a provided mbuf to refer to the provided external storage
 * buffer and setup a reference count for said buffer.  If the setting
 * up of the reference count fails, the M_EXT bit will not be set.  If
 * successfull, the M_EXT bit is set in the mbuf's flags.
 *
 * Arguments:
 *    mb     The existing mbuf to which to attach the provided buffer.
 *    buf    The address of the provided external storage buffer.
 *    size   The size of the provided buffer.
 *    freef  A pointer to a routine that is responsible for freeing the
 *           provided external storage buffer.
 *    args   A pointer to an argument structure (of any type) to be passed
 *           to the provided freef routine (may be NULL).
 *    flags  Any other flags to be passed to the provided mbuf.
 *    type   The type that the external storage buffer should be
 *           labeled with.
 *
 * Returns:
 *    Nothing.
 */
void
m_extadd(struct mbuf *mb, caddr_t buf, u_int size,
    void (*freef)(void *, void *), void *arg1, void *arg2, int flags, int type)
{
        KASSERT(type != EXT_CLUSTER, ("%s: EXT_CLUSTER not allowed", __func__));

        if (type != EXT_EXTREF)
                mb->m_ext.ref_cnt = (u_int *)uma_zalloc(zone_ext_refcnt, M_NOWAIT);
        if (mb->m_ext.ref_cnt != NULL) {
                *(mb->m_ext.ref_cnt) = 1;
                mb->m_flags |= (M_EXT | flags);
                mb->m_ext.ext_buf = buf;
                mb->m_data = mb->m_ext.ext_buf;
                mb->m_ext.ext_size = size;
                mb->m_ext.ext_free = freef;
                mb->m_ext.ext_arg1 = arg1;
                mb->m_ext.ext_arg2 = arg2;
                mb->m_ext.ext_type = type;
        }
}

/*
 * Non-directly-exported function to clean up after 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 attached storage if this mbuf is the only reference to it. */
        if (*(m->m_ext.ref_cnt) == 1 ||
            atomic_fetchadd_int(m->m_ext.ref_cnt, -1) == 1) {
                switch (m->m_ext.ext_type) {
                case EXT_PACKET:        /* The packet zone is special. */
                        if (*(m->m_ext.ref_cnt) == 0)
                                *(m->m_ext.ref_cnt) = 1;
                        uma_zfree(zone_pack, m);
                        return;         /* Job done. */
                case EXT_CLUSTER:
                        uma_zfree(zone_clust, m->m_ext.ext_buf);
                        break;
                case EXT_JUMBOP:
                        uma_zfree(zone_jumbop, m->m_ext.ext_buf);
                        break;
                case EXT_JUMBO9:
                        uma_zfree(zone_jumbo9, m->m_ext.ext_buf);
                        break;
                case EXT_JUMBO16:
                        uma_zfree(zone_jumbo16, m->m_ext.ext_buf);
                        break;
                case EXT_SFBUF:
                case EXT_NET_DRV:
                case EXT_MOD_TYPE:
                case EXT_DISPOSABLE:
                        *(m->m_ext.ref_cnt) = 0;
                        uma_zfree(zone_ext_refcnt, __DEVOLATILE(u_int *,
                                m->m_ext.ref_cnt));
                        /* FALLTHROUGH */
                case EXT_EXTREF:
                        KASSERT(m->m_ext.ext_free != NULL,
                                ("%s: ext_free not set", __func__));
                        (*(m->m_ext.ext_free))(m->m_ext.ext_arg1,
                            m->m_ext.ext_arg2);
                        break;
                default:
                        KASSERT(m->m_ext.ext_type == 0,
                                ("%s: unknown ext_type", __func__));
                }
        }
        if (skipmbuf)
                return;
        
        /*
         * 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_arg1 = NULL;
        m->m_ext.ext_arg2 = NULL;
        m->m_ext.ref_cnt = NULL;
        m->m_ext.ext_size = 0;
        m->m_ext.ext_type = 0;
        m->m_flags &= ~M_EXT;
        uma_zfree(zone_mbuf, m);
}

/*
 * Attach 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_arg1 = m->m_ext.ext_arg1;
        n->m_ext.ext_arg2 = m->m_ext.ext_arg2;
        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;
        n->m_flags |= m->m_flags & M_RDONLY;
}

/*
 * Clean up mbuf (chain) from any tags and packet headers.
 * If "all" is set then the first mbuf in the chain will be
 * cleaned too.
 */
void
m_demote(struct mbuf *m0, int all)
{
        struct mbuf *m;

        for (m = all ? m0 : m0->m_next; m != NULL; m = m->m_next) {
                if (m->m_flags & M_PKTHDR) {
                        m_tag_delete_chain(m, NULL);
                        m->m_flags &= ~M_PKTHDR;
                        bzero(&m->m_pkthdr, sizeof(struct pkthdr));
                }
                if (m != m0 && m->m_nextpkt != NULL) {
                        KASSERT(m->m_nextpkt == NULL,
                            ("%s: m_nextpkt not NULL", __func__));
                        m_freem(m->m_nextpkt);
                        m->m_nextpkt = NULL;
                }
                m->m_flags = m->m_flags & (M_EXT|M_RDONLY|M_FREELIST|M_NOFREE);
        }
}

/*
 * Sanity checks on mbuf (chain) for use in KASSERT() and general
 * debugging.
 * Returns 0 or panics when bad and 1 on all tests passed.
 * Sanitize, 0 to run M_SANITY_ACTION, 1 to garble things so they
 * blow up later.
 */
int
m_sanity(struct mbuf *m0, int sanitize)
{
        struct mbuf *m;
        caddr_t a, b;
        int pktlen = 0;

#ifdef INVARIANTS
#define M_SANITY_ACTION(s)      panic("mbuf %p: " s, m)
#else 
#define M_SANITY_ACTION(s)      printf("mbuf %p: " s, m)
#endif

        for (m = m0; m != NULL; m = m->m_next) {
                /*
                 * Basic pointer checks.  If any of these fails then some
                 * unrelated kernel memory before or after us is trashed.
                 * No way to recover from that.
                 */
                a = ((m->m_flags & M_EXT) ? m->m_ext.ext_buf :
                        ((m->m_flags & M_PKTHDR) ? (caddr_t)(&m->m_pktdat) :
                         (caddr_t)(&m->m_dat)) );
                b = (caddr_t)(a + (m->m_flags & M_EXT ? m->m_ext.ext_size :
                        ((m->m_flags & M_PKTHDR) ? MHLEN : MLEN)));
                if ((caddr_t)m->m_data < a)
                        M_SANITY_ACTION("m_data outside mbuf data range left");
                if ((caddr_t)m->m_data > b)
                        M_SANITY_ACTION("m_data outside mbuf data range right");
                if ((caddr_t)m->m_data + m->m_len > b)
                        M_SANITY_ACTION("m_data + m_len exeeds mbuf space");
                if ((m->m_flags & M_PKTHDR) && m->m_pkthdr.header) {
                        if ((caddr_t)m->m_pkthdr.header < a ||
                            (caddr_t)m->m_pkthdr.header > b)
                                M_SANITY_ACTION("m_pkthdr.header outside mbuf data range");
                }

                /* m->m_nextpkt may only be set on first mbuf in chain. */
                if (m != m0 && m->m_nextpkt != NULL) {
                        if (sanitize) {
                                m_freem(m->m_nextpkt);
                                m->m_nextpkt = (struct mbuf *)0xDEADC0DE;
                        } else
                                M_SANITY_ACTION("m->m_nextpkt on in-chain mbuf");
                }

                /* packet length (not mbuf length!) calculation */
                if (m0->m_flags & M_PKTHDR)
                        pktlen += m->m_len;

                /* m_tags may only be attached to first mbuf in chain. */
                if (m != m0 && m->m_flags & M_PKTHDR &&
                    !SLIST_EMPTY(&m->m_pkthdr.tags)) {
                        if (sanitize) {
                                m_tag_delete_chain(m, NULL);
                                /* put in 0xDEADC0DE perhaps? */
                        } else
                                M_SANITY_ACTION("m_tags on in-chain mbuf");
                }

                /* M_PKTHDR may only be set on first mbuf in chain */
                if (m != m0 && m->m_flags & M_PKTHDR) {
                        if (sanitize) {
                                bzero(&m->m_pkthdr, sizeof(m->m_pkthdr));
                                m->m_flags &= ~M_PKTHDR;
                                /* put in 0xDEADCODE and leave hdr flag in */
                        } else
                                M_SANITY_ACTION("M_PKTHDR on in-chain mbuf");
                }
        }
        m = m0;
        if (pktlen && pktlen != m->m_pkthdr.len) {
                if (sanitize)
                        m->m_pkthdr.len = 0;
                else
                        M_SANITY_ACTION("m_pkthdr.len != mbuf chain length");
        }
        return 1;

#undef  M_SANITY_ACTION
}


/*
 * "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)
{

#if 0
        /* see below for why these are not enabled */
        M_ASSERTPKTHDR(to);
        /* Note: with MAC, this may not be a good assertion. */
        KASSERT(SLIST_EMPTY(&to->m_pkthdr.tags),
            ("m_move_pkthdr: to has tags"));
#endif
#ifdef MAC
        /*
         * XXXMAC: It could be this should also occur for non-MAC?
         */
        if (to->m_flags & M_PKTHDR)
                m_tag_delete_chain(to, NULL);
#endif
        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;
}

/*
 * 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)
{

#if 0
        /*
         * The mbuf allocator only initializes the pkthdr
         * when the mbuf is allocated with MGETHDR. Many users
         * (e.g. m_copy*, m_prepend) use MGET and then
         * smash the pkthdr as needed causing these
         * assertions to trip.  For now just disable them.
         */
        M_ASSERTPKTHDR(to);
        /* Note: with MAC, this may not be a good assertion. */
        KASSERT(SLIST_EMPTY(&to->m_pkthdr.tags), ("m_dup_pkthdr: to has tags"));
#endif
        MBUF_CHECKSLEEP(how);
#ifdef MAC
        if (to->m_flags & M_PKTHDR)
                m_tag_delete_chain(to, NULL);
#endif
        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)));
}

/*
 * 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);
}

/*
 * 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_WAIT/M_DONTWAIT 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));
        MBUF_CHECKSLEEP(wait);
        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
                        bcopy(mtod(m, caddr_t)+off, mtod(n, caddr_t),
                            (u_int)n->m_len);
                if (len != M_COPYALL)
                        len -= n->m_len;
                off = 0;
                m = m->m_next;
                np = &n->m_next;
        }
        if (top == NULL)
                mbstat.m_mcfail++;      /* XXX: No consistency. */

        return (top);
nospace:
        m_freem(top);
        mbstat.m_mcfail++;      /* XXX: No consistency. */
        return (NULL);
}

/*
 * Returns mbuf chain with new head for the prepending case.
 * Copies from mbuf (chain) n from off for len to mbuf (chain) m
 * either prepending or appending the data.
 * The resulting mbuf (chain) m is fully writeable.
 * m is destination (is made writeable)
 * n is source, off is offset in source, len is len from offset
 * dir, 0 append, 1 prepend
 * how, wait or nowait
 */

static int
m_bcopyxxx(void *s, void *t, u_int len)
{
        bcopy(s, t, (size_t)len);
        return 0;
}

struct mbuf *
m_copymdata(struct mbuf *m, struct mbuf *n, int off, int len,
    int prep, int how)
{
        struct mbuf *mm, *x, *z, *prev = NULL;
        caddr_t p;
        int i, nlen = 0;
        caddr_t buf[MLEN];

        KASSERT(m != NULL && n != NULL, ("m_copymdata, no target or source"));
        KASSERT(off >= 0, ("m_copymdata, negative off %d", off));
        KASSERT(len >= 0, ("m_copymdata, negative len %d", len));
        KASSERT(prep == 0 || prep == 1, ("m_copymdata, unknown direction %d", prep));

        mm = m;
        if (!prep) {
                while(mm->m_next) {
                        prev = mm;
                        mm = mm->m_next;
                }
        }
        for (z = n; z != NULL; z = z->m_next)
                nlen += z->m_len;
        if (len == M_COPYALL)
                len = nlen - off;
        if (off + len > nlen || len < 1)
                return NULL;

        if (!M_WRITABLE(mm)) {
                /* XXX: Use proper m_xxx function instead. */
                x = m_getcl(how, MT_DATA, mm->m_flags);
                if (x == NULL)
                        return NULL;
                bcopy(mm->m_ext.ext_buf, x->m_ext.ext_buf, x->m_ext.ext_size);
                p = x->m_ext.ext_buf + (mm->m_data - mm->m_ext.ext_buf);
                x->m_data = p;
                mm->m_next = NULL;
                if (mm != m)
                        prev->m_next = x;
                m_free(mm);
                mm = x;
        }

        /*
         * Append/prepend the data.  Allocating mbufs as necessary.
         */
        /* Shortcut if enough free space in first/last mbuf. */
        if (!prep && M_TRAILINGSPACE(mm) >= len) {
                m_apply(n, off, len, m_bcopyxxx, mtod(mm, caddr_t) +
                         mm->m_len);
                mm->m_len += len;
                mm->m_pkthdr.len += len;
                return m;
        }
        if (prep && M_LEADINGSPACE(mm) >= len) {
                mm->m_data = mtod(mm, caddr_t) - len;
                m_apply(n, off, len, m_bcopyxxx, mtod(mm, caddr_t));
                mm->m_len += len;
                mm->m_pkthdr.len += len;
                return mm;
        }

        /* Expand first/last mbuf to cluster if possible. */
        if (!prep && !(mm->m_flags & M_EXT) && len > M_TRAILINGSPACE(mm)) {
                bcopy(mm->m_data, &buf, mm->m_len);
                m_clget(mm, how);
                if (!(mm->m_flags & M_EXT))
                        return NULL;
                bcopy(&buf, mm->m_ext.ext_buf, mm->m_len);
                mm->m_data = mm->m_ext.ext_buf;
                mm->m_pkthdr.header = NULL;
        }
        if (prep && !(mm->m_flags & M_EXT) && len > M_LEADINGSPACE(mm)) {
                bcopy(mm->m_data, &buf, mm->m_len);
                m_clget(mm, how);
                if (!(mm->m_flags & M_EXT))
                        return NULL;
                bcopy(&buf, (caddr_t *)mm->m_ext.ext_buf +
                       mm->m_ext.ext_size - mm->m_len, mm->m_len);
                mm->m_data = (caddr_t)mm->m_ext.ext_buf +
                              mm->m_ext.ext_size - mm->m_len;
                mm->m_pkthdr.header = NULL;
        }

        /* Append/prepend as many mbuf (clusters) as necessary to fit len. */
        if (!prep && len > M_TRAILINGSPACE(mm)) {
                if (!m_getm(mm, len - M_TRAILINGSPACE(mm), how, MT_DATA))
                        return NULL;
        }
        if (prep && len > M_LEADINGSPACE(mm)) {
                if (!(z = m_getm(NULL, len - M_LEADINGSPACE(mm), how, MT_DATA)))
                        return NULL;
                i = 0;
                for (x = z; x != NULL; x = x->m_next) {
                        i += x->m_flags & M_EXT ? x->m_ext.ext_size :
                              (x->m_flags & M_PKTHDR ? MHLEN : MLEN);
                        if (!x->m_next)
                                break;
                }
                z->m_data += i - len;
                m_move_pkthdr(mm, z);
                x->m_next = mm;
                mm = z;
        }

        /* Seek to start position in source mbuf. Optimization for long chains. */
        while (off > 0) {
                if (off < n->m_len)
                        break;
                off -= n->m_len;
                n = n->m_next;
        }

        /* Copy data into target mbuf. */
        z = mm;
        while (len > 0) {
                KASSERT(z != NULL, ("m_copymdata, falling off target edge"));
                i = M_TRAILINGSPACE(z);
                m_apply(n, off, i, m_bcopyxxx, mtod(z, caddr_t) + z->m_len);
                z->m_len += i;
                /* fixup pkthdr.len if necessary */
                if ((prep ? mm : m)->m_flags & M_PKTHDR)
                        (prep ? mm : m)->m_pkthdr.len += i;
                off += i;
                len -= i;
                z = z->m_next;
        }
        return (prep ? mm : m);
}

/*
 * Copy an entire packet, including header (which must be present).
 * An optimization of the common case `m_copym(m, 0, M_COPYALL, how)'.
 * Note that the copy is read-only, because clusters are not copied,
 * only their reference counts are incremented.
 * Preserve alignment of the first mbuf so if the creator has left
 * some room at the beginning (e.g. for inserting protocol headers)
 * the copies still have the room available.
 */
struct mbuf *
m_copypacket(struct mbuf *m, int how)
{
        struct mbuf *top, *n, *o;

        MBUF_CHECKSLEEP(how);
        MGET(n, how, m->m_type);
        top = n;
        if (n == NULL)
                goto nospace;

        if (!m_dup_pkthdr(n, m, how))
                goto nospace;
        n->m_len = m->m_len;
        if (m->m_flags & M_EXT) {
                n->m_data = m->m_data;
                mb_dupcl(n, m);
        } else {
                n->m_data = n->m_pktdat + (m->m_data - m->m_pktdat );
                bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
        }

        m = m->m_next;
        while (m) {
                MGET(o, how, m->m_type);
                if (o == NULL)
                        goto nospace;

                n->m_next = o;
                n = n->m_next;

                n->m_len = m->m_len;
                if (m->m_flags & M_EXT) {
                        n->m_data = m->m_data;
                        mb_dupcl(n, m);
                } else {
                        bcopy(mtod(m, char *), mtod(n, char *), n->m_len);
                }

                m = m->m_next;
        }
        return top;
nospace:
        m_freem(top);
        mbstat.m_mcfail++;      /* XXX: No consistency. */ 
        return (NULL);
}

/*
 * 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);
                bcopy(mtod(m, caddr_t) + off, cp, count);
                len -= count;
                cp += count;
                off = 0;
                m = m->m_next;
        }
}

/*
 * Copy a packet header mbuf chain into a completely new chain, including
 * copying any mbuf clusters.  Use this instead of m_copypacket() when
 * you need a writable copy of an mbuf chain.
 */
struct mbuf *
m_dup(struct mbuf *m, int how)
{
        struct mbuf **p, *top = NULL;
        int remain, moff, nsize;

        MBUF_CHECKSLEEP(how);
        /* Sanity check */
        if (m == NULL)
                return (NULL);
        M_ASSERTPKTHDR(m);

        /* While there's more data, get a new mbuf, tack it on, and fill it */
        remain = m->m_pkthdr.len;
        moff = 0;
        p = &top;
        while (remain > 0 || top == NULL) {     /* allow m->m_pkthdr.len == 0 */
                struct mbuf *n;

                /* Get the next new mbuf */
                if (remain >= MINCLSIZE) {
                        n = m_getcl(how, m->m_type, 0);
                        nsize = MCLBYTES;
                } else {
                        n = m_get(how, m->m_type);
                        nsize = MLEN;
                }
                if (n == NULL)
                        goto nospace;

                if (top == NULL) {              /* First one, must be PKTHDR */
                        if (!m_dup_pkthdr(n, m, how)) {
                                m_free(n);
                                goto nospace;
                        }
                        if ((n->m_flags & M_EXT) == 0)
                                nsize = MHLEN;
                        n->m_flags &= ~M_RDONLY;
                }
                n->m_len = 0;

                /* Link it into the new chain */
                *p = n;
                p = &n->m_next;

                /* Copy data from original mbuf(s) into new mbuf */
                while (n->m_len < nsize && m != NULL) {
                        int chunk = min(nsize - n->m_len, m->m_len - moff);

                        bcopy(m->m_data + moff, n->m_data + n->m_len, chunk);
                        moff += chunk;
                        n->m_len += chunk;
                        remain -= chunk;
                        if (moff == m->m_len) {
                                m = m->m_next;
                                moff = 0;
                        }
                }

                /* Check correct total mbuf length */
                KASSERT((remain > 0 && m != NULL) || (remain == 0 && m == NULL),
                        ("%s: bogus m_pkthdr.len", __func__));
        }
        return (top);

nospace:
        m_freem(top);
        mbstat.m_mcfail++;      /* XXX: No consistency. */
        return (NULL);
}

/*
 * 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_WRITABLE(m) ||
                    M_TRAILINGSPACE(m) < n->m_len) {
                        /* just join the two chains */
                        m->m_next = n;
                        return;
                }
                /* splat the data from one into the other */
                bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
                    (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;
                        }
                }
                if (mp->m_flags & M_PKTHDR)
                        mp->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;
                }
        }
}

/*
 * 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_DONTWAIT, n->m_type);
                if (m == NULL)
                        goto bad;
                m->m_len = 0;
                if (n->m_flags & M_PKTHDR)
                        M_MOVE_PKTHDR(m, n);
        }
        space = &m->m_dat[MLEN] - (m->m_data + m->m_len);
        do {
                count = min(min(max(len, max_protohdr), space), n->m_len);
                bcopy(mtod(n, caddr_t), mtod(m, caddr_t) + m->m_len,
                  (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);
        mbstat.m_mpfail++;      /* XXX: No consistency. */
        return (NULL);
}

/*
 * Like m_pullup(), except a new mbuf is always allocated, and we allow
 * the amount of empty space before the data in the new mbuf to be specified
 * (in the event that the caller expects to prepend later).
 */
int MSFail;

struct mbuf *
m_copyup(struct mbuf *n, int len, int dstoff)
{
        struct mbuf *m;
        int count, space;

        if (len > (MHLEN - dstoff))
                goto bad;
        MGET(m, M_DONTWAIT, n->m_type);
        if (m == NULL)
                goto bad;
        m->m_len = 0;
        if (n->m_flags & M_PKTHDR)
                M_MOVE_PKTHDR(m, n);
        m->m_data += dstoff;
        space = &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),
                    (unsigned)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);
        MSFail++;
        return (NULL);
}

/*
 * 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 && 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 {
                bcopy(mtod(m, caddr_t) + len, mtod(n, caddr_t), remain);
        }
        n->m_len = remain;
        m->m_len = len;
        n->m_next = m->m_next;
        m->m_next = NULL;
        return (n);
}
/*
 * Routine to copy from device local memory into mbufs.
 * Note that `off' argument is offset into first mbuf of target chain from
 * which to begin copying the data to.
 */
struct mbuf *
m_devget(char *buf, int totlen, int off, struct ifnet *ifp,
    void (*copy)(char *from, caddr_t to, u_int len))
{
        struct mbuf *m;
        struct mbuf *top = NULL, **mp = &top;
        int len;

        if (off < 0 || off > MHLEN)
                return (NULL);

        while (totlen > 0) {
                if (top == NULL) {      /* First one, must be PKTHDR */
                        if (totlen + off >= MINCLSIZE) {
                                m = m_getcl(M_DONTWAIT, MT_DATA, M_PKTHDR);
                                len = MCLBYTES;
                        } else {
                                m = m_gethdr(M_DONTWAIT, MT_DATA);
                                len = MHLEN;

                                /* Place initial small packet/header at end of mbuf */
                                if (m && totlen + off + max_linkhdr <= MLEN) {
                                        m->m_data += max_linkhdr;
                                        len -= max_linkhdr;
                                }
                        }
                        if (m == NULL)
                                return NULL;
                        m->m_pkthdr.rcvif = ifp;
                        m->m_pkthdr.len = totlen;
                } else {
                        if (totlen + off >= MINCLSIZE) {
                                m = m_getcl(M_DONTWAIT, MT_DATA, 0);
                                len = MCLBYTES;
                        } else {
                                m = m_get(M_DONTWAIT, MT_DATA);
                                len = MLEN;
                        }
                        if (m == NULL) {
                                m_freem(top);
                                return NULL;
                        }
                }
                if (off) {
                        m->m_data += off;
                        len -= off;
                        off = 0;
                }
                m->m_len = len = min(totlen, len);
                if (copy)
                        copy(buf, mtod(m, caddr_t), (u_int)len);
                else
                        bcopy(buf, mtod(m, caddr_t), (u_int)len);
                buf += len;
                *mp = m;
                mp = &m->m_next;
                totlen -= len;
        }
        return (top);
}

/*
 * 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, c_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_DONTWAIT, m->m_type);
                        if (n == NULL)
                                goto out;
                        bzero(mtod(n, caddr_t), MLEN);
                        n->m_len = min(MLEN, len + off);
                        m->m_next = n;
                }
                m = m->m_next;
        }
        while (len > 0) {
                if (m->m_next == NULL && (len > m->m_len - off)) {
                        m->m_len += min(len - (m->m_len - off),
                            M_TRAILINGSPACE(m));
                }
                mlen = min (m->m_len - off, len);
                bcopy(cp, off + mtod(m, caddr_t), (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_DONTWAIT, 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;
}

/*
 * Append the specified data to the indicated mbuf chain,
 * Extend the mbuf chain if the new data does not fit in
 * existing space.
 *
 * Return 1 if able to complete the job; otherwise 0.
 */
int
m_append(struct mbuf *m0, int len, c_caddr_t cp)
{
        struct mbuf *m, *n;
        int remainder, space;

        for (m = m0; m->m_next != NULL; m = m->m_next)
                ;
        remainder = len;
        space = M_TRAILINGSPACE(m);
        if (space > 0) {
                /*
                 * Copy into available space.
                 */
                if (space > remainder)
                        space = remainder;
                bcopy(cp, mtod(m, caddr_t) + m->m_len, space);
                m->m_len += space;
                cp += space, remainder -= space;
        }
        while (remainder > 0) {
                /*
                 * Allocate a new mbuf; could check space
                 * and allocate a cluster instead.
                 */
                n = m_get(M_DONTWAIT, m->m_type);
                if (n == NULL)
                        break;
                n->m_len = min(MLEN, remainder);
                bcopy(cp, mtod(n, caddr_t), n->m_len);
                cp += n->m_len, remainder -= n->m_len;
                m->m_next = n;
                m = n;
        }
        if (m0->m_flags & M_PKTHDR)
                m0->m_pkthdr.len += len - remainder;
        return (remainder == 0);
}

/*
 * 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);
}

/*
 * Return a pointer to mbuf/offset of location in mbuf chain.
 */
struct mbuf *
m_getptr(struct mbuf *m, int loc, int *off)
{

        while (loc >= 0) {
                /* Normal end of search. */
                if (m->m_len > loc) {
                        *off = loc;
                        return (m);
                } else {
                        loc -= m->m_len;
                        if (m->m_next == NULL) {
                                if (loc == 0) {
                                        /* Point at the end of valid data. */
                                        *off = m->m_len;
                                        return (m);
                                }
                                return (NULL);
                        }
                        m = m->m_next;
                }
        }
        return (NULL);
}

void
m_print(const struct mbuf *m, int maxlen)
{
        int len;
        int pdata;
        const struct mbuf *m2;

        if (m == NULL) {
                printf("mbuf: %p\n", m);
                return;
        }

        if (m->m_flags & M_PKTHDR)
                len = m->m_pkthdr.len;
        else
                len = -1;
        m2 = m;
        while (m2 != NULL && (len == -1 || len)) {
                pdata = m2->m_len;
                if (maxlen != -1 && pdata > maxlen)
                        pdata = maxlen;
                printf("mbuf: %p len: %d, next: %p, %b%s", m2, m2->m_len,
                    m2->m_next, m2->m_flags, "\20\20freelist\17skipfw"
                    "\11proto5\10proto4\7proto3\6proto2\5proto1\4rdonly"
                    "\3eor\2pkthdr\1ext", pdata ? "" : "\n");
                if (pdata)
                        printf(", %*D\n", pdata, (u_char *)m2->m_data, "-");
                if (len != -1)
                        len -= m2->m_len;
                m2 = m2->m_next;
        }
        if (len > 0)
                printf("%d bytes unaccounted for.\n", len);
        return;
}

u_int
m_fixhdr(struct mbuf *m0)
{
        u_int len;

        len = m_length(m0, NULL);
        m0->m_pkthdr.len = len;
        return (len);
}

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);
}

/*
 * Defragment a mbuf chain, returning the shortest possible
 * chain of mbufs and clusters.  If allocation fails and
 * this cannot be completed, NULL will be returned, but
 * the passed in chain will be unchanged.  Upon success,
 * the original chain will be freed, and the new chain
 * will be returned.
 *
 * If a non-packet header is passed in, the original
 * mbuf (chain?) will be returned unharmed.
 */
struct mbuf *
m_defrag(struct mbuf *m0, int how)
{
        struct mbuf *m_new = NULL, *m_final = NULL;
        int progress = 0, length;

        MBUF_CHECKSLEEP(how);
        if (!(m0->m_flags & M_PKTHDR))
                return (m0);

        m_fixhdr(m0); /* Needed sanity check */

#ifdef MBUF_STRESS_TEST
        if (m_defragrandomfailures) {
                int temp = arc4random() & 0xff;
                if (temp == 0xba)
                        goto nospace;
        }
#endif
        
        if (m0->m_pkthdr.len > MHLEN)
                m_final = m_getcl(how, MT_DATA, M_PKTHDR);
        else
                m_final = m_gethdr(how, MT_DATA);

        if (m_final == NULL)
                goto nospace;

        if (m_dup_pkthdr(m_final, m0, how) == 0)
                goto nospace;

        m_new = m_final;

        while (progress < m0->m_pkthdr.len) {
                length = m0->m_pkthdr.len - progress;
                if (length > MCLBYTES)
                        length = MCLBYTES;

                if (m_new == NULL) {
                        if (length > MLEN)
                                m_new = m_getcl(how, MT_DATA, 0);
                        else
                                m_new = m_get(how, MT_DATA);
                        if (m_new == NULL)
                                goto nospace;
                }

                m_copydata(m0, progress, length, mtod(m_new, caddr_t));
                progress += length;
                m_new->m_len = length;
                if (m_new != m_final)
                        m_cat(m_final, m_new);
                m_new = NULL;
        }
#ifdef MBUF_STRESS_TEST
        if (m0->m_next == NULL)
                m_defraguseless++;
#endif
        m_freem(m0);
        m0 = m_final;
#ifdef MBUF_STRESS_TEST
        m_defragpackets++;
        m_defragbytes += m0->m_pkthdr.len;
#endif
        return (m0);
nospace:
#ifdef MBUF_STRESS_TEST
        m_defragfailure++;
#endif
        if (m_final)
                m_freem(m_final);
        return (NULL);
}

/*
 * Defragment an mbuf chain, returning at most maxfrags separate
 * mbufs+clusters.  If this is not possible NULL is returned and
 * the original mbuf chain is left in it's present (potentially
 * modified) state.  We use two techniques: collapsing consecutive
 * mbufs and replacing consecutive mbufs by a cluster.
 *
 * NB: this should really be named m_defrag but that name is taken
 */
struct mbuf *
m_collapse(struct mbuf *m0, int how, int maxfrags)
{
        struct mbuf *m, *n, *n2, **prev;
        u_int curfrags;

        /*
         * Calculate the current number of frags.
         */
        curfrags = 0;
        for (m = m0; m != NULL; m = m->m_next)
                curfrags++;
        /*
         * First, try to collapse mbufs.  Note that we always collapse
         * towards the front so we don't need to deal with moving the
         * pkthdr.  This may be suboptimal if the first mbuf has much
         * less data than the following.
         */
        m = m0;
again:
        for (;;) {
                n = m->m_next;
                if (n == NULL)
                        break;
                if (M_WRITABLE(m) &&
                    n->m_len < M_TRAILINGSPACE(m)) {
                        bcopy(mtod(n, void *), mtod(m, char *) + m->m_len,
                                n->m_len);
                        m->m_len += n->m_len;
                        m->m_next = n->m_next;
                        m_free(n);
                        if (--curfrags <= maxfrags)
                                return m0;
                } else
                        m = n;
        }
        KASSERT(maxfrags > 1,
                ("maxfrags %u, but normal collapse failed", maxfrags));
        /*
         * Collapse consecutive mbufs to a cluster.
         */
        prev = &m0->m_next;             /* NB: not the first mbuf */
        while ((n = *prev) != NULL) {
                if ((n2 = n->m_next) != NULL &&
                    n->m_len + n2->m_len < MCLBYTES) {
                        m = m_getcl(how, MT_DATA, 0);
                        if (m == NULL)
                                goto bad;
                        bcopy(mtod(n, void *), mtod(m, void *), n->m_len);
                        bcopy(mtod(n2, void *), mtod(m, char *) + n->m_len,
                                n2->m_len);
                        m->m_len = n->m_len + n2->m_len;
                        m->m_next = n2->m_next;
                        *prev = m;
                        m_free(n);
                        m_free(n2);
                        if (--curfrags <= maxfrags)     /* +1 cl -2 mbufs */
                                return m0;
                        /*
                         * Still not there, try the normal collapse
                         * again before we allocate another cluster.
                         */
                        goto again;
                }
                prev = &n->m_next;
        }
        /*
         * No place where we can collapse to a cluster; punt.
         * This can occur if, for example, you request 2 frags
         * but the packet requires that both be clusters (we
         * never reallocate the first mbuf to avoid moving the
         * packet header).
         */
bad:
        return NULL;
}

#ifdef MBUF_STRESS_TEST

/*
 * Fragment an mbuf chain.  There's no reason you'd ever want to do
 * this in normal usage, but it's great for stress testing various
 * mbuf consumers.
 *
 * If fragmentation is not possible, the original chain will be
 * returned.
 *
 * Possible length values:
 * 0     no fragmentation will occur
 * > 0  each fragment will be of the specified length
 * -1   each fragment will be the same random value in length
 * -2   each fragment's length will be entirely random
 * (Random values range from 1 to 256)
 */
struct mbuf *
m_fragment(struct mbuf *m0, int how, int length)
{
        struct mbuf *m_new = NULL, *m_final = NULL;
        int progress = 0;

        if (!(m0->m_flags & M_PKTHDR))
                return (m0);
        
        if ((length == 0) || (length < -2))
                return (m0);

        m_fixhdr(m0); /* Needed sanity check */

        m_final = m_getcl(how, MT_DATA, M_PKTHDR);

        if (m_final == NULL)
                goto nospace;

        if (m_dup_pkthdr(m_final, m0, how) == 0)
                goto nospace;

        m_new = m_final;

        if (length == -1)
                length = 1 + (arc4random() & 255);

        while (progress < m0->m_pkthdr.len) {
                int fraglen;

                if (length > 0)
                        fraglen = length;
                else
                        fraglen = 1 + (arc4random() & 255);
                if (fraglen > m0->m_pkthdr.len - progress)
                        fraglen = m0->m_pkthdr.len - progress;

                if (fraglen > MCLBYTES)
                        fraglen = MCLBYTES;

                if (m_new == NULL) {
                        m_new = m_getcl(how, MT_DATA, 0);
                        if (m_new == NULL)
                                goto nospace;
                }

                m_copydata(m0, progress, fraglen, mtod(m_new, caddr_t));
                progress += fraglen;
                m_new->m_len = fraglen;
                if (m_new != m_final)
                        m_cat(m_final, m_new);
                m_new = NULL;
        }
        m_freem(m0);
        m0 = m_final;
        return (m0);
nospace:
        if (m_final)
                m_freem(m_final);
        /* Return the original chain on failure */
        return (m0);
}

#endif

/*
 * 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, max(total + align, 1), how, MT_DATA, flags);
        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 = 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);
}

/*
 * Copy an mbuf chain into a uio limited by len if set.
 */
int
m_mbuftouio(struct uio *uio, struct mbuf *m, int len)
{
        int error, length, total;
        int progress = 0;

        if (len > 0)
                total = min(uio->uio_resid, len);
        else
                total = uio->uio_resid;

        /* Fill the uio with data from the mbufs. */
        for (; m != NULL; m = m->m_next) {
                length = min(m->m_len, total - progress);

                error = uiomove(mtod(m, void *), length, uio);
                if (error)
                        return (error);

                progress += length;
        }

        return (0);
}

/*
 * Set the m_data pointer of a newly-allocated mbuf
 * to place an object of the specified size at the
 * end of the mbuf, longword aligned.
 */
void
m_align(struct mbuf *m, int len)
{
        int adjust;

        if (m->m_flags & M_EXT)
                adjust = m->m_ext.ext_size - len;
        else if (m->m_flags & M_PKTHDR)
                adjust = MHLEN - len;
        else
                adjust = MLEN - len;
        m->m_data += adjust &~ (sizeof(long)-1);
}

/*
 * Create a writable copy of the mbuf chain.  While doing this
 * we compact the chain with a goal of producing a chain with
 * at most two mbufs.  The second mbuf in this chain is likely
 * to be a cluster.  The primary purpose of this work is to create
 * a writable packet for encryption, compression, etc.  The
 * secondary goal is to linearize the data so the data can be
 * passed to crypto hardware in the most efficient manner possible.
 */
struct mbuf *
m_unshare(struct mbuf *m0, int how)
{
        struct mbuf *m, *mprev;
        struct mbuf *n, *mfirst, *mlast;
        int len, off;

        mprev = NULL;
        for (m = m0; m != NULL; m = mprev->m_next) {
                /*
                 * Regular mbufs are ignored unless there's a cluster
                 * in front of it that we can use to coalesce.  We do
                 * the latter mainly so later clusters can be coalesced
                 * also w/o having to handle them specially (i.e. convert
                 * mbuf+cluster -> cluster).  This optimization is heavily
                 * influenced by the assumption that we're running over
                 * Ethernet where MCLBYTES is large enough that the max
                 * packet size will permit lots of coalescing into a
                 * single cluster.  This in turn permits efficient
                 * crypto operations, especially when using hardware.
                 */
                if ((m->m_flags & M_EXT) == 0) {
                        if (mprev && (mprev->m_flags & M_EXT) &&
                            m->m_len <= M_TRAILINGSPACE(mprev)) {
                                /* XXX: this ignores mbuf types */
                                memcpy(mtod(mprev, caddr_t) + mprev->m_len,
                                       mtod(m, caddr_t), m->m_len);
                                mprev->m_len += m->m_len;
                                mprev->m_next = m->m_next;      /* unlink from chain */
                                m_free(m);                      /* reclaim mbuf */
#if 0
                                newipsecstat.ips_mbcoalesced++;
#endif
                        } else {
                                mprev = m;
                        }
                        continue;
                }
                /*
                 * Writable mbufs are left alone (for now).
                 */
                if (M_WRITABLE(m)) {
                        mprev = m;
                        continue;
                }

                /*
                 * Not writable, replace with a copy or coalesce with
                 * the previous mbuf if possible (since we have to copy
                 * it anyway, we try to reduce the number of mbufs and
                 * clusters so that future work is easier).
                 */
                KASSERT(m->m_flags & M_EXT, ("m_flags 0x%x", m->m_flags));
                /* NB: we only coalesce into a cluster or larger */
                if (mprev != NULL && (mprev->m_flags & M_EXT) &&
                    m->m_len <= M_TRAILINGSPACE(mprev)) {
                        /* XXX: this ignores mbuf types */
                        memcpy(mtod(mprev, caddr_t) + mprev->m_len,
                               mtod(m, caddr_t), m->m_len);
                        mprev->m_len += m->m_len;
                        mprev->m_next = m->m_next;      /* unlink from chain */
                        m_free(m);                      /* reclaim mbuf */
#if 0
                        newipsecstat.ips_clcoalesced++;
#endif
                        continue;
                }

                /*
                 * Allocate new space to hold the copy...
                 */
                /* XXX why can M_PKTHDR be set past the first mbuf? */
                if (mprev == NULL && (m->m_flags & M_PKTHDR)) {
                        /*
                         * NB: if a packet header is present we must
                         * allocate the mbuf separately from any cluster
                         * because M_MOVE_PKTHDR will smash the data
                         * pointer and drop the M_EXT marker.
                         */
                        MGETHDR(n, how, m->m_type);
                        if (n == NULL) {
                                m_freem(m0);
                                return (NULL);
                        }
                        M_MOVE_PKTHDR(n, m);
                        MCLGET(n, how);
                        if ((n->m_flags & M_EXT) == 0) {
                                m_free(n);
                                m_freem(m0);
                                return (NULL);
                        }
                } else {
                        n = m_getcl(how, m->m_type, m->m_flags);
                        if (n == NULL) {
                                m_freem(m0);
                                return (NULL);
                        }
                }
                /*
                 * ... and copy the data.  We deal with jumbo mbufs
                 * (i.e. m_len > MCLBYTES) by splitting them into
                 * clusters.  We could just malloc a buffer and make
                 * it external but too many device drivers don't know
                 * how to break up the non-contiguous memory when
                 * doing DMA.
                 */
                len = m->m_len;
                off = 0;
                mfirst = n;
                mlast = NULL;
                for (;;) {
                        int cc = min(len, MCLBYTES);
                        memcpy(mtod(n, caddr_t), mtod(m, caddr_t) + off, cc);
                        n->m_len = cc;
                        if (mlast != NULL)
                                mlast->m_next = n;
                        mlast = n;      
#if 0
                        newipsecstat.ips_clcopied++;
#endif

                        len -= cc;
                        if (len <= 0)
                                break;
                        off += cc;

                        n = m_getcl(how, m->m_type, m->m_flags);
                        if (n == NULL) {
                                m_freem(mfirst);
                                m_freem(m0);
                                return (NULL);
                        }
                }
                n->m_next = m->m_next; 
                if (mprev == NULL)
                        m0 = mfirst;            /* new head of chain */
                else
                        mprev->m_next = mfirst; /* replace old mbuf */
                m_free(m);                      /* release old mbuf */
                mprev = mfirst;
        }
        return (m0);
}

#ifdef MBUF_PROFILING

#define MP_BUCKETS 32 /* don't just change this as things may overflow.*/
struct mbufprofile {
        uintmax_t wasted[MP_BUCKETS];
        uintmax_t used[MP_BUCKETS];
        uintmax_t segments[MP_BUCKETS];
} mbprof;

#define MP_MAXDIGITS 21 /* strlen("16,000,000,000,000,000,000") == 21 */
#define MP_NUMLINES 6
#define MP_NUMSPERLINE 16
#define MP_EXTRABYTES 64        /* > strlen("used:\nwasted:\nsegments:\n") */
/* work out max space needed and add a bit of spare space too */
#define MP_MAXLINE ((MP_MAXDIGITS+1) * MP_NUMSPERLINE)
#define MP_BUFSIZE ((MP_MAXLINE * MP_NUMLINES) + 1 + MP_EXTRABYTES)

char mbprofbuf[MP_BUFSIZE];

void
m_profile(struct mbuf *m)
{
        int segments = 0;
        int used = 0;
        int wasted = 0;
        
        while (m) {
                segments++;
                used += m->m_len;
                if (m->m_flags & M_EXT) {
                        wasted += MHLEN - sizeof(m->m_ext) +
                            m->m_ext.ext_size - m->m_len;
                } else {
                        if (m->m_flags & M_PKTHDR)
                                wasted += MHLEN - m->m_len;
                        else
                                wasted += MLEN - m->m_len;
                }
                m = m->m_next;
        }
        /* be paranoid.. it helps */
        if (segments > MP_BUCKETS - 1)
                segments = MP_BUCKETS - 1;
        if (used > 100000)
                used = 100000;
        if (wasted > 100000)
                wasted = 100000;
        /* store in the appropriate bucket */
        /* don't bother locking. if it's slightly off, so what? */
        mbprof.segments[segments]++;
        mbprof.used[fls(used)]++;
        mbprof.wasted[fls(wasted)]++;
}

static void
mbprof_textify(void)
{
        int offset;
        char *c;
        uint64_t *p;
        

        p = &mbprof.wasted[0];
        c = mbprofbuf;
        offset = snprintf(c, MP_MAXLINE + 10, 
            "wasted:\n"
            "%ju %ju %ju %ju %ju %ju %ju %ju "
            "%ju %ju %ju %ju %ju %ju %ju %ju\n",
            p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7],
            p[8], p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
#ifdef BIG_ARRAY
        p = &mbprof.wasted[16];
        c += offset;
        offset = snprintf(c, MP_MAXLINE, 
            "%ju %ju %ju %ju %ju %ju %ju %ju "
            "%ju %ju %ju %ju %ju %ju %ju %ju\n",
            p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7],
            p[8], p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
#endif
        p = &mbprof.used[0];
        c += offset;
        offset = snprintf(c, MP_MAXLINE + 10, 
            "used:\n"
            "%ju %ju %ju %ju %ju %ju %ju %ju "
            "%ju %ju %ju %ju %ju %ju %ju %ju\n",
            p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7],
            p[8], p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
#ifdef BIG_ARRAY
        p = &mbprof.used[16];
        c += offset;
        offset = snprintf(c, MP_MAXLINE, 
            "%ju %ju %ju %ju %ju %ju %ju %ju "
            "%ju %ju %ju %ju %ju %ju %ju %ju\n",
            p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7],
            p[8], p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
#endif
        p = &mbprof.segments[0];
        c += offset;
        offset = snprintf(c, MP_MAXLINE + 10, 
            "segments:\n"
            "%ju %ju %ju %ju %ju %ju %ju %ju "
            "%ju %ju %ju %ju %ju %ju %ju %ju\n",
            p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7],
            p[8], p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
#ifdef BIG_ARRAY
        p = &mbprof.segments[16];
        c += offset;
        offset = snprintf(c, MP_MAXLINE, 
            "%ju %ju %ju %ju %ju %ju %ju %ju "
            "%ju %ju %ju %ju %ju %ju %ju %jju",
            p[0], p[1], p[2], p[3], p[4], p[5], p[6], p[7],
            p[8], p[9], p[10], p[11], p[12], p[13], p[14], p[15]);
#endif
}

static int
mbprof_handler(SYSCTL_HANDLER_ARGS)
{
        int error;

        mbprof_textify();
        error = SYSCTL_OUT(req, mbprofbuf, strlen(mbprofbuf) + 1);
        return (error);
}

static int
mbprof_clr_handler(SYSCTL_HANDLER_ARGS)
{
        int clear, error;
 
        clear = 0;
        error = sysctl_handle_int(oidp, &clear, 0, req);
        if (error || !req->newptr)
                return (error);
 
        if (clear) {
                bzero(&mbprof, sizeof(mbprof));
        }
 
        return (error);
}


SYSCTL_PROC(_kern_ipc, OID_AUTO, mbufprofile, CTLTYPE_STRING|CTLFLAG_RD,
            NULL, 0, mbprof_handler, "A", "mbuf profiling statistics");

SYSCTL_PROC(_kern_ipc, OID_AUTO, mbufprofileclr, CTLTYPE_INT|CTLFLAG_RW,
            NULL, 0, mbprof_clr_handler, "I", "clear mbuf profiling statistics");
#endif