/* vi: set sw=4 ts=4: */
/*
 * Mini start-stop-daemon implementation(s) for busybox
 *
 * Written by Marek Michalkiewicz <marekm@i17linuxb.ists.pwr.wroc.pl>,
 * Adapted for busybox David Kimdon <dwhedon@gordian.com>
 *
 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
 */

/*
This is how it is supposed to work:

start-stop-daemon [OPTIONS] [--start|--stop] [[--] arguments...]

One (only) of these must be given:
        -S,--start              Start
        -K,--stop               Stop

Search for matching processes.
If --stop is given, stop all matching processes (by sending a signal).
If --start is given, start a new process unless a matching process was found.

Options controlling process matching
(if multiple conditions are specified, all must match):
        -u,--user USERNAME|UID  Only consider this user's processes
        -n,--name PROCESS_NAME  Look for processes by matching PROCESS_NAME
                                with comm field in /proc/$PID/stat.
                                Only basename is compared:
                                "ntpd" == "./ntpd" == "/path/to/ntpd".
[TODO: can PROCESS_NAME be a full pathname? Should we require full match then
with /proc/$PID/exe or argv[0] (comm can't be matched, it never contains path)]
        -x,--exec EXECUTABLE    Look for processes that were started with this
                                command in /proc/$PID/exe and /proc/$PID/cmdline
                                (/proc/$PID/cmdline is a bbox extension)
                                Unlike -n, we match against the full path:
                                "ntpd" != "./ntpd" != "/path/to/ntpd"
        -p,--pidfile PID_FILE   Look for processes with PID from this file

Options which are valid for --start only:
        -x,--exec EXECUTABLE    Program to run (1st arg of execvp). Mandatory.
        -a,--startas NAME       argv[0] (defaults to EXECUTABLE)
        -b,--background         Put process into background
        -N,--nicelevel N        Add N to process' nice level
        -c,--chuid USER[:[GRP]] Change to specified user [and group]
        -m,--make-pidfile       Write PID to the pidfile
                                (both -m and -p must be given!)

Options which are valid for --stop only:
        -s,--signal SIG         Signal to send (default:TERM)
        -t,--test               Exit with status 0 if process is found
                                (we don't actually start or stop daemons)

Misc options:
        -o,--oknodo             Exit with status 0 if nothing is done
        -q,--quiet              Quiet
        -v,--verbose            Verbose
*/

//usage:#define start_stop_daemon_trivial_usage
//usage:       "[OPTIONS] [-S|-K] ... [-- ARGS...]"
//usage:#define start_stop_daemon_full_usage "\n\n"
//usage:       "Search for matching processes, and then\n"
//usage:       "-K: stop all matching processes.\n"
//usage:       "-S: start a process unless a matching process is found.\n"
//usage:        IF_FEATURE_START_STOP_DAEMON_LONG_OPTIONS(
//usage:     "\nProcess matching:"
//usage:     "\n        -u,--user USERNAME|UID  Match only this user's processes"
//usage:     "\n        -n,--name NAME          Match processes with NAME"
//usage:     "\n                                in comm field in /proc/PID/stat"
//usage:     "\n        -x,--exec EXECUTABLE    Match processes with this command"
//usage:     "\n                                in /proc/PID/{exe,cmdline}"
//usage:     "\n        -p,--pidfile FILE       Match a process with PID from the file"
//usage:     "\n        All specified conditions must match"
//usage:     "\n-S only:"
//usage:     "\n        -x,--exec EXECUTABLE    Program to run"
//usage:     "\n        -a,--startas NAME       Zeroth argument"
//usage:     "\n        -b,--background         Background"
//usage:        IF_FEATURE_START_STOP_DAEMON_FANCY(
//usage:     "\n        -N,--nicelevel N        Change nice level"
//usage:        )
//usage:     "\n        -c,--chuid USER[:[GRP]] Change to user/group"
//usage:     "\n        -m,--make-pidfile       Write PID to the pidfile specified by -p"
//usage:     "\n-K only:"
//usage:     "\n        -s,--signal SIG         Signal to send"
//usage:     "\n        -t,--test               Match only, exit with 0 if a process is found"
//usage:     "\nOther:"
//usage:        IF_FEATURE_START_STOP_DAEMON_FANCY(
//usage:     "\n        -o,--oknodo             Exit with status 0 if nothing is done"
//usage:     "\n        -v,--verbose            Verbose"
//usage:        )
//usage:     "\n        -q,--quiet              Quiet"
//usage:        )
//usage:        IF_NOT_FEATURE_START_STOP_DAEMON_LONG_OPTIONS(
//usage:     "\nProcess matching:"
//usage:     "\n        -u USERNAME|UID Match only this user's processes"
//usage:     "\n        -n NAME         Match processes with NAME"
//usage:     "\n                        in comm field in /proc/PID/stat"
//usage:     "\n        -x EXECUTABLE   Match processes with this command"
//usage:     "\n                        command in /proc/PID/cmdline"
//usage:     "\n        -p FILE         Match a process with PID from the file"
//usage:     "\n        All specified conditions must match"
//usage:     "\n-S only:"
//usage:     "\n        -x EXECUTABLE   Program to run"
//usage:     "\n        -a NAME         Zeroth argument"
//usage:     "\n        -b              Background"
//usage:        IF_FEATURE_START_STOP_DAEMON_FANCY(
//usage:     "\n        -N N            Change nice level"
//usage:        )
//usage:     "\n        -c USER[:[GRP]] Change to user/group"
//usage:     "\n        -m              Write PID to the pidfile specified by -p"
//usage:     "\n-K only:"
//usage:     "\n        -s SIG          Signal to send"
//usage:     "\n        -t              Match only, exit with 0 if a process is found"
//usage:     "\nOther:"
//usage:        IF_FEATURE_START_STOP_DAEMON_FANCY(
//usage:     "\n        -o              Exit with status 0 if nothing is done"
//usage:     "\n        -v              Verbose"
//usage:        )
//usage:     "\n        -q              Quiet"
//usage:        )

#include <sys/resource.h>

/* Override ENABLE_FEATURE_PIDFILE */
#define WANT_PIDFILE 1
#include "libbb.h"

struct pid_list {
        struct pid_list *next;
        pid_t pid;
};

enum {
        CTX_STOP       = (1 <<  0),
        CTX_START      = (1 <<  1),
        OPT_BACKGROUND = (1 <<  2), // -b
        OPT_QUIET      = (1 <<  3), // -q
        OPT_TEST       = (1 <<  4), // -t
        OPT_MAKEPID    = (1 <<  5), // -m
        OPT_a          = (1 <<  6), // -a
        OPT_n          = (1 <<  7), // -n
        OPT_s          = (1 <<  8), // -s
        OPT_u          = (1 <<  9), // -u
        OPT_c          = (1 << 10), // -c
        OPT_x          = (1 << 11), // -x
        OPT_p          = (1 << 12), // -p
        OPT_OKNODO     = (1 << 13) * ENABLE_FEATURE_START_STOP_DAEMON_FANCY, // -o
        OPT_VERBOSE    = (1 << 14) * ENABLE_FEATURE_START_STOP_DAEMON_FANCY, // -v
        OPT_NICELEVEL  = (1 << 15) * ENABLE_FEATURE_START_STOP_DAEMON_FANCY, // -N
};
#define QUIET (option_mask32 & OPT_QUIET)
#define TEST  (option_mask32 & OPT_TEST)

struct globals {
        struct pid_list *found_procs;
        char *userspec;
        char *cmdname;
        char *execname;
        char *pidfile;
        char *execname_cmpbuf;
        unsigned execname_sizeof;
        int user_id;
        smallint signal_nr;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define userspec          (G.userspec            )
#define cmdname           (G.cmdname             )
#define execname          (G.execname            )
#define pidfile           (G.pidfile             )
#define user_id           (G.user_id             )
#define signal_nr         (G.signal_nr           )
#define INIT_G() do { \
        user_id = -1; \
        signal_nr = 15; \
} while (0)

#ifdef OLDER_VERSION_OF_X
/* -x,--exec EXECUTABLE
 * Look for processes with matching /proc/$PID/exe.
 * Match is performed using device+inode.
 */
static int pid_is_exec(pid_t pid)
{
        struct stat st;
        char buf[sizeof("/proc/%u/exe") + sizeof(int)*3];

        sprintf(buf, "/proc/%u/exe", (unsigned)pid);
        if (stat(buf, &st) < 0)
                return 0;
        if (st.st_dev == execstat.st_dev
         && st.st_ino == execstat.st_ino)
                return 1;
        return 0;
}
#endif

static int pid_is_exec(pid_t pid)
{
        ssize_t bytes;
        char buf[sizeof("/proc/%u/cmdline") + sizeof(int)*3];
        char *procname, *exelink;
        int match;

        procname = buf + sprintf(buf, "/proc/%u/exe", (unsigned)pid) - 3;

        exelink = xmalloc_readlink(buf);
        match = (exelink && strcmp(execname, exelink) == 0);
        free(exelink);
        if (match)
                return match;

        strcpy(procname, "cmdline");
        bytes = open_read_close(buf, G.execname_cmpbuf, G.execname_sizeof);
        if (bytes > 0) {
                G.execname_cmpbuf[bytes] = '\0';
                return strcmp(execname, G.execname_cmpbuf) == 0;
        }
        return 0;
}

static int pid_is_name(pid_t pid)
{
        /* /proc/PID/stat is "PID (comm_15_bytes_max) ..." */
        char buf[32]; /* should be enough */
        char *p, *pe;

        sprintf(buf, "/proc/%u/stat", (unsigned)pid);
        if (open_read_close(buf, buf, sizeof(buf) - 1) < 0)
                return 0;
        buf[sizeof(buf) - 1] = '\0'; /* paranoia */
        p = strchr(buf, '(');
        if (!p)
                return 0;
        pe = strrchr(++p, ')');
        if (!pe)
                return 0;
        *pe = '\0';
        /* we require comm to match and to not be truncated */
        /* in Linux, if comm is 15 chars, it may be a truncated
         * name, so we don't allow that to match */
        if (strlen(p) >= COMM_LEN - 1) /* COMM_LEN is 16 */
                return 0;
        return strcmp(p, cmdname) == 0;
}

static int pid_is_user(int pid)
{
        struct stat sb;
        char buf[sizeof("/proc/") + sizeof(int)*3];

        sprintf(buf, "/proc/%u", (unsigned)pid);
        if (stat(buf, &sb) != 0)
                return 0;
        return (sb.st_uid == (uid_t)user_id);
}

static void check(int pid)
{
        struct pid_list *p;

        if (execname && !pid_is_exec(pid)) {
                return;
        }
        if (cmdname && !pid_is_name(pid)) {
                return;
        }
        if (userspec && !pid_is_user(pid)) {
                return;
        }
        p = xmalloc(sizeof(*p));
        p->next = G.found_procs;
        p->pid = pid;
        G.found_procs = p;
}

static void do_pidfile(void)
{
        FILE *f;
        unsigned pid;

        f = fopen_for_read(pidfile);
        if (f) {
                if (fscanf(f, "%u", &pid) == 1)
                        check(pid);
                fclose(f);
        } else if (errno != ENOENT)
                bb_perror_msg_and_die("open pidfile %s", pidfile);
}

static void do_procinit(void)
{
        DIR *procdir;
        struct dirent *entry;
        int pid;

        if (pidfile) {
                do_pidfile();
                return;
        }

        procdir = xopendir("/proc");

        pid = 0;
        while (1) {
                errno = 0; /* clear any previous error */
                entry = readdir(procdir);
// TODO: this check is too generic, it's better
// to check for exact errno(s) which mean that we got stale entry
                if (errno) /* Stale entry, process has died after opendir */
                        continue;
                if (!entry) /* EOF, no more entries */
                        break;
                pid = bb_strtou(entry->d_name, NULL, 10);
                if (errno) /* NaN */
                        continue;
                check(pid);
        }
        closedir(procdir);
        if (!pid)
                bb_error_msg_and_die("nothing in /proc - not mounted?");
}

static int do_stop(void)
{
        char *what;
        struct pid_list *p;
        int killed = 0;

        if (cmdname) {
                if (ENABLE_FEATURE_CLEAN_UP) what = xstrdup(cmdname);
                if (!ENABLE_FEATURE_CLEAN_UP) what = cmdname;
        } else if (execname) {
                if (ENABLE_FEATURE_CLEAN_UP) what = xstrdup(execname);
                if (!ENABLE_FEATURE_CLEAN_UP) what = execname;
        } else if (pidfile) {
                what = xasprintf("process in pidfile '%s'", pidfile);
        } else if (userspec) {
                what = xasprintf("process(es) owned by '%s'", userspec);
        } else {
                bb_error_msg_and_die("internal error, please report");
        }

        if (!G.found_procs) {
                if (!QUIET)
                        printf("no %s found; none killed\n", what);
                killed = -1;
                goto ret;
        }
        for (p = G.found_procs; p; p = p->next) {
                if (kill(p->pid, TEST ? 0 : signal_nr) == 0) {
                        killed++;
                } else {
                        bb_perror_msg("warning: killing process %u", (unsigned)p->pid);
                        p->pid = 0;
                        if (TEST) {
                                /* Example: -K --test --pidfile PIDFILE detected
                                 * that PIDFILE's pid doesn't exist */
                                killed = -1;
                                goto ret;
                        }
                }
        }
        if (!QUIET && killed) {
                printf("stopped %s (pid", what);
                for (p = G.found_procs; p; p = p->next)
                        if (p->pid)
                                printf(" %u", (unsigned)p->pid);
                puts(")");
        }
 ret:
        if (ENABLE_FEATURE_CLEAN_UP)
                free(what);
        return killed;
}

#if ENABLE_FEATURE_START_STOP_DAEMON_LONG_OPTIONS
static const char start_stop_daemon_longopts[] ALIGN1 =
        "stop\0"         No_argument       "K"
        "start\0"        No_argument       "S"
        "background\0"   No_argument       "b"
        "quiet\0"        No_argument       "q"
        "test\0"         No_argument       "t"
        "make-pidfile\0" No_argument       "m"
#if ENABLE_FEATURE_START_STOP_DAEMON_FANCY
        "oknodo\0"       No_argument       "o"
        "verbose\0"      No_argument       "v"
        "nicelevel\0"    Required_argument "N"
#endif
        "startas\0"      Required_argument "a"
        "name\0"         Required_argument "n"
        "signal\0"       Required_argument "s"
        "user\0"         Required_argument "u"
        "chuid\0"        Required_argument "c"
        "exec\0"         Required_argument "x"
        "pidfile\0"      Required_argument "p"
#if ENABLE_FEATURE_START_STOP_DAEMON_FANCY
        "retry\0"        Required_argument "R"
#endif
        ;
#endif

int start_stop_daemon_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int start_stop_daemon_main(int argc UNUSED_PARAM, char **argv)
{
        unsigned opt;
        char *signame;
        char *startas;
        char *chuid;
#ifdef OLDER_VERSION_OF_X
        struct stat execstat;
#endif
#if ENABLE_FEATURE_START_STOP_DAEMON_FANCY
//      char *retry_arg = NULL;
//      int retries = -1;
        char *opt_N;
#endif

        INIT_G();

#if ENABLE_FEATURE_START_STOP_DAEMON_LONG_OPTIONS
        applet_long_options = start_stop_daemon_longopts;
#endif

        /* -K or -S is required; they are mutually exclusive */
        /* -p is required if -m is given */
        /* -xpun (at least one) is required if -K is given */
        /* -xa (at least one) is required if -S is given */
        /* -q turns off -v */
        opt_complementary = "K:S:K--S:S--K:m?p:K?xpun:S?xa"
                IF_FEATURE_START_STOP_DAEMON_FANCY("q-v");
        opt = getopt32(argv, "KSbqtma:n:s:u:c:x:p:"
                IF_FEATURE_START_STOP_DAEMON_FANCY("ovN:R:"),
                &startas, &cmdname, &signame, &userspec, &chuid, &execname, &pidfile
                IF_FEATURE_START_STOP_DAEMON_FANCY(,&opt_N)
                /* We accept and ignore -R <param> / --retry <param> */
                IF_FEATURE_START_STOP_DAEMON_FANCY(,NULL)
        );

        if (opt & OPT_s) {
                signal_nr = get_signum(signame);
                if (signal_nr < 0) bb_show_usage();
        }

        if (!(opt & OPT_a))
                startas = execname;
        if (!execname) /* in case -a is given and -x is not */
                execname = startas;
        if (execname) {
                G.execname_sizeof = strlen(execname) + 1;
                G.execname_cmpbuf = xmalloc(G.execname_sizeof + 1);
        }

//      IF_FEATURE_START_STOP_DAEMON_FANCY(
//              if (retry_arg)
//                      retries = xatoi_positive(retry_arg);
//      )
        //argc -= optind;
        argv += optind;

        if (userspec) {
                user_id = bb_strtou(userspec, NULL, 10);
                if (errno)
                        user_id = xuname2uid(userspec);
        }
        /* Both start and stop need to know current processes */
        do_procinit();

        if (opt & CTX_STOP) {
                int i = do_stop();
                return (opt & OPT_OKNODO) ? 0 : (i <= 0);
        }

        if (G.found_procs) {
                if (!QUIET)
                        printf("%s is already running\n%u\n", execname, (unsigned)G.found_procs->pid);
                return !(opt & OPT_OKNODO);
        }

#ifdef OLDER_VERSION_OF_X
        if (execname)
                xstat(execname, &execstat);
#endif

        *--argv = startas;
        if (opt & OPT_BACKGROUND) {
#if BB_MMU
                bb_daemonize(DAEMON_DEVNULL_STDIO + DAEMON_CLOSE_EXTRA_FDS + DAEMON_DOUBLE_FORK);
                /* DAEMON_DEVNULL_STDIO is superfluous -
                 * it's always done by bb_daemonize() */
#else
                pid_t pid = xvfork();
                if (pid != 0) {
                        /* parent */
                        /* why _exit? the child may have changed the stack,
                         * so "return 0" may do bad things */
                        _exit(EXIT_SUCCESS);
                }
                /* Child */
                setsid(); /* detach from controlling tty */
                /* Redirect stdio to /dev/null, close extra FDs.
                 * We do not actually daemonize because of DAEMON_ONLY_SANITIZE */
                bb_daemonize_or_rexec(DAEMON_DEVNULL_STDIO
                        + DAEMON_CLOSE_EXTRA_FDS
                        + DAEMON_ONLY_SANITIZE,
                        NULL /* argv, unused */ );
#endif
        }
        if (opt & OPT_MAKEPID) {
                /* User wants _us_ to make the pidfile */
                write_pidfile(pidfile);
        }
        if (opt & OPT_c) {
                struct bb_uidgid_t ugid = { -1, -1 };
                parse_chown_usergroup_or_die(&ugid, chuid);
                if (ugid.uid != (uid_t) -1) {
                        struct passwd *pw = xgetpwuid(ugid.uid);
                        if (ugid.gid != (gid_t) -1)
                                pw->pw_gid = ugid.gid;
                        /* initgroups, setgid, setuid: */
                        change_identity(pw);
                } else if (ugid.gid != (gid_t) -1) {
                        xsetgid(ugid.gid);
                        setgroups(1, &ugid.gid);
                }
        }
#if ENABLE_FEATURE_START_STOP_DAEMON_FANCY
        if (opt & OPT_NICELEVEL) {
                /* Set process priority */
                int prio = getpriority(PRIO_PROCESS, 0) + xatoi_range(opt_N, INT_MIN/2, INT_MAX/2);
                if (setpriority(PRIO_PROCESS, 0, prio) < 0) {
                        bb_perror_msg_and_die("setpriority(%d)", prio);
                }
        }
#endif
        execvp(startas, argv);
        bb_perror_msg_and_die("can't execute '%s'", startas);
}