uipc_mbuf2.c

来自「eCos操作系统源码」· C语言 代码 · 共 686 行 · 第 1/2 页

//==========================================================================
//
//      src/sys/kern/uipc_mbuf2.c
//
//==========================================================================
//####BSDCOPYRIGHTBEGIN####
//
// -------------------------------------------
//
// Portions of this software may have been derived from OpenBSD, 
// FreeBSD or other sources, and are covered by the appropriate
// copyright disclaimers included herein.
//
// Portions created by Red Hat are
// Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
//
// -------------------------------------------
//
//####BSDCOPYRIGHTEND####
//==========================================================================

/*	$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.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 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/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>

#ifdef __bsdi__
#define M_SHAREDCLUSTER(m) \
	(((m)->m_flags & M_EXT) != 0 && \
	 ((m)->m_ext.ext_func || mclrefcnt[mtocl((m)->m_ext.ext_buf)] > 1))
#elif defined(__NetBSD__) || defined(__OpenBSD__)
#define M_SHAREDCLUSTER(m) \
	(((m)->m_flags & M_EXT) != 0 && \
	 ((m)->m_ext.ext_free || MCLISREFERENCED((m))))
#else
#define M_SHAREDCLUSTER(m) \
	(((m)->m_flags & M_EXT) != 0 && \
	 ((m)->m_ext.ext_free || mclrefcnt[mtocl((m)->m_ext.ext_buf)] > 1))
#endif

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

/*
 * 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 on shared cluster (sharedcluster)
 */
struct mbuf *
m_pulldown(m, off, len, offp)
	struct mbuf *m;
	int off, len;
	int *offp;
{
	struct mbuf *n, *o;
	int hlen, tlen, olen;
	int sharedcluster;
#ifdef PULLDOWN_STAT
	static struct mbuf *prev = NULL;
	int prevlen = 0, prevmlen = 0;
#endif

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

#ifdef PULLDOWN_STAT
	mbstat.m_pulldowns++;
#endif

#ifdef PULLDOWN_STAT
	/* statistics for m_pullup */
	mbstat.m_pullups++;
	if (off + len > MHLEN)
		mbstat.m_pullup_fail++;
	else {
		int dlen, mlen;

		dlen = (prev == m) ? prevlen : m->m_len;
		mlen = (prev == m) ? prevmlen : m->m_len + M_TRAILINGSPACE(m);

		if (dlen >= off + len)
			mbstat.m_pullups--; /* call will not be made! */
		else if ((m->m_flags & M_EXT) != 0) {
			mbstat.m_pullup_alloc++;
			mbstat.m_pullup_copy++;
		} else {
			if (mlen >= off + len)
				mbstat.m_pullup_copy++;
			else {
				mbstat.m_pullup_alloc++;
				mbstat.m_pullup_copy++;
			}
		}

		prevlen = off + len;
		prevmlen = MHLEN;
	}

	/* statistics for m_pullup2 */
	mbstat.m_pullup2++;
	if (off + len > MCLBYTES)
		mbstat.m_pullup2_fail++;
	else {
		int dlen, mlen;

		dlen = (prev == m) ? prevlen : m->m_len;
		mlen = (prev == m) ? prevmlen : m->m_len + M_TRAILINGSPACE(m);
		prevlen = off + len;
		prevmlen = mlen;

		if (dlen >= off + len)
			mbstat.m_pullup2--; /* call will not be made! */
		else if ((m->m_flags & M_EXT) != 0) {
			mbstat.m_pullup2_alloc++;
			mbstat.m_pullup2_copy++;
			prevmlen = (off + len > MHLEN) ? MCLBYTES : MHLEN;
		} else {
			if (mlen >= off + len)
				mbstat.m_pullup2_copy++;
			else {
				mbstat.m_pullup2_alloc++;
				mbstat.m_pullup2_copy++;
				prevmlen = (off + len > MHLEN) ? MCLBYTES
							       : MHLEN;
			}
		}
	}

	prev = m;
#endif

#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 */
	}

	sharedcluster = M_SHAREDCLUSTER(n);

	/*
	 * 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 && !sharedcluster)
		goto ok;

#ifdef PULLDOWN_STAT
	mbstat.m_pulldown_copy++;
#endif

	/*
	 * 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) {
#ifdef __NetBSD__
		o = m_dup(n, off, n->m_len - off, M_DONTWAIT);
#else
		o = m_dup1(n, off, n->m_len - off, M_DONTWAIT);
#endif
		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 &&
	    !sharedcluster) {
		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 &&
	    !sharedcluster) {
		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.
	 */
#ifdef PULLDOWN_STAT
	mbstat.m_pulldown_alloc++;
#endif
	MGET(o, M_DONTWAIT, m->m_type);
	if (o && len > MLEN) {
		MCLGET(o, M_DONTWAIT);
		if ((o->m_flags & M_EXT) == 0) {
			m_free(o);
			o = NULL;
		}
	}
	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;