text: /* dhcpc.c
   *
   * udhcp DHCP client
   *
   * Russ Dill <Russ.Dill@asu.edu> July 2001
   *
   * 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 <sys/time.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 "dhcpd.h"
  #include "dhcpc.h"
  #include "options.h"
  #include "clientpacket.h"
  #include "clientsocket.h"
  #include "script.h"
  #include "socket.h"
  #include "common.h"
  #include "signalpipe.h"
  
  static int state;
  static unsigned long requested_ip; /* = 0 */
  static unsigned long server_addr;
  static unsigned long timeout;
  static int packet_num; /* = 0 */
  static int fd = -1;
  
  #define LISTEN_NONE 0
  #define LISTEN_KERNEL 1
  #define LISTEN_RAW 2
  static int listen_mode;
  
  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",
  	pidfile: NULL,
  	script: DEFAULT_SCRIPT,
  	clientid: NULL,
  	hostname: NULL,
  	ifindex: 0,
  	arp: "\0\0\0\0\0\0",		/* appease gcc-3.0 */
  };
  
  #ifndef IN_BUSYBOX
  static void __attribute__ ((noreturn)) show_usage(void)
  {
  	printf(
  "Usage: udhcpc [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"
  "  -p, --pidfile=file              Store process ID of daemon in file\n"
  "  -q, --quit                      Quit after obtaining lease\n"
  "  -r, --request=IP                IP address to request (default: none)\n"
  "  -s, --script=file               Run file at dhcp events (default:\n"
  "                                  " DEFAULT_SCRIPT ")\n"
  "  -v, --version                   Display version\n"
  	);
  	exit(0);
  }
  #else
  #define show_usage bb_show_usage
  extern void show_usage(void) __attribute__ ((noreturn));
  #endif
  
  
  /* 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");
  	if (fd >= 0) close(fd);
  	fd = -1;
  	listen_mode = new_mode;
  }
  
  
  /* perform a renew */
  static void perform_renew(void)
  {
  	LOG(LOG_INFO, "Performing a DHCP renew");
  	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, "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 buffer[16];
  	struct in_addr temp_addr;
  
  	/* send release packet */
  	if (state == BOUND || state == RENEWING || state == REBINDING) {
  		temp_addr.s_addr = server_addr;
  		sprintf(buffer, "%s", inet_ntoa(temp_addr));
  		temp_addr.s_addr = requested_ip;
  		LOG(LOG_INFO, "Unicasting a release of %s to %s",
  				inet_ntoa(temp_addr), buffer);
  		send_release(server_addr, requested_ip); /* unicast */
  		run_script(NULL, "deconfig");
  	}
  	LOG(LOG_INFO, "Entering released state");
  
  	change_mode(LISTEN_NONE);
  	state = RELEASED;
  	timeout = 0x7fffffff;
  }
  
  
  static void client_background(void)
  {
  	background(client_config.pidfile);
  	client_config.foreground = 1; /* Do not fork again. */
  	client_config.background_if_no_lease = 0;
  }
  
  
  #ifdef COMBINED_BINARY
  int udhcpc_main(int argc, char *argv[])
  #else
  int main(int argc, char *argv[])
  #endif
  {
  	uint8_t *temp, *message;
  	unsigned long t1 = 0, t2 = 0, xid = 0;
  	unsigned long start = 0, lease;
  	fd_set rfds;
  	int retval;
  	struct timeval tv;
  	int c, len;
  	struct dhcpMessage packet;
  	struct in_addr temp_addr;
  	long now;
  	int max_fd;
  	int sig;
  
  	static const 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'},
  		{"pidfile",	required_argument,	0, 'p'},
  		{"quit",	no_argument,		0, 'q'},
  		{"request",	required_argument,	0, 'r'},
  		{"script",	required_argument,	0, 's'},
  		{"version",	no_argument,		0, 'v'},
  		{0, 0, 0, 0}
  	};
  
  	/* get options */
  	while (1) {
  		int option_index = 0;
  		c = getopt_long(argc, argv, "c:fbH:h:i:np:qr:s: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 = xmalloc(len + 2);
  			client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
  			client_config.clientid[OPT_LEN] = len;
  			client_config.clientid[OPT_DATA] = '\0';
  			strncpy(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 = xmalloc(len + 2);
  			client_config.hostname[OPT_CODE] = DHCP_HOST_NAME;
  			client_config.hostname[OPT_LEN] = len;
  			strncpy(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 'p':
  			client_config.pidfile = optarg;
  			break;
  		case 'q':
  			client_config.quit_after_lease = 1;
  			break;
  		case 'r':
  			requested_ip = inet_addr(optarg);
  			break;
  		case 's':
  			client_config.script = optarg;
  			break;
  		case 'v':
  			printf("udhcpcd, version %s\n\n", VERSION);
  			return 0;
  			break;
  		default:
  			show_usage();
  		}
  	}
  
  	/* Start the log, sanitize fd's, and write a pid file */
  	start_log_and_pid("udhcpc", client_config.pidfile);
  
  	if (read_interface(client_config.interface, &client_config.ifindex,
  			   NULL, client_config.arp) < 0)
  		return 1;
  
  	if (!client_config.clientid) {
  		client_config.clientid = xmalloc(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 the signal pipe */
  	udhcp_sp_setup();
  
  	state = INIT_SELECTING;
  	run_script(NULL, "deconfig");
  	change_mode(LISTEN_RAW);
  
  	for (;;) {
  
  		tv.tv_sec = timeout - uptime();
  		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(LOG_ERR, "FATAL: couldn't listen on socket, %m");
  				return 0;
  			}
  		}
  		max_fd = udhcp_sp_fd_set(&rfds, fd);
  
  		if (tv.tv_sec > 0) {
  			DEBUG(LOG_INFO, "Waiting on select...");
  			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
  		} else retval = 0; /* If we already timed out, fall through */
  
  		now = uptime();
  		if (retval == 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 {
  					run_script(NULL, "leasefail");
  					if (client_config.background_if_no_lease) {
  						LOG(LOG_INFO, "No lease, forking to background.");
  						client_background();
  					} else if (client_config.abort_if_no_lease) {
  						LOG(LOG_INFO, "No lease, failing.");
  						return 1;
  				  	}
  					/* 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)
  						send_renew(xid, server_addr, requested_ip); /* unicast */
  					else send_selecting(xid, server_addr, requested_ip); /* broadcast */
  
  					timeout = now + ((packet_num == 2) ? 10 : 2);
  					packet_num++;
  				} else {
  					/* timed out, go back to init state */
  					if (state == RENEW_REQUESTED) run_script(NULL, "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");
  				/* 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");
  				} else {
  					/* send a request packet */
  					send_renew(xid, server_addr, requested_ip); /* unicast */
  
  					t1 = (t2 - t1) / 2 + 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(LOG_INFO, "Lease lost, entering init state");
  					run_script(NULL, "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) / 2 + t2;
  					timeout = t2 + start;
  				}
  				break;
  			case RELEASED:
  				/* yah, I know, *you* say it would never happen */
  				timeout = 0x7fffffff;
  				break;
  			}
  		} else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(fd, &rfds)) {
  			/* a packet is ready, read it */
  
  			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, %m, reopening socket");
  				change_mode(listen_mode); /* just close and reopen */
  			}
  			if (len < 0) continue;
  
  			if (packet.xid != xid) {
  				DEBUG(LOG_INFO, "Ignoring XID %lx (our xid is %lx)",
  					(unsigned long) packet.xid, xid);
  				continue;
  			}
  
  			if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
  				DEBUG(LOG_ERR, "couldnt get option from packet -- ignoring");
  				continue;
  			}
  
  			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");
  					}
  				}
  				break;
  			case RENEW_REQUESTED:
  			case REQUESTING:
  			case RENEWING:
  			case REBINDING:
  				if (*message == DHCPACK) {
  					if (!(temp = get_option(&packet, DHCP_LEASE_TIME))) {
  						LOG(LOG_ERR, "No lease time with ACK, using 1 hour lease");
  						lease = 60 * 60;
  					} else {
  						memcpy(&lease, temp, 4);
  						lease = ntohl(lease);
  					}
  
  					/* enter bound state */
  					t1 = lease / 2;
  
  					/* little fixed point for n * .875 */
  					t2 = (lease * 0x7) >> 3;
  					temp_addr.s_addr = packet.yiaddr;
  					LOG(LOG_INFO, "Lease of %s obtained, lease time %ld",
  						inet_ntoa(temp_addr), lease);
  					start = now;
  					timeout = t1 + start;
  					requested_ip = packet.yiaddr;
  					run_script(&packet,
  						   ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
  
  					state = BOUND;
  					change_mode(LISTEN_NONE);
  					if (client_config.quit_after_lease)
  						return 0;
  					if (!client_config.foreground)
  						client_background();
  
  				} else if (*message == DHCPNAK) {
  					/* return to init state */
  					LOG(LOG_INFO, "Received DHCP NAK");
  					run_script(&packet, "nak");
  					if (state != REQUESTING)
  						run_script(NULL, "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, RELEASED: - ignore all packets */
  			}
  		} else if (retval > 0 && (sig = udhcp_sp_read(&rfds))) {
  			switch (sig) {
  			case SIGUSR1:
  				perform_renew();
  				break;
  			case SIGUSR2:
  				perform_release();
  				break;
  			case SIGTERM:
  				LOG(LOG_INFO, "Received SIGTERM");
  				return 0;
  			}
  		} else if (retval == -1 && errno == EINTR) {
  			/* a signal was caught */
  		} else {
  			/* An error occured */
  			DEBUG(LOG_ERR, "Error on select");
  		}
  
  	}
  	return 0;
  }
  