radix.c

eCos操作系统源码

//==========================================================================
//
//      src/sys/net/radix.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####
//==========================================================================

/*
 * Copyright (c) 1988, 1989, 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.
 *
 *	@(#)radix.c	8.4 (Berkeley) 11/2/94
 * $FreeBSD: src/sys/net/radix.c,v 1.20.2.2 2001/03/06 00:56:50 obrien Exp $
 */

/*
 * Routines to build and maintain radix trees for routing lookups.
 */
#ifndef _RADIX_H_
#include <sys/param.h>
#ifdef	_KERNEL
#include <sys/malloc.h>
#define	M_DONTWAIT M_NOWAIT
#include <sys/domain.h>
#else
#include <stdlib.h>
#endif
#include <net/radix.h>
#endif

static int	rn_walktree_from __P((struct radix_node_head *h, void *a,
				      void *m, walktree_f_t *f, void *w));
static int rn_walktree __P((struct radix_node_head *, walktree_f_t *, void *));
static struct radix_node
	 *rn_insert __P((void *, struct radix_node_head *, int *,
			struct radix_node [2])),
	 *rn_newpair __P((void *, int, struct radix_node[2])),
	 *rn_search __P((void *, struct radix_node *)),
	 *rn_search_m __P((void *, struct radix_node *, void *));

static int	max_keylen;
static struct radix_mask *rn_mkfreelist;
static struct radix_node_head *mask_rnhead;
static char *addmask_key;
static char normal_chars[] = {0, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, -1};
static char *rn_zeros, *rn_ones;

#define rn_masktop (mask_rnhead->rnh_treetop)
#undef Bcmp
#define Bcmp(a, b, l) \
	(l == 0 ? 0 : bcmp((caddr_t)(a), (caddr_t)(b), (u_long)l))

static int	rn_lexobetter __P((void *m_arg, void *n_arg));
static struct radix_mask *
		rn_new_radix_mask __P((struct radix_node *tt,
				       struct radix_mask *next));
static int	rn_satsifies_leaf __P((char *trial, struct radix_node *leaf,
				       int skip));

/*
 * The data structure for the keys is a radix tree with one way
 * branching removed.  The index rn_bit at an internal node n represents a bit
 * position to be tested.  The tree is arranged so that all descendants
 * of a node n have keys whose bits all agree up to position rn_bit - 1.
 * (We say the index of n is rn_bit.)
 *
 * There is at least one descendant which has a one bit at position rn_bit,
 * and at least one with a zero there.
 *
 * A route is determined by a pair of key and mask.  We require that the
 * bit-wise logical and of the key and mask to be the key.
 * We define the index of a route to associated with the mask to be
 * the first bit number in the mask where 0 occurs (with bit number 0
 * representing the highest order bit).
 *
 * We say a mask is normal if every bit is 0, past the index of the mask.
 * If a node n has a descendant (k, m) with index(m) == index(n) == rn_bit,
 * and m is a normal mask, then the route applies to every descendant of n.
 * If the index(m) < rn_bit, this implies the trailing last few bits of k
 * before bit b are all 0, (and hence consequently true of every descendant
 * of n), so the route applies to all descendants of the node as well.
 *
 * Similar logic shows that a non-normal mask m such that
 * index(m) <= index(n) could potentially apply to many children of n.
 * Thus, for each non-host route, we attach its mask to a list at an internal
 * node as high in the tree as we can go.
 *
 * The present version of the code makes use of normal routes in short-
 * circuiting an explict mask and compare operation when testing whether
 * a key satisfies a normal route, and also in remembering the unique leaf
 * that governs a subtree.
 */

static struct radix_node *
rn_search(v_arg, head)
	void *v_arg;
	struct radix_node *head;
{
	register struct radix_node *x;
	register caddr_t v;

	for (x = head, v = v_arg; x->rn_bit >= 0;) {
		if (x->rn_bmask & v[x->rn_offset])
			x = x->rn_right;
		else
			x = x->rn_left;
	}
	return (x);
}

static struct radix_node *
rn_search_m(v_arg, head, m_arg)
	struct radix_node *head;
	void *v_arg, *m_arg;
{
	register struct radix_node *x;
	register caddr_t v = v_arg, m = m_arg;

	for (x = head; x->rn_bit >= 0;) {
		if ((x->rn_bmask & m[x->rn_offset]) &&
		    (x->rn_bmask & v[x->rn_offset]))
			x = x->rn_right;
		else
			x = x->rn_left;
	}
	return x;
}

int
rn_refines(m_arg, n_arg)
	void *m_arg, *n_arg;
{
	register caddr_t m = m_arg, n = n_arg;
	register caddr_t lim, lim2 = lim = n + *(u_char *)n;
	int longer = (*(u_char *)n++) - (int)(*(u_char *)m++);
	int masks_are_equal = 1;

	if (longer > 0)
		lim -= longer;
	while (n < lim) {
		if (*n & ~(*m))
			return 0;
		if (*n++ != *m++)
			masks_are_equal = 0;
	}
	while (n < lim2)
		if (*n++)
			return 0;
	if (masks_are_equal && (longer < 0))
		for (lim2 = m - longer; m < lim2; )
			if (*m++)
				return 1;
	return (!masks_are_equal);
}

struct radix_node *
rn_lookup(v_arg, m_arg, head)
	void *v_arg, *m_arg;
	struct radix_node_head *head;
{
	register struct radix_node *x;
	caddr_t netmask = 0;

	if (m_arg) {
		x = rn_addmask(m_arg, 1, head->rnh_treetop->rn_offset);
		if (x == 0)
			return (0);
		netmask = x->rn_key;
	}
	x = rn_match(v_arg, head);
	if (x && netmask) {
		while (x && x->rn_mask != netmask)
			x = x->rn_dupedkey;
	}
	return x;
}

static int
rn_satsifies_leaf(trial, leaf, skip)
	char *trial;
	register struct radix_node *leaf;
	int skip;
{
	register char *cp = trial, *cp2 = leaf->rn_key, *cp3 = leaf->rn_mask;
	char *cplim;
	int length = min(*(u_char *)cp, *(u_char *)cp2);

	if (cp3 == 0)
		cp3 = rn_ones;
	else
		length = min(length, *(u_char *)cp3);
	cplim = cp + length; cp3 += skip; cp2 += skip;
	for (cp += skip; cp < cplim; cp++, cp2++, cp3++)
		if ((*cp ^ *cp2) & *cp3)
			return 0;
	return 1;
}

struct radix_node *
rn_match(v_arg, head)
	void *v_arg;
	struct radix_node_head *head;
{
	caddr_t v = v_arg;
	register struct radix_node *t = head->rnh_treetop, *x;
	register caddr_t cp = v, cp2;
	caddr_t cplim;
	struct radix_node *saved_t, *top = t;
	int off = t->rn_offset, vlen = *(u_char *)cp, matched_off;
	register int test, b, rn_bit;

	/*
	 * Open code rn_search(v, top) to avoid overhead of extra
	 * subroutine call.
	 */
	for (; t->rn_bit >= 0; ) {
		if (t->rn_bmask & cp[t->rn_offset])
			t = t->rn_right;
		else
			t = t->rn_left;
	}
	/*
	 * See if we match exactly as a host destination
	 * or at least learn how many bits match, for normal mask finesse.
	 *
	 * It doesn't hurt us to limit how many bytes to check
	 * to the length of the mask, since if it matches we had a genuine
	 * match and the leaf we have is the most specific one anyway;
	 * if it didn't match with a shorter length it would fail
	 * with a long one.  This wins big for class B&C netmasks which
	 * are probably the most common case...
	 */
	if (t->rn_mask)
		vlen = *(u_char *)t->rn_mask;
	cp += off; cp2 = t->rn_key + off; cplim = v + vlen;
	for (; cp < cplim; cp++, cp2++)
		if (*cp != *cp2)
			goto on1;
	/*
	 * This extra grot is in case we are explicitly asked
	 * to look up the default.  Ugh!
	 *
	 * Never return the root node itself, it seems to cause a
	 * lot of confusion.
	 */
	if (t->rn_flags & RNF_ROOT)
		t = t->rn_dupedkey;
	return t;
on1:
	test = (*cp ^ *cp2) & 0xff; /* find first bit that differs */
	for (b = 7; (test >>= 1) > 0;)
		b--;
	matched_off = cp - v;
	b += matched_off << 3;
	rn_bit = -1 - b;
	/*
	 * If there is a host route in a duped-key chain, it will be first.
	 */
	if ((saved_t = t)->rn_mask == 0)
		t = t->rn_dupedkey;
	for (; t; t = t->rn_dupedkey)
		/*
		 * Even if we don't match exactly as a host,
		 * we may match if the leaf we wound up at is
		 * a route to a net.
		 */
		if (t->rn_flags & RNF_NORMAL) {
			if (rn_bit <= t->rn_bit)
				return t;
		} else if (rn_satsifies_leaf(v, t, matched_off))
				return t;
	t = saved_t;
	/* start searching up the tree */
	do {
		register struct radix_mask *m;
		t = t->rn_parent;
		m = t->rn_mklist;
		/*
		 * If non-contiguous masks ever become important
		 * we can restore the masking and open coding of
		 * the search and satisfaction test and put the
		 * calculation of "off" back before the "do".
		 */
		while (m) {
			if (m->rm_flags & RNF_NORMAL) {
				if (rn_bit <= m->rm_bit)
					return (m->rm_leaf);
			} else {
				off = min(t->rn_offset, matched_off);
				x = rn_search_m(v, t, m->rm_mask);
				while (x && x->rn_mask != m->rm_mask)
					x = x->rn_dupedkey;
				if (x && rn_satsifies_leaf(v, x, off))
					return x;
			}
			m = m->rm_mklist;
		}
	} while (t != top);
	return 0;
}

#ifdef RN_DEBUG
int	rn_nodenum;
struct	radix_node *rn_clist;
int	rn_saveinfo;
int	rn_debug =  1;
#endif

static struct radix_node *
rn_newpair(v, b, nodes)
	void *v;
	int b;
	struct radix_node nodes[2];
{
	register struct radix_node *tt = nodes, *t = tt + 1;
	t->rn_bit = b;
	t->rn_bmask = 0x80 >> (b & 7);
	t->rn_left = tt;
	t->rn_offset = b >> 3;
	tt->rn_bit = -1;
	tt->rn_key = (caddr_t)v;
	tt->rn_parent = t;
	tt->rn_flags = t->rn_flags = RNF_ACTIVE;
	tt->rn_mklist = t->rn_mklist = 0;
#ifdef RN_DEBUG
	tt->rn_info = rn_nodenum++; t->rn_info = rn_nodenum++;
	tt->rn_twin = t;
	tt->rn_ybro = rn_clist;
	rn_clist = tt;
#endif
	return t;
}

static struct radix_node *
rn_insert(v_arg, head, dupentry, nodes)
	void *v_arg;
	struct radix_node_head *head;
	int *dupentry;
	struct radix_node nodes[2];
{
	caddr_t v = v_arg;
	struct radix_node *top = head->rnh_treetop;
	int head_off = top->rn_offset, vlen = (int)*((u_char *)v);
	register struct radix_node *t = rn_search(v_arg, top);
	register caddr_t cp = v + head_off;
	register int b;
	struct radix_node *tt;
    	/*
	 * Find first bit at which v and t->rn_key differ
	 */
    {
	register caddr_t cp2 = t->rn_key + head_off;
	register int cmp_res;
	caddr_t cplim = v + vlen;

	while (cp < cplim)
		if (*cp2++ != *cp++)
			goto on1;
	*dupentry = 1;
	return t;
on1:
	*dupentry = 0;
	cmp_res = (cp[-1] ^ cp2[-1]) & 0xff;
	for (b = (cp - v) << 3; cmp_res; b--)
		cmp_res >>= 1;
    }
    {
	register struct radix_node *p, *x = top;
	cp = v;
	do {
		p = x;
		if (cp[x->rn_offset] & x->rn_bmask)
			x = x->rn_right;
		else
			x = x->rn_left;
	} while (b > (unsigned) x->rn_bit);
				/* x->rn_bit < b && x->rn_bit >= 0 */
#ifdef RN_DEBUG
	if (rn_debug)
		log(LOG_DEBUG, "rn_insert: Going In:\n"), traverse(p);
#endif
	t = rn_newpair(v_arg, b, nodes); 
	tt = t->rn_left;
	if ((cp[p->rn_offset] & p->rn_bmask) == 0)
		p->rn_left = t;
	else
		p->rn_right = t;
	x->rn_parent = t;
	t->rn_parent = p; /* frees x, p as temp vars below */
	if ((cp[t->rn_offset] & t->rn_bmask) == 0) {
		t->rn_right = x;
	} else {
		t->rn_right = tt;
		t->rn_left = x;
	}
#ifdef RN_DEBUG
	if (rn_debug)
		log(LOG_DEBUG, "rn_insert: Coming Out:\n"), traverse(p);
#endif
    }
	return (tt);
}

struct radix_node *
rn_addmask(n_arg, search, skip)
	int search, skip;
	void *n_arg;
{
	caddr_t netmask = (caddr_t)n_arg;
	register struct radix_node *x;
	register caddr_t cp, cplim;
	register int b = 0, mlen, j;
	int maskduplicated, m0, isnormal;
	struct radix_node *saved_x;
	static int last_zeroed = 0;

	if ((mlen = *(u_char *)netmask) > max_keylen)
		mlen = max_keylen;
	if (skip == 0)
		skip = 1;
	if (mlen <= skip)
		return (mask_rnhead->rnh_nodes);
	if (skip > 1)
		Bcopy(rn_ones + 1, addmask_key + 1, skip - 1);
	if ((m0 = mlen) > skip)
		Bcopy(netmask + skip, addmask_key + skip, mlen - skip);
	/*
	 * Trim trailing zeroes.
	 */
	for (cp = addmask_key + mlen; (cp > addmask_key) && cp[-1] == 0;)
		cp--;
	mlen = cp - addmask_key;
	if (mlen <= skip) {
		if (m0 >= last_zeroed)
			last_zeroed = mlen;
		return (mask_rnhead->rnh_nodes);
	}
	if (m0 < last_zeroed)
		Bzero(addmask_key + m0, last_zeroed - m0);
	*addmask_key = last_zeroed = mlen;
	x = rn_search(addmask_key, rn_masktop);
	if (Bcmp(addmask_key, x->rn_key, mlen) != 0)
		x = 0;
	if (x || search)
		return (x);
	R_Malloc(x, struct radix_node *, max_keylen + 2 * sizeof (*x));
	if ((saved_x = x) == 0)
		return (0);
	Bzero(x, max_keylen + 2 * sizeof (*x));
	netmask = cp = (caddr_t)(x + 2);
	Bcopy(addmask_key, cp, mlen);
	x = rn_insert(cp, mask_rnhead, &maskduplicated, x);
	if (maskduplicated) {
		log(LOG_ERR, "rn_addmask: mask impossibly already in tree");
		Free(saved_x);
		return (x);
	}
	/*
	 * Calculate index of mask, and check for normalcy.
	 */
	cplim = netmask + mlen; isnormal = 1;
	for (cp = netmask + skip; (cp < cplim) && *(u_char *)cp == 0xff;)
		cp++;
	if (cp != cplim) {
		for (j = 0x80; (j & *cp) != 0; j >>= 1)
			b++;
		if (*cp != normal_chars[b] || cp != (cplim - 1))
			isnormal = 0;
	}
	b += (cp - netmask) << 3;
	x->rn_bit = -1 - b;
	if (isnormal)
		x->rn_flags |= RNF_NORMAL;
	return (x);
}

static int	/* XXX: arbitrary ordering for non-contiguous masks */
rn_lexobetter(m_arg, n_arg)
	void *m_arg, *n_arg;
{
	register u_char *mp = m_arg, *np = n_arg, *lim;

	if (*mp > *np)
		return 1;  /* not really, but need to check longer one first */
	if (*mp == *np)
		for (lim = mp + *mp; mp < lim;)
			if (*mp++ > *np++)
				return 1;
	return 0;
}

static struct radix_mask *
rn_new_radix_mask(tt, next)
	register struct radix_node *tt;
	register struct radix_mask *next;
{
	register struct radix_mask *m;

	MKGet(m);
	if (m == 0) {
		log(LOG_ERR, "Mask for route not entered\n");
		return (0);
	}
	Bzero(m, sizeof *m);
	m->rm_bit = tt->rn_bit;
	m->rm_flags = tt->rn_flags;