lpr: add more accurate comments
[oweals/busybox.git] / networking / udhcp / dhcpc.c
index 7e7f94a5ad63ec97f86b20ead30057e66374c300..bc067615229e036871a5fe70e2e06235f1f66dca 100644 (file)
@@ -1,3 +1,4 @@
+/* vi: set sw=4 ts=4: */
 /* dhcpc.c
  *
  * udhcp DHCP client
  * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
  */
 
-#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 <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"
-#include "clientpacket.h"
-#include "clientsocket.h"
-#include "script.h"
-#include "socket.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;
+
+
+static int timeout; /* = 0. Must be signed */
+static uint32_t requested_ip; /* = 0 */
+static uint32_t server_addr;
+static int sockfd = -1;
 
 #define LISTEN_NONE 0
 #define LISTEN_KERNEL 1
 #define LISTEN_RAW 2
-static int listen_mode;
+static smallint 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,
-       .vendorclass = NULL,
-       .hostname = NULL,
-       .fqdn = NULL,
-       .ifindex = 0,
-       .retries = 3,
-       .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         Set client identifier - type is first char\n"
-"  -C, --clientid-none             Suppress default client identifier\n"
-"  -V, --vendorclass=CLASSID       Set vendor class identifier\n"
-"  -H, --hostname=HOSTNAME         Client hostname\n"
-"  -h                              Alias for -H\n"
-"  -F, --fqdn=FQDN                 Client fully qualified domain name\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
+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(LOG_INFO, "entering %s listen mode",
+       DEBUG("entering %s listen mode",
                new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
-       if (fd >= 0) close(fd);
-       fd = -1;
+       if (sockfd >= 0) {
+               close(sockfd);
+               sockfd = -1;
+       }
        listen_mode = new_mode;
 }
 
@@ -108,368 +49,448 @@ static void change_mode(int new_mode)
 /* perform a renew */
 static void perform_renew(void)
 {
-       LOG(LOG_INFO, "Performing a DHCP renew");
+       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;
                break;
        case RENEW_REQUESTED: /* impatient are we? fine, square 1 */
-               run_script(NULL, "deconfig");
+               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)
 {
-       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;
-               LOG(LOG_INFO, "Unicasting a release of %s to %s",
+               bb_info_msg("Unicasting a release of %s to %s",
                                inet_ntoa(temp_addr), buffer);
                send_release(server_addr, requested_ip); /* unicast */
-               run_script(NULL, "deconfig");
+               udhcp_run_script(NULL, "deconfig");
        }
-       LOG(LOG_INFO, "Entering released state");
+       bb_info_msg("Entering released state");
 
-       change_mode(LISTEN_NONE);
+       change_listen_mode(LISTEN_NONE);
        state = RELEASED;
-       timeout = 0x7fffffff;
+       timeout = INT_MAX;
 }
 
 
 static void client_background(void)
 {
-       background(client_config.pidfile);
-       client_config.foreground = 1; /* Do not fork again. */
+#if !BB_MMU
+       bb_error_msg("cannot background in uclinux (yet)");
+/* ... mainly because udhcpc calls client_background()
+ * in _the _middle _of _udhcpc _run_, not at the start!
+ * If that will be properly disabled for NOMMU, client_background()
+ * will work on NOMMU too */
+#else
+       bb_daemonize(0);
+       logmode &= ~LOGMODE_STDIO;
+       /* rewrite pidfile, as our pid is different now */
+       write_pidfile(client_config.pidfile);
+#endif
+       /* Do not fork again. */
+       client_config.foreground = 1;
        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
+static uint8_t* alloc_dhcp_option(int code, const char *str, int extra)
+{
+       uint8_t *storage;
+       int len = strlen(str);
+       if (len > 255) len = 255;
+       storage = xzalloc(len + extra + OPT_DATA);
+       storage[OPT_CODE] = code;
+       storage[OPT_LEN] = len + extra;
+       memcpy(storage + extra + OPT_DATA, str, len);
+       return storage;
+}
+
+
+int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
+int udhcpc_main(int argc ATTRIBUTE_UNUSED, char **argv)
 {
        uint8_t *temp, *message;
-       unsigned long t1 = 0, t2 = 0, xid = 0;
-       unsigned long start = 0, lease;
-       fd_set rfds;
+       char *str_c, *str_V, *str_h, *str_F, *str_r;
+       USE_FEATURE_UDHCP_PORT(char *str_P;)
+       llist_t *list_O = NULL;
+#if ENABLE_FEATURE_UDHCPC_ARPING
+       char *str_W;
+#endif
+       int tryagain_timeout = 20;
+       int discover_timeout = 3;
+       int discover_retries = 3;
+       uint32_t xid = 0;
+       uint32_t lease_seconds = 0; /* can be given as 32-bit quantity */
+       int packet_num;
+       /* t1, t2... what a wonderful names... */
+       unsigned t1 = t1; /* for gcc */
+       unsigned t2 = t2;
+       unsigned timestamp_got_lease = timestamp_got_lease;
+       unsigned opt;
+       int max_fd;
        int retval;
+       int len;
        struct timeval tv;
-       int c, len;
-       struct dhcpMessage packet;
        struct in_addr temp_addr;
-       long now;
-       int max_fd;
-       int sig;
-       int no_clientid = 0;
-
-       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'},
-               {"request",     required_argument,      0, 'r'},
-               {"script",      required_argument,      0, 's'},
-               {"version",     no_argument,            0, 'v'},
-               {"retries",     required_argument,      0, 't'},                
-               {0, 0, 0, 0}
-       };
+       struct dhcpMessage packet;
+       fd_set rfds;
 
-       /* get options */
-       while (1) {
-               int option_index = 0;
-               c = getopt_long(argc, argv, "c:CV:fbH:h:F:i:np:qr:s:t:v", arg_options, &option_index);
-               if (c == -1) break;
-
-               switch (c) {
-               case 'c':
-                       if (no_clientid) show_usage();
-                       len = strlen(optarg) > 255 ? 255 : strlen(optarg);
-                       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((char*)client_config.clientid + OPT_DATA, optarg, len);
-                       break;
-               case 'C':
-                       if (client_config.clientid) show_usage();
-                       no_clientid = 1;
-                       break;
-               case 'V':
-                       len = strlen(optarg) > 255 ? 255 : strlen(optarg);
-                       free(client_config.vendorclass);
-                       client_config.vendorclass = xmalloc(len + 2);
-                       client_config.vendorclass[OPT_CODE] = DHCP_VENDOR;
-                       client_config.vendorclass[OPT_LEN] = len;
-                       strncpy((char*)client_config.vendorclass + 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);
-                       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((char*)client_config.hostname + 2, optarg, len);
-                       break;
-               case 'F':
-                       len = strlen(optarg) > 255 ? 255 : strlen(optarg);
-                       free(client_config.fqdn);
-                       client_config.fqdn = xmalloc(len + 5);
-                       client_config.fqdn[OPT_CODE] = DHCP_FQDN;
-                       client_config.fqdn[OPT_LEN] = len + 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"
-                       N: 1 => Client requests Server to not update DNS
-                       */
-                       client_config.fqdn[OPT_LEN + 1] = 0x1;
-                       client_config.fqdn[OPT_LEN + 2] = 0;
-                       client_config.fqdn[OPT_LEN + 3] = 0;
-                       strncpy((char*)client_config.fqdn + 5, 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 't':
-                       client_config.retries = atoi(optarg);
-                       break;
-               case 'v':
-                       printf("udhcpcd, version %s\n\n", VERSION);
-                       return 0;
-                       break;
-               default:
-                       show_usage();
-               }
+       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,
+               OPT_S = 1 << 18,
+               OPT_A = 1 << 19,
+#if ENABLE_FEATURE_UDHCPC_ARPING
+               OPT_a = 1 << 20,
+               OPT_W = 1 << 21,
+#endif
+               OPT_P = 1 << 22,
+       };
+#if ENABLE_GETOPT_LONG
+       static const char udhcpc_longopts[] ALIGN1 =
+               "clientid\0"       Required_argument "c"
+               "clientid-none\0"  No_argument       "C"
+               "vendorclass\0"    Required_argument "V"
+               "foreground\0"     No_argument       "f"
+               "background\0"     No_argument       "b"
+               "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"
+#if ENABLE_FEATURE_UDHCPC_ARPING
+               "arping\0"         No_argument       "a"
+#endif
+               "request-option\0" Required_argument "O"
+#if ENABLE_FEATURE_UDHCP_PORT
+               "client-port\0"    Required_argument "P"
+#endif
+               ;
+#endif
+       /* Default options. */
+#if ENABLE_FEATURE_UDHCP_PORT
+       SERVER_PORT = 67;
+       CLIENT_PORT = 68;
+#endif
+       client_config.interface = "eth0";
+       client_config.script = DEFAULT_SCRIPT;
+
+       /* Parse command line */
+       /* Cc: mutually exclusive; O: list; -T,-t,-A take numeric param */
+       opt_complementary = "c--C:C--c:O::T+:t+:A+";
+#if ENABLE_GETOPT_LONG
+       applet_long_options = udhcpc_longopts;
+#endif
+       opt = getopt32(argv, "c:CV:fbH:h:F:i:np:qRr:s:T:t:vSA:"
+               USE_FEATURE_UDHCPC_ARPING("aW:")
+               USE_FEATURE_UDHCP_PORT("P:")
+               "O:"
+               , &str_c, &str_V, &str_h, &str_h, &str_F
+               , &client_config.interface, &client_config.pidfile, &str_r
+               , &client_config.script
+               , &discover_timeout, &discover_retries, &tryagain_timeout
+               USE_FEATURE_UDHCPC_ARPING(, &str_W)
+               USE_FEATURE_UDHCP_PORT(, &str_P)
+               , &list_O
+               );
+
+       if (opt & OPT_c)
+               client_config.clientid = alloc_dhcp_option(DHCP_CLIENT_ID, str_c, 0);
+       //if (opt & OPT_C)
+       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|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"
+               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) discover_timeout = xatoi_u(str_T);
+       // if (opt & OPT_t) discover_retries = xatoi_u(str_t);
+       // if (opt & OPT_A) tryagain_timeout = xatoi_u(str_A);
+       if (opt & OPT_v) {
+               puts("version "BB_VER);
+               return 0;
+       }
+       if (opt & OPT_S) {
+               openlog(applet_name, LOG_PID, LOG_LOCAL0);
+               logmode |= LOGMODE_SYSLOG;
+       }
+#if ENABLE_FEATURE_UDHCP_PORT
+       if (opt & OPT_P) {
+               CLIENT_PORT = xatou16(str_P);
+               SERVER_PORT = CLIENT_PORT - 1;
+       }
+#endif
+       while (list_O) {
+               int n = index_in_strings(dhcp_option_strings, list_O->data);
+               if (n < 0)
+                       bb_error_msg_and_die("unknown option '%s'", list_O->data);
+               n = dhcp_options[n].code;
+               client_config.opt_mask[n >> 3] |= 1 << (n & 7);
+               list_O = list_O->link;
        }
-
-       /* 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)
+                          NULL, client_config.arp))
                return 1;
 
+       /* Make sure fd 0,1,2 are open */
+       bb_sanitize_stdio();
+       /* Equivalent of doing a fflush after every \n */
+       setlinebuf(stdout);
+
+       /* Create pidfile */
+       write_pidfile(client_config.pidfile);
+       /* if (!..) bb_perror_msg("cannot create pidfile %s", pidfile); */
+
+       /* Goes to stdout and possibly syslog */
+       bb_info_msg("%s (v"BB_VER") started", applet_name);
+
        /* if not set, and not suppressed, setup the default client ID */
-       if (!client_config.clientid && !no_clientid) {
-               client_config.clientid = xmalloc(6 + 3);
-               client_config.clientid[OPT_CODE] = DHCP_CLIENT_ID;
-               client_config.clientid[OPT_LEN] = 7;
+       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 + 3, client_config.arp, 6);
-       }
-
-       if (!client_config.vendorclass) {
-               client_config.vendorclass = xmalloc(sizeof("udhcp "VERSION) + 2);
-               client_config.vendorclass[OPT_CODE] = DHCP_VENDOR;
-               client_config.vendorclass[OPT_LEN] = sizeof("udhcp "VERSION) - 1;
-               client_config.vendorclass[OPT_DATA] = 1;
-               memcpy(&client_config.vendorclass[OPT_DATA],
-                       "udhcp "VERSION, sizeof("udhcp "VERSION) - 1);
+               memcpy(client_config.clientid + OPT_DATA+1, client_config.arp, 6);
        }
 
+       if (!client_config.vendorclass)
+               client_config.vendorclass = alloc_dhcp_option(DHCP_VENDOR, "udhcp "BB_VER, 0);
 
        /* setup the signal pipe */
        udhcp_sp_setup();
 
        state = INIT_SELECTING;
-       run_script(NULL, "deconfig");
-       change_mode(LISTEN_RAW);
+       udhcp_run_script(NULL, "deconfig");
+       change_listen_mode(LISTEN_RAW);
+       packet_num = 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_sec = timeout;
                tv.tv_usec = 0;
 
-               if (listen_mode != LISTEN_NONE && fd < 0) {
+               if (listen_mode != LISTEN_NONE && sockfd < 0) {
                        if (listen_mode == LISTEN_KERNEL)
-                               fd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
+                               sockfd = 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;
-                       }
+                               sockfd = raw_socket(client_config.ifindex);
                }
-               max_fd = udhcp_sp_fd_set(&rfds, fd);
+               max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 
+               retval = 0; /* If we already timed out, fall through, else... */
                if (tv.tv_sec > 0) {
-                       DEBUG(LOG_INFO, "Waiting on select...");
+                       DEBUG("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? signal was caught, don't panic */
+                       if (errno != EINTR) {
+                               /* Else: an error occured, panic! */
+                               bb_perror_msg_and_die("select");
+                       }
+                       continue;
+               }
 
-               now = uptime();
+               /* If timeout dropped to zero, time to become active:
+                * resend discover/renew/whatever
+                */
                if (retval == 0) {
-                       /* timeout dropped to zero */
                        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 + ((packet_num == 2) ? 4 : 2);
+                                       timeout = discover_timeout;
                                        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;
+                                       continue;
                                }
-                               break;
+                               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");
+                                       retval = 1;
+                                       goto ret;
+                               }
+                               /* wait to try again */
+                               timeout = tryagain_timeout;
+                               packet_num = 0;
+                               continue;
                        case RENEW_REQUESTED:
                        case REQUESTING:
-                               if (packet_num < client_config.retries) {
+                               if (packet_num < discover_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);
+                                       timeout = ((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);
+                                       continue;
                                }
-                               break;
+                               /* timed out, go back to init state */
+                               if (state == RENEW_REQUESTED)
+                                       udhcp_run_script(NULL, "deconfig");
+                               change_listen_mode(LISTEN_RAW);
+                               state = INIT_SELECTING;
+                               timeout = 0;
+                               packet_num = 0;
+                               continue;
                        case BOUND:
                                /* Lease is starting to run out, time to enter renewing state */
+                               change_listen_mode(LISTEN_KERNEL);
+                               DEBUG("Entering renew 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 {
+                               if ((t2 - t1) > (lease_seconds / (4*60*60) + 1)) {
                                        /* send a request packet */
                                        send_renew(xid, server_addr, requested_ip); /* unicast */
-
-                                       t1 = (t2 - t1) / 2 + t1;
-                                       timeout = t1 + start;
+                                       t1 += (t2 - t1) / 2;
+                                       timeout = t1 - ((int)monotonic_sec() - timestamp_got_lease);
+                                       continue;
                                }
-                               break;
+                               /* Timed out, enter rebinding state */
+                               DEBUG("Entering rebinding state");
+                               state = REBINDING;
+                               timeout = (t2 - t1);
+                               continue;
                        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 {
+                               /* Lease is *really* about to run out,
+                                * try to find DHCP server using broadcast */
+                               if ((lease_seconds - t2) > (lease_seconds / (4*60*60) + 1)) {
                                        /* send a request packet */
                                        send_renew(xid, 0, requested_ip); /* broadcast */
-
-                                       t2 = (lease - t2) / 2 + t2;
-                                       timeout = t2 + start;
+                                       t2 += (lease_seconds - t2) / 2;
+                                       timeout = t2 - ((int)monotonic_sec() - timestamp_got_lease);
+                                       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");
+                               change_listen_mode(LISTEN_RAW);
+                               state = INIT_SELECTING;
+                               timeout = 0;
+                               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 */
+               }
+
+               /* select() didn't timeout, something did happen. */
+               /* Is is a packet? */
+               if (listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
+                       /* A packet is ready, read it */
 
                        if (listen_mode == LISTEN_KERNEL)
-                               len = get_packet(&packet, fd);
-                       else len = get_raw_packet(&packet, fd);
+                               len = udhcp_recv_packet(&packet, sockfd);
+                       else
+                               len = get_raw_packet(&packet, sockfd);
 
-                       if (len == -1 && errno != EINTR) {
-                               DEBUG(LOG_INFO, "error on read, %m, reopening socket");
-                               change_mode(listen_mode); /* just close and reopen */
+                       if (len == -1) { /* error is severe, reopen socket */
+                               DEBUG("error on read, %s, reopening socket", strerror(errno));
+                               change_listen_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);
+                               DEBUG("Ignoring XID %x (our xid is %x)",
+                                       (unsigned)packet.xid, (unsigned)xid);
                                continue;
                        }
+
                        /* Ignore packets that aren't for us */
                        if (memcmp(packet.chaddr, client_config.arp, 6)) {
-                               DEBUG(LOG_INFO, "packet does not have our chaddr -- ignoring");
+                               DEBUG("Packet does not have our chaddr - ignoring");
                                continue;
                        }
 
-                       if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
-                               DEBUG(LOG_ERR, "couldnt get option from packet -- ignoring");
+                       message = get_option(&packet, DHCP_MESSAGE_TYPE);
+                       if (message == NULL) {
+                               bb_error_msg("cannot get message type from packet - ignoring");
                                continue;
                        }
 
@@ -477,89 +498,133 @@ int main(int argc, char *argv[])
                        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");
+                       /* 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 */
                                        }
+                                       /* can be misaligned, thus memcpy */
+                                       memcpy(&server_addr, temp, 4);
+                                       xid = packet.xid;
+                                       requested_ip = packet.yiaddr;
+
+                                       /* enter requesting state */
+                                       state = REQUESTING;
+                                       timeout = 0;
+                                       packet_num = 0;
                                }
-                               break;
+                               continue;
                        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;
+                                       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 {
-                                               memcpy(&lease, temp, 4);
-                                               lease = ntohl(lease);
+                                               /* can be misaligned, thus memcpy */
+                                               memcpy(&lease_seconds, temp, 4);
+                                               lease_seconds = ntohl(lease_seconds);
                                        }
-
+#if ENABLE_FEATURE_UDHCPC_ARPING
+                                       if (opt & OPT_a) {
+                                               if (!arpping(packet.yiaddr,
+                                                           (uint32_t) 0,
+                                                           client_config.arp,
+                                                           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;
+                                                       continue; /* back to main loop */
+                                               }
+                                       }
+#endif
                                        /* enter bound state */
-                                       t1 = lease / 2;
+                                       t1 = lease_seconds / 2;
 
                                        /* little fixed point for n * .875 */
-                                       t2 = (lease * 0x7) >> 3;
+                                       t2 = (lease_seconds * 7) >> 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;
+                                       bb_info_msg("Lease of %s obtained, lease time %u",
+                                               inet_ntoa(temp_addr), (unsigned)lease_seconds);
+                                       timestamp_got_lease = monotonic_sec();
+                                       timeout = t1;
                                        requested_ip = packet.yiaddr;
-                                       run_script(&packet,
+                                       udhcp_run_script(&packet,
                                                   ((state == RENEWING || state == REBINDING) ? "renew" : "bound"));
 
                                        state = BOUND;
-                                       change_mode(LISTEN_NONE);
-                                       if (client_config.quit_after_lease)
-                                               return 0;
+                                       change_listen_mode(LISTEN_NONE);
+                                       if (client_config.quit_after_lease) {
+                                               if (client_config.release_on_quit)
+                                                       perform_release();
+                                               goto ret0;
+                                       }
                                        if (!client_config.foreground)
                                                client_background();
 
-                               } else if (*message == DHCPNAK) {
+                                       continue; /* back to main loop */
+                               }
+                               if (*message == DHCPNAK) {
                                        /* return to init state */
-                                       LOG(LOG_INFO, "Received DHCP NAK");
-                                       run_script(&packet, "nak");
+                                       bb_info_msg("Received DHCP NAK");
+                                       udhcp_run_script(&packet, "nak");
                                        if (state != REQUESTING)
-                                               run_script(NULL, "deconfig");
+                                               udhcp_run_script(NULL, "deconfig");
+                                       change_listen_mode(LISTEN_RAW);
+                                       sleep(3); /* avoid excessive network traffic */
                                        state = INIT_SELECTING;
-                                       timeout = now;
                                        requested_ip = 0;
+                                       timeout = 0;
                                        packet_num = 0;
-                                       change_mode(LISTEN_RAW);
-                                       sleep(3); /* avoid excessive network traffic */
                                }
-                               break;
+                               continue;
                        /* case BOUND, RELEASED: - ignore all packets */
                        }
-               } else if (retval > 0 && (sig = udhcp_sp_read(&rfds))) {
-                       switch (sig) {
+                       continue; /* back to main loop */
+               }
+
+               /* select() didn't timeout, something did happen.
+                * But it wasn't a packet. It's a signal pipe then. */
+               {
+                       int signo = udhcp_sp_read(&rfds);
+                       switch (signo) {
                        case SIGUSR1:
                                perform_renew();
+                               /* start things over */
+                               packet_num = 0;
+                               /* Kill any timeouts because the user wants this to hurry along */
+                               timeout = 0;
                                break;
                        case SIGUSR2:
                                perform_release();
                                break;
                        case SIGTERM:
-                               LOG(LOG_INFO, "Received SIGTERM");
-                               return 0;
+                               bb_info_msg("Received SIGTERM");
+                               if (client_config.release_on_quit)
+                                       perform_release();
+                               goto ret0;
                        }
-               } else if (retval == -1 && errno == EINTR) {
-                       /* a signal was caught */
-               } else {
-                       /* An error occured */
-                       DEBUG(LOG_ERR, "Error on select");
                }
-
-       }
-       return 0;
+       } /* for (;;) - main loop ends */
+
+ ret0:
+       retval = 0;
+ ret:
+       /*if (client_config.pidfile) - remove_pidfile has it's own check */
+               remove_pidfile(client_config.pidfile);
+       return retval;
 }