FreeBSD/Linux Kernel Cross Reference
sys/net/radix.c

     /*-
      * SPDX-License-Identifier: BSD-3-Clause
      *
      * 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     8.5 (Berkeley) 5/19/95
     * $FreeBSD$
     */
    
    /*
     * Routines to build and maintain radix trees for routing lookups.
     */
    #include <sys/param.h>
    #ifdef  _KERNEL
    #include <sys/lock.h>
    #include <sys/mutex.h>
    #include <sys/rmlock.h>
    #include <sys/systm.h>
    #include <sys/malloc.h>
    #include <sys/syslog.h>
    #include <net/radix.h>
    #else /* !_KERNEL */
    #include <stdio.h>
    #include <strings.h>
    #include <stdlib.h>
    #define log(x, arg...)  fprintf(stderr, ## arg)
    #define panic(x)        fprintf(stderr, "PANIC: %s", x), exit(1)
    #define min(a, b) ((a) < (b) ? (a) : (b) )
    #include <net/radix.h>
    #endif /* !_KERNEL */
    
    static struct radix_node
             *rn_insert(void *, struct radix_head *, int *,
                 struct radix_node [2]),
             *rn_newpair(void *, int, struct radix_node[2]),
             *rn_search(const void *, struct radix_node *),
             *rn_search_m(const void *, struct radix_node *, void *);
    static struct radix_node *rn_addmask(const void *, struct radix_mask_head *, int,int);
    
    static void rn_detachhead_internal(struct radix_head *);
    
    #define RADIX_MAX_KEY_LEN       32
    
    static char rn_zeros[RADIX_MAX_KEY_LEN];
    static char rn_ones[RADIX_MAX_KEY_LEN] = {
            -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1,
            -1, -1, -1, -1, -1, -1, -1, -1,
    };
    
    static int      rn_lexobetter(const void *m_arg, const void *n_arg);
    static struct radix_mask *
                    rn_new_radix_mask(struct radix_node *tt,
                        struct radix_mask *next);
    static int      rn_satisfies_leaf(const 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.
    */
   
   /*
    * Most of the functions in this code assume that the key/mask arguments
    * are sockaddr-like structures, where the first byte is an u_char
    * indicating the size of the entire structure.
    *
    * To make the assumption more explicit, we use the LEN() macro to access
    * this field. It is safe to pass an expression with side effects
    * to LEN() as the argument is evaluated only once.
    * We cast the result to int as this is the dominant usage.
    */
   #define LEN(x) ( (int) (*(const u_char *)(x)) )
   
   /*
    * XXX THIS NEEDS TO BE FIXED
    * In the code, pointers to keys and masks are passed as either
    * 'void *' (because callers use to pass pointers of various kinds), or
    * 'caddr_t' (which is fine for pointer arithmetics, but not very
    * clean when you dereference it to access data). Furthermore, caddr_t
    * is really 'char *', while the natural type to operate on keys and
    * masks would be 'u_char'. This mismatch require a lot of casts and
    * intermediate variables to adapt types that clutter the code.
    */
   
   /*
    * Search a node in the tree matching the key.
    */
   static struct radix_node *
   rn_search(const void *v_arg, struct radix_node *head)
   {
           struct radix_node *x;
           c_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);
   }
   
   /*
    * Same as above, but with an additional mask.
    * XXX note this function is used only once.
    */
   static struct radix_node *
   rn_search_m(const void *v_arg, struct radix_node *head, void *m_arg)
   {
           struct radix_node *x;
           c_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(const void *m_arg, const void *n_arg)
   {
           c_caddr_t m = m_arg, n = n_arg;
           c_caddr_t lim, lim2 = lim = n + LEN(n);
           int longer = LEN(n++) - LEN(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);
   }
   
   /*
    * Search for exact match in given @head.
    * Assume host bits are cleared in @v_arg if @m_arg is not NULL
    * Note that prefixes with /32 or /128 masks are treated differently
    * from host routes.
    */
   struct radix_node *
   rn_lookup(const void *v_arg, const void *m_arg, struct radix_head *head)
   {
           struct radix_node *x;
           caddr_t netmask;
   
           if (m_arg != NULL) {
                   /*
                    * Most common case: search exact prefix/mask
                    */
                   x = rn_addmask(m_arg, head->rnh_masks, 1,
                       head->rnh_treetop->rn_offset);
                   if (x == NULL)
                           return (NULL);
                   netmask = x->rn_key;
   
                   x = rn_match(v_arg, head);
   
                   while (x != NULL && x->rn_mask != netmask)
                           x = x->rn_dupedkey;
   
                   return (x);
           }
   
           /*
            * Search for host address.
            */
           if ((x = rn_match(v_arg, head)) == NULL)
                   return (NULL);
   
           /* Check if found key is the same */
           if (LEN(x->rn_key) != LEN(v_arg) || bcmp(x->rn_key, v_arg, LEN(v_arg)))
                   return (NULL);
   
           /* Check if this is not host route */
           if (x->rn_mask != NULL)
                   return (NULL);
   
           return (x);
   }
   
   static int
   rn_satisfies_leaf(const char *trial, struct radix_node *leaf, int skip)
   {
           const char *cp = trial, *cp2 = leaf->rn_key, *cp3 = leaf->rn_mask;
           const char *cplim;
           int length = min(LEN(cp), LEN(cp2));
   
           if (cp3 == NULL)
                   cp3 = rn_ones;
           else
                   length = min(length, LEN(cp3));
           cplim = cp + length; cp3 += skip; cp2 += skip;
           for (cp += skip; cp < cplim; cp++, cp2++, cp3++)
                   if ((*cp ^ *cp2) & *cp3)
                           return (0);
           return (1);
   }
   
   /*
    * Search for longest-prefix match in given @head
    */
   struct radix_node *
   rn_match(const void *v_arg, struct radix_head *head)
   {
           c_caddr_t v = v_arg;
           struct radix_node *t = head->rnh_treetop, *x;
           c_caddr_t cp = v, cp2;
           c_caddr_t cplim;
           struct radix_node *saved_t, *top = t;
           int off = t->rn_offset, vlen = LEN(cp), matched_off;
           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_satisfies_leaf(v, t, matched_off))
                                   return (t);
           t = saved_t;
           /* start searching up the tree */
           do {
                   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_satisfies_leaf(v, x, off))
                                           return (x);
                           }
                           m = m->rm_mklist;
                   }
           } while (t != top);
           return (0);
   }
   
   /*
    * Returns the next (wider) prefix for the key defined by @rn
    *  if exists.
    */
   struct radix_node *
   rn_nextprefix(struct radix_node *rn)
   {
           for (rn = rn->rn_dupedkey; rn != NULL; rn = rn->rn_dupedkey) {
                   if (!(rn->rn_flags & RNF_ROOT))
                           return (rn);
           }
           return (NULL);
   }
   
   #ifdef RN_DEBUG
   int     rn_nodenum;
   struct  radix_node *rn_clist;
   int     rn_saveinfo;
   int     rn_debug =  1;
   #endif
   
   /*
    * Whenever we add a new leaf to the tree, we also add a parent node,
    * so we allocate them as an array of two elements: the first one must be
    * the leaf (see RNTORT() in route.c), the second one is the parent.
    * This routine initializes the relevant fields of the nodes, so that
    * the leaf is the left child of the parent node, and both nodes have
    * (almost) all all fields filled as appropriate.
    * (XXX some fields are left unset, see the '#if 0' section).
    * The function returns a pointer to the parent node.
    */
   
   static struct radix_node *
   rn_newpair(void *v, int b, struct radix_node nodes[2])
   {
           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;
   
   #if 0  /* XXX perhaps we should fill these fields as well. */
           t->rn_parent = t->rn_right = NULL;
   
           tt->rn_mask = NULL;
           tt->rn_dupedkey = NULL;
           tt->rn_bmask = 0;
   #endif
           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(void *v_arg, struct radix_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 = LEN(v);
           struct radix_node *t = rn_search(v_arg, top);
           caddr_t cp = v + head_off;
           unsigned b;
           struct radix_node *p, *tt, *x;
           /*
            * Find first bit at which v and t->rn_key differ
            */
           caddr_t cp2 = t->rn_key + head_off;
           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;
   
           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);
   }
   
   static struct radix_node *
   rn_addmask(const void *n_arg, struct radix_mask_head *maskhead, int search, int skip)
   {
           const unsigned char *netmask = n_arg;
           const unsigned char *c, *clim;
           unsigned char *cp;
           struct radix_node *x;
           int b = 0, mlen, j;
           int maskduplicated, isnormal;
           struct radix_node *saved_x;
           unsigned char addmask_key[RADIX_MAX_KEY_LEN];
   
           if ((mlen = LEN(netmask)) > RADIX_MAX_KEY_LEN)
                   mlen = RADIX_MAX_KEY_LEN;
           if (skip == 0)
                   skip = 1;
           if (mlen <= skip)
                   return (maskhead->mask_nodes);
   
           bzero(addmask_key, RADIX_MAX_KEY_LEN);
           if (skip > 1)
                   bcopy(rn_ones + 1, addmask_key + 1, skip - 1);
           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)
                   return (maskhead->mask_nodes);
           *addmask_key = mlen;
           x = rn_search(addmask_key, maskhead->head.rnh_treetop);
           if (bcmp(addmask_key, x->rn_key, mlen) != 0)
                   x = NULL;
           if (x || search)
                   return (x);
           R_Zalloc(x, struct radix_node *, RADIX_MAX_KEY_LEN + 2 * sizeof (*x));
           if ((saved_x = x) == NULL)
                   return (0);
           netmask = cp = (unsigned char *)(x + 2);
           bcopy(addmask_key, cp, mlen);
           x = rn_insert(cp, &maskhead->head, &maskduplicated, x);
           if (maskduplicated) {
                   log(LOG_ERR, "rn_addmask: mask impossibly already in tree");
                   R_Free(saved_x);
                   return (x);
           }
           /*
            * Calculate index of mask, and check for normalcy.
            * First find the first byte with a 0 bit, then if there are
            * more bits left (remember we already trimmed the trailing 0's),
            * the bits should be contiguous, otherwise we have got
            * a non-contiguous mask.
            */
   #define CONTIG(_c)      (((~(_c) + 1) & (_c)) == (unsigned char)(~(_c) + 1))
           clim = netmask + mlen;
           isnormal = 1;
           for (c = netmask + skip; (c < clim) && *(const u_char *)c == 0xff;)
                   c++;
           if (c != clim) {
                   for (j = 0x80; (j & *c) != 0; j >>= 1)
                           b++;
                   if (!CONTIG(*c) || c != (clim - 1))
                           isnormal = 0;
           }
           b += (c - 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(const void *m_arg, const void *n_arg)
   {
           const u_char *mp = m_arg, *np = n_arg, *lim;
   
           if (LEN(mp) > LEN(np))
                   return (1);  /* not really, but need to check longer one first */
           if (LEN(mp) == LEN(np))
                   for (lim = mp + LEN(mp); mp < lim;)
                           if (*mp++ > *np++)
                                   return (1);
           return (0);
   }
   
   static struct radix_mask *
   rn_new_radix_mask(struct radix_node *tt, struct radix_mask *next)
   {
           struct radix_mask *m;
   
           R_Malloc(m, struct radix_mask *, sizeof (struct radix_mask));
           if (m == NULL) {
                   log(LOG_ERR, "Failed to allocate route mask\n");
                   return (0);
           }
           bzero(m, sizeof(*m));
           m->rm_bit = tt->rn_bit;
           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);
   }
   
   struct radix_node *
   rn_addroute(void *v_arg, const void *n_arg, struct radix_head *head,
       struct radix_node treenodes[2])
   {
           caddr_t v = (caddr_t)v_arg, netmask = NULL;
           struct radix_node *t, *x = NULL, *tt;
           struct radix_node *saved_tt, *top = head->rnh_treetop;
           short b = 0, b_leaf = 0;
           int keyduplicated;
           caddr_t mmask;
           struct radix_mask *m, **mp;
   
           /*
            * 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)  {
                   x = rn_addmask(n_arg, head->rnh_masks, 0, top->rn_offset);
                   if (x == NULL)
                           return (0);
                   b_leaf = x->rn_bit;
                   b = -1 - x->rn_bit;
                   netmask = x->rn_key;
           }
           /*
            * Deal with duplicated keys: attach node to previous instance
            */
           saved_tt = tt = rn_insert(v, head, &keyduplicated, treenodes);
           if (keyduplicated) {
                   for (t = tt; tt; t = tt, tt = tt->rn_dupedkey) {
                           if (tt->rn_mask == netmask)
                                   return (0);
                           if (netmask == 0 ||
                               (tt->rn_mask &&
                                ((b_leaf < tt->rn_bit) /* index(netmask) > node */
                                 || rn_refines(netmask, tt->rn_mask)
                                 || rn_lexobetter(netmask, tt->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 (tt == saved_tt) {
                           struct  radix_node *xx = x;
                           /* link in at head of list */
                           (tt = treenodes)->rn_dupedkey = t;
                           tt->rn_flags = t->rn_flags;
                           tt->rn_parent = x = t->rn_parent;
                           t->rn_parent = tt;                      /* parent */
                           if (x->rn_left == t)
                                   x->rn_left = tt;
                           else
                                   x->rn_right = tt;
                           saved_tt = tt; x = xx;
                   } else {
                           (tt = treenodes)->rn_dupedkey = t->rn_dupedkey;
                           t->rn_dupedkey = tt;
                           tt->rn_parent = t;                      /* parent */
                           if (tt->rn_dupedkey)                    /* parent */
                                   tt->rn_dupedkey->rn_parent = tt; /* parent */
                   }
   #ifdef RN_DEBUG
                   t=tt+1; tt->rn_info = rn_nodenum++; t->rn_info = rn_nodenum++;
                   tt->rn_twin = t; tt->rn_ybro = rn_clist; rn_clist = tt;
   #endif
                   tt->rn_key = (caddr_t) v;
                   tt->rn_bit = -1;
                   tt->rn_flags = RNF_ACTIVE;
           }
           /*
            * Put mask in tree.
            */
           if (netmask) {
                   tt->rn_mask = netmask;
                   tt->rn_bit = x->rn_bit;
                   tt->rn_flags |= x->rn_flags & RNF_NORMAL;
           }
           t = saved_tt->rn_parent;
           if (keyduplicated)
                   goto on2;
           b_leaf = -1 - t->rn_bit;
           if (t->rn_right == saved_tt)
                   x = t->rn_left;
           else
                   x = t->rn_right;
           /* Promote general routes from below */
           if (x->rn_bit < 0) {
               for (mp = &t->rn_mklist; x; x = x->rn_dupedkey)
                   if (x->rn_mask && (x->rn_bit >= 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) {
                   /*
                    * Skip over masks whose index is > that of new node
                    */
                   for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist)
                           if (m->rm_bit >= b_leaf)
                                   break;
                   t->rn_mklist = m; *mp = NULL;
           }
   on2:
           /* Add new route to highest possible ancestor's list */
           if ((netmask == 0) || (b > t->rn_bit ))
                   return (tt); /* can't lift at all */
           b_leaf = tt->rn_bit;
           do {
                   x = t;
                   t = t->rn_parent;
           } while (b <= t->rn_bit && x != top);
           /*
            * 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.
            */
           for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist) {
                   if (m->rm_bit < b_leaf)
                           continue;
                   if (m->rm_bit > b_leaf)
                           break;
                   if (m->rm_flags & RNF_NORMAL) {
                           mmask = m->rm_leaf->rn_mask;
                           if (tt->rn_flags & RNF_NORMAL) {
                               log(LOG_ERR,
                                   "Non-unique normal route, mask not entered\n");
                                   return (tt);
                           }
                   } else
                           mmask = m->rm_mask;
                   if (mmask == netmask) {
                           m->rm_refs++;
                           tt->rn_mklist = m;
                           return (tt);
                   }
                   if (rn_refines(netmask, mmask)
                       || rn_lexobetter(netmask, mmask))
                           break;
           }
           *mp = rn_new_radix_mask(tt, *mp);
           return (tt);
   }
   
   struct radix_node *
   rn_delete(const void *v_arg, const void *netmask_arg, struct radix_head *head)
   {
           struct radix_node *t, *p, *x, *tt;
           struct radix_mask *m, *saved_m, **mp;
           struct radix_node *dupedkey, *saved_tt, *top;
           c_caddr_t v;
           c_caddr_t netmask;
           int b, head_off, vlen;
   
           v = v_arg;
           netmask = netmask_arg;
           x = head->rnh_treetop;
           tt = rn_search(v, x);
           head_off = x->rn_offset;
           vlen =  LEN(v);
           saved_tt = tt;
           top = x;
           if (tt == NULL ||
               bcmp(v + head_off, tt->rn_key + head_off, vlen - head_off))
                   return (0);
           /*
            * Delete our route from mask lists.
            */
           if (netmask) {
                   x = rn_addmask(netmask, head->rnh_masks, 1, head_off);
                   if (x == NULL)
                           return (0);
                   netmask = x->rn_key;
                   while (tt->rn_mask != netmask)
                           if ((tt = tt->rn_dupedkey) == NULL)
                                   return (0);
           }
           if (tt->rn_mask == 0 || (saved_m = m = tt->rn_mklist) == NULL)
                   goto on1;
           if (tt->rn_flags & RNF_NORMAL) {
                   if (m->rm_leaf != tt || m->rm_refs > 0) {
                           log(LOG_ERR, "rn_delete: inconsistent annotation\n");
                           return (0);  /* dangling ref could cause disaster */
                   }
           } else {
                   if (m->rm_mask != tt->rn_mask) {
                           log(LOG_ERR, "rn_delete: inconsistent annotation\n");
                           goto on1;
                   }
                   if (--m->rm_refs >= 0)
                           goto on1;
           }
           b = -1 - tt->rn_bit;
           t = saved_tt->rn_parent;
           if (b > t->rn_bit)
                   goto on1; /* Wasn't lifted at all */
           do {
                   x = t;
                   t = t->rn_parent;
           } while (b <= t->rn_bit && x != top);
           for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist)
                   if (m == saved_m) {
                           *mp = m->rm_mklist;
                           R_Free(m);
                           break;
                   }
           if (m == NULL) {
                   log(LOG_ERR, "rn_delete: couldn't find our annotation\n");
                   if (tt->rn_flags & RNF_NORMAL)
                           return (0); /* Dangling ref to us */
           }
   on1:
           /*
            * Eliminate us from tree
            */
           if (tt->rn_flags & RNF_ROOT)
                   return (0);
   #ifdef RN_DEBUG
           /* Get us out of the creation list */
           for (t = rn_clist; t && t->rn_ybro != tt; t = t->rn_ybro) {}
           if (t) t->rn_ybro = tt->rn_ybro;
   #endif
           t = tt->rn_parent;
           dupedkey = saved_tt->rn_dupedkey;
           if (dupedkey) {
                   /*
                    * Here, tt is the deletion target and
                    * saved_tt is the head of the dupekey chain.
                    */
                   if (tt == saved_tt) {
                           /* remove from head of chain */
                           x = dupedkey; x->rn_parent = t;
                           if (t->rn_left == tt)
                                   t->rn_left = x;
                           else
                                   t->rn_right = x;
                   } else {
                           /* find node in front of tt on the chain */
                           for (x = p = saved_tt; p && p->rn_dupedkey != tt;)
                                   p = p->rn_dupedkey;
                           if (p) {
                                   p->rn_dupedkey = tt->rn_dupedkey;
                                   if (tt->rn_dupedkey)            /* parent */
                                           tt->rn_dupedkey->rn_parent = p;
                                                                   /* parent */
                           } else log(LOG_ERR, "rn_delete: couldn't find us\n");
                   }
                   t = tt + 1;
                   if  (t->rn_flags & RNF_ACTIVE) {
   #ifndef RN_DEBUG
                           *++x = *t;
                           p = t->rn_parent;
   #else
                           b = t->rn_info;
                           *++x = *t;
                           t->rn_info = b;
                           p = t->rn_parent;
   #endif
                           if (p->rn_left == t)
                                   p->rn_left = x;
                           else
                                   p->rn_right = x;
                           x->rn_left->rn_parent = x;
                           x->rn_right->rn_parent = x;
                   }
                   goto out;
           }
           if (t->rn_left == tt)
                   x = t->rn_right;
           else
                   x = t->rn_left;
           p = t->rn_parent;
           if (p->rn_right == t)
                   p->rn_right = x;
           else
                   p->rn_left = x;
           x->rn_parent = p;
           /*
            * Demote routes attached to us.
            */
           if (t->rn_mklist) {
                   if (x->rn_bit >= 0) {
                           for (mp = &x->rn_mklist; (m = *mp);)
                                   mp = &m->rm_mklist;
                           *mp = t->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 = t->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)
                                                   R_Free(m);
                                           m = mm;
                                   }
                           if (m)
                                   log(LOG_ERR,
                                       "rn_delete: Orphaned Mask %p at %p\n",
                                       m, x);
                   }
           }
           /*
            * We may be holding an active internal node in the tree.
            */
           x = tt + 1;
           if (t != x) {
   #ifndef RN_DEBUG
                   *t = *x;
   #else
                   b = t->rn_info;
                   *t = *x;
                   t->rn_info = b;
   #endif
                   t->rn_left->rn_parent = t;
                   t->rn_right->rn_parent = t;
                   p = x->rn_parent;
                   if (p->rn_left == x)
                           p->rn_left = t;
                   else
                           p->rn_right = t;
           }
   out:
           tt->rn_flags &= ~RNF_ACTIVE;
           tt[1].rn_flags &= ~RNF_ACTIVE;
           return (tt);
   }
   
   /*
    * This is the same as rn_walktree() except for the parameters and the
    * exit.
    */
   int
   rn_walktree_from(struct radix_head *h, void *a, void *m,
       walktree_f_t *f, void *w)
   {
           int error;
           struct radix_node *base, *next;
           u_char *xa = (u_char *)a;
           u_char *xm = (u_char *)m;
           struct radix_node *rn, *last = NULL; /* shut up gcc */
           int stopping = 0;
           int lastb;
   
           KASSERT(m != NULL, ("%s: mask needs to be specified", __func__));
   
           /*
            * rn_search_m is sort-of-open-coded here. We cannot use the
            * function because we need to keep track of the last node seen.
            */
           /* printf("about to search\n"); */
           for (rn = h->rnh_treetop; rn->rn_bit >= 0; ) {
                   last = rn;
                   /* printf("rn_bit %d, rn_bmask %x, xm[rn_offset] %x\n",
                          rn->rn_bit, rn->rn_bmask, xm[rn->rn_offset]); */
                   if (!(rn->rn_bmask & xm[rn->rn_offset])) {
                           break;
                   }
                   if (rn->rn_bmask & xa[rn->rn_offset]) {
                           rn = rn->rn_right;
                   } else {
                           rn = rn->rn_left;
                   }
           }
           /* printf("done searching\n"); */
   
           /*
            * Two cases: either we stepped off the end of our mask,
            * in which case last == rn, or we reached a leaf, in which
            * case we want to start from the leaf.
            */
           if (rn->rn_bit >= 0)
                   rn = last;
           lastb = last->rn_bit;
   
           /* printf("rn %p, lastb %d\n", rn, lastb);*/
   
          /*
           * 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.
           */
          while (rn->rn_bit >= 0)
                  rn = rn->rn_left;
  
          while (!stopping) {
                  /* printf("node %p (%d)\n", rn, rn->rn_bit); */
                  base = rn;
                  /* If at right child go back up, otherwise, go right */
                  while (rn->rn_parent->rn_right == rn
                         && !(rn->rn_flags & RNF_ROOT)) {
                          rn = rn->rn_parent;
  
                          /* if went up beyond last, stop */
                          if (rn->rn_bit <= lastb) {
                                  stopping = 1;
                                  /* printf("up too far\n"); */
                                  /*
                                   * XXX we should jump to the 'Process leaves'
                                   * part, because the values of 'rn' and 'next'
                                   * we compute will not be used. Not a big deal
                                   * because this loop will terminate, but it is
                                   * inefficient and hard to understand!
                                   */
                          }
                  }
                  
                  /* 
                   * At the top of the tree, no need to traverse the right
                   * half, prevent the traversal of the entire tree in the
                   * case of default route.
                   */
                  if (rn->rn_parent->rn_flags & RNF_ROOT)
                          stopping = 1;
  
                  /* Find the next *leaf* since next node might vanish, too */
                  for (rn = rn->rn_parent->rn_right; rn->rn_bit >= 0;)
                          rn = rn->rn_left;
                  next = rn;
                  /* Process leaves */
                  while ((rn = base) != NULL) {
                          base = rn->rn_dupedkey;
                          /* printf("leaf %p\n", rn); */
                          if (!(rn->rn_flags & RNF_ROOT)
                              && (error = (*f)(rn, w)))
                                  return (error);
                  }
                  rn = next;
  
                  if (rn->rn_flags & RNF_ROOT) {
                          /* printf("root, stopping"); */
                          stopping = 1;
                  }
          }
          return (0);
  }
  
  int
  rn_walktree(struct radix_head *h, walktree_f_t *f, 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_bit >= 0)
                  rn = rn->rn_left;
          for (;;) {
                  base = rn;
                  /* If at right child go back up, otherwise, go right */
                  while (rn->rn_parent->rn_right == rn
                         && (rn->rn_flags & RNF_ROOT) == 0)
                          rn = rn->rn_parent;
                  /* Find the next *leaf* since next node might vanish, too */
                  for (rn = rn->rn_parent->rn_right; rn->rn_bit >= 0;)
                          rn = rn->rn_left;
                  next = rn;
                  /* Process leaves */
                  while ((rn = base)) {
                          base = rn->rn_dupedkey;
                          if (!(rn->rn_flags & RNF_ROOT)
                              && (error = (*f)(rn, w)))
                                  return (error);
                  }
                  rn = next;
                  if (rn->rn_flags & RNF_ROOT)
                          return (0);
          }
          /* NOTREACHED */
  }
  
  /*
   * Initialize an empty tree. This has 3 nodes, which are passed
   * via base_nodes (in the order <left,root,right>) and are
   * marked RNF_ROOT so they cannot be freed.
   * The leaves have all-zero and all-one keys, with significant
   * bits starting at 'off'.
   */
  void
  rn_inithead_internal(struct radix_head *rh, struct radix_node *base_nodes, int off)
  {
          struct radix_node *t, *tt, *ttt;
  
          t = rn_newpair(rn_zeros, off, base_nodes);
          ttt = base_nodes + 2;
          t->rn_right = ttt;
          t->rn_parent = t;
          tt = t->rn_left;        /* ... which in turn is base_nodes */
          tt->rn_flags = t->rn_flags = RNF_ROOT | RNF_ACTIVE;
          tt->rn_bit = -1 - off;
          *ttt = *tt;
          ttt->rn_key = rn_ones;
  
          rh->rnh_treetop = t;
  }
  
  static void
  rn_detachhead_internal(struct radix_head *head)
  {
  
          KASSERT((head != NULL),
              ("%s: head already freed", __func__));
  
          /* Free <left,root,right> nodes. */
          R_Free(head);
  }
  
  /* Functions used by 'struct radix_node_head' users */
  
  int
  rn_inithead(void **head, int off)
  {
          struct radix_node_head *rnh;
          struct radix_mask_head *rmh;
  
          rnh = *head;
          rmh = NULL;
  
          if (*head != NULL)
                  return (1);
  
          R_Zalloc(rnh, struct radix_node_head *, sizeof (*rnh));
          R_Zalloc(rmh, struct radix_mask_head *, sizeof (*rmh));
          if (rnh == NULL || rmh == NULL) {
                  if (rnh != NULL)
                          R_Free(rnh);
                  if (rmh != NULL)
                          R_Free(rmh);
                  return (0);
          }
  
          /* Init trees */
          rn_inithead_internal(&rnh->rh, rnh->rnh_nodes, off);
          rn_inithead_internal(&rmh->head, rmh->mask_nodes, 0);
          *head = rnh;
          rnh->rh.rnh_masks = rmh;
  
          /* Finally, set base callbacks */
          rnh->rnh_addaddr = rn_addroute;
          rnh->rnh_deladdr = rn_delete;
          rnh->rnh_matchaddr = rn_match;
          rnh->rnh_lookup = rn_lookup;
          rnh->rnh_walktree = rn_walktree;
          rnh->rnh_walktree_from = rn_walktree_from;
  
          return (1);
  }
  
  static int
  rn_freeentry(struct radix_node *rn, void *arg)
  {
          struct radix_head * const rnh = arg;
          struct radix_node *x;
  
          x = (struct radix_node *)rn_delete(rn + 2, NULL, rnh);
          if (x != NULL)
                  R_Free(x);
          return (0);
  }
  
  int
  rn_detachhead(void **head)
  {
          struct radix_node_head *rnh;
  
          KASSERT((head != NULL && *head != NULL),
              ("%s: head already freed", __func__));
  
          rnh = (struct radix_node_head *)(*head);
  
          rn_walktree(&rnh->rh.rnh_masks->head, rn_freeentry, rnh->rh.rnh_masks);
          rn_detachhead_internal(&rnh->rh.rnh_masks->head);
          rn_detachhead_internal(&rnh->rh);
  
          *head = NULL;
  
          return (1);
  }

Cache object: e3677de6ad350c77c09096087b3b5554