xref: /freebsd-src/sbin/dhclient/options.c (revision 1d386b48a555f61cb7325543adbbb5c3f3407a66)

/*	$OpenBSD: options.c,v 1.15 2004/12/26 03:17:07 deraadt Exp $	*/

/* DHCP options parsing and reassembly. */

/*-
 * SPDX-License-Identifier: BSD-3-Clause
 *
 * Copyright (c) 1995, 1996, 1997, 1998 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 <sys/cdefs.h>
#include <ctype.h>

#define DHCP_OPTION_DATA
#include "dhcpd.h"

static int bad_options = 0;
static int bad_options_max = 5;

void	parse_options(struct packet *);
void	parse_option_buffer(struct packet *, unsigned char *, int);
unsigned store_options(unsigned char *, int, struct tree_cache **,
	    unsigned char *, int, int, int, int);
void	expand_domain_search(struct packet *packet);
int	find_search_domain_name_len(struct option_data *option, size_t *offset);
void	expand_search_domain_name(struct option_data *option, size_t *offset,
	    unsigned char **domain_search);


/*
 * Parse all available options out of the specified packet.
 */
void
parse_options(struct packet *packet)
{
	/* Initially, zero all option pointers. */
	memset(packet->options, 0, sizeof(packet->options));

	/* If we don't see the magic cookie, there's nothing to parse. */
	if (memcmp(packet->raw->options, DHCP_OPTIONS_COOKIE, 4)) {
		packet->options_valid = 0;
		return;
	}

	/*
	 * Go through the options field, up to the end of the packet or
	 * the End field.
	 */
	parse_option_buffer(packet, &packet->raw->options[4],
	    packet->packet_length - DHCP_FIXED_NON_UDP - 4);

	/*
	 * If we parsed a DHCP Option Overload option, parse more
	 * options out of the buffer(s) containing them.
	 */
	if (packet->options_valid &&
	    packet->options[DHO_DHCP_OPTION_OVERLOAD].data) {
		if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 1)
			parse_option_buffer(packet,
			    (unsigned char *)packet->raw->file,
			    sizeof(packet->raw->file));
		if (packet->options[DHO_DHCP_OPTION_OVERLOAD].data[0] & 2)
			parse_option_buffer(packet,
			    (unsigned char *)packet->raw->sname,
			    sizeof(packet->raw->sname));
	}

	/* Expand DHCP Domain Search option. */
	if (packet->options_valid) {
		expand_domain_search(packet);
	}
}

/*
 * Parse options out of the specified buffer, storing addresses of
 * option values in packet->options and setting packet->options_valid if
 * no errors are encountered.
 */
void
parse_option_buffer(struct packet *packet,
    unsigned char *buffer, int length)
{
	unsigned char *s, *t, *end = buffer + length;
	int len, code;

	for (s = buffer; *s != DHO_END && s < end; ) {
		code = s[0];

		/* Pad options don't have a length - just skip them. */
		if (code == DHO_PAD) {
			s++;
			continue;
		}
		if (s + 2 > end) {
			len = 65536;
			goto bogus;
		}

		/*
		 * All other fields (except end, see above) have a
		 * one-byte length.
		 */
		len = s[1];

		/*
		 * If the length is outrageous, silently skip the rest,
		 * and mark the packet bad. Unfortunately some crappy
		 * dhcp servers always seem to give us garbage on the
		 * end of a packet. so rather than keep refusing, give
		 * up and try to take one after seeing a few without
		 * anything good.
		 */
		if (s + len + 2 > end) {
		    bogus:
			bad_options++;
			warning("option %s (%d) %s.",
			    dhcp_options[code].name, len,
			    "larger than buffer");
			if (bad_options == bad_options_max) {
				packet->options_valid = 1;
				bad_options = 0;
				warning("Many bogus options seen in offers. "
				    "Taking this offer in spite of bogus "
				    "options - hope for the best!");
			} else {
				warning("rejecting bogus offer.");
				packet->options_valid = 0;
			}
			return;
		}
		/*
		 * If we haven't seen this option before, just make
		 * space for it and copy it there.
		 */
		if (!packet->options[code].data) {
			if (!(t = calloc(1, len + 1)))
				error("Can't allocate storage for option %s.",
				    dhcp_options[code].name);
			/*
			 * Copy and NUL-terminate the option (in case
			 * it's an ASCII string.
			 */
			memcpy(t, &s[2], len);
			t[len] = 0;
			packet->options[code].len = len;
			packet->options[code].data = t;
		} else {
			/*
			 * If it's a repeat, concatenate it to whatever
			 * we last saw.   This is really only required
			 * for clients, but what the heck...
			 */
			t = calloc(1, len + packet->options[code].len + 1);
			if (!t)
				error("Can't expand storage for option %s.",
				    dhcp_options[code].name);
			memcpy(t, packet->options[code].data,
				packet->options[code].len);
			memcpy(t + packet->options[code].len,
				&s[2], len);
			packet->options[code].len += len;
			t[packet->options[code].len] = 0;
			free(packet->options[code].data);
			packet->options[code].data = t;
		}
		s += len + 2;
	}
	packet->options_valid = 1;
}

/*
 * Expand DHCP Domain Search option. The value of this option is
 * encoded like DNS' list of labels. See:
 *   RFC 3397
 *   RFC 1035
 */
void
expand_domain_search(struct packet *packet)
{
	size_t offset;
	int expanded_len, next_domain_len;
	struct option_data *option;
	unsigned char *domain_search, *cursor;

	if (packet->options[DHO_DOMAIN_SEARCH].data == NULL)
		return;

	option = &packet->options[DHO_DOMAIN_SEARCH];

	/* Compute final expanded length. */
	expanded_len = 0;
	offset = 0;
	while (offset < option->len) {
		next_domain_len = find_search_domain_name_len(option, &offset);
		if (next_domain_len < 0)
			/* The Domain Search option value is invalid. */
			return;

		/* We add 1 for the space between domain names. */
		expanded_len += next_domain_len + 1;
	}
	if (expanded_len > 0)
		/* Remove 1 for the superfluous trailing space. */
		--expanded_len;

	domain_search = malloc(expanded_len + 1);
	if (domain_search == NULL)
		error("Can't allocate storage for expanded domain-search\n");

	offset = 0;
	cursor = domain_search;
	while (offset < option->len) {
		expand_search_domain_name(option, &offset, &cursor);
		cursor[0] = ' ';
		cursor++;
	}
	domain_search[expanded_len] = '\0';

	free(option->data);
	option->len = expanded_len;
	option->data = domain_search;
}

int
find_search_domain_name_len(struct option_data *option, size_t *offset)
{
	int domain_name_len, label_len, pointed_len;
	size_t i, pointer;

	domain_name_len = 0;

	i = *offset;
	while (i < option->len) {
		label_len = option->data[i];
		if (label_len == 0) {
			/*
			 * A zero-length label marks the end of this
			 * domain name.
			 */
			*offset = i + 1;
			return (domain_name_len);
		} else if (label_len & 0xC0) {
			/* This is a pointer to another list of labels. */
			if (i + 1 >= option->len) {
				/* The pointer is truncated. */
				warning("Truncated pointer in DHCP Domain "
				    "Search option.");
				return (-1);
			}

			pointer = ((label_len & ~(0xC0)) << 8) +
			    option->data[i + 1];
			if (pointer >= *offset) {
				/*
				 * The pointer must indicate a prior
				 * occurrence.
				 */
				warning("Invalid forward pointer in DHCP "
				    "Domain Search option compression.");
				return (-1);
			}

			pointed_len = find_search_domain_name_len(option,
			    &pointer);
			if (pointed_len < 0)
				return (-1);
			domain_name_len += pointed_len;

			*offset = i + 2;
			return (domain_name_len);
		}

		if (i + label_len >= option->len) {
			warning("Truncated label in DHCP Domain Search "
			    "option.");
			return (-1);
		}

		/*
		 * Update the domain name length with the length of the
		 * current label, plus a trailing dot ('.').
		 */
		domain_name_len += label_len + 1;

		/* Move cursor. */
		i += label_len + 1;
	}

	warning("Truncated DHCP Domain Search option.");

	return (-1);
}

void
expand_search_domain_name(struct option_data *option, size_t *offset,
    unsigned char **domain_search)
{
	int label_len;
	size_t i, pointer;
	unsigned char *cursor;

	/*
	 * This is the same loop than the function above
	 * (find_search_domain_name_len). Therefore, we remove checks,
	 * they're already done. Here, we just make the copy.
	 */
	i = *offset;
	cursor = *domain_search;
	while (i < option->len) {
		label_len = option->data[i];
		if (label_len == 0) {
			/*
			 * A zero-length label marks the end of this
			 * domain name.
			 */
			*offset = i + 1;
			*domain_search = cursor;
			return;
		} else if (label_len & 0xC0) {
			/* This is a pointer to another list of labels. */
			pointer = ((label_len & ~(0xC0)) << 8) +
			    option->data[i + 1];

			expand_search_domain_name(option, &pointer, &cursor);

			*offset = i + 2;
			*domain_search = cursor;
			return;
		}

		/* Copy the label found. */
		memcpy(cursor, option->data + i + 1, label_len);
		cursor[label_len] = '.';

		/* Move cursor. */
		i += label_len + 1;
		cursor += label_len + 1;
	}
}

/*
 * cons options into a big buffer, and then split them out into the
 * three separate buffers if needed.  This allows us to cons up a set of
 * vendor options using the same routine.
 */
int
cons_options(struct packet *inpacket, struct dhcp_packet *outpacket,
    int mms, struct tree_cache **options,
    int overload, /* Overload flags that may be set. */
    int terminate, int bootpp, u_int8_t *prl, int prl_len)
{
	unsigned char priority_list[300], buffer[4096];
	unsigned priority_len;
	size_t main_buffer_size;
	unsigned option_size, bufix, mainbufix;
	int length;

	/*
	 * If the client has provided a maximum DHCP message size, use
	 * that; otherwise, if it's BOOTP, only 64 bytes; otherwise use
	 * up to the minimum IP MTU size (576 bytes).
	 *
	 * XXX if a BOOTP client specifies a max message size, we will
	 * honor it.
	 */
	if (!mms &&
	    inpacket &&
	    inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data &&
	    (inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].len >=
	    sizeof(u_int16_t)))
		mms = getUShort(
		    inpacket->options[DHO_DHCP_MAX_MESSAGE_SIZE].data);

	if (mms)
		main_buffer_size = mms - DHCP_FIXED_LEN;
	else if (bootpp)
		main_buffer_size = 64;
	else
		main_buffer_size = 576 - DHCP_FIXED_LEN;

	if (main_buffer_size > sizeof(buffer))
		main_buffer_size = sizeof(buffer);

	/* Preload the option priority list with mandatory options. */
	priority_len = 0;
	priority_list[priority_len++] = DHO_DHCP_MESSAGE_TYPE;
	priority_list[priority_len++] = DHO_DHCP_SERVER_IDENTIFIER;
	priority_list[priority_len++] = DHO_DHCP_LEASE_TIME;
	priority_list[priority_len++] = DHO_DHCP_MESSAGE;

	/*
	 * If the client has provided a list of options that it wishes
	 * returned, use it to prioritize.  Otherwise, prioritize based
	 * on the default priority list.
	 */
	if (inpacket &&
	    inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data) {
		unsigned prlen =
		    inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].len;
		if (prlen + priority_len > sizeof(priority_list))
			prlen = sizeof(priority_list) - priority_len;

		memcpy(&priority_list[priority_len],
		    inpacket->options[DHO_DHCP_PARAMETER_REQUEST_LIST].data,
		    prlen);
		priority_len += prlen;
		prl = priority_list;
	} else if (prl) {
		if (prl_len + priority_len > sizeof(priority_list))
			prl_len = sizeof(priority_list) - priority_len;

		memcpy(&priority_list[priority_len], prl, prl_len);
		priority_len += prl_len;
		prl = priority_list;
	} else {
		memcpy(&priority_list[priority_len],
		    dhcp_option_default_priority_list,
		    sizeof_dhcp_option_default_priority_list);
		priority_len += sizeof_dhcp_option_default_priority_list;
	}

	/* Copy the options into the big buffer... */
	option_size = store_options(
	    buffer,
	    (main_buffer_size - 7 + ((overload & 1) ? DHCP_FILE_LEN : 0) +
		((overload & 2) ? DHCP_SNAME_LEN : 0)),
	    options, priority_list, priority_len, main_buffer_size,
	    (main_buffer_size + ((overload & 1) ? DHCP_FILE_LEN : 0)),
	    terminate);

	/* Put the cookie up front... */
	memcpy(outpacket->options, DHCP_OPTIONS_COOKIE, 4);
	mainbufix = 4;

	/*
	 * If we're going to have to overload, store the overload option
	 * at the beginning.  If we can, though, just store the whole
	 * thing in the packet's option buffer and leave it at that.
	 */
	if (option_size <= main_buffer_size - mainbufix) {
		memcpy(&outpacket->options[mainbufix],
		    buffer, option_size);
		mainbufix += option_size;
		if (mainbufix < main_buffer_size)
			outpacket->options[mainbufix++] = DHO_END;
		length = DHCP_FIXED_NON_UDP + mainbufix;
	} else {
		outpacket->options[mainbufix++] = DHO_DHCP_OPTION_OVERLOAD;
		outpacket->options[mainbufix++] = 1;
		if (option_size >
		    main_buffer_size - mainbufix + DHCP_FILE_LEN)
			outpacket->options[mainbufix++] = 3;
		else
			outpacket->options[mainbufix++] = 1;

		memcpy(&outpacket->options[mainbufix],
		    buffer, main_buffer_size - mainbufix);
		bufix = main_buffer_size - mainbufix;
		length = DHCP_FIXED_NON_UDP + mainbufix;
		if (overload & 1) {
			if (option_size - bufix <= DHCP_FILE_LEN) {
				memcpy(outpacket->file,
				    &buffer[bufix], option_size - bufix);
				mainbufix = option_size - bufix;
				if (mainbufix < DHCP_FILE_LEN)
					outpacket->file[mainbufix++] = (char)DHO_END;
				while (mainbufix < DHCP_FILE_LEN)
					outpacket->file[mainbufix++] = (char)DHO_PAD;
			} else {
				memcpy(outpacket->file,
				    &buffer[bufix], DHCP_FILE_LEN);
				bufix += DHCP_FILE_LEN;
			}
		}
		if ((overload & 2) && option_size < bufix) {
			memcpy(outpacket->sname,
			    &buffer[bufix], option_size - bufix);

			mainbufix = option_size - bufix;
			if (mainbufix < DHCP_SNAME_LEN)
				outpacket->file[mainbufix++] = (char)DHO_END;
			while (mainbufix < DHCP_SNAME_LEN)
				outpacket->file[mainbufix++] = (char)DHO_PAD;
		}
	}
	return (length);
}

/*
 * Store all the requested options into the requested buffer.
 */
unsigned
store_options(unsigned char *buffer, int buflen, struct tree_cache **options,
    unsigned char *priority_list, int priority_len, int first_cutoff,
    int second_cutoff, int terminate)
{
	int bufix = 0, option_stored[256], i, ix, tto;

	/* Zero out the stored-lengths array. */
	memset(option_stored, 0, sizeof(option_stored));

	/*
	 * Copy out the options in the order that they appear in the
	 * priority list...
	 */
	for (i = 0; i < priority_len; i++) {
		/* Code for next option to try to store. */
		int code = priority_list[i];
		int optstart;

		/*
		 * Number of bytes left to store (some may already have
		 * been stored by a previous pass).
		 */
		int length;

		/* If no data is available for this option, skip it. */
		if (!options[code]) {
			continue;
		}

		/*
		 * The client could ask for things that are mandatory,
		 * in which case we should avoid storing them twice...
		 */
		if (option_stored[code])
			continue;
		option_stored[code] = 1;

		/* We should now have a constant length for the option. */
		length = options[code]->len;

		/* Do we add a NUL? */
		if (terminate && dhcp_options[code].format[0] == 't') {
			length++;
			tto = 1;
		} else
			tto = 0;

		/* Try to store the option. */

		/*
		 * If the option's length is more than 255, we must
		 * store it in multiple hunks.   Store 255-byte hunks
		 * first.  However, in any case, if the option data will
		 * cross a buffer boundary, split it across that
		 * boundary.
		 */
		ix = 0;

		optstart = bufix;
		while (length) {
			unsigned char incr = length > 255 ? 255 : length;

			/*
			 * If this hunk of the buffer will cross a
			 * boundary, only go up to the boundary in this
			 * pass.
			 */
			if (bufix < first_cutoff &&
			    bufix + incr > first_cutoff)
				incr = first_cutoff - bufix;
			else if (bufix < second_cutoff &&
			    bufix + incr > second_cutoff)
				incr = second_cutoff - bufix;

			/*
			 * If this option is going to overflow the
			 * buffer, skip it.
			 */
			if (bufix + 2 + incr > buflen) {
				bufix = optstart;
				break;
			}

			/* Everything looks good - copy it in! */
			buffer[bufix] = code;
			buffer[bufix + 1] = incr;
			if (tto && incr == length) {
				memcpy(buffer + bufix + 2,
				    options[code]->value + ix, incr - 1);
				buffer[bufix + 2 + incr - 1] = 0;
			} else
				memcpy(buffer + bufix + 2,
				    options[code]->value + ix, incr);
			length -= incr;
			ix += incr;
			bufix += 2 + incr;
		}
	}
	return (bufix);
}

/*
 * Format the specified option so that a human can easily read it.
 */
const char *
pretty_print_option(unsigned int code, unsigned char *data, int len,
    int emit_commas, int emit_quotes)
{
	static char optbuf[32768]; /* XXX */
	int hunksize = 0, numhunk = -1, numelem = 0;
	char fmtbuf[32], *op = optbuf;
	int i, j, k, opleft = sizeof(optbuf);
	unsigned char *dp = data;
	struct in_addr foo;
	char comma;

	/* Code should be between 0 and 255. */
	if (code > 255)
		error("pretty_print_option: bad code %d", code);

	if (emit_commas)
		comma = ',';
	else
		comma = ' ';

	/* Figure out the size of the data. */
	for (i = 0; dhcp_options[code].format[i]; i++) {
		if (!numhunk) {
			warning("%s: Excess information in format string: %s",
			    dhcp_options[code].name,
			    &(dhcp_options[code].format[i]));
			break;
		}
		numelem++;
		fmtbuf[i] = dhcp_options[code].format[i];
		switch (dhcp_options[code].format[i]) {
		case 'A':
			--numelem;
			fmtbuf[i] = 0;
			numhunk = 0;
			break;
		case 'X':
			for (k = 0; k < len; k++)
				if (!isascii(data[k]) ||
				    !isprint(data[k]))
					break;
			if (k == len) {
				fmtbuf[i] = 't';
				numhunk = -2;
			} else {
				fmtbuf[i] = 'x';
				hunksize++;
				comma = ':';
				numhunk = 0;
			}
			fmtbuf[i + 1] = 0;
			break;
		case 't':
			fmtbuf[i] = 't';
			fmtbuf[i + 1] = 0;
			numhunk = -2;
			break;
		case 'I':
		case 'l':
		case 'L':
			hunksize += 4;
			break;
		case 's':
		case 'S':
			hunksize += 2;
			break;
		case 'b':
		case 'B':
		case 'f':
			hunksize++;
			break;
		case 'e':
			break;
		default:
			warning("%s: garbage in format string: %s",
			    dhcp_options[code].name,
			    &(dhcp_options[code].format[i]));
			break;
		}
	}

	/* Check for too few bytes... */
	if (hunksize > len) {
		warning("%s: expecting at least %d bytes; got %d",
		    dhcp_options[code].name, hunksize, len);
		return ("<error>");
	}
	/* Check for too many bytes... */
	if (numhunk == -1 && hunksize < len)
		warning("%s: %d extra bytes",
		    dhcp_options[code].name, len - hunksize);

	/* If this is an array, compute its size. */
	if (!numhunk)
		numhunk = len / hunksize;
	/* See if we got an exact number of hunks. */
	if (numhunk > 0 && numhunk * hunksize < len)
		warning("%s: %d extra bytes at end of array",
		    dhcp_options[code].name, len - numhunk * hunksize);

	/* A one-hunk array prints the same as a single hunk. */
	if (numhunk < 0)
		numhunk = 1;

	/* Cycle through the array (or hunk) printing the data. */
	for (i = 0; i < numhunk; i++) {
		for (j = 0; j < numelem; j++) {
			int opcount;
			switch (fmtbuf[j]) {
			case 't':
				if (emit_quotes) {
					*op++ = '"';
					opleft--;
				}
				for (; dp < data + len; dp++) {
					if (!isascii(*dp) ||
					    !isprint(*dp)) {
						if (dp + 1 != data + len ||
						    *dp != 0) {
							snprintf(op, opleft,
							    "\\%03o", *dp);
							op += 4;
							opleft -= 4;
						}
					} else if (*dp == '"' ||
					    *dp == '\'' ||
					    *dp == '$' ||
					    *dp == '`' ||
					    *dp == '\\') {
						*op++ = '\\';
						*op++ = *dp;
						opleft -= 2;
					} else {
						*op++ = *dp;
						opleft--;
					}
				}
				if (emit_quotes) {
					*op++ = '"';
					opleft--;
				}

				*op = 0;
				break;
			case 'I':
				foo.s_addr = htonl(getULong(dp));
				opcount = strlcpy(op, inet_ntoa(foo), opleft);
				if (opcount >= opleft)
					goto toobig;
				opleft -= opcount;
				dp += 4;
				break;
			case 'l':
				opcount = snprintf(op, opleft, "%ld",
				    (long)getLong(dp));
				if (opcount >= opleft || opcount == -1)
					goto toobig;
				opleft -= opcount;
				dp += 4;
				break;
			case 'L':
				opcount = snprintf(op, opleft, "%lu",
				    (unsigned long)getULong(dp));
				if (opcount >= opleft || opcount == -1)
					goto toobig;
				opleft -= opcount;
				dp += 4;
				break;
			case 's':
				opcount = snprintf(op, opleft, "%d",
				    getShort(dp));
				if (opcount >= opleft || opcount == -1)
					goto toobig;
				opleft -= opcount;
				dp += 2;
				break;
			case 'S':
				opcount = snprintf(op, opleft, "%u",
				    getUShort(dp));
				if (opcount >= opleft || opcount == -1)
					goto toobig;
				opleft -= opcount;
				dp += 2;
				break;
			case 'b':
				opcount = snprintf(op, opleft, "%d",
				    *(char *)dp++);
				if (opcount >= opleft || opcount == -1)
					goto toobig;
				opleft -= opcount;
				break;
			case 'B':
				opcount = snprintf(op, opleft, "%d", *dp++);
				if (opcount >= opleft || opcount == -1)
					goto toobig;
				opleft -= opcount;
				break;
			case 'x':
				opcount = snprintf(op, opleft, "%x", *dp++);
				if (opcount >= opleft || opcount == -1)
					goto toobig;
				opleft -= opcount;
				break;
			case 'f':
				opcount = strlcpy(op,
				    *dp++ ? "true" : "false", opleft);
				if (opcount >= opleft)
					goto toobig;
				opleft -= opcount;
				break;
			default:
				warning("Unexpected format code %c", fmtbuf[j]);
			}
			op += strlen(op);
			opleft -= strlen(op);
			if (opleft < 1)
				goto toobig;
			if (j + 1 < numelem && comma != ':') {
				*op++ = ' ';
				opleft--;
			}
		}
		if (i + 1 < numhunk) {
			*op++ = comma;
			opleft--;
		}
		if (opleft < 1)
			goto toobig;

	}
	return (optbuf);
 toobig:
	warning("dhcp option too large");
	return ("<error>");
}

void
do_packet(struct interface_info *interface, struct dhcp_packet *packet,
    int len, unsigned int from_port, struct iaddr from, struct hardware *hfrom)
{
	struct packet tp;
	int i;

	if (packet->hlen > sizeof(packet->chaddr)) {
		note("Discarding packet with invalid hlen.");
		return;
	}

	memset(&tp, 0, sizeof(tp));
	tp.raw = packet;
	tp.packet_length = len;
	tp.client_port = from_port;
	tp.client_addr = from;
	tp.interface = interface;
	tp.haddr = hfrom;

	parse_options(&tp);
	if (tp.options_valid &&
	    tp.options[DHO_DHCP_MESSAGE_TYPE].data)
		tp.packet_type = tp.options[DHO_DHCP_MESSAGE_TYPE].data[0];
	if (tp.packet_type)
		dhcp(&tp);
	else
		bootp(&tp);

	/* Free the data associated with the options. */
	for (i = 0; i < 256; i++)
		free(tp.options[i].data);
}