busybox/networking/udhcp/options.c

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/* vi: set sw=4 ts=4: */
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/*
* options.c -- DHCP server option packet tools
* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
*/
#include "common.h"
#include "dhcpd.h"
#include "options.h"
/* Supported options are easily added here */
const struct dhcp_option dhcp_options[] = {
/* opt_name[12] flags code */
{"subnet", OPTION_IP | OPTION_REQ, 0x01}, /* DHCP_SUBNET */
{"timezone", OPTION_S32, 0x02}, /* DHCP_TIME_OFFSET */
{"router", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x03}, /* DHCP_ROUTER */
{"timesvr", OPTION_IP | OPTION_LIST, 0x04}, /* DHCP_TIME_SERVER */
{"namesvr", OPTION_IP | OPTION_LIST, 0x05}, /* DHCP_NAME_SERVER */
{"dns", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x06}, /* DHCP_DNS_SERVER */
{"logsvr", OPTION_IP | OPTION_LIST, 0x07}, /* DHCP_LOG_SERVER */
{"cookiesvr", OPTION_IP | OPTION_LIST, 0x08}, /* DHCP_COOKIE_SERVER */
{"lprsvr", OPTION_IP | OPTION_LIST, 0x09}, /* DHCP_LPR_SERVER */
{"hostname", OPTION_STRING | OPTION_REQ, 0x0c}, /* DHCP_HOST_NAME */
{"bootsize", OPTION_U16, 0x0d}, /* DHCP_BOOT_SIZE */
{"domain", OPTION_STRING | OPTION_LIST | OPTION_REQ, 0x0f}, /* DHCP_DOMAIN_NAME */
{"swapsvr", OPTION_IP, 0x10}, /* DHCP_SWAP_SERVER */
{"rootpath", OPTION_STRING, 0x11}, /* DHCP_ROOT_PATH */
{"ipttl", OPTION_U8, 0x17}, /* DHCP_IP_TTL */
{"mtu", OPTION_U16, 0x1a}, /* DHCP_MTU */
{"broadcast", OPTION_IP | OPTION_REQ, 0x1c}, /* DHCP_BROADCAST */
{"nisdomain", OPTION_STRING | OPTION_REQ, 0x28}, /* DHCP_NTP_SERVER */
{"nissrv", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x29}, /* DHCP_WINS_SERVER */
{"ntpsrv", OPTION_IP | OPTION_LIST | OPTION_REQ, 0x2a}, /* DHCP_REQUESTED_IP */
{"wins", OPTION_IP | OPTION_LIST, 0x2c}, /* DHCP_LEASE_TIME */
{"requestip", OPTION_IP, 0x32}, /* DHCP_OPTION_OVER */
{"lease", OPTION_U32, 0x33}, /* DHCP_MESSAGE_TYPE */
{"dhcptype", OPTION_U8, 0x35}, /* DHCP_SERVER_ID */
{"serverid", OPTION_IP, 0x36}, /* DHCP_PARAM_REQ */
{"message", OPTION_STRING, 0x38}, /* DHCP_MESSAGE */
// TODO: 1) some options should not be parsed & passed to script -
// maxsize sure should not, since it cannot appear in server responses!
// grep for opt_name is fix the mess.
// 2) Using fixed-sized char[] vector wastes space.
{"maxsize", OPTION_U16, 0x39}, /* DHCP_MAX_SIZE */
{"vendorclass", OPTION_STRING, 0x3C}, /* DHCP_VENDOR */
{"clientid", OPTION_STRING, 0x3D}, /* DHCP_CLIENT_ID */
{"tftp", OPTION_STRING, 0x42},
{"bootfile", OPTION_STRING, 0x43},
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{"userclass", OPTION_STRING, 0x4D},
#if ENABLE_FEATURE_RFC3397
{"search", OPTION_STR1035 | OPTION_LIST | OPTION_REQ, 0x77},
#endif
/* MSIE's "Web Proxy Autodiscovery Protocol" support */
{"wpad", OPTION_STRING, 0xfc},
{} /* zero-padded terminating entry */
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};
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/* Lengths of the different option types */
const unsigned char option_lengths[] ALIGN1 = {
[OPTION_IP] = 4,
[OPTION_IP_PAIR] = 8,
[OPTION_BOOLEAN] = 1,
[OPTION_STRING] = 1,
#if ENABLE_FEATURE_RFC3397
[OPTION_STR1035] = 1,
#endif
[OPTION_U8] = 1,
[OPTION_U16] = 2,
[OPTION_S16] = 2,
[OPTION_U32] = 4,
[OPTION_S32] = 4
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};
/* 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;
int curr = OPTION_FIELD;
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optionptr = packet->options;
i = 0;
length = sizeof(packet->options);
while (1) {
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if (i >= length) {
bb_error_msg("bogus packet, option fields too long");
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return NULL;
}
if (optionptr[i + OPT_CODE] == code) {
if (i + 1 + optionptr[i + OPT_LEN] >= length) {
bb_error_msg("bogus packet, option fields too long");
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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) {
bb_error_msg("bogus packet, option fields too long");
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return NULL;
}
over = optionptr[i + 3];
i += optionptr[OPT_LEN] + 2;
break;
case DHCP_END:
if (curr == OPTION_FIELD && (over & FILE_FIELD)) {
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optionptr = packet->file;
i = 0;
length = sizeof(packet->file);
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curr = FILE_FIELD;
} else if (curr == FILE_FIELD && (over & SNAME_FIELD)) {
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optionptr = packet->sname;
i = 0;
length = sizeof(packet->sname);
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curr = SNAME_FIELD;
} else
return NULL;
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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 >= DHCP_OPTIONS_BUFSIZE) {
bb_error_msg("option 0x%02x did not fit into the packet",
string[OPT_CODE]);
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return 0;
}
DEBUG("adding option 0x%02x", string[OPT_CODE]);
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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)
{
const struct dhcp_option *dh;
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for (dh = dhcp_options; dh->code; dh++) {
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if (dh->code == code) {
uint8_t option[6], len;
option[OPT_CODE] = code;
len = option_lengths[dh->flags & TYPE_MASK];
option[OPT_LEN] = len;
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if (BB_BIG_ENDIAN) data <<= 8 * (4 - len);
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/* 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);
}
}
bb_error_msg("cannot add option 0x%02x", code);
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return 0;
}