busybox/networking/udhcp/options.c

/*
 * options.c -- DHCP server option packet tools
 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
 */

#include <stdlib.h>
#include <string.h>

#include "common.h"
#include "dhcpd.h"
#include "options.h"
#include "files.h"


/* supported options are easily added here */
struct dhcp_option dhcp_options[] = {
	/* name[10]	flags					code */
	{"subnet",	OPTION_IP | OPTION_REQ,			0x01},
	{"timezone",	OPTION_S32,				0x02},
	{"router",	OPTION_IP | OPTION_LIST | OPTION_REQ,	0x03},
	{"timesvr",	OPTION_IP | OPTION_LIST,		0x04},
	{"namesvr",	OPTION_IP | OPTION_LIST,		0x05},
	{"dns",		OPTION_IP | OPTION_LIST | OPTION_REQ,	0x06},
	{"logsvr",	OPTION_IP | OPTION_LIST,		0x07},
	{"cookiesvr",	OPTION_IP | OPTION_LIST,		0x08},
	{"lprsvr",	OPTION_IP | OPTION_LIST,		0x09},
	{"hostname",	OPTION_STRING | OPTION_REQ,		0x0c},
	{"bootsize",	OPTION_U16,				0x0d},
	{"domain",	OPTION_STRING | OPTION_REQ,		0x0f},
	{"swapsvr",	OPTION_IP,				0x10},
	{"rootpath",	OPTION_STRING,				0x11},
	{"ipttl",	OPTION_U8,				0x17},
	{"mtu",		OPTION_U16,				0x1a},
	{"broadcast",	OPTION_IP | OPTION_REQ,			0x1c},
	{"nisdomain",	OPTION_STRING | OPTION_REQ,		0x28},
	{"nissrv",	OPTION_IP | OPTION_LIST | OPTION_REQ,	0x29},
	{"ntpsrv",	OPTION_IP | OPTION_LIST | OPTION_REQ,	0x2a},
	{"wins",	OPTION_IP | OPTION_LIST,		0x2c},
	{"requestip",	OPTION_IP,				0x32},
	{"lease",	OPTION_U32,				0x33},
	{"dhcptype",	OPTION_U8,				0x35},
	{"serverid",	OPTION_IP,				0x36},
	{"message",	OPTION_STRING,				0x38},
	{"tftp",	OPTION_STRING,				0x42},
	{"bootfile",	OPTION_STRING,				0x43},
	{"",		0x00,				0x00}
};

/* Lengths of the different option types */
int option_lengths[] = {
	[OPTION_IP] =		4,
	[OPTION_IP_PAIR] =	8,
	[OPTION_BOOLEAN] =	1,
	[OPTION_STRING] =	1,
	[OPTION_U8] =		1,
	[OPTION_U16] =		2,
	[OPTION_S16] =		2,
	[OPTION_U32] =		4,
	[OPTION_S32] =		4
};


/* get an option with bounds checking (warning, not aligned). */
uint8_t *get_option(struct dhcpMessage *packet, int code)
{
	int i, length;
	uint8_t *optionptr;
	int over = 0, done = 0, curr = OPTION_FIELD;

	optionptr = packet->options;
	i = 0;
	length = 308;
	while (!done) {
		if (i >= length) {
			LOG(LOG_WARNING, "bogus packet, option fields too long.");
			return NULL;
		}
		if (optionptr[i + OPT_CODE] == code) {
			if (i + 1 + optionptr[i + OPT_LEN] >= length) {
				LOG(LOG_WARNING, "bogus packet, option fields too long.");
				return NULL;
			}
			return optionptr + i + 2;
		}
		switch (optionptr[i + OPT_CODE]) {
		case DHCP_PADDING:
			i++;
			break;
		case DHCP_OPTION_OVER:
			if (i + 1 + optionptr[i + OPT_LEN] >= length) {
				LOG(LOG_WARNING, "bogus packet, option fields too long.");
				return NULL;
			}
			over = optionptr[i + 3];
			i += optionptr[OPT_LEN] + 2;
			break;
		case DHCP_END:
			if (curr == OPTION_FIELD && over & FILE_FIELD) {
				optionptr = packet->file;
				i = 0;
				length = 128;
				curr = FILE_FIELD;
			} else if (curr == FILE_FIELD && over & SNAME_FIELD) {
				optionptr = packet->sname;
				i = 0;
				length = 64;
				curr = SNAME_FIELD;
			} else done = 1;
			break;
		default:
			i += optionptr[OPT_LEN + i] + 2;
		}
	}
	return NULL;
}


/* return the position of the 'end' option (no bounds checking) */
int end_option(uint8_t *optionptr)
{
	int i = 0;

	while (optionptr[i] != DHCP_END) {
		if (optionptr[i] == DHCP_PADDING) i++;
		else i += optionptr[i + OPT_LEN] + 2;
	}
	return i;
}


/* add an option string to the options (an option string contains an option code,
 * length, then data) */
int add_option_string(uint8_t *optionptr, uint8_t *string)
{
	int end = end_option(optionptr);

	/* end position + string length + option code/length + end option */
	if (end + string[OPT_LEN] + 2 + 1 >= 308) {
		LOG(LOG_ERR, "Option 0x%02x did not fit into the packet!", string[OPT_CODE]);
		return 0;
	}
	DEBUG(LOG_INFO, "adding option 0x%02x", string[OPT_CODE]);
	memcpy(optionptr + end, string, string[OPT_LEN] + 2);
	optionptr[end + string[OPT_LEN] + 2] = DHCP_END;
	return string[OPT_LEN] + 2;
}


/* add a one to four byte option to a packet */
int add_simple_option(uint8_t *optionptr, uint8_t code, uint32_t data)
{
	struct dhcp_option *dh;

	for (dh=dhcp_options; dh->code; dh++) {
		if (dh->code == code) {
			uint8_t option[6], len;

			option[OPT_CODE] = code;
			len = option_lengths[dh->flags & TYPE_MASK];
			option[OPT_LEN] = len;
			if (__BYTE_ORDER == __BIG_ENDIAN)
				data <<= 8 * (4 - len);
			/* This memcpy is for broken processors which can't
			 * handle a simple unaligned 32-bit assignment */
			memcpy(&option[OPT_DATA], &data, 4);
			return add_option_string(optionptr, option);
		}
	}

	DEBUG(LOG_ERR, "Could not add option 0x%02x", code);
	return 0;
}