src/sys/net/radix.c

/*	$OpenBSD: radix.c,v 1.61 2022/01/02 22:36:04 jsg Exp $	*/
/*	$NetBSD: radix.c,v 1.20 2003/08/07 16:32:56 agc Exp $	*/

/*
 * 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. 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	8.6 (Berkeley) 10/17/95
 */

/*
 * Routines to build and maintain radix trees for routing lookups.
 */

#ifndef _KERNEL
#include "kern_compat.h"
#else
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/syslog.h>
#include <sys/pool.h>
#endif

#include <net/radix.h>

#define SALEN(sa)	(*(u_char *)(sa))

/*
 * Read-only variables, allocated & filled during rn_init().
 */
static char		*rn_zeros;	/* array of 0s */
static char		*rn_ones;	/* array of 1s */
static unsigned int	 max_keylen;	/* size of the above arrays */
#define KEYLEN_LIMIT	 64		/* maximum allowed keylen */


struct radix_node_head	*mask_rnhead;	/* head of shared mask tree */
struct pool		 rtmask_pool;	/* pool for radix_mask structures */

static inline int rn_satisfies_leaf(char *, struct radix_node *, int);
static inline int rn_lexobetter(void *, void *);
static inline struct radix_mask *rn_new_radix_mask(struct radix_node *,
    struct radix_mask *);

int rn_refines(void *, void *);
int rn_inithead0(struct radix_node_head *, int);
struct radix_node *rn_addmask(void *, int, int);
struct radix_node *rn_insert(void *, struct radix_node_head *, int *,
    struct radix_node [2]);
struct radix_node *rn_newpair(void *, int, struct radix_node[2]);
void rn_link_dupedkey(struct radix_node *, struct radix_node *, int);

static inline struct radix_node *rn_search(void *, struct radix_node *);
struct radix_node *rn_search_m(void *, struct radix_node *, void *);
int rn_add_dupedkey(struct radix_node *, struct radix_node_head *,
    struct radix_node [2], u_int8_t);
void rn_fixup_nodes(struct radix_node *);
static inline struct radix_node *rn_lift_node(struct radix_node *);
void rn_add_radix_mask(struct radix_node *, int);
int rn_del_radix_mask(struct radix_node *);
static inline void rn_swap_nodes(struct radix_node *, struct radix_node *);

/*
 * The data structure for the keys is a radix tree with one way
 * branching removed.  The index rn_b 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_b - 1.
 * (We say the index of n is rn_b.)
 *
 * There is at least one descendant which has a one bit at position rn_b,
 * 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_b,
 * and m is a normal mask, then the route applies to every descendant of n.
 * If the index(m) < rn_b, 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 explicit 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 inline struct radix_node *
rn_search(void *v_arg, struct radix_node *head)
{
	struct radix_node *x = head;
	caddr_t v = v_arg;

	while (x->rn_b >= 0) {
		if (x->rn_bmask & v[x->rn_off])
			x = x->rn_r;
		else
			x = x->rn_l;
	}
	return (x);
}

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

	while (x->rn_b >= 0) {
		if ((x->rn_bmask & m[x->rn_off]) &&
		    (x->rn_bmask & v[x->rn_off]))
			x = x->rn_r;
		else
			x = x->rn_l;
	}
	return x;
}

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

	lim2 = lim = n + *(u_char *)n;
	longer = (*(u_char *)n++) - (int)(*(u_char *)m++);
	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);
}

/* return a perfect match if m_arg is set, else do a regular rn_match */
struct radix_node *
rn_lookup(void *v_arg, void *m_arg, struct radix_node_head *head)
{
	struct radix_node *x, *tm;
	caddr_t netmask = 0;

	if (m_arg) {
		tm = rn_addmask(m_arg, 1, head->rnh_treetop->rn_off);
		if (tm == NULL)
			return (NULL);
		netmask = tm->rn_key;
	}
	x = rn_match(v_arg, head);
	if (x && netmask) {
		while (x && x->rn_mask != netmask)
			x = x->rn_dupedkey;
	}
	/* Never return internal nodes to the upper layer. */
	if (x && (x->rn_flags & RNF_ROOT))
		return (NULL);
	return x;
}

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

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

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

	t = rn_search(v, top);
	/*
	 * 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 = SALEN(t->rn_mask);
	else
		vlen = SALEN(v);
	cp = v + 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!
	 */
	if (t->rn_flags & RNF_ROOT)
		t = t->rn_dupedkey;

	KASSERT(t == NULL || (t->rn_flags & RNF_ROOT) == 0);
	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_b = -1 - b;
	/*
	 * If there is a host route in a duped-key chain, it will be first.
	 */
	saved_t = t;
	if (t->rn_mask == NULL)
		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_b <= t->rn_b) {
				KASSERT((t->rn_flags & RNF_ROOT) == 0);
				return t;
			}
		} else if (rn_satisfies_leaf(v, t, matched_off)) {
			KASSERT((t->rn_flags & RNF_ROOT) == 0);
			return t;
		}
	t = saved_t;
	/* start searching up the tree */
	do {
		struct radix_mask *m;
		t = t->rn_p;
		m = t->rn_mklist;
		while (m) {
			/*
			 * 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".
			 */
			if (m->rm_flags & RNF_NORMAL) {
				if (rn_b <= m->rm_b) {
					KASSERT((m->rm_leaf->rn_flags &
					    RNF_ROOT) == 0);
					return (m->rm_leaf);
				}
			} else {
				struct radix_node *x;
				off = min(t->rn_off, 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_satisfies_leaf(v, x, off)) {
					KASSERT((x->rn_flags & RNF_ROOT) == 0);
					return x;
				}
			}
			m = m->rm_mklist;
		}
	} while (t != top);
	return NULL;
}

struct radix_node *
rn_newpair(void *v, int b, struct radix_node nodes[2])
{
	struct radix_node *tt = nodes, *t = nodes + 1;
	t->rn_b = b;
	t->rn_bmask = 0x80 >> (b & 7);
	t->rn_l = tt;
	t->rn_off = b >> 3;
	tt->rn_b = -1;
	tt->rn_key = v;
	tt->rn_p = t;
	tt->rn_flags = t->rn_flags = RNF_ACTIVE;
	return t;
}

struct radix_node *
rn_insert(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;
	struct radix_node *t, *tt;
	int off = top->rn_off;
	int b;

	t = rn_search(v_arg, top);
	/*
	 * Find first bit at which v and t->rn_key differ
	 */
    {
	caddr_t cp, cp2, cplim;
	int vlen, cmp_res;

	vlen =  SALEN(v);
	cp = v + off;
	cp2 = t->rn_key + off;
	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;
    }
    {
	struct radix_node *p, *x = top;
	caddr_t cp = v;
	do {
		p = x;
		if (cp[x->rn_off] & x->rn_bmask)
			x = x->rn_r;
		else
			x = x->rn_l;
	} while (b > (unsigned int) x->rn_b); /* x->rn_b < b && x->rn_b >= 0 */
	t = rn_newpair(v_arg, b, nodes);
	tt = t->rn_l;
	if ((cp[p->rn_off] & p->rn_bmask) == 0)
		p->rn_l = t;
	else
		p->rn_r = t;
	x->rn_p = t;
	t->rn_p = p; /* frees x, p as temp vars below */
	if ((cp[t->rn_off] & t->rn_bmask) == 0) {
		t->rn_r = x;
	} else {
		t->rn_r = tt;
		t->rn_l = x;
	}
    }
	return (tt);
}

struct radix_node *
rn_addmask(void *n_arg, int search, int skip)
{
	caddr_t netmask = n_arg;
	struct radix_node *tm, *saved_tm;
	caddr_t cp, cplim;
	int b = 0, mlen, j;
	int maskduplicated, m0, isnormal;
	char addmask_key[KEYLEN_LIMIT];

	if ((mlen = SALEN(netmask)) > max_keylen)
		mlen = max_keylen;
	if (skip == 0)
		skip = 1;
	if (mlen <= skip)
		return (mask_rnhead->rnh_nodes);	/* rn_zero root node */
	if (skip > 1)
		memcpy(addmask_key + 1, rn_ones + 1, skip - 1);
	if ((m0 = mlen) > skip)
		memcpy(addmask_key + skip, netmask + 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)
		return (mask_rnhead->rnh_nodes);
	memset(addmask_key + m0, 0, max_keylen - m0);
	SALEN(addmask_key) = mlen;
	tm = rn_search(addmask_key, mask_rnhead->rnh_treetop);
	if (memcmp(addmask_key, tm->rn_key, mlen) != 0)
		tm = NULL;
	if (tm || search)
		return (tm);
	tm = malloc(max_keylen + 2 * sizeof(*tm), M_RTABLE, M_NOWAIT | M_ZERO);
	if (tm == NULL)
		return (0);
	saved_tm = tm;
	netmask = cp = (caddr_t)(tm + 2);
	memcpy(cp, addmask_key, mlen);
	tm = rn_insert(cp, mask_rnhead, &maskduplicated, tm);
	if (maskduplicated) {
		log(LOG_ERR, "%s: mask impossibly already in tree\n", __func__);
		free(saved_tm, M_RTABLE, max_keylen + 2 * sizeof(*saved_tm));
		return (tm);
	}
	/*
	 * 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) {
		static const char normal_chars[] = {
			0, 0x80, 0xc0, 0xe0, 0xf0, 0xf8, 0xfc, 0xfe, -1
		};
		for (j = 0x80; (j & *cp) != 0; j >>= 1)
			b++;
		if (*cp != normal_chars[b] || cp != (cplim - 1))
			isnormal = 0;
	}
	b += (cp - netmask) << 3;
	tm->rn_b = -1 - b;
	if (isnormal)
		tm->rn_flags |= RNF_NORMAL;
	return (tm);
}

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

	/*
	 * Longer masks might not really be lexicographically better,
	 * but longer masks always have precedence since they must be checked
	 * first. The netmasks were normalized before calling this function and
	 * don't have unneeded trailing zeros.
	 */
	if (SALEN(mp) > SALEN(np))
		return 1;
	if (SALEN(mp) < SALEN(np))
		return 0;
	/*
	 * Must return the first difference between the masks
	 * to ensure deterministic sorting.
	 */
	return (memcmp(mp, np, *mp) > 0);
}

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

	m = pool_get(&rtmask_pool, PR_NOWAIT | PR_ZERO);
	if (m == NULL) {
		log(LOG_ERR, "Mask for route not entered\n");
		return (0);
	}
	m->rm_b = tt->rn_b;
	m->rm_flags = tt->rn_flags;
	if (tt->rn_flags & RNF_NORMAL)
		m->rm_leaf = tt;
	else
		m->rm_mask = tt->rn_mask;
	m->rm_mklist = next;
	tt->rn_mklist = m;
	return m;
}

/*
 * Find the point where the rn_mklist needs to be changed.
 */
static inline struct radix_node *
rn_lift_node(struct radix_node *t)
{
	struct radix_node *x = t;
	int b = -1 - t->rn_b;

	/* rewind possible dupedkey list to head */
	while (t->rn_b < 0)
		t = t->rn_p;

	/* can't lift node above head of dupedkey list, give up */
	if (b > t->rn_b)
		return (NULL);

	do {
		x = t;
		t = t->rn_p;
	} while (b <= t->rn_b && x != t);

	return (x);
}

void
rn_add_radix_mask(struct radix_node *tt, int keyduplicated)
{
	caddr_t netmask, mmask;
	struct radix_node *x;
	struct radix_mask *m, **mp;
	int b_leaf = tt->rn_b;

	/* Add new route to highest possible ancestor's list */
	if (tt->rn_mask == NULL)
		return; /* can't lift at all */
	x = rn_lift_node(tt);
	if (x == NULL)
		return; /* didn't lift either */

	/*
	 * Search through routes associated with node to
	 * insert new route according to index.
	 * Need same criteria as when sorting dupedkeys to avoid
	 * double loop on deletion.
	 */
	netmask = tt->rn_mask;
	for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist) {
		if (m->rm_b < b_leaf)
			continue;
		if (m->rm_b > b_leaf)
			break;
		if (m->rm_flags & RNF_NORMAL) {
			if (keyduplicated) {
				if (m->rm_leaf->rn_p == tt)
					/* new route is better */
					m->rm_leaf = tt;
#ifdef DIAGNOSTIC
				else {
					struct radix_node *t;

					for (t = m->rm_leaf;
					    t && t->rn_mklist == m;
					    t = t->rn_dupedkey)
						if (t == tt)
							break;
					if (t == NULL) {
						log(LOG_ERR, "Non-unique "
						    "normal route on dupedkey, "
						    "mask not entered\n");
						return;
					}
				}
#endif
				m->rm_refs++;
				tt->rn_mklist = m;
				return;
			} else if (tt->rn_flags & RNF_NORMAL) {
				log(LOG_ERR, "Non-unique normal route,"
				    " mask not entered\n");
				return;
			}
			mmask = m->rm_leaf->rn_mask;
		} else
			mmask = m->rm_mask;
		if (mmask == netmask) {
			m->rm_refs++;
			tt->rn_mklist = m;
			return;
		}
		if (rn_refines(netmask, mmask) || rn_lexobetter(netmask, mmask))
			break;
	}
	*mp = rn_new_radix_mask(tt, *mp);
}

int
rn_add_dupedkey(struct radix_node *saved_tt, struct radix_node_head *head,
    struct radix_node *tt, u_int8_t prio)
{
	caddr_t netmask = tt->rn_mask;
	struct radix_node *x = saved_tt, *xp;
	int before = -1;
	int b_leaf = 0;

	if (netmask)
		b_leaf = tt->rn_b;

	for (xp = x; x; xp = x, x = x->rn_dupedkey) {
		if (x->rn_mask == netmask)
			return (-1);
		if (netmask == NULL ||
		    (x->rn_mask &&
		     ((b_leaf < x->rn_b) || /* index(netmask) > node */
		       rn_refines(netmask, x->rn_mask) ||
		       rn_lexobetter(netmask, x->rn_mask))))
			break;
	}
	/*
	 * If the mask is not duplicated, we wouldn't
	 * find it among possible duplicate key entries
	 * anyway, so the above test doesn't hurt.
	 *
	 * We sort the masks for a duplicated key the same way as
	 * in a masklist -- most specific to least specific.
	 * This may require the unfortunate nuisance of relocating
	 * the head of the list.
	 *
	 * We also reverse, or doubly link the list through the
	 * parent pointer.
	 */

	if ((x == saved_tt && before) || before == 1)
		before = 1;
	else
		before = 0;
	rn_link_dupedkey(tt, xp, before);

	return (0);
}

/*
 * Insert tt after x or in place of x if before is true.
 */
void
rn_link_dupedkey(struct radix_node *tt, struct radix_node *x, int before)
{
	if (before) {
		if (x->rn_p->rn_b > 0) {
			/* link in at head of list */
			tt->rn_dupedkey = x;
			tt->rn_flags = x->rn_flags;
			tt->rn_p = x->rn_p;
			x->rn_p = tt;
			if (tt->rn_p->rn_l == x)
				tt->rn_p->rn_l = tt;
			else
				tt->rn_p->rn_r = tt;
		} else {
			tt->rn_dupedkey = x;
			x->rn_p->rn_dupedkey = tt;
			tt->rn_p = x->rn_p;
			x->rn_p = tt;
		}
	} else {
		tt->rn_dupedkey = x->rn_dupedkey;
		x->rn_dupedkey = tt;
		tt->rn_p = x;
		if (tt->rn_dupedkey)
			tt->rn_dupedkey->rn_p = tt;
	}
}

/*
 * This function ensures that routes are properly promoted upwards.
 * It adjusts the rn_mklist of the parent node to make sure overlapping
 * routes can be found.
 *
 * There are two cases:
 * - leaf nodes with possible rn_dupedkey list
 * - internal nodes with maybe their own mklist
 * If the mask of the route is bigger than the current branch bit then
 * a rn_mklist entry needs to be made.
 */
void
rn_fixup_nodes(struct radix_node *tt)
{
	struct radix_node *tp, *x;
	struct radix_mask *m, **mp;
	int b_leaf;

	tp = tt->rn_p;
	if (tp->rn_r == tt)
		x = tp->rn_l;
	else
		x = tp->rn_r;

	b_leaf = -1 - tp->rn_b;
	if (x->rn_b < 0) {	/* x is a leaf node */
		struct	radix_node *xx = NULL;

		for (mp = &tp->rn_mklist; x; xx = x, x = x->rn_dupedkey) {
			if (xx && xx->rn_mklist && xx->rn_mask == x->rn_mask &&
			    x->rn_mklist == 0) {
				/* multipath route */
				x->rn_mklist = xx->rn_mklist;
				x->rn_mklist->rm_refs++;
			}
			if (x->rn_mask && (x->rn_b >= b_leaf) &&
			    x->rn_mklist == 0) {
				*mp = m = rn_new_radix_mask(x, 0);
				if (m)
					mp = &m->rm_mklist;
			}
		}
	} else if (x->rn_mklist) {	/* x is an internal node */
		/*
		 * Skip over masks whose index is > that of new node
		 */
		for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist)
			if (m->rm_b >= b_leaf)
				break;
		tp->rn_mklist = m;
		*mp = 0;
	}
}

struct radix_node *
rn_addroute(void *v_arg, void *n_arg, struct radix_node_head *head,
    struct radix_node treenodes[2], u_int8_t prio)
{
	caddr_t v = v_arg;
	struct radix_node *top = head->rnh_treetop;
	struct radix_node *tt, *saved_tt, *tm = NULL;
	int keyduplicated;

	/*
	 * In dealing with non-contiguous masks, there may be
	 * many different routes which have the same mask.
	 * We will find it useful to have a unique pointer to
	 * the mask to speed avoiding duplicate references at
	 * nodes and possibly save time in calculating indices.
	 */
	if (n_arg)  {
		if ((tm = rn_addmask(n_arg, 0, top->rn_off)) == 0)
			return (0);
	}

	tt = rn_insert(v, head, &keyduplicated, treenodes);

	if (keyduplicated) {
		saved_tt = tt;
		tt = treenodes;

		tt->rn_key = v_arg;
		tt->rn_b = -1;
		tt->rn_flags = RNF_ACTIVE;
	}

	/* Put mask into the node. */
	if (tm) {
		tt->rn_mask = tm->rn_key;
		tt->rn_b = tm->rn_b;
		tt->rn_flags |= tm->rn_flags & RNF_NORMAL;
	}

	/* Either insert into dupedkey list or as a leaf node.  */
	if (keyduplicated) {
		if (rn_add_dupedkey(saved_tt, head, tt, prio))
			return (NULL);
	} else {
		rn_fixup_nodes(tt);
	}

	/* finally insert a radix_mask element if needed */
	rn_add_radix_mask(tt, keyduplicated);
	return (tt);
}

/*
 * Cleanup mask list, tt points to route that needs to be cleaned
 */
int
rn_del_radix_mask(struct radix_node *tt)
{
	struct radix_node *x;
	struct radix_mask *m, *saved_m, **mp;

	/*
	 * Cleanup mask list from possible references to this route.
	 */
	saved_m = m = tt->rn_mklist;
	if (tt->rn_mask == NULL || m == NULL)
		return (0);

	if (tt->rn_flags & RNF_NORMAL) {
		if (m->rm_leaf != tt && m->rm_refs == 0) {
			log(LOG_ERR, "rn_delete: inconsistent normal "
			    "annotation\n");
			return (-1);
		}
		if (m->rm_leaf != tt) {
			if (--m->rm_refs >= 0)
				return (0);
			else
				log(LOG_ERR, "rn_delete: "
				    "inconsistent mklist refcount\n");
		}
		/*
		 * If we end up here tt should be m->rm_leaf and therefore
		 * tt should be the head of a multipath chain.
		 * If this is not the case the table is no longer consistent.
		 */
		if (m->rm_refs > 0) {
			if (tt->rn_dupedkey == NULL ||
			    tt->rn_dupedkey->rn_mklist != m) {
				log(LOG_ERR, "rn_delete: inconsistent "
				    "dupedkey list\n");
				return (-1);
			}
			m->rm_leaf = tt->rn_dupedkey;
			--m->rm_refs;
			return (0);
		}
		/* else tt is last and only route */
	} else {
		if (m->rm_mask != tt->rn_mask) {
			log(LOG_ERR, "rn_delete: inconsistent annotation\n");
			return (0);
		}
		if (--m->rm_refs >= 0)
			return (0);
	}

	/*
	 * No other references hold to the radix_mask remove it from
	 * the tree.
	 */
	x = rn_lift_node(tt);
	if (x == NULL)
		return (0);	/* Wasn't lifted at all */

	/* Finally eliminate the radix_mask from the tree */
	for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist)
		if (m == saved_m) {
			*mp = m->rm_mklist;
			pool_put(&rtmask_pool, m);
			break;
		}

	if (m == NULL) {
		log(LOG_ERR, "rn_delete: couldn't find our annotation\n");
		if (tt->rn_flags & RNF_NORMAL)
			return (-1); /* Dangling ref to us */
	}

	return (0);
}

/* swap two internal nodes and fixup the parent and child pointers */
static inline void
rn_swap_nodes(struct radix_node *from, struct radix_node *to)
{
	*to = *from;
	if (from->rn_p->rn_l == from)
		from->rn_p->rn_l = to;
	else
		from->rn_p->rn_r = to;

	to->rn_l->rn_p = to;
	to->rn_r->rn_p = to;
}

struct radix_node *
rn_delete(void *v_arg, void *n_arg, struct radix_node_head *head,
    struct radix_node *rn)
{
	caddr_t v = v_arg;
	caddr_t netmask = n_arg;
	struct radix_node *top = head->rnh_treetop;
	struct radix_node *tt, *tp, *pp, *x;
	struct radix_node *dupedkey_tt, *saved_tt;
	int off = top->rn_off;
	int vlen;

	vlen = SALEN(v);

	/*
	 * Implement a lookup similar to rn_lookup but we need to save
	 * the radix leaf node (where th rn_dupedkey list starts) so
	 * it is not possible to use rn_lookup.
	 */
	tt = rn_search(v, top);
	/* make sure the key is a perfect match */
	if (memcmp(v + off, tt->rn_key + off, vlen - off))
		return (NULL);

	/*
	 * Here, tt is the deletion target, and
	 * saved_tt is the head of the dupedkey chain.
	 * dupedkey_tt will point to the start of the multipath chain.
	 */
	saved_tt = tt;

	/*
	 * make tt point to the start of the rn_dupedkey list of multipath
	 * routes.
	 */
	if (netmask) {
		struct radix_node *tm;

		if ((tm = rn_addmask(netmask, 1, off)) == NULL)
			return (NULL);
		netmask = tm->rn_key;
		while (tt->rn_mask != netmask)
			if ((tt = tt->rn_dupedkey) == NULL)
				return (NULL);
	}

	/* save start of multi path chain for later use */
	dupedkey_tt = tt;

	KASSERT((tt->rn_flags & RNF_ROOT) == 0);

	/* remove possible radix_mask */
	if (rn_del_radix_mask(tt))
		return (NULL);

	/*
	 * Finally eliminate us from tree
	 */
	tp = tt->rn_p;
	if (saved_tt->rn_dupedkey) {
		if (tt == saved_tt) {
			x = saved_tt->rn_dupedkey;
			x->rn_p = tp;
			if (tp->rn_l == tt)
				tp->rn_l = x;
			else
				tp->rn_r = x;
			/* head changed adjust dupedkey pointer */
			dupedkey_tt = x;
		} else {
			x = saved_tt;
			/* dupedkey will change so adjust pointer */
			if (dupedkey_tt == tt)
				dupedkey_tt = tt->rn_dupedkey;
			tp->rn_dupedkey = tt->rn_dupedkey;
			if (tt->rn_dupedkey)
				tt->rn_dupedkey->rn_p = tp;
		}

		/*
		 * We may be holding an active internal node in the tree.
		 */
		if  (tt[1].rn_flags & RNF_ACTIVE)
			rn_swap_nodes(&tt[1], &x[1]);

		/* over and out */
		goto out;
	}

	/* non-rn_dupedkey case, remove tt and tp node from the tree */
	if (tp->rn_l == tt)
		x = tp->rn_r;
	else
		x = tp->rn_l;
	pp = tp->rn_p;
	if (pp->rn_r == tp)
		pp->rn_r = x;
	else
		pp->rn_l = x;
	x->rn_p = pp;

	/*
	 * Demote routes attached to us (actually on the internal parent node).
	 */
	if (tp->rn_mklist) {
		struct radix_mask *m, **mp;
		if (x->rn_b >= 0) {
			for (mp = &x->rn_mklist; (m = *mp);)
				mp = &m->rm_mklist;
			*mp = tp->rn_mklist;
		} else {
			/* If there are any key,mask pairs in a sibling
			   duped-key chain, some subset will appear sorted
			   in the same order attached to our mklist */
			for (m = tp->rn_mklist; m && x; x = x->rn_dupedkey)
				if (m == x->rn_mklist) {
					struct radix_mask *mm = m->rm_mklist;
					x->rn_mklist = 0;
					if (--(m->rm_refs) < 0)
						pool_put(&rtmask_pool, m);
					else if (m->rm_flags & RNF_NORMAL)
						/*
						 * don't progress because this
						 * a multipath route. Next
						 * route will use the same m.
						 */
						mm = m;
					m = mm;
				}
			if (m)
				log(LOG_ERR, "%s %p at %p\n",
				    "rn_delete: Orphaned Mask", m, x);
		}
	}

	/*
	 * We may be holding an active internal node in the tree.
	 * If so swap our internal node (t) with the parent node (tp)
	 * since that one was just removed from the tree.
	 */
	if (tp != &tt[1])
		rn_swap_nodes(&tt[1], tp);

	/* no rn_dupedkey list so no need to fixup multipath chains */
out:
	tt[0].rn_flags &= ~RNF_ACTIVE;
	tt[1].rn_flags &= ~RNF_ACTIVE;
	return (tt);
}

int
rn_walktree(struct radix_node_head *h, int (*f)(struct radix_node *, void *,
    u_int), void *w)
{
	int error;
	struct radix_node *base, *next;
	struct radix_node *rn = h->rnh_treetop;

	/*
	 * This gets complicated because we may delete the node
	 * while applying the function f to it, so we need to calculate
	 * the successor node in advance.
	 */
	/* First time through node, go left */
	while (rn->rn_b >= 0)
		rn = rn->rn_l;
	for (;;) {
		base = rn;
		/* If at right child go back up, otherwise, go right */
		while (rn->rn_p->rn_r == rn && (rn->rn_flags & RNF_ROOT) == 0)
			rn = rn->rn_p;
		/* Find the next *leaf* since next node might vanish, too */
		for (rn = rn->rn_p->rn_r; rn->rn_b >= 0;)
			rn = rn->rn_l;
		next = rn;
		/* Process leaves */
		while ((rn = base) != NULL) {
			base = rn->rn_dupedkey;
			if (!(rn->rn_flags & RNF_ROOT) &&
			    (error = (*f)(rn, w, h->rnh_rtableid)))
				return (error);
		}
		rn = next;
		if (rn->rn_flags & RNF_ROOT)
			return (0);
	}
	/* NOTREACHED */
}

int
rn_initmask(void)
{
	if (mask_rnhead != NULL)
		return (0);

	KASSERT(max_keylen > 0);

	mask_rnhead = malloc(sizeof(*mask_rnhead), M_RTABLE, M_NOWAIT);
	if (mask_rnhead == NULL)
		return (1);

	rn_inithead0(mask_rnhead, 0);
	return (0);
}

int
rn_inithead(void **head, int off)
{
	struct radix_node_head *rnh;

	if (*head != NULL)
		return (1);

	if (rn_initmask())
		panic("failed to initialize the mask tree");

	rnh = malloc(sizeof(*rnh), M_RTABLE, M_NOWAIT);
	if (rnh == NULL)
		return (0);
	*head = rnh;
	rn_inithead0(rnh, off);
	return (1);
}

int
rn_inithead0(struct radix_node_head *rnh, int offset)
{
	struct radix_node *t, *tt, *ttt;
	int off = offset * NBBY;

	memset(rnh, 0, sizeof(*rnh));
	t = rn_newpair(rn_zeros, off, rnh->rnh_nodes);
	ttt = rnh->rnh_nodes + 2;
	t->rn_r = ttt;
	t->rn_p = t;
	tt = t->rn_l;
	tt->rn_flags = t->rn_flags = RNF_ROOT | RNF_ACTIVE;
	tt->rn_b = -1 - off;
	*ttt = *tt;
	ttt->rn_key = rn_ones;
	rnh->rnh_treetop = t;
	return (1);
}

/*
 * rn_init() can be called multiple time with a different key length
 * as long as no radix tree head has been allocated.
 */
void
rn_init(unsigned int keylen)
{
	char *cp, *cplim;

	KASSERT(keylen <= KEYLEN_LIMIT);

	if (max_keylen == 0) {
		pool_init(&rtmask_pool, sizeof(struct radix_mask), 0,
		    IPL_SOFTNET, 0, "rtmask", NULL);
	}

	if (keylen <= max_keylen)
		return;

	KASSERT(mask_rnhead == NULL);

	free(rn_zeros, M_RTABLE, 2 * max_keylen);
	rn_zeros = mallocarray(2, keylen, M_RTABLE, M_NOWAIT | M_ZERO);
	if (rn_zeros == NULL)
		panic("cannot initialize a radix tree without memory");
	max_keylen = keylen;

	cp = rn_ones = rn_zeros + max_keylen;
	cplim = rn_ones + max_keylen;
	while (cp < cplim)
		*cp++ = -1;
}