xref: /freebsd/sys/kern/uipc_mbuf2.c (revision 29363fb4)

/*	$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 $	*/

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * 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.
 * 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.
 */

#include <sys/cdefs.h>
/*#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. */
	KASSERT(m != NULL, ("%s: fix caller: m is NULL off %d len %d offp %p\n",
	    __func__, off, len, offp));
	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 */
	}

	/*
	 * The following comment is dated but still partially applies:
	 *
	 * 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 possession 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.
	 */
	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)
		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_len >= tlen) {
		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_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;
	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, uint16_t 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, uint16_t 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, const 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;
}