dhcp-option.c revision 04b28be1a306fd2ba454d3ee333d63df71aa3873
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright (C) 2013 Intel Corporation. All rights reserved.
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <stdio.h>
#include "dhcp-internal.h"
static int option_append(uint8_t options[], size_t size, size_t *offset,
uint8_t code, size_t optlen, const void *optval) {
assert(options);
assert(offset);
if (code != DHCP_OPTION_END)
/* always make sure there is space for an END option */
size --;
switch (code) {
case DHCP_OPTION_PAD:
case DHCP_OPTION_END:
if (size < *offset + 1)
return -ENOBUFS;
options[*offset] = code;
*offset += 1;
break;
default:
if (size < *offset + optlen + 2)
return -ENOBUFS;
options[*offset] = code;
options[*offset + 1] = optlen;
if (optlen) {
assert(optval);
memcpy(&options[*offset + 2], optval, optlen);
}
*offset += optlen + 2;
break;
}
return 0;
}
int dhcp_option_append(DHCPMessage *message, size_t size, size_t *offset,
uint8_t overload,
uint8_t code, size_t optlen, const void *optval) {
size_t file_offset = 0, sname_offset =0;
bool file, sname;
int r;
assert(message);
assert(offset);
file = overload & DHCP_OVERLOAD_FILE;
sname = overload & DHCP_OVERLOAD_SNAME;
if (*offset < size) {
/* still space in the options array */
r = option_append(message->options, size, offset, code, optlen, optval);
if (r >= 0)
return 0;
else if (r == -ENOBUFS && (file || sname)) {
/* did not fit, but we have more buffers to try
close the options array and move the offset to its end */
r = option_append(message->options, size, offset, DHCP_OPTION_END, 0, NULL);
if (r < 0)
return r;
*offset = size;
} else
return r;
}
if (overload & DHCP_OVERLOAD_FILE) {
file_offset = *offset - size;
if (file_offset < sizeof(message->file)) {
/* still space in the 'file' array */
r = option_append(message->file, sizeof(message->file), &file_offset, code, optlen, optval);
if (r >= 0) {
*offset = size + file_offset;
return 0;
} else if (r == -ENOBUFS && sname) {
/* did not fit, but we have more buffers to try
close the file array and move the offset to its end */
r = option_append(message->options, size, offset, DHCP_OPTION_END, 0, NULL);
if (r < 0)
return r;
*offset = size + sizeof(message->file);
} else
return r;
}
}
if (overload & DHCP_OVERLOAD_SNAME) {
sname_offset = *offset - size - (file ? sizeof(message->file) : 0);
if (sname_offset < sizeof(message->sname)) {
/* still space in the 'sname' array */
r = option_append(message->sname, sizeof(message->sname), &sname_offset, code, optlen, optval);
if (r >= 0) {
*offset = size + (file ? sizeof(message->file) : 0) + sname_offset;
return 0;
} else {
/* no space, or other error, give up */
return r;
}
}
}
return -ENOBUFS;
}
static int parse_options(const uint8_t options[], size_t buflen, uint8_t *overload,
uint8_t *message_type, dhcp_option_cb_t cb,
void *user_data) {
uint8_t code, len;
size_t offset = 0;
while (offset < buflen) {
switch (options[offset]) {
case DHCP_OPTION_PAD:
offset++;
break;
case DHCP_OPTION_END:
return 0;
case DHCP_OPTION_MESSAGE_TYPE:
if (buflen < offset + 3)
return -ENOBUFS;
len = options[++offset];
if (len != 1)
return -EINVAL;
if (message_type)
*message_type = options[++offset];
else
offset++;
offset++;
break;
case DHCP_OPTION_OVERLOAD:
if (buflen < offset + 3)
return -ENOBUFS;
len = options[++offset];
if (len != 1)
return -EINVAL;
if (overload)
*overload = options[++offset];
else
offset++;
offset++;
break;
default:
if (buflen < offset + 3)
return -ENOBUFS;
code = options[offset];
len = options[++offset];
if (buflen < ++offset + len)
return -EINVAL;
if (cb)
cb(code, len, &options[offset], user_data);
offset += len;
break;
}
}
if (offset < buflen)
return -EINVAL;
return 0;
}
int dhcp_option_parse(DHCPMessage *message, size_t len,
dhcp_option_cb_t cb, void *user_data) {
uint8_t overload = 0;
uint8_t message_type = 0;
int r;
if (!message)
return -EINVAL;
if (len < sizeof(DHCPMessage))
return -EINVAL;
len -= sizeof(DHCPMessage);
r = parse_options(message->options, len, &overload, &message_type,
cb, user_data);
if (r < 0)
return r;
if (overload & DHCP_OVERLOAD_FILE) {
r = parse_options(message->file, sizeof(message->file),
NULL, &message_type, cb, user_data);
if (r < 0)
return r;
}
if (overload & DHCP_OVERLOAD_SNAME) {
r = parse_options(message->sname, sizeof(message->sname),
NULL, &message_type, cb, user_data);
if (r < 0)
return r;
}
if (message_type)
return message_type;
return -ENOMSG;
}