/* tree.c

   Routines for manipulating parse trees... */

/*
 * Copyright (c) 1995, 1996, 1997 The Internet Software Consortium.
 * 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 Internet Software Consortium 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 INTERNET SOFTWARE CONSORTIUM 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 INTERNET SOFTWARE CONSORTIUM 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.
 *
 * This software has been written for the Internet Software Consortium
 * by Ted Lemon <mellon@fugue.com> in cooperation with Vixie
 * Enterprises.  To learn more about the Internet Software Consortium,
 * see ``http://www.vix.com/isc''.  To learn more about Vixie
 * Enterprises, see ``http://www.vix.com''.
 */

#include "dhcpd.h"

static TIME tree_evaluate_recurse PROTO ((int *, unsigned char **, int *,
					  struct tree *));
static TIME do_host_lookup PROTO ((int *, unsigned char **, int *,
					  struct dns_host_entry *));
static void do_data_copy PROTO ((int *, unsigned char **, int *,
				 unsigned char *, int));

pair cons (car, cdr)
	caddr_t car;
	pair cdr;
{
	pair foo = (pair)dmalloc (sizeof *foo, "cons");
	if (!foo)
		error ("no memory for cons.");
	foo -> car = car;
	foo -> cdr = cdr;
	return foo;
}

struct tree_cache *tree_cache (tree)
	struct tree *tree;
{
	struct tree_cache *tc;

	tc = new_tree_cache ("tree_cache");
	if (!tc)
		return 0;
	tc -> value = (unsigned char *)0;
	tc -> len = tc -> buf_size = 0;
	tc -> timeout = 0;
	tc -> tree = tree;
	return tc;
}

struct tree *tree_host_lookup (name)
	char *name;
{
	struct tree *nt;
	nt = new_tree ("tree_host_lookup");
	if (!nt)
		error ("No memory for host lookup tree node.");
	nt -> op = TREE_HOST_LOOKUP;
	nt -> data.host_lookup.host = enter_dns_host (name);
	return nt;
}

struct dns_host_entry *enter_dns_host (name)
	char *name;
{
	struct dns_host_entry *dh;

	if (!(dh = (struct dns_host_entry *)dmalloc
	      (sizeof (struct dns_host_entry), "enter_dns_host"))
	    || !(dh -> hostname = dmalloc (strlen (name) + 1,
					   "enter_dns_host")))
		error ("Can't allocate space for new host.");
	strcpy (dh -> hostname, name);
	dh -> data = (unsigned char *)0;
	dh -> data_len = 0;
	dh -> buf_len = 0;
	dh -> timeout = 0;
	return dh;
}

struct tree *tree_const (data, len)
	unsigned char *data;
	int len;
{
	struct tree *nt;
	if (!(nt = new_tree ("tree_const"))
	    || !(nt -> data.const_val.data =
		 (unsigned char *)dmalloc (len, "tree_const")))
		error ("No memory for constant data tree node.");
	nt -> op = TREE_CONST;
	memcpy (nt -> data.const_val.data, data, len);
	nt -> data.const_val.len = len;
	return nt;
}

struct tree *tree_concat (left, right)
	struct tree *left, *right;
{
	struct tree *nt;

	/* If we're concatenating a null tree to a non-null tree, just
	   return the non-null tree; if both trees are null, return
	   a null tree. */
	if (!left)
		return right;
	if (!right)
		return left;

	/* If both trees are constant, combine them. */
	if (left -> op == TREE_CONST && right -> op == TREE_CONST) {
		unsigned char *buf = dmalloc (left -> data.const_val.len
					      + right -> data.const_val.len,
					      "tree_concat");
		if (!buf)
			error ("No memory to concatenate constants.");
		memcpy (buf, left -> data.const_val.data,
			left -> data.const_val.len);
		memcpy (buf + left -> data.const_val.len,
			right -> data.const_val.data,
			right -> data.const_val.len);
		dfree (left -> data.const_val.data, "tree_concat");
		dfree (right -> data.const_val.data, "tree_concat");
		left -> data.const_val.data = buf;
		left -> data.const_val.len += right -> data.const_val.len;
		free_tree (right, "tree_concat");
		return left;
	}
			
	/* Otherwise, allocate a new node to concatenate the two. */
	if (!(nt = new_tree ("tree_concat")))
		error ("No memory for data tree concatenation node.");
	nt -> op = TREE_CONCAT;
	nt -> data.concat.left = left;
	nt -> data.concat.right = right;
	return nt;
}

struct tree *tree_limit (tree, limit)
	struct tree *tree;
	int limit;
{
	struct tree *rv;

	/* If the tree we're limiting is constant, limit it now. */
	if (tree -> op == TREE_CONST) {
		if (tree -> data.const_val.len > limit)
			tree -> data.const_val.len = limit;
		return tree;
	}

	/* Otherwise, put in a node which enforces the limit on evaluation. */
	rv = new_tree ("tree_limit");
	if (!rv)
		return (struct tree *)0;
	rv -> op = TREE_LIMIT;
	rv -> data.limit.tree = tree;
	rv -> data.limit.limit = limit;
	return rv;
}

int tree_evaluate (tree_cache)
	struct tree_cache *tree_cache;
{
	unsigned char *bp = tree_cache -> value;
	int bc = tree_cache -> buf_size;
	int bufix = 0;

	/* If there's no tree associated with this cache, it evaluates
	   to a constant and that was detected at startup. */
	if (!tree_cache -> tree)
		return 1;

	/* Try to evaluate the tree without allocating more memory... */
	tree_cache -> timeout = tree_evaluate_recurse (&bufix, &bp, &bc,
						       tree_cache -> tree);

	/* No additional allocation needed? */
	if (bufix <= bc) {
		tree_cache -> len = bufix;
		return 1;
	}

	/* If we can't allocate more memory, return with what we
	   have (maybe nothing). */
	if (!(bp = (unsigned char *)dmalloc (bufix, "tree_evaluate")))
		return 0;

	/* Record the change in conditions... */
	bc = bufix;
	bufix = 0;

	/* Note that the size of the result shouldn't change on the
	   second call to tree_evaluate_recurse, since we haven't
	   changed the ``current'' time. */
	tree_evaluate_recurse (&bufix, &bp, &bc, tree_cache -> tree);

	/* Free the old buffer if needed, then store the new buffer
	   location and size and return. */
	if (tree_cache -> value)
		dfree (tree_cache -> value, "tree_evaluate");
	tree_cache -> value = bp;
	tree_cache -> len = bufix;
	tree_cache -> buf_size = bc;
	return 1;
}

static TIME tree_evaluate_recurse (bufix, bufp, bufcount, tree)
	int *bufix;
	unsigned char **bufp;
	int *bufcount;
	struct tree *tree;
{
	int limit;
	TIME t1, t2;

	switch (tree -> op) {
	      case TREE_CONCAT:
		t1 = tree_evaluate_recurse (bufix, bufp, bufcount,
					   tree -> data.concat.left);
		t2 = tree_evaluate_recurse (bufix, bufp, bufcount,
					   tree -> data.concat.right);
		if (t1 > t2)
			return t2;
		return t1;

	      case TREE_HOST_LOOKUP:
		return do_host_lookup (bufix, bufp, bufcount,
				       tree -> data.host_lookup.host);

	      case TREE_CONST:
		do_data_copy (bufix, bufp, bufcount,
			      tree -> data.const_val.data,
			      tree -> data.const_val.len);
		t1 = MAX_TIME;
		return t1;

	      case TREE_LIMIT:
		limit = *bufix + tree -> data.limit.limit;
		t1 = tree_evaluate_recurse (bufix, bufp, bufcount,
					    tree -> data.limit.tree);
		*bufix = limit;
		return t1;

	      default:
		warn ("Bad node id in tree: %d.");
		t1 = MAX_TIME;
		return t1;
	}
}

static TIME do_host_lookup (bufix, bufp, bufcount, dns)
	int *bufix;
	unsigned char **bufp;
	int *bufcount;
	struct dns_host_entry *dns;
{
	struct hostent *h;
	int i;
	int new_len;

#ifdef DEBUG_EVAL
	debug ("time: now = %d  dns = %d %d  diff = %d",
	       cur_time, dns -> timeout, cur_time - dns -> timeout);
#endif

	/* If the record hasn't timed out, just copy the data and return. */
	if (cur_time <= dns -> timeout) {
#ifdef DEBUG_EVAL
		debug ("easy copy: %x %d %x",
		       dns -> data, dns -> data_len,
		       dns -> data ? *(int *)(dns -> data) : 0);
#endif
		do_data_copy (bufix, bufp, bufcount,
			      dns -> data, dns -> data_len);
		return dns -> timeout;
	}
#ifdef DEBUG_EVAL
	debug ("Looking up %s", dns -> hostname);
#endif

	/* Otherwise, look it up... */
	h = gethostbyname (dns -> hostname);
	if (h == NULL) {
		switch (h_errno) {
		      case HOST_NOT_FOUND:
			warn ("%s: host unknown.", dns -> hostname);
			break;
		      case TRY_AGAIN:
			warn ("%s: temporary name server failure",
			      dns -> hostname);
			break;
		      case NO_RECOVERY:
			warn ("%s: name server failed", dns -> hostname);
			break;
		      case NO_DATA:
			warn ("%s: no A record associated with address",
			      dns -> hostname);
		}
		/* Okay to try again after a minute. */
		return cur_time + 60;
	}

#ifdef DEBUG_EVAL
	debug ("Lookup succeeded; first address is %x",
	       h -> h_addr_list [0]);
#endif

	/* Count the number of addresses we got... */
	for (i = 0; h -> h_addr_list [i]; i++)
		;
	
	/* Do we need to allocate more memory? */
	new_len = i * h -> h_length;
	if (dns -> buf_len < i) {
		unsigned char *buf =
			(unsigned char *)dmalloc (new_len, "do_host_lookup");
		/* If we didn't get more memory, use what we have. */
		if (!buf) {
			new_len = dns -> buf_len;
			if (!dns -> buf_len) {
				dns -> timeout = cur_time + 60;
				return dns -> timeout;
			}
		} else {
			if (dns -> data)
				dfree (dns -> data, "do_host_lookup");
			dns -> data = buf;
			dns -> buf_len = new_len;
		}
	}

	/* Addresses are conveniently stored one to the buffer, so we
	   have to copy them out one at a time... :'( */
	for (i = 0; i < new_len / h -> h_length; i++) {
		memcpy (dns -> data + h -> h_length * i,
			h -> h_addr_list [i], h -> h_length);
	}
#ifdef DEBUG_EVAL
	debug ("dns -> data: %x  h -> h_addr_list [0]: %x",
	       *(int *)(dns -> data), h -> h_addr_list [0]);
#endif
	dns -> data_len = new_len;

	/* Set the timeout for an hour from now.
	   XXX This should really use the time on the DNS reply. */
	dns -> timeout = cur_time + 3600;

#ifdef DEBUG_EVAL
	debug ("hard copy: %x %d %x",
	       dns -> data, dns -> data_len, *(int *)(dns -> data));
#endif
	do_data_copy (bufix, bufp, bufcount, dns -> data, dns -> data_len);
	return dns -> timeout;
}

static void do_data_copy (bufix, bufp, bufcount, data, len)
	int *bufix;
	unsigned char **bufp;
	int *bufcount;
	unsigned char *data;
	int len;
{
	int space = *bufcount - *bufix;

	/* If there's more space than we need, use only what we need. */
	if (space > len)
		space = len;

	/* Copy as much data as will fit, then increment the buffer index
	   by the amount we actually had to copy, which could be more. */
	if (space > 0)
		memcpy (*bufp + *bufix, data, space);
	*bufix += len;
}