emo/ndhc
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity
ndhc/ndhc/dhcpc.c
Nicholas J. Kain c999fee9f5 Initial CMake support. 
Fix an off-by-one array initialization.
Clean up VERSION a bit.
2010-11-12 04:44:25 -05:00

597 lines
15 KiB
C
Raw Blame History

/* dhcpc.c
*
* ndhc DHCP client
*
* Russ Dill <Russ.Dill@asu.edu> July 2001
* Nicholas Kain <njk@-N0SPaM-.kain.us> 2004
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*/
#include <stdio.h>
#include <sys/time.h>
#include <sys/types.h>
#include <sys/file.h>
#include <unistd.h>
#include <getopt.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <time.h>
#include <string.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <errno.h>
#include <sys/capability.h>
#include <sys/prctl.h>
#include <pwd.h>
#include <grp.h>
#include "dhcpd.h"
#include "dhcpc.h"
#include "options.h"
#include "clientpacket.h"
#include "packet.h"
#include "script.h"
#include "socket.h"
#include "log.h"
#include "rootcap.h"
#include "nstrl.h"
#define VERSION "1.0"
static unsigned long requested_ip, server_addr, timeout;
static unsigned long lease, t1, t2, xid, start;
static int state, packet_num, fd, listen_mode;
static sig_atomic_t pending_exit, pending_renew, pending_release;
enum {
LISTEN_NONE,
LISTEN_KERNEL,
LISTEN_RAW
};
struct client_config_t client_config = {
/* Default options. */
.abort_if_no_lease = 0,
.foreground = 0,
.quit_after_lease = 0,
.background_if_no_lease = 0,
.interface = "eth0",
.script = "none",
.clientid = NULL,
.hostname = NULL,
.ifindex = 0,
.arp = "\0",
};
static void show_usage(void)
{
printf(
"Usage: ndhc [OPTIONS]\n\n"
" -c, --clientid=CLIENTID Client identifier\n"
" -H, --hostname=HOSTNAME Client hostname\n"
" -h Alias for -H\n"
" -f, --foreground Do not fork after getting lease\n"
" -b, --background Fork to background if lease cannot be\n"
" immediately negotiated.\n"
" -i, --interface=INTERFACE Interface to use (default: eth0)\n"
" -n, --now Exit with failure if lease cannot be\n"
" immediately negotiated.\n"
" -q, --quit Quit after obtaining lease\n"
" -r, --request=IP IP address to request (default: none)\n"
" -u, --user Change privileges to this user\n"
" -C, --chroot Directory to which udhcp should chroot\n"
" -v, --version Display version\n"
);
exit(EXIT_SUCCESS);
}
/* just a little helper */
static void change_mode(int new_mode)
{
debug(LOG_INFO, "entering %s listen mode",
new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
close(fd);
fd = -1;
listen_mode = new_mode;
}
/* perform a renew */
static void perform_renew(void)
{
log_line(LOG_INFO, "Performing a DHCP renew...\n");
switch (state) {
case BOUND:
change_mode(LISTEN_KERNEL);
case RENEWING:
case REBINDING:
state = RENEW_REQUESTED;
break;
case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
run_script(NULL, SCRIPT_DECONFIG);
case REQUESTING:
case RELEASED:
change_mode(LISTEN_RAW);
state = INIT_SELECTING;
break;
case INIT_SELECTING:
break;
}
/* start things over */
packet_num = 0;
/* Kill any timeouts because the user wants this to hurry along */
timeout = 0;
}
/* perform a release */
static void perform_release(void)
{
char buf[32];
struct in_addr temp_addr;
memset(buf, '\0', sizeof buf);
/* send release packet */
if (state == BOUND || state == RENEWING || state == REBINDING) {
temp_addr.s_addr = server_addr;
snprintf(buf, sizeof buf, "%s", inet_ntoa(temp_addr));
temp_addr.s_addr = requested_ip;
log_line(LOG_INFO, "Unicasting a release of %s to %s.\n",
inet_ntoa(temp_addr), buf);
send_release(server_addr, requested_ip); /* unicast */
run_script(NULL, SCRIPT_DECONFIG);
}
log_line(LOG_INFO, "Entering released state.\n");
change_mode(LISTEN_NONE);
state = RELEASED;
timeout = 0x7fffffff;
}
static void signal_handler(int sig)
{
switch (sig) {
case SIGUSR1:
pending_renew = 1;
break;
case SIGUSR2:
pending_release = 1;
break;
case SIGTERM:
pending_exit = 1;
break;
}
}
static void background(void)
{
if (daemon(0, 0) == -1) {
perror("fork");
exit(EXIT_SUCCESS);
}
client_config.foreground = 1; /* Do not fork again. */
}
static void handle_timeout(void)
{
time_t now = time(0);
/* timeout dropped to zero */
switch (state) {
case INIT_SELECTING:
if (packet_num < 3) {
if (packet_num == 0)
xid = random_xid();
/* send discover packet */
send_discover(xid, requested_ip); /* broadcast */
timeout = now + ((packet_num == 2) ? 4 : 2);
packet_num++;
} else {
if (client_config.background_if_no_lease) {
log_line(LOG_INFO, "No lease, going to background.\n");
background();
} else if (client_config.abort_if_no_lease) {
log_line(LOG_INFO, "No lease, failing.\n");
exit(EXIT_FAILURE);
}
/* wait to try again */
packet_num = 0;
timeout = now + 60;
}
break;
case RENEW_REQUESTED:
case REQUESTING:
if (packet_num < 3) {
/* send request packet */
if (state == RENEW_REQUESTED)
/* unicast */
send_renew(xid, server_addr, requested_ip);
else
/* broadcast */
send_selecting(xid, server_addr, requested_ip);
timeout = now + ((packet_num == 2) ? 10 : 2);
packet_num++;
} else {
/* timed out, go back to init state */
if (state == RENEW_REQUESTED)
run_script(NULL, SCRIPT_DECONFIG);
state = INIT_SELECTING;
timeout = now;
packet_num = 0;
change_mode(LISTEN_RAW);
}
break;
case BOUND:
/* Lease is starting to run out, time to enter renewing state */
state = RENEWING;
change_mode(LISTEN_KERNEL);
debug(LOG_INFO, "Entering renew state.\n");
/* fall right through */
case RENEWING:
/* Either set a new T1, or enter REBINDING state */
if ((t2 - t1) <= (lease / 14400 + 1)) {
/* timed out, enter rebinding state */
state = REBINDING;
timeout = now + (t2 - t1);
debug(LOG_INFO, "Entering rebinding state.\n");
} else {
/* send a request packet */
send_renew(xid, server_addr, requested_ip); /* unicast */
t1 = ((t2 - t1) >> 1) + t1;
timeout = t1 + start;
}
break;
case REBINDING:
/* Either set a new T2, or enter INIT state */
if ((lease - t2) <= (lease / 14400 + 1)) {
/* timed out, enter init state */
state = INIT_SELECTING;
log_line(LOG_INFO, "Lease lost, entering init state.\n");
run_script(NULL, SCRIPT_DECONFIG);
timeout = now;
packet_num = 0;
change_mode(LISTEN_RAW);
} else {
/* send a request packet */
send_renew(xid, 0, requested_ip); /* broadcast */
t2 = ((lease - t2) >> 1) + t2;
timeout = t2 + start;
}
break;
case RELEASED:
/* yah, I know, *you* say it would never happen */
timeout = 0x7fffffff;
break;
}
}
static void handle_packet(void)
{
unsigned char *temp = NULL, *message = NULL;
int len;
time_t now = time(0);
struct in_addr temp_addr;
struct dhcpMessage packet;
debug(LOG_INFO, "got a packet\n");
if (listen_mode == LISTEN_KERNEL)
len = get_packet(&packet, fd);
else
len = get_raw_packet(&packet, fd);
if (len == -1 && errno != EINTR) {
debug(LOG_INFO, "error on read, %s, reopening socket.\n",
strerror(errno));
change_mode(listen_mode); /* just close and reopen */
}
if (len < 0)
return;
if (packet.xid != xid) {
debug(LOG_INFO, "Ignoring XID %lx (our xid is %lx).\n",
(unsigned long) packet.xid, xid);
return;
}
if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
debug(LOG_ERR, "couldnt get option from packet -- ignoring\n");
return;
}
switch (state) {
case INIT_SELECTING:
/* Must be a DHCPOFFER to one of our xid's */
if (*message == DHCPOFFER) {
if ((temp = get_option(&packet, DHCP_SERVER_ID))) {
memcpy(&server_addr, temp, 4);
xid = packet.xid;
requested_ip = packet.yiaddr;
/* enter requesting state */
state = REQUESTING;
timeout = now;
packet_num = 0;
} else {
debug(LOG_ERR, "No server ID in message\n");
}
}
break;
case RENEW_REQUESTED:
case REQUESTING:
case RENEWING:
case REBINDING:
if (*message == DHCPACK) {
if (!(temp = get_option(&packet, DHCP_LEASE_TIME))) {
log_line(LOG_ERR,
"No lease time received, assuming 1h.\n");
lease = 60 * 60;
} else {
memcpy(&lease, temp, 4);
lease = ntohl(lease);
}
/* enter bound state */
t1 = lease >> 1;
/* little fixed point for n * .875 */
t2 = (lease * 0x7) >> 3;
temp_addr.s_addr = packet.yiaddr;
log_line(LOG_INFO,
"Lease of %s obtained, lease time %ld.\n",
inet_ntoa(temp_addr), lease);
start = now;
timeout = t1 + start;
requested_ip = packet.yiaddr;
run_script(&packet,
((state == RENEWING || state == REBINDING)
? SCRIPT_RENEW : SCRIPT_BOUND));
state = BOUND;
change_mode(LISTEN_NONE);
if (client_config.quit_after_lease)
exit(EXIT_SUCCESS);
if (!client_config.foreground)
background();
} else if (*message == DHCPNAK) {
/* return to init state */
log_line(LOG_INFO, "Received DHCP NAK.\n");
run_script(&packet, SCRIPT_NAK);
if (state != REQUESTING)
run_script(NULL, SCRIPT_DECONFIG);
state = INIT_SELECTING;
timeout = now;
requested_ip = 0;
packet_num = 0;
change_mode(LISTEN_RAW);
sleep(3); /* avoid excessive network traffic */
}
break;
case BOUND:
case RELEASED:
default:
break;
}
}
static int do_work(void)
{
struct timeval tv;
fd_set rfds;
for (;;) {
/* Handle signals asynchronously. */
if (pending_renew)
perform_renew();
if (pending_release)
perform_release();
if (pending_exit) {
log_line(LOG_INFO, "Received SIGTERM. Exiting gracefully.\n");
exit(EXIT_SUCCESS);
}
tv.tv_sec = timeout - time(0);
tv.tv_usec = 0;
if (listen_mode != LISTEN_NONE && fd < 0) {
if (listen_mode == LISTEN_KERNEL)
fd = listen_socket(INADDR_ANY, CLIENT_PORT,
client_config.interface);
else
fd = raw_socket(client_config.ifindex);
if (fd < 0) {
log_line(LOG_ERR, "FATAL: couldn't listen on socket: %s.\n",
strerror(errno));
exit(EXIT_FAILURE);
}
}
if (tv.tv_sec <= 0) {
handle_timeout();
continue;
}
FD_ZERO(&rfds);
if (fd >= 0)
FD_SET(fd, &rfds);
debug(LOG_INFO, "Waiting on select...\n");
if (select(fd + 1, &rfds, NULL, NULL, &tv) == -1) {
switch (errno) {
case EBADF:
fd = -1;
default:
debug(LOG_ERR, "Error: \"%s\" on select!\n",
strerror(errno));
case EINTR: /* Signal received, go back to top. */
continue;
}
}
debug(LOG_INFO, "select suceeded\n");
if (listen_mode != LISTEN_NONE && FD_ISSET(fd, &rfds))
handle_packet();
}
}
int main(int argc, char **argv)
{
char *chroot_dir = NULL;
int c, len;
struct passwd *pwd;
uid_t uid = 0;
gid_t gid = 0;
static struct option arg_options[] = {
{"clientid", required_argument, 0, 'c'},
{"foreground", no_argument, 0, 'f'},
{"background", no_argument, 0, 'b'},
{"hostname", required_argument, 0, 'H'},
{"hostname", required_argument, 0, 'h'},
{"interface", required_argument, 0, 'i'},
{"now", no_argument, 0, 'n'},
{"quit", no_argument, 0, 'q'},
{"request", required_argument, 0, 'r'},
{"version", no_argument, 0, 'v'},
{"user", required_argument, 0, 'u'},
{"chroot", required_argument, 0, 'C'},
{"help", no_argument, 0, '?'},
{0, 0, 0, 0}
};
/* get options */
while (1) {
int option_index = 0;
c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:u:C:v", arg_options,
&option_index);
if (c == -1) break;
switch (c) {
case 'c':
len = strlen(optarg) > 255 ? 255 : strlen(optarg);
if (client_config.clientid)
free(client_config.clientid);
client_config.clientid = malloc(len + 2);
client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
client_config.clientid[OPT_LEN] = len;
client_config.clientid[OPT_DATA] = '\0';
strlcpy((char *)client_config.clientid + OPT_DATA, optarg, len);
break;
case 'f':
client_config.foreground = 1;
break;
case 'b':
client_config.background_if_no_lease = 1;
break;
case 'h':
case 'H':
len = strlen(optarg) > 255 ? 255 : strlen(optarg);
if (client_config.hostname)
free(client_config.hostname);
client_config.hostname = malloc(len + 2);
client_config.hostname[OPT_CODE] = DHCP_HOST_NAME;
client_config.hostname[OPT_LEN] = len;
strlcpy((char*)client_config.hostname + 2, optarg, len);
break;
case 'i':
client_config.interface = optarg;
break;
case 'n':
client_config.abort_if_no_lease = 1;
break;
case 'q':
client_config.quit_after_lease = 1;
break;
case 'r':
requested_ip = inet_addr(optarg);
break;
case 'u':
pwd = getpwnam(optarg);
if (pwd) {
uid = (int)pwd->pw_uid;
gid = (int)pwd->pw_gid;
} else {
printf("Bad username provided.\n");
exit(EXIT_FAILURE);
}
break;
case 'C':
len = strlen(optarg) > 255 ? 255 : strlen(optarg);
chroot_dir = malloc(len + 2);
memset(chroot_dir, '\0', len + 2);
strlcpy(chroot_dir, optarg, len);
break;
case 'v':
printf("ndhc, version " VERSION "\n\n");
exit(EXIT_SUCCESS);
break;
default:
show_usage();
}
}
log_line(LOG_INFO, "ndhc client " VERSION " started.\n");
if (read_interface(client_config.interface, &client_config.ifindex,
NULL, client_config.arp) < 0)
exit(EXIT_FAILURE);
if (!client_config.clientid) {
client_config.clientid = malloc(6 + 3);
client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
client_config.clientid[OPT_LEN] = 7;
client_config.clientid[OPT_DATA] = 1;
memcpy(client_config.clientid + 3, client_config.arp, 6);
}
/* setup signal handlers */
signal(SIGUSR1, signal_handler);
signal(SIGUSR2, signal_handler);
signal(SIGTERM, signal_handler);
if (chdir(chroot_dir)) {
printf("Failed to chdir(%s)!\n", chroot_dir);
exit(EXIT_FAILURE);
}
if (chroot(chroot_dir)) {
printf("Failed to chroot(%s)!\n", chroot_dir);
exit(EXIT_FAILURE);
}
drop_root(uid, gid,
"cap_net_bind_service,cap_net_broadcast,cap_net_raw=ep");
state = INIT_SELECTING;
run_script(NULL, SCRIPT_DECONFIG);
change_mode(LISTEN_RAW);
do_work();
return EXIT_SUCCESS;
}
Reference in New Issue View Git Blame Copy Permalink