X-Git-Url: https://git.librecmc.org/?a=blobdiff_plain;f=networking%2Fudhcp%2Fdhcpc.c;h=9a2fe35e4d169e0b03047cef61e441d4ea4f46c9;hb=695fa51c80047eb25cc82e6e1630b4545a6bc0b6;hp=f69b687b21315f18df17ddadacc9c1aba0e48dd7;hpb=e2d3ded3549edd58fe3b39f2254c65f0808bcac2;p=oweals%2Fbusybox.git

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index f69b687b2..9a2fe35e4 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -7,43 +7,60 @@
  *
  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
  */
-
-#include <getopt.h>
-
+#include <syslog.h>
+/* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */
+#define WANT_PIDFILE 1
 #include "common.h"
 #include "dhcpd.h"
 #include "dhcpc.h"
 #include "options.h"
 
 
-static int state;
-/* Something is definitely wrong here. IPv4 addresses
- * in variables of type long?? BTW, we use inet_ntoa()
- * in the code. Manpage says that struct in_addr has a member of type long (!)
- * which holds IPv4 address, and the struct is passed by value (!!)
- */
-static unsigned long requested_ip; /* = 0 */
-static unsigned long server_addr;
-static unsigned long timeout;
-static int packet_num; /* = 0 */
-static int fd = -1;
+static int sockfd = -1;
 
-#define LISTEN_NONE 0
+#define LISTEN_NONE   0
 #define LISTEN_KERNEL 1
-#define LISTEN_RAW 2
-static int listen_mode;
-
-struct client_config_t client_config;
+#define LISTEN_RAW    2
+static smallint listen_mode;
+
+/* initial state: (re)start DHCP negotiation */
+#define INIT_SELECTING  0
+/* discover was sent, DHCPOFFER reply received */
+#define REQUESTING      1
+/* select/renew was sent, DHCPACK reply received */
+#define BOUND           2
+/* half of lease passed, want to renew it by sending unicast renew requests */
+#define RENEWING        3
+/* renew requests were not answered, lease is almost over, send broadcast renew */
+#define REBINDING       4
+/* manually requested renew (SIGUSR1) */
+#define RENEW_REQUESTED 5
+/* release, possibly manually requested (SIGUSR2) */
+#define RELEASED        6
+static smallint state;
+
+/* struct client_config_t client_config is in bb_common_bufsiz1 */
 
 
 /* just a little helper */
-static void change_mode(int new_mode)
+static void change_listen_mode(int new_mode)
 {
-	DEBUG("entering %s listen mode",
-		new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
-	if (fd >= 0) close(fd);
-	fd = -1;
+	log1("Entering listen mode: %s",
+		new_mode != LISTEN_NONE
+			? (new_mode == LISTEN_KERNEL ? "kernel" : "raw")
+			: "none"
+	);
+
 	listen_mode = new_mode;
+	if (sockfd >= 0) {
+		close(sockfd);
+		sockfd = -1;
+	}
+	if (new_mode == LISTEN_KERNEL)
+		sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface);
+	else if (new_mode != LISTEN_NONE)
+		sockfd = udhcp_raw_socket(client_config.ifindex);
+	/* else LISTEN_NONE: sockfd stay closed */
 }
 
 
@@ -53,7 +70,7 @@ static void perform_renew(void)
 	bb_info_msg("Performing a DHCP renew");
 	switch (state) {
 	case BOUND:
-		change_mode(LISTEN_KERNEL);
+		change_listen_mode(LISTEN_KERNEL);
 	case RENEWING:
 	case REBINDING:
 		state = RENEW_REQUESTED;
@@ -62,31 +79,25 @@ static void perform_renew(void)
 		udhcp_run_script(NULL, "deconfig");
 	case REQUESTING:
 	case RELEASED:
-		change_mode(LISTEN_RAW);
+		change_listen_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)
+static void perform_release(uint32_t requested_ip, uint32_t server_addr)
 {
-	char buffer[16];
+	char buffer[sizeof("255.255.255.255")];
 	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));
+		strcpy(buffer, inet_ntoa(temp_addr));
 		temp_addr.s_addr = requested_ip;
 		bb_info_msg("Unicasting a release of %s to %s",
 				inet_ntoa(temp_addr), buffer);
@@ -95,18 +106,20 @@ static void perform_release(void)
 	}
 	bb_info_msg("Entering released state");
 
-	change_mode(LISTEN_NONE);
+	change_listen_mode(LISTEN_NONE);
 	state = RELEASED;
-	timeout = 0x7fffffff;
 }
 
 
+#if BB_MMU
 static void client_background(void)
 {
-	udhcp_background(client_config.pidfile);
-	client_config.foreground = 1; /* Do not fork again. */
-	client_config.background_if_no_lease = 0;
+	bb_daemonize(0);
+	logmode &= ~LOGMODE_STDIO;
+	/* rewrite pidfile, as our pid is different now */
+	write_pidfile(client_config.pidfile);
 }
+#endif
 
 
 static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
@@ -122,385 +135,546 @@ static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
 }
 
 
-int udhcpc_main(int argc, char *argv[])
+int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 {
 	uint8_t *temp, *message;
-	char *str_c, *str_V, *str_h, *str_F, *str_r, *str_T, *str_t;
-	unsigned long t1 = 0, t2 = 0, xid = 0;
-	unsigned long start = 0, lease = 0;
-	long now;
+	char *str_c, *str_V, *str_h, *str_F, *str_r;
+	IF_FEATURE_UDHCP_PORT(char *str_P;)
+	llist_t *list_O = NULL;
+	int tryagain_timeout = 20;
+	int discover_timeout = 3;
+	int discover_retries = 3;
+	uint32_t server_addr = server_addr; /* for compiler */
+	uint32_t requested_ip = 0;
+	uint32_t xid = 0;
+	uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
+	int packet_num;
+	int timeout; /* must be signed */
+	unsigned already_waited_sec;
 	unsigned opt;
 	int max_fd;
-	int sig;
 	int retval;
-	int len;
-	int no_clientid = 0;
-	fd_set rfds;
 	struct timeval tv;
-	struct dhcpMessage packet;
-	struct in_addr temp_addr;
+	struct dhcp_packet packet;
+	fd_set rfds;
 
+#if ENABLE_LONG_OPTS
+	static const char udhcpc_longopts[] ALIGN1 =
+		"clientid\0"       Required_argument "c"
+		"clientid-none\0"  No_argument       "C"
+		"vendorclass\0"    Required_argument "V"
+		"hostname\0"       Required_argument "H"
+		"fqdn\0"           Required_argument "F"
+		"interface\0"      Required_argument "i"
+		"now\0"            No_argument       "n"
+		"pidfile\0"        Required_argument "p"
+		"quit\0"           No_argument       "q"
+		"release\0"        No_argument       "R"
+		"request\0"        Required_argument "r"
+		"script\0"         Required_argument "s"
+		"timeout\0"        Required_argument "T"
+		"version\0"        No_argument       "v"
+		"retries\0"        Required_argument "t"
+		"tryagain\0"       Required_argument "A"
+		"syslog\0"         No_argument       "S"
+		"request-option\0" Required_argument "O"
+		"no-default-options\0" No_argument   "o"
+		"foreground\0"     No_argument       "f"
+		"background\0"     No_argument       "b"
+		IF_FEATURE_UDHCPC_ARPING("arping\0"	No_argument       "a")
+		IF_FEATURE_UDHCP_PORT("client-port\0"	Required_argument "P")
+		;
+#endif
 	enum {
 		OPT_c = 1 << 0,
 		OPT_C = 1 << 1,
 		OPT_V = 1 << 2,
-		OPT_f = 1 << 3,
-		OPT_b = 1 << 4,
-		OPT_H = 1 << 5,
-		OPT_h = 1 << 6,
-		OPT_F = 1 << 7,
-		OPT_i = 1 << 8,
-		OPT_n = 1 << 9,
-		OPT_p = 1 << 10,
-		OPT_q = 1 << 11,
-		OPT_R = 1 << 12,
-		OPT_r = 1 << 13,
-		OPT_s = 1 << 14,
-		OPT_T = 1 << 15,
-		OPT_t = 1 << 16,
-		OPT_v = 1 << 17,
-	};
-	static const struct option arg_options[] = {
-		{ "clientid",   required_argument,      0, 'c' },
-		{ "clientid-none", no_argument,         0, 'C' },
-		{ "vendorclass", required_argument,     0, 'V' },
-		{ "foreground", no_argument,            0, 'f' },
-		{ "background", no_argument,            0, 'b' },
-		{ "hostname",   required_argument,      0, 'H' },
-		{ "hostname",   required_argument,      0, 'h' },
-		{ "fqdn",       required_argument,      0, 'F' },
-		{ "interface",  required_argument,      0, 'i' },
-		{ "now",        no_argument,            0, 'n' },
-		{ "pidfile",    required_argument,      0, 'p' },
-		{ "quit",       no_argument,            0, 'q' },
-		{ "release",    no_argument,            0, 'R' },
-		{ "request",    required_argument,      0, 'r' },
-		{ "script",     required_argument,      0, 's' },
-		{ "timeout",    required_argument,      0, 'T' },
-		{ "version",    no_argument,            0, 'v' },
-		{ "retries",    required_argument,      0, 't' },
-		{ 0, 0, 0, 0 }
+		OPT_H = 1 << 3,
+		OPT_h = 1 << 4,
+		OPT_F = 1 << 5,
+		OPT_i = 1 << 6,
+		OPT_n = 1 << 7,
+		OPT_p = 1 << 8,
+		OPT_q = 1 << 9,
+		OPT_R = 1 << 10,
+		OPT_r = 1 << 11,
+		OPT_s = 1 << 12,
+		OPT_T = 1 << 13,
+		OPT_t = 1 << 14,
+		OPT_S = 1 << 15,
+		OPT_A = 1 << 16,
+		OPT_O = 1 << 17,
+		OPT_o = 1 << 18,
+		OPT_f = 1 << 19,
+/* The rest has variable bit positions, need to be clever */
+		OPTBIT_f = 19,
+		USE_FOR_MMU(             OPTBIT_b,)
+		IF_FEATURE_UDHCPC_ARPING(OPTBIT_a,)
+		IF_FEATURE_UDHCP_PORT(   OPTBIT_P,)
+		USE_FOR_MMU(             OPT_b = 1 << OPTBIT_b,)
+		IF_FEATURE_UDHCPC_ARPING(OPT_a = 1 << OPTBIT_a,)
+		IF_FEATURE_UDHCP_PORT(   OPT_P = 1 << OPTBIT_P,)
 	};
 
 	/* Default options. */
+	IF_FEATURE_UDHCP_PORT(SERVER_PORT = 67;)
+	IF_FEATURE_UDHCP_PORT(CLIENT_PORT = 68;)
 	client_config.interface = "eth0";
 	client_config.script = DEFAULT_SCRIPT;
-	client_config.retries = 3;
-	client_config.timeout = 3;
 
 	/* Parse command line */
-	opt_complementary = "?:c--C:C--c" // mutually exclusive
-	                    ":hH:Hh"; // -h and -H are the same
-	applet_long_options = arg_options;
-	opt = getopt32(argc, argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:v",
-		&str_c, &str_V, &str_h, &str_h, &str_F,
-		&client_config.interface, &client_config.pidfile, &str_r,
-		&client_config.script, &str_T, &str_t
+	/* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */
+	opt_complementary = "c--C:C--c:O::T+:t+:A+"
+#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
+		":vv"
+#endif
+		;
+	IF_LONG_OPTS(applet_long_options = udhcpc_longopts;)
+	opt = getopt32(argv, "c:CV:H:h:F:i:np:qRr:s:T:t:SA:O:of"
+		USE_FOR_MMU("b")
+		IF_FEATURE_UDHCPC_ARPING("a")
+		IF_FEATURE_UDHCP_PORT("P:")
+		"v"
+		, &str_c, &str_V, &str_h, &str_h, &str_F
+		, &client_config.interface, &client_config.pidfile, &str_r /* i,p */
+		, &client_config.script /* s */
+		, &discover_timeout, &discover_retries, &tryagain_timeout /* T,t,A */
+		, &list_O
+		IF_FEATURE_UDHCP_PORT(, &str_P)
+#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
+		, &dhcp_verbose
+#endif
 		);
-
 	if (opt & OPT_c)
 		client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
-	if (opt & OPT_C)
-		no_clientid = 1;
 	if (opt & OPT_V)
 		client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, str_V, 0);
-	if (opt & OPT_f)
-		client_config.foreground = 1;
-	if (opt & OPT_b)
-		client_config.background_if_no_lease = 1;
-	if (opt & OPT_h)
+	if (opt & (OPT_h|OPT_H))
 		client_config.hostname = alloc_dhcp_option(DHCP_HOST_NAME, str_h, 0);
 	if (opt & OPT_F) {
 		client_config.fqdn = alloc_dhcp_option(DHCP_FQDN, str_F, 3);
 		/* Flags: 0000NEOS
 		S: 1 => Client requests Server to update A RR in DNS as well as PTR
 		O: 1 => Server indicates to client that DNS has been updated regardless
-		E: 1 => Name data is DNS format, i.e. <4>host<6>domain<4>com<0> not "host.domain.com"
+		E: 1 => Name data is DNS format, i.e. <4>host<6>domain<3>com<0> not "host.domain.com"
 		N: 1 => Client requests Server to not update DNS
 		*/
 		client_config.fqdn[OPT_DATA + 0] = 0x1;
 		/* client_config.fqdn[OPT_DATA + 1] = 0; - redundant */
 		/* client_config.fqdn[OPT_DATA + 2] = 0; - redundant */
 	}
-	// if (opt & OPT_i) client_config.interface = ...
-	if (opt & OPT_n)
-		client_config.abort_if_no_lease = 1;
-	// if (opt & OPT_p) client_config.pidfile = ...
-	if (opt & OPT_q)
-		client_config.quit_after_lease = 1;
-	if (opt & OPT_R)
-		client_config.release_on_quit = 1;
 	if (opt & OPT_r)
 		requested_ip = inet_addr(str_r);
-	// if (opt & OPT_s) client_config.script = ...
-	if (opt & OPT_T)
-		client_config.timeout = xatoi_u(str_T);
-	if (opt & OPT_t)
-		client_config.retries = xatoi_u(str_t);
-	if (opt & OPT_v) {
-		printf("version %s\n\n", BB_VER);
-		return 0;
+#if ENABLE_FEATURE_UDHCP_PORT
+	if (opt & OPT_P) {
+		CLIENT_PORT = xatou16(str_P);
+		SERVER_PORT = CLIENT_PORT - 1;
+	}
+#endif
+	if (opt & OPT_o)
+		client_config.no_default_options = 1;
+	while (list_O) {
+		char *optstr = llist_pop(&list_O);
+		int n = index_in_strings(dhcp_option_strings, optstr);
+		if (n < 0)
+			bb_error_msg_and_die("unknown option '%s'", optstr);
+		n = dhcp_options[n].code;
+		client_config.opt_mask[n >> 3] |= 1 << (n & 7);
 	}
 
-	/* Start the log, sanitize fd's, and write a pid file */
-	udhcp_start_log_and_pid(client_config.pidfile);
-
-	if (read_interface(client_config.interface, &client_config.ifindex,
-			   NULL, client_config.arp) < 0)
+	if (udhcp_read_interface(client_config.interface,
+			&client_config.ifindex,
+			NULL,
+			client_config.client_mac)
+	) {
 		return 1;
+	}
+
+#if !BB_MMU
+	/* on NOMMU reexec (i.e., background) early */
+	if (!(opt & OPT_f)) {
+		bb_daemonize_or_rexec(0 /* flags */, argv);
+		logmode = LOGMODE_NONE;
+	}
+#endif
+	if (opt & OPT_S) {
+		openlog(applet_name, LOG_PID, LOG_DAEMON);
+		logmode |= LOGMODE_SYSLOG;
+	}
+
+	/* Make sure fd 0,1,2 are open */
+	bb_sanitize_stdio();
+	/* Equivalent of doing a fflush after every \n */
+	setlinebuf(stdout);
 
-	/* if not set, and not suppressed, setup the default client ID */
-	if (!client_config.clientid && !no_clientid) {
+	/* Create pidfile */
+	write_pidfile(client_config.pidfile);
+
+	/* Goes to stdout (unless NOMMU) and possibly syslog */
+	bb_info_msg("%s (v"BB_VER") started", applet_name);
+
+	/* If not set, and not suppressed, set up the default client ID */
+	if (!client_config.clientid && !(opt & OPT_C)) {
 		client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, "", 7);
 		client_config.clientid[OPT_DATA] = 1;
-		memcpy(client_config.clientid + OPT_DATA+1, client_config.arp, 6);
+		memcpy(client_config.clientid + OPT_DATA+1, client_config.client_mac, 6);
 	}
 
 	if (!client_config.vendorclass)
 		client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 
-	/* setup the signal pipe */
+	/* Set up the signal pipe */
 	udhcp_sp_setup();
 
 	state = INIT_SELECTING;
 	udhcp_run_script(NULL, "deconfig");
-	change_mode(LISTEN_RAW);
+	change_listen_mode(LISTEN_RAW);
+	packet_num = 0;
+	timeout = 0;
+	already_waited_sec = 0;
 
+	/* Main event loop. select() waits on signal pipe and possibly
+	 * on sockfd.
+	 * "continue" statements in code below jump to the top of the loop.
+	 */
 	for (;;) {
-		tv.tv_sec = timeout - uptime();
-		tv.tv_usec = 0;
+		/* silence "uninitialized!" warning */
+		unsigned timestamp_before_wait = timestamp_before_wait;
 
-		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) {
-				bb_perror_msg("FATAL: cannot listen on socket");
-				return 0;
-			}
-		}
-		max_fd = udhcp_sp_fd_set(&rfds, fd);
+		//bb_error_msg("sockfd:%d, listen_mode:%d", sockfd, listen_mode);
+
+		/* Was opening raw or udp socket here
+		 * if (listen_mode != LISTEN_NONE && sockfd < 0),
+		 * but on fast network renew responses return faster
+		 * than we open sockets. Thus this code is moved
+		 * to change_listen_mode(). Thus we open listen socket
+		 * BEFORE we send renew request (see "case BOUND:"). */
+
+		max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 
-		if (tv.tv_sec > 0) {
-			DEBUG("Waiting on select...");
+		tv.tv_sec = timeout - already_waited_sec;
+		tv.tv_usec = 0;
+		retval = 0; /* If we already timed out, fall through, else... */
+		if ((int)tv.tv_sec > 0) {
+			timestamp_before_wait = (unsigned)monotonic_sec();
+			log1("Waiting on select...");
 			retval = select(max_fd + 1, &rfds, NULL, NULL, &tv);
-		} else retval = 0; /* If we already timed out, fall through */
+			if (retval < 0) {
+				/* EINTR? A signal was caught, don't panic */
+				if (errno == EINTR) {
+					already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
+					continue;
+				}
+				/* Else: an error occured, panic! */
+				bb_perror_msg_and_die("select");
+			}
+		}
 
-		now = uptime();
+		/* If timeout dropped to zero, time to become active:
+		 * resend discover/renew/whatever
+		 */
 		if (retval == 0) {
-			/* timeout dropped to zero */
+			/* We will restart the wait in any case */
+			already_waited_sec = 0;
+
 			switch (state) {
 			case INIT_SELECTING:
-				if (packet_num < client_config.retries) {
+				if (packet_num < discover_retries) {
 					if (packet_num == 0)
 						xid = random_xid();
-
-					/* send discover packet */
-					send_discover(xid, requested_ip); /* broadcast */
-
-					timeout = now + client_config.timeout;
+					/* broadcast */
+					send_discover(xid, requested_ip);
+					timeout = discover_timeout;
 					packet_num++;
-				} else {
-					udhcp_run_script(NULL, "leasefail");
-					if (client_config.background_if_no_lease) {
-						bb_info_msg("No lease, forking to background");
-						client_background();
-					} else if (client_config.abort_if_no_lease) {
-						bb_info_msg("No lease, failing");
-						return 1;
-					}
-					/* wait to try again */
-					packet_num = 0;
-					timeout = now + 60;
+					continue;
 				}
-				break;
-			case RENEW_REQUESTED:
+ leasefail:
+				udhcp_run_script(NULL, "leasefail");
+#if BB_MMU /* -b is not supported on NOMMU */
+				if (opt & OPT_b) { /* background if no lease */
+					bb_info_msg("No lease, forking to background");
+					client_background();
+					/* do not background again! */
+					opt = ((opt & ~OPT_b) | OPT_f);
+				} else
+#endif
+				if (opt & OPT_n) { /* abort if no lease */
+					bb_info_msg("No lease, failing");
+					retval = 1;
+					goto ret;
+				}
+				/* wait before trying again */
+				timeout = tryagain_timeout;
+				packet_num = 0;
+				continue;
 			case REQUESTING:
-				if (packet_num < client_config.retries) {
-					/* 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);
+				if (packet_num < discover_retries) {
+					/* send broadcast select packet */
+					send_select(xid, server_addr, requested_ip);
+					timeout = discover_timeout;
 					packet_num++;
-				} else {
-					/* timed out, go back to init state */
-					if (state == RENEW_REQUESTED) udhcp_run_script(NULL, "deconfig");
-					state = INIT_SELECTING;
-					timeout = now;
-					packet_num = 0;
-					change_mode(LISTEN_RAW);
+					continue;
 				}
-				break;
+				/* Timed out, go back to init state.
+				 * "discover...select...discover..." loops
+				 * were seen in the wild. Treat them similarly
+				 * to "no response to discover" case */
+				change_listen_mode(LISTEN_RAW);
+				state = INIT_SELECTING;
+				goto leasefail;
 			case BOUND:
-				/* Lease is starting to run out, time to enter renewing state */
+				/* 1/2 lease passed, enter renewing state */
 				state = RENEWING;
-				change_mode(LISTEN_KERNEL);
-				DEBUG("Entering renew state");
+				change_listen_mode(LISTEN_KERNEL);
+				log1("Entering renew state");
 				/* fall right through */
+			case RENEW_REQUESTED: /* manual (SIGUSR1) renew */
+			case_RENEW_REQUESTED:
 			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("Entering rebinding state");
-				} else {
-					/* send a request packet */
-					send_renew(xid, server_addr, requested_ip); /* unicast */
-
-					t1 = (t2 - t1) / 2 + t1;
-					timeout = t1 + start;
+				if (timeout > 60) {
+					/* send an unicast renew request */
+			/* Sometimes observed to fail (EADDRNOTAVAIL) to bind
+			 * a new UDP socket for sending inside send_renew.
+			 * I hazard to guess existing listening socket
+			 * is somehow conflicting with it, but why is it
+			 * not deterministic then?! Strange.
+			 * Anyway, it does recover by eventually failing through
+			 * into INIT_SELECTING state.
+			 */
+					send_renew(xid, server_addr, requested_ip);
+					timeout >>= 1;
+					continue;
 				}
-				break;
+				/* Timed out, enter rebinding state */
+				log1("Entering rebinding state");
+				state = REBINDING;
+				/* fall right through */
 			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;
-					bb_info_msg("Lease lost, entering init state");
-					udhcp_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;
+				/* Switch to bcast receive */
+				change_listen_mode(LISTEN_RAW);
+				/* Lease is *really* about to run out,
+				 * try to find DHCP server using broadcast */
+				if (timeout > 0) {
+					/* send a broadcast renew request */
+					send_renew(xid, 0 /*INADDR_ANY*/, requested_ip);
+					timeout >>= 1;
+					continue;
 				}
-				break;
-			case RELEASED:
-				/* yah, I know, *you* say it would never happen */
-				timeout = 0x7fffffff;
-				break;
+				/* Timed out, enter init state */
+				bb_info_msg("Lease lost, entering init state");
+				udhcp_run_script(NULL, "deconfig");
+				state = INIT_SELECTING;
+				/*timeout = 0; - already is */
+				packet_num = 0;
+				continue;
+			/* case RELEASED: */
 			}
-		} else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(fd, &rfds)) {
-			/* a packet is ready, read it */
+			/* yah, I know, *you* say it would never happen */
+			timeout = INT_MAX;
+			continue; /* back to main loop */
+		} /* if select timed out */
+
+		/* select() didn't timeout, something happened */
+
+		/* Is it a signal? */
+		/* note: udhcp_sp_read checks FD_ISSET before reading */
+		switch (udhcp_sp_read(&rfds)) {
+		case SIGUSR1:
+			perform_renew();
+			if (state == RENEW_REQUESTED)
+				goto case_RENEW_REQUESTED;
+			/* Start things over */
+			packet_num = 0;
+			/* Kill any timeouts, user wants this to hurry along */
+			timeout = 0;
+			continue;
+		case SIGUSR2:
+			perform_release(requested_ip, server_addr);
+			timeout = INT_MAX;
+			continue;
+		case SIGTERM:
+			bb_info_msg("Received SIGTERM");
+			if (opt & OPT_R) /* release on quit */
+				perform_release(requested_ip, server_addr);
+			goto ret0;
+		}
 
-			if (listen_mode == LISTEN_KERNEL)
-				len = udhcp_get_packet(&packet, fd);
-			else len = get_raw_packet(&packet, fd);
+		/* Is it a packet? */
+		if (listen_mode == LISTEN_NONE || !FD_ISSET(sockfd, &rfds))
+			continue; /* no */
 
-			if (len == -1 && errno != EINTR) {
-				DEBUG("error on read, %s, reopening socket", strerror(errno));
-				change_mode(listen_mode); /* just close and reopen */
-			}
-			if (len < 0) continue;
+		{
+			int len;
 
-			if (packet.xid != xid) {
-				DEBUG("Ignoring XID %lx (our xid is %lx)",
-					(unsigned long) packet.xid, xid);
-				continue;
+			/* A packet is ready, read it */
+			if (listen_mode == LISTEN_KERNEL)
+				len = udhcp_recv_kernel_packet(&packet, sockfd);
+			else
+				len = udhcp_recv_raw_packet(&packet, sockfd);
+			if (len == -1) {
+				/* Error is severe, reopen socket */
+				bb_info_msg("Read error: %s, reopening socket", strerror(errno));
+				sleep(discover_timeout); /* 3 seconds by default */
+				change_listen_mode(listen_mode); /* just close and reopen */
 			}
-
-			/* Ignore packets that aren't for us */
-			if (memcmp(packet.chaddr, client_config.arp, 6)) {
-				DEBUG("Packet does not have our chaddr - ignoring");
+			/* If this packet will turn out to be unrelated/bogus,
+			 * we will go back and wait for next one.
+			 * Be sure timeout is properly decreased. */
+			already_waited_sec += (unsigned)monotonic_sec() - timestamp_before_wait;
+			if (len < 0)
 				continue;
-			}
+		}
 
-			if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
-				bb_error_msg("cannot get option from packet - ignoring");
-				continue;
-			}
+		if (packet.xid != xid) {
+			log1("xid %x (our is %x), ignoring packet",
+				(unsigned)packet.xid, (unsigned)xid);
+			continue;
+		}
 
-			switch (state) {
-			case INIT_SELECTING:
-				/* Must be a DHCPOFFER to one of our xid's */
-				if (*message == DHCPOFFER) {
-					temp = get_option(&packet, DHCP_SERVER_ID);
-					if (temp) {
-						server_addr = *(uint32_t*)temp;
-						xid = packet.xid;
-						requested_ip = packet.yiaddr;
-
-						/* enter requesting state */
-						state = REQUESTING;
-						timeout = now;
+		/* Ignore packets that aren't for us */
+		if (packet.hlen != 6
+		 || memcmp(packet.chaddr, client_config.client_mac, 6)
+		) {
+//FIXME: need to also check that last 10 bytes are zero
+			log1("chaddr does not match, ignoring packet"); // log2?
+			continue;
+		}
+
+		message = get_option(&packet, DHCP_MESSAGE_TYPE);
+		if (message == NULL) {
+			bb_error_msg("no message type option, ignoring packet");
+			continue;
+		}
+
+		switch (state) {
+		case INIT_SELECTING:
+			/* Must be a DHCPOFFER to one of our xid's */
+			if (*message == DHCPOFFER) {
+		/* TODO: why we don't just fetch server's IP from IP header? */
+				temp = get_option(&packet, DHCP_SERVER_ID);
+				if (!temp) {
+					bb_error_msg("no server ID in message");
+					continue;
+					/* still selecting - this server looks bad */
+				}
+				/* it IS unaligned sometimes, don't "optimize" */
+				move_from_unaligned32(server_addr, temp);
+				xid = packet.xid;
+				requested_ip = packet.yiaddr;
+
+				/* enter requesting state */
+				state = REQUESTING;
+				timeout = 0;
+				packet_num = 0;
+				already_waited_sec = 0;
+			}
+			continue;
+		case REQUESTING:
+		case RENEWING:
+		case RENEW_REQUESTED:
+		case REBINDING:
+			if (*message == DHCPACK) {
+				temp = get_option(&packet, DHCP_LEASE_TIME);
+				if (!temp) {
+					bb_error_msg("no lease time with ACK, using 1 hour lease");
+					lease_seconds = 60 * 60;
+				} else {
+					/* it IS unaligned sometimes, don't "optimize" */
+					move_from_unaligned32(lease_seconds, temp);
+					lease_seconds = ntohl(lease_seconds);
+					lease_seconds &= 0x0fffffff; /* paranoia: must not be prone to overflows */
+					if (lease_seconds < 10) /* and not too small */
+						lease_seconds = 10;
+				}
+#if ENABLE_FEATURE_UDHCPC_ARPING
+				if (opt & OPT_a) {
+/* RFC 2131 3.1 paragraph 5:
+ * "The client receives the DHCPACK message with configuration
+ * parameters. The client SHOULD perform a final check on the
+ * parameters (e.g., ARP for allocated network address), and notes
+ * the duration of the lease specified in the DHCPACK message. At this
+ * point, the client is configured. If the client detects that the
+ * address is already in use (e.g., through the use of ARP),
+ * the client MUST send a DHCPDECLINE message to the server and restarts
+ * the configuration process..." */
+					if (!arpping(packet.yiaddr,
+							NULL,
+							(uint32_t) 0,
+							client_config.client_mac,
+							client_config.interface)
+					) {
+						bb_info_msg("Offered address is in use "
+							"(got ARP reply), declining");
+						send_decline(xid, server_addr, packet.yiaddr);
+
+						if (state != REQUESTING)
+							udhcp_run_script(NULL, "deconfig");
+						change_listen_mode(LISTEN_RAW);
+						state = INIT_SELECTING;
+						requested_ip = 0;
+						timeout = tryagain_timeout;
 						packet_num = 0;
-					} else {
-						bb_error_msg("no server ID in message");
+						already_waited_sec = 0;
+						continue; /* back to main loop */
 					}
 				}
-				break;
-			case RENEW_REQUESTED:
-			case REQUESTING:
-			case RENEWING:
-			case REBINDING:
-				if (*message == DHCPACK) {
-					temp = get_option(&packet, DHCP_LEASE_TIME);
-					if (!temp) {
-						bb_error_msg("no lease time with ACK, using 1 hour lease");
-						lease = 60 * 60;
-					} else {
-						lease = ntohl(*(uint32_t*)temp);
-					}
-
-					/* enter bound state */
-					t1 = lease / 2;
-
-					/* little fixed point for n * .875 */
-					t2 = (lease * 0x7) >> 3;
+#endif
+				/* enter bound state */
+				timeout = lease_seconds / 2;
+				{
+					struct in_addr temp_addr;
 					temp_addr.s_addr = packet.yiaddr;
-					bb_info_msg("Lease of %s obtained, lease time %ld",
-						inet_ntoa(temp_addr), lease);
-					start = now;
-					timeout = t1 + start;
-					requested_ip = packet.yiaddr;
-					udhcp_run_script(&packet,
-						   ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
-
-					state = BOUND;
-					change_mode(LISTEN_NONE);
-					if (client_config.quit_after_lease) {
-						if (client_config.release_on_quit)
-							perform_release();
-						return 0;
-					}
-					if (!client_config.foreground)
-						client_background();
-
-				} else if (*message == DHCPNAK) {
-					/* return to init state */
-					bb_info_msg("Received DHCP NAK");
-					udhcp_run_script(&packet, "nak");
-					if (state != REQUESTING)
-						udhcp_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 */
+					bb_info_msg("Lease of %s obtained, lease time %u",
+						inet_ntoa(temp_addr), (unsigned)lease_seconds);
 				}
-				break;
-			/* case BOUND, RELEASED: - ignore all packets */
+				requested_ip = packet.yiaddr;
+				udhcp_run_script(&packet, state == REQUESTING ? "bound" : "renew");
+
+				state = BOUND;
+				change_listen_mode(LISTEN_NONE);
+				if (opt & OPT_q) { /* quit after lease */
+					if (opt & OPT_R) /* release on quit */
+						perform_release(requested_ip, server_addr);
+					goto ret0;
+				}
+				/* future renew failures should not exit (JM) */
+				opt &= ~OPT_n;
+#if BB_MMU /* NOMMU case backgrounded earlier */
+				if (!(opt & OPT_f)) {
+					client_background();
+					/* do not background again! */
+					opt = ((opt & ~OPT_b) | OPT_f);
+				}
+#endif
+				already_waited_sec = 0;
+				continue; /* back to main loop */
 			}
-		} else if (retval > 0 && (sig = udhcp_sp_read(&rfds))) {
-			switch (sig) {
-			case SIGUSR1:
-				perform_renew();
-				break;
-			case SIGUSR2:
-				perform_release();
-				break;
-			case SIGTERM:
-				bb_info_msg("Received SIGTERM");
-				if (client_config.release_on_quit)
-					perform_release();
-				return 0;
+			if (*message == DHCPNAK) {
+				/* return to init state */
+				bb_info_msg("Received DHCP NAK");
+				udhcp_run_script(&packet, "nak");
+				if (state != REQUESTING)
+					udhcp_run_script(NULL, "deconfig");
+				change_listen_mode(LISTEN_RAW);
+				sleep(3); /* avoid excessive network traffic */
+				state = INIT_SELECTING;
+				requested_ip = 0;
+				timeout = 0;
+				packet_num = 0;
+				already_waited_sec = 0;
 			}
-		} else if (retval == -1 && errno == EINTR) {
-			/* a signal was caught */
-		} else {
-			/* An error occured */
-			bb_perror_msg("select");
+			continue;
+		/* case BOUND: - ignore all packets */
+		/* case RELEASED: - ignore all packets */
 		}
-
-	}
-	return 0;
+		/* back to main loop */
+	} /* for (;;) - main loop ends */
+
+ ret0:
+	retval = 0;
+ ret:
+	/*if (client_config.pidfile) - remove_pidfile has its own check */
+		remove_pidfile(client_config.pidfile);
+	return retval;
 }