uipc_mbuf2.c

Go to the documentation of this file.

/*      $KAME: uipc_mbuf2.c,v 1.31 2001/11/28 11:08:53 itojun Exp $     */
/*      $NetBSD: uipc_mbuf.c,v 1.40 1999/04/01 00:23:25 thorpej Exp $   */

/*-
 * Copyright (C) 1999 WIDE Project.
 * 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 project 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 PROJECT 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 PROJECT 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.
 */
/*-
 * 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 8.4 (Berkeley) 2/14/95
 */

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

/*#define PULLDOWN_DEBUG*/

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/mutex.h>

#include <security/mac/mac_framework.h>

static MALLOC_DEFINE(M_PACKET_TAGS, MBUF_TAG_MEM_NAME,
    "packet-attached information");

/* can't call it m_dup(), as freebsd[34] uses m_dup() with different arg */
static struct mbuf *m_dup1(struct mbuf *, int, int, int);

/*
 * ensure that [off, off + len) is contiguous on the mbuf chain "m".
 * packet chain before "off" is kept untouched.
 * if offp == NULL, the target will start at <retval, 0> on resulting chain.
 * if offp != NULL, the target will start at <retval, *offp> on resulting chain.
 *
 * on error return (NULL return value), original "m" will be freed.
 *
 * XXX: M_TRAILINGSPACE/M_LEADINGSPACE only permitted on writable ext_buf.
 */
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. */
        if (m == NULL)
                panic("m == NULL in m_pulldown()");
        if (len > MCLBYTES) {
                m_freem(m);
                return NULL;    /* impossible */
        }

#ifdef PULLDOWN_DEBUG
    {
        struct mbuf *t;
        printf("before:");
        for (t = m; t; t = t->m_next)
                printf(" %d", t->m_len);
        printf("\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 */
        }

        /*
         * XXX: This code is flawed because it considers a "writable" mbuf
         *      data region to require all of the following:
         *        (i) mbuf _has_ to have M_EXT set; if it is just a regular
         *            mbuf, it is still not considered "writable."
         *        (ii) since mbuf has M_EXT, the ext_type _has_ to be
         *             EXT_CLUSTER. Anything else makes it non-writable.
         *        (iii) M_WRITABLE() must evaluate true.
         *      Ideally, the requirement should only be (iii).
         *
         * If we're writable, we're sure we're writable, because the ref. count
         * cannot increase from 1, as that would require posession of mbuf
         * n by someone else (which is impossible). However, if we're _not_
         * writable, we may eventually become writable )if the ref. count drops
         * to 1), but we'll fail to notice it unless we re-evaluate
         * M_WRITABLE(). For now, we only evaluate once at the beginning and
         * live with this.
         */
        /*
         * XXX: This is dumb. If we're just a regular mbuf with no M_EXT,
         *      then we're not "writable," according to this code.
         */
        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_DONTWAIT);
                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;
                bcopy(mtod(n, caddr_t) + off, mtod(n->m_next, caddr_t), 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)
                o = m_getcl(M_DONTWAIT, m->m_type, 0);
        else
                o = m_get(M_DONTWAIT, m->m_type);
        if (!o) {
                m_freem(m);
                return NULL;    /* ENOBUFS */
        }
        /* get hlen from <n, off> into <o, 0> */
        o->m_len = hlen;
        bcopy(mtod(n, caddr_t) + off, mtod(o, caddr_t), 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;
        printf("after:");
        for (t = m; t; t = t->m_next)
                printf("%c%d", t == n ? '*' : ' ', t->m_len);
        printf(" (off=%d)\n", off);
    }
#endif
        if (offp)
                *offp = off;
        return n;
}

static struct mbuf *
m_dup1(struct mbuf *m, int off, int len, int wait)
{
        struct mbuf *n;
        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)
                        n = m_getcl(wait, m->m_type, M_PKTHDR);
                else
                        n = m_getcl(wait, m->m_type, 0);
        } 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;
}

/* Free a packet tag. */
void
m_tag_free_default(struct m_tag *t)
{
#ifdef MAC
        if (t->m_tag_id == PACKET_TAG_MACLABEL)
                mac_mbuf_tag_destroy(t);
#endif
        free(t, M_PACKET_TAGS);
}

/* 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;

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

/* 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", m, 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);
}

/*
 * Strip off all tags that would normally vanish when
 * passing through a network interface.  Only persistent
 * tags will exist after this; these are expected to remain
 * so long as the mbuf chain exists, regardless of the
 * path the mbufs take.
 */
void
m_tag_delete_nonpersistent(struct mbuf *m)
{
        struct m_tag *p, *q;

        SLIST_FOREACH_SAFE(p, &m->m_pkthdr.tags, m_tag_link, q)
                if ((p->m_tag_id & MTAG_PERSISTENT) == 0)
                        m_tag_delete(m, p);
}

/* Find a tag, starting from a given position. */
struct m_tag *
m_tag_locate(struct mbuf *m, uint32_t cookie, int type, struct m_tag *t)
{
        struct m_tag *p;

        KASSERT(m, ("m_tag_locate: null mbuf"));
        if (t == NULL)
                p = SLIST_FIRST(&m->m_pkthdr.tags);
        else
                p = SLIST_NEXT(t, m_tag_link);
        while (p != NULL) {
                if (p->m_tag_cookie == cookie && p->m_tag_id == type)
                        return p;
                p = SLIST_NEXT(p, m_tag_link);
        }
        return NULL;
}

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

        MBUF_CHECKSLEEP(how);
        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);
#ifdef MAC
        /*
         * XXXMAC: we should probably pass off the initialization, and
         * copying here?  can we hide that PACKET_TAG_MACLABEL is
         * special from the mbuf code?
         */
        if (t->m_tag_id == PACKET_TAG_MACLABEL) {
                if (mac_mbuf_tag_init(p, how) != 0) {
                        m_tag_free(p);
                        return (NULL);
                }
                mac_mbuf_tag_copy(t, p);
        } else
#endif
                bcopy(t + 1, p + 1, t->m_tag_len); /* Copy the data */
        return p;
}

/*
 * Copy two tag chains. The destination mbuf (to) loses any attached
 * tags even if the operation fails. This should not be a problem, as
 * m_tag_copy_chain() is typically called with a newly-allocated
 * destination mbuf.
 */
int
m_tag_copy_chain(struct mbuf *to, struct mbuf *from, int how)
{
        struct m_tag *p, *t, *tprev = NULL;

        MBUF_CHECKSLEEP(how);
        KASSERT(to && from,
                ("m_tag_copy_chain: null argument, to %p from %p", to, 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;
}