/* vi: set sw=4 ts=4: */
/*      $Slackware: inetd.c 1.79s 2001/02/06 13:18:00 volkerdi Exp $    */
/*      $OpenBSD: inetd.c,v 1.79 2001/01/30 08:30:57 deraadt Exp $      */
/*      $NetBSD: inetd.c,v 1.11 1996/02/22 11:14:41 mycroft Exp $       */
/* Busybox port by Vladimir Oleynik (C) 2001-2005 <dzo@simtreas.ru>     */
/* IPv6 support, many bug fixes by Denys Vlasenko (c) 2008 */
/*
 * Copyright (c) 1983,1991 The Regents of the University of California.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS" AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/* Inetd - Internet super-server
 *
 * This program invokes configured services when a connection
 * from a peer is established or a datagram arrives.
 * Connection-oriented services are invoked each time a
 * connection is made, by creating a process.  This process
 * is passed the connection as file descriptor 0 and is
 * expected to do a getpeername to find out peer's host
 * and port.
 * Datagram oriented services are invoked when a datagram
 * arrives; a process is created and passed a pending message
 * on file descriptor 0. peer's address can be obtained
 * using recvfrom.
 *
 * Inetd uses a configuration file which is read at startup
 * and, possibly, at some later time in response to a hangup signal.
 * The configuration file is "free format" with fields given in the
 * order shown below.  Continuation lines for an entry must begin with
 * a space or tab.  All fields must be present in each entry.
 *
 *      service_name                    must be in /etc/services
 *      socket_type                     stream/dgram/raw/rdm/seqpacket
 *      protocol                        must be in /etc/protocols
 *                                      (usually "tcp" or "udp")
 *      wait/nowait[.max]               single-threaded/multi-threaded, max #
 *      user[.group] or user[:group]    user/group to run daemon as
 *      server_program                  full path name
 *      server_program_arguments        maximum of MAXARGS (20)
 *
 * For RPC services
 *      service_name/version            must be in /etc/rpc
 *      socket_type                     stream/dgram/raw/rdm/seqpacket
 *      rpc/protocol                    "rpc/tcp" etc
 *      wait/nowait[.max]               single-threaded/multi-threaded
 *      user[.group] or user[:group]    user to run daemon as
 *      server_program                  full path name
 *      server_program_arguments        maximum of MAXARGS (20)
 *
 * For non-RPC services, the "service name" can be of the form
 * hostaddress:servicename, in which case the hostaddress is used
 * as the host portion of the address to listen on.  If hostaddress
 * consists of a single '*' character, INADDR_ANY is used.
 *
 * A line can also consist of just
 *      hostaddress:
 * where hostaddress is as in the preceding paragraph.  Such a line must
 * have no further fields; the specified hostaddress is remembered and
 * used for all further lines that have no hostaddress specified,
 * until the next such line (or EOF).  (This is why * is provided to
 * allow explicit specification of INADDR_ANY.)  A line
 *      *:
 * is implicitly in effect at the beginning of the file.
 *
 * The hostaddress specifier may (and often will) contain dots;
 * the service name must not.
 *
 * For RPC services, host-address specifiers are accepted and will
 * work to some extent; however, because of limitations in the
 * portmapper interface, it will not work to try to give more than
 * one line for any given RPC service, even if the host-address
 * specifiers are different.
 *
 * Comment lines are indicated by a '#' in column 1.
 */

/* inetd rules for passing file descriptors to children
 * (http://www.freebsd.org/cgi/man.cgi?query=inetd):
 *
 * The wait/nowait entry specifies whether the server that is invoked by
 * inetd will take over the socket associated with the service access point,
 * and thus whether inetd should wait for the server to exit before listen-
 * ing for new service requests.  Datagram servers must use "wait", as
 * they are always invoked with the original datagram socket bound to the
 * specified service address.  These servers must read at least one datagram
 * from the socket before exiting.  If a datagram server connects to its
 * peer, freeing the socket so inetd can receive further messages on the
 * socket, it is said to be a "multi-threaded" server; it should read one
 * datagram from the socket and create a new socket connected to the peer.
 * It should fork, and the parent should then exit to allow inetd to check
 * for new service requests to spawn new servers.  Datagram servers which
 * process all incoming datagrams on a socket and eventually time out are
 * said to be "single-threaded".  The comsat(8), biff(1) and talkd(8)
 * utilities are both examples of the latter type of datagram server.  The
 * tftpd(8) utility is an example of a multi-threaded datagram server.
 *
 * Servers using stream sockets generally are multi-threaded and use the
 * "nowait" entry. Connection requests for these services are accepted by
 * inetd, and the server is given only the newly-accepted socket connected
 * to a client of the service.  Most stream-based services operate in this
 * manner.  Stream-based servers that use "wait" are started with the lis-
 * tening service socket, and must accept at least one connection request
 * before exiting.  Such a server would normally accept and process incoming
 * connection requests until a timeout.
 */

/* Despite of above doc saying that dgram services must use "wait",
 * "udp nowait" servers are implemented in busyboxed inetd.
 * IPv6 addresses are also implemented. However, they may look ugly -
 * ":::service..." means "address '::' (IPv6 wildcard addr)":"service"...
 * You have to put "tcp6"/"udp6" in protocol field to select IPv6.
 */

/* Here's the scoop concerning the user[:group] feature:
 * 1) group is not specified:
 *      a) user = root: NO setuid() or setgid() is done
 *      b) other:       initgroups(name, primary group)
 *                      setgid(primary group as found in passwd)
 *                      setuid()
 * 2) group is specified:
 *      a) user = root: setgid(specified group)
 *                      NO initgroups()
 *                      NO setuid()
 *      b) other:       initgroups(name, specified group)
 *                      setgid(specified group)
 *                      setuid()
 */

//usage:#define inetd_trivial_usage
//usage:       "[-fe] [-q N] [-R N] [CONFFILE]"
//usage:#define inetd_full_usage "\n\n"
//usage:       "Listen for network connections and launch programs\n"
//usage:     "\n        -f      Run in foreground"
//usage:     "\n        -e      Log to stderr"
//usage:     "\n        -q N    Socket listen queue (default: 128)"
//usage:     "\n        -R N    Pause services after N connects/min"
//usage:     "\n                (default: 0 - disabled)"

#include <syslog.h>
#include <sys/resource.h> /* setrlimit */
#include <sys/socket.h> /* un.h may need this */
#include <sys/un.h>

#include "libbb.h"

#if ENABLE_FEATURE_INETD_RPC
# if defined(__UCLIBC__) && ! defined(__UCLIBC_HAS_RPC__)
#  error "You need to build uClibc with UCLIBC_HAS_RPC for NFS support"
# endif
# include <rpc/rpc.h>
# include <rpc/pmap_clnt.h>
#endif

#if !BB_MMU
/* stream version of chargen is forking but not execing,
 * can't do that (easily) on NOMMU */
#undef  ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN
#define ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN 0
#endif

#define CNT_INTERVAL    60      /* servers in CNT_INTERVAL sec. */
#define RETRYTIME       60      /* retry after bind or server fail */

// TODO: explain, or get rid of setrlimit games

#ifndef RLIMIT_NOFILE
#define RLIMIT_NOFILE   RLIMIT_OFILE
#endif

#ifndef OPEN_MAX
#define OPEN_MAX        64
#endif

/* Reserve some descriptors, 3 stdio + at least: 1 log, 1 conf. file */
#define FD_MARGIN       8

#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DISCARD \
 || ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_ECHO    \
 || ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN \
 || ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_TIME    \
 || ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DAYTIME
# define INETD_BUILTINS_ENABLED
#endif

typedef struct servtab_t {
        /* The most frequently referenced one: */
        int se_fd;                            /* open descriptor */
        /* NB: 'biggest fields last' saves on code size (~250 bytes) */
        /* [addr:]service socktype proto wait user[:group] prog [args] */
        char *se_local_hostname;              /* addr to listen on */
        char *se_service;                     /* "80" or "www" or "mount/2[-3]" */
        /* socktype is in se_socktype */      /* "stream" "dgram" "raw" "rdm" "seqpacket" */
        char *se_proto;                       /* "unix" or "[rpc/]tcp[6]" */
#if ENABLE_FEATURE_INETD_RPC
        int se_rpcprog;                       /* rpc program number */
        int se_rpcver_lo;                     /* rpc program lowest version */
        int se_rpcver_hi;                     /* rpc program highest version */
#define is_rpc_service(sep)       ((sep)->se_rpcver_lo != 0)
#else
#define is_rpc_service(sep)       0
#endif
        pid_t se_wait;                        /* 0:"nowait", 1:"wait", >1:"wait" */
                                              /* and waiting for this pid */
        socktype_t se_socktype;               /* SOCK_STREAM/DGRAM/RDM/... */
        family_t se_family;                   /* AF_UNIX/INET[6] */
        /* se_proto_no is used by RPC code only... hmm */
        smallint se_proto_no;                 /* IPPROTO_TCP/UDP, n/a for AF_UNIX */
        smallint se_checked;                  /* looked at during merge */
        unsigned se_max;                      /* allowed instances per minute */
        unsigned se_count;                    /* number started since se_time */
        unsigned se_time;                     /* when we started counting */
        char *se_user;                        /* user name to run as */
        char *se_group;                       /* group name to run as, can be NULL */
#ifdef INETD_BUILTINS_ENABLED
        const struct builtin *se_builtin;     /* if built-in, description */
#endif
        struct servtab_t *se_next;
        len_and_sockaddr *se_lsa;
        char *se_program;                     /* server program */
#define MAXARGV 20
        char *se_argv[MAXARGV + 1];           /* program arguments */
} servtab_t;

#ifdef INETD_BUILTINS_ENABLED
/* Echo received data */
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_ECHO
static void FAST_FUNC echo_stream(int, servtab_t *);
static void FAST_FUNC echo_dg(int, servtab_t *);
#endif
/* Internet /dev/null */
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DISCARD
static void FAST_FUNC discard_stream(int, servtab_t *);
static void FAST_FUNC discard_dg(int, servtab_t *);
#endif
/* Return 32 bit time since 1900 */
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_TIME
static void FAST_FUNC machtime_stream(int, servtab_t *);
static void FAST_FUNC machtime_dg(int, servtab_t *);
#endif
/* Return human-readable time */
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DAYTIME
static void FAST_FUNC daytime_stream(int, servtab_t *);
static void FAST_FUNC daytime_dg(int, servtab_t *);
#endif
/* Familiar character generator */
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN
static void FAST_FUNC chargen_stream(int, servtab_t *);
static void FAST_FUNC chargen_dg(int, servtab_t *);
#endif

struct builtin {
        /* NB: not necessarily NUL terminated */
        char bi_service7[7];      /* internally provided service name */
        uint8_t bi_fork;          /* 1 if stream fn should run in child */
        void (*bi_stream_fn)(int, servtab_t *) FAST_FUNC;
        void (*bi_dgram_fn)(int, servtab_t *) FAST_FUNC;
};

static const struct builtin builtins[] = {
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_ECHO
        { "echo", 1, echo_stream, echo_dg },
#endif
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DISCARD
        { "discard", 1, discard_stream, discard_dg },
#endif
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN
        { "chargen", 1, chargen_stream, chargen_dg },
#endif
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_TIME
        { "time", 0, machtime_stream, machtime_dg },
#endif
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DAYTIME
        { "daytime", 0, daytime_stream, daytime_dg },
#endif
};
#endif /* INETD_BUILTINS_ENABLED */

struct globals {
        rlim_t rlim_ofile_cur;
        struct rlimit rlim_ofile;
        servtab_t *serv_list;
        int global_queuelen;
        int maxsock;         /* max fd# in allsock, -1: unknown */
        /* whenever maxsock grows, prev_maxsock is set to new maxsock,
         * but if maxsock is set to -1, prev_maxsock is not changed */
        int prev_maxsock;
        unsigned max_concurrency;
        smallint alarm_armed;
        uid_t real_uid; /* user ID who ran us */
        const char *config_filename;
        parser_t *parser;
        char *default_local_hostname;
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN
        char *end_ring;
        char *ring_pos;
        char ring[128];
#endif
        fd_set allsock;
        /* Used in next_line(), and as scratch read buffer */
        char line[256];          /* _at least_ 256, see LINE_SIZE */
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
enum { LINE_SIZE = COMMON_BUFSIZE - offsetof(struct globals, line) };
struct BUG_G_too_big {
        char BUG_G_too_big[sizeof(G) <= COMMON_BUFSIZE ? 1 : -1];
};
#define rlim_ofile_cur  (G.rlim_ofile_cur )
#define rlim_ofile      (G.rlim_ofile     )
#define serv_list       (G.serv_list      )
#define global_queuelen (G.global_queuelen)
#define maxsock         (G.maxsock        )
#define prev_maxsock    (G.prev_maxsock   )
#define max_concurrency (G.max_concurrency)
#define alarm_armed     (G.alarm_armed    )
#define real_uid        (G.real_uid       )
#define config_filename (G.config_filename)
#define parser          (G.parser         )
#define default_local_hostname (G.default_local_hostname)
#define first_ps_byte   (G.first_ps_byte  )
#define last_ps_byte    (G.last_ps_byte   )
#define end_ring        (G.end_ring       )
#define ring_pos        (G.ring_pos       )
#define ring            (G.ring           )
#define allsock         (G.allsock        )
#define line            (G.line           )
#define INIT_G() do { \
        rlim_ofile_cur = OPEN_MAX; \
        global_queuelen = 128; \
        config_filename = "/etc/inetd.conf"; \
} while (0)

#if 1
# define dbg(...) ((void)0)
#else
# define dbg(...) \
do { \
        int dbg_fd = open("inetd_debug.log", O_WRONLY | O_CREAT | O_APPEND, 0666); \
        if (dbg_fd >= 0) { \
                fdprintf(dbg_fd, "%d: ", getpid()); \
                fdprintf(dbg_fd, __VA_ARGS__); \
                close(dbg_fd); \
        } \
} while (0)
#endif

static void maybe_close(int fd)
{
        if (fd >= 0) {
                close(fd);
                dbg("closed fd:%d\n", fd);
        }
}

// TODO: move to libbb?
static len_and_sockaddr *xzalloc_lsa(int family)
{
        len_and_sockaddr *lsa;
        int sz;

        sz = sizeof(struct sockaddr_in);
        if (family == AF_UNIX)
                sz = sizeof(struct sockaddr_un);
#if ENABLE_FEATURE_IPV6
        if (family == AF_INET6)
                sz = sizeof(struct sockaddr_in6);
#endif
        lsa = xzalloc(LSA_LEN_SIZE + sz);
        lsa->len = sz;
        lsa->u.sa.sa_family = family;
        return lsa;
}

static void rearm_alarm(void)
{
        if (!alarm_armed) {
                alarm_armed = 1;
                alarm(RETRYTIME);
        }
}

static void block_CHLD_HUP_ALRM(sigset_t *m)
{
        sigemptyset(m);
        sigaddset(m, SIGCHLD);
        sigaddset(m, SIGHUP);
        sigaddset(m, SIGALRM);
        sigprocmask(SIG_BLOCK, m, m); /* old sigmask is stored in m */
}

static void restore_sigmask(sigset_t *m)
{
        sigprocmask(SIG_SETMASK, m, NULL);
}

#if ENABLE_FEATURE_INETD_RPC
static void register_rpc(servtab_t *sep)
{
        int n;
        struct sockaddr_in ir_sin;
        socklen_t size;

        size = sizeof(ir_sin);
        if (getsockname(sep->se_fd, (struct sockaddr *) &ir_sin, &size) < 0) {
                bb_perror_msg("getsockname");
                return;
        }

        for (n = sep->se_rpcver_lo; n <= sep->se_rpcver_hi; n++) {
                pmap_unset(sep->se_rpcprog, n);
                if (!pmap_set(sep->se_rpcprog, n, sep->se_proto_no, ntohs(ir_sin.sin_port)))
                        bb_perror_msg("%s %s: pmap_set(%u,%u,%u,%u)",
                                sep->se_service, sep->se_proto,
                                sep->se_rpcprog, n, sep->se_proto_no, ntohs(ir_sin.sin_port));
        }
}

static void unregister_rpc(servtab_t *sep)
{
        int n;

        for (n = sep->se_rpcver_lo; n <= sep->se_rpcver_hi; n++) {
                if (!pmap_unset(sep->se_rpcprog, n))
                        bb_perror_msg("pmap_unset(%u,%u)", sep->se_rpcprog, n);
        }
}
#endif /* FEATURE_INETD_RPC */

static void bump_nofile(void)
{
        enum { FD_CHUNK = 32 };
        struct rlimit rl;

        /* Never fails under Linux (except if you pass it bad arguments) */
        getrlimit(RLIMIT_NOFILE, &rl);
        rl.rlim_cur = MIN(rl.rlim_max, rl.rlim_cur + FD_CHUNK);
        rl.rlim_cur = MIN(FD_SETSIZE, rl.rlim_cur + FD_CHUNK);
        if (rl.rlim_cur <= rlim_ofile_cur) {
                bb_error_msg("can't extend file limit, max = %d",
                                                (int) rl.rlim_cur);
                return;
        }

        if (setrlimit(RLIMIT_NOFILE, &rl) < 0) {
                bb_perror_msg("setrlimit");
                return;
        }

        rlim_ofile_cur = rl.rlim_cur;
}

static void remove_fd_from_set(int fd)
{
        if (fd >= 0) {
                FD_CLR(fd, &allsock);
                dbg("stopped listening on fd:%d\n", fd);
                maxsock = -1;
                dbg("maxsock:%d\n", maxsock);
        }
}

static void add_fd_to_set(int fd)
{
        if (fd >= 0) {
                FD_SET(fd, &allsock);
                dbg("started listening on fd:%d\n", fd);
                if (maxsock >= 0 && fd > maxsock) {
                        prev_maxsock = maxsock = fd;
                        dbg("maxsock:%d\n", maxsock);
                        if ((rlim_t)fd > rlim_ofile_cur - FD_MARGIN)
                                bump_nofile();
                }
        }
}

static void recalculate_maxsock(void)
{
        int fd = 0;

        /* We may have no services, in this case maxsock should still be >= 0
         * (code elsewhere is not happy with maxsock == -1) */
        maxsock = 0;
        while (fd <= prev_maxsock) {
                if (FD_ISSET(fd, &allsock))
                        maxsock = fd;
                fd++;
        }
        dbg("recalculated maxsock:%d\n", maxsock);
        prev_maxsock = maxsock;
        if ((rlim_t)maxsock > rlim_ofile_cur - FD_MARGIN)
                bump_nofile();
}

static void prepare_socket_fd(servtab_t *sep)
{
        int r, fd;

        fd = socket(sep->se_family, sep->se_socktype, 0);
        if (fd < 0) {
                bb_perror_msg("socket");
                return;
        }
        setsockopt_reuseaddr(fd);

#if ENABLE_FEATURE_INETD_RPC
        if (is_rpc_service(sep)) {
                struct passwd *pwd;

                /* zero out the port for all RPC services; let bind()
                 * find one. */
                set_nport(&sep->se_lsa->u.sa, 0);

                /* for RPC services, attempt to use a reserved port
                 * if they are going to be running as root. */
                if (real_uid == 0 && sep->se_family == AF_INET
                 && (pwd = getpwnam(sep->se_user)) != NULL
                 && pwd->pw_uid == 0
                ) {
                        r = bindresvport(fd, &sep->se_lsa->u.sin);
                } else {
                        r = bind(fd, &sep->se_lsa->u.sa, sep->se_lsa->len);
                }
                if (r == 0) {
                        int saveerrno = errno;
                        /* update lsa with port# */
                        getsockname(fd, &sep->se_lsa->u.sa, &sep->se_lsa->len);
                        errno = saveerrno;
                }
        } else
#endif
        {
                if (sep->se_family == AF_UNIX) {
                        struct sockaddr_un *sun;
                        sun = (struct sockaddr_un*)&(sep->se_lsa->u.sa);
                        unlink(sun->sun_path);
                }
                r = bind(fd, &sep->se_lsa->u.sa, sep->se_lsa->len);
        }
        if (r < 0) {
                bb_perror_msg("%s/%s: bind",
                                sep->se_service, sep->se_proto);
                close(fd);
                rearm_alarm();
                return;
        }

        if (sep->se_socktype == SOCK_STREAM) {
                listen(fd, global_queuelen);
                dbg("new sep->se_fd:%d (stream)\n", fd);
        } else {
                dbg("new sep->se_fd:%d (!stream)\n", fd);
        }

        add_fd_to_set(fd);
        sep->se_fd = fd;
}

static int reopen_config_file(void)
{
        free(default_local_hostname);
        default_local_hostname = xstrdup("*");
        if (parser != NULL)
                config_close(parser);
        parser = config_open(config_filename);
        return (parser != NULL);
}

static void close_config_file(void)
{
        if (parser) {
                config_close(parser);
                parser = NULL;
        }
}

static void free_servtab_strings(servtab_t *cp)
{
        int i;

        free(cp->se_local_hostname);
        free(cp->se_service);
        free(cp->se_proto);
        free(cp->se_user);
        free(cp->se_group);
        free(cp->se_lsa); /* not a string in fact */
        free(cp->se_program);
        for (i = 0; i < MAXARGV; i++)
                free(cp->se_argv[i]);
}

static servtab_t *new_servtab(void)
{
        servtab_t *newtab = xzalloc(sizeof(servtab_t));
        newtab->se_fd = -1; /* paranoia */
        return newtab;
}

static servtab_t *dup_servtab(servtab_t *sep)
{
        servtab_t *newtab;
        int argc;

        newtab = new_servtab();
        *newtab = *sep; /* struct copy */
        /* deep-copying strings */
        newtab->se_service = xstrdup(newtab->se_service);
        newtab->se_proto = xstrdup(newtab->se_proto);
        newtab->se_user = xstrdup(newtab->se_user);
        newtab->se_group = xstrdup(newtab->se_group);
        newtab->se_program = xstrdup(newtab->se_program);
        for (argc = 0; argc <= MAXARGV; argc++)
                newtab->se_argv[argc] = xstrdup(newtab->se_argv[argc]);
        /* NB: se_fd, se_hostaddr and se_next are always
         * overwrittend by callers, so we don't bother resetting them
         * to NULL/0/-1 etc */

        return newtab;
}

/* gcc generates much more code if this is inlined */
static servtab_t *parse_one_line(void)
{
        int argc;
        char *token[6+MAXARGV];
        char *p, *arg;
        char *hostdelim;
        servtab_t *sep;
        servtab_t *nsep;
 new:
        sep = new_servtab();
 more:
        argc = config_read(parser, token, 6+MAXARGV, 1, "# \t", PARSE_NORMAL);
        if (!argc) {
                free(sep);
                return NULL;
        }

        /* [host:]service socktype proto wait user[:group] prog [args] */
        /* Check for "host:...." line */
        arg = token[0];
        hostdelim = strrchr(arg, ':');
        if (hostdelim) {
                *hostdelim = '\0';
                sep->se_local_hostname = xstrdup(arg);
                arg = hostdelim + 1;
                if (*arg == '\0' && argc == 1) {
                        /* Line has just "host:", change the
                         * default host for the following lines. */
                        free(default_local_hostname);
                        default_local_hostname = sep->se_local_hostname;
                        goto more;
                }
        } else
                sep->se_local_hostname = xstrdup(default_local_hostname);

        /* service socktype proto wait user[:group] prog [args] */
        sep->se_service = xstrdup(arg);

        /* socktype proto wait user[:group] prog [args] */
        if (argc < 6) {
 parse_err:
                bb_error_msg("parse error on line %u, line is ignored",
                                parser->lineno);
                free_servtab_strings(sep);
                /* Just "goto more" can make sep to carry over e.g.
                 * "rpc"-ness (by having se_rpcver_lo != 0).
                 * We will be more paranoid: */
                free(sep);
                goto new;
        }

        {
                static const int8_t SOCK_xxx[] ALIGN1 = {
                        -1,
                        SOCK_STREAM, SOCK_DGRAM, SOCK_RDM,
                        SOCK_SEQPACKET, SOCK_RAW
                };
                sep->se_socktype = SOCK_xxx[1 + index_in_strings(
                        "stream""\0" "dgram""\0" "rdm""\0"
                        "seqpacket""\0" "raw""\0"
                        , token[1])];
        }

        /* {unix,[rpc/]{tcp,udp}[6]} wait user[:group] prog [args] */
        sep->se_proto = arg = xstrdup(token[2]);
        if (strcmp(arg, "unix") == 0) {
                sep->se_family = AF_UNIX;
        } else {
                char *six;
                sep->se_family = AF_INET;
                six = last_char_is(arg, '6');
                if (six) {
#if ENABLE_FEATURE_IPV6
                        *six = '\0';
                        sep->se_family = AF_INET6;
#else
                        bb_error_msg("%s: no support for IPv6", sep->se_proto);
                        goto parse_err;
#endif
                }
                if (strncmp(arg, "rpc/", 4) == 0) {
#if ENABLE_FEATURE_INETD_RPC
                        unsigned n;
                        arg += 4;
                        p = strchr(sep->se_service, '/');
                        if (p == NULL) {
                                bb_error_msg("no rpc version: '%s'", sep->se_service);
                                goto parse_err;
                        }
                        *p++ = '\0';
                        n = bb_strtou(p, &p, 10);
                        if (n > INT_MAX) {
 bad_ver_spec:
                                bb_error_msg("bad rpc version");
                                goto parse_err;
                        }
                        sep->se_rpcver_lo = sep->se_rpcver_hi = n;
                        if (*p == '-') {
                                p++;
                                n = bb_strtou(p, &p, 10);
                                if (n > INT_MAX || (int)n < sep->se_rpcver_lo)
                                        goto bad_ver_spec;
                                sep->se_rpcver_hi = n;
                        }
                        if (*p != '\0')
                                goto bad_ver_spec;
#else
                        bb_error_msg("no support for rpc services");
                        goto parse_err;
#endif
                }
                /* we don't really need getprotobyname()! */
                if (strcmp(arg, "tcp") == 0)
                        sep->se_proto_no = IPPROTO_TCP; /* = 6 */
                if (strcmp(arg, "udp") == 0)
                        sep->se_proto_no = IPPROTO_UDP; /* = 17 */
                if (six)
                        *six = '6';
                if (!sep->se_proto_no) /* not tcp/udp?? */
                        goto parse_err;
        }

        /* [no]wait[.max] user[:group] prog [args] */
        arg = token[3];
        sep->se_max = max_concurrency;
        p = strchr(arg, '.');
        if (p) {
                *p++ = '\0';
                sep->se_max = bb_strtou(p, NULL, 10);
                if (errno)
                        goto parse_err;
        }
        sep->se_wait = (arg[0] != 'n' || arg[1] != 'o');
        if (!sep->se_wait) /* "no" seen */
                arg += 2;
        if (strcmp(arg, "wait") != 0)
                goto parse_err;

        /* user[:group] prog [args] */
        sep->se_user = xstrdup(token[4]);
        arg = strchr(sep->se_user, '.');
        if (arg == NULL)
                arg = strchr(sep->se_user, ':');
        if (arg) {
                *arg++ = '\0';
                sep->se_group = xstrdup(arg);
        }

        /* prog [args] */
        sep->se_program = xstrdup(token[5]);
#ifdef INETD_BUILTINS_ENABLED
        if (strcmp(sep->se_program, "internal") == 0
         && strlen(sep->se_service) <= 7
         && (sep->se_socktype == SOCK_STREAM
             || sep->se_socktype == SOCK_DGRAM)
        ) {
                unsigned i;
                for (i = 0; i < ARRAY_SIZE(builtins); i++)
                        if (strncmp(builtins[i].bi_service7, sep->se_service, 7) == 0)
                                goto found_bi;
                bb_error_msg("unknown internal service %s", sep->se_service);
                goto parse_err;
 found_bi:
                sep->se_builtin = &builtins[i];
                /* stream builtins must be "nowait", dgram must be "wait" */
                if (sep->se_wait != (sep->se_socktype == SOCK_DGRAM))
                        goto parse_err;
        }
#endif
        argc = 0;
        while ((arg = token[6+argc]) != NULL && argc < MAXARGV)
                sep->se_argv[argc++] = xstrdup(arg);
        /* Some inetd.conf files have no argv's, not even argv[0].
         * Fix them up.
         * (Technically, programs can be execed with argv[0] = NULL,
         * but many programs do not like that at all) */
        if (argc == 0)
                sep->se_argv[0] = xstrdup(sep->se_program);

        /* catch mixups. "<service> stream udp ..." == wtf */
        if (sep->se_socktype == SOCK_STREAM) {
                if (sep->se_proto_no == IPPROTO_UDP)
                        goto parse_err;
        }
        if (sep->se_socktype == SOCK_DGRAM) {
                if (sep->se_proto_no == IPPROTO_TCP)
                        goto parse_err;
        }

//      bb_info_msg(
//              "ENTRY[%s][%s][%s][%d][%d][%d][%d][%d][%s][%s][%s]",
//              sep->se_local_hostname, sep->se_service, sep->se_proto, sep->se_wait, sep->se_proto_no,
//              sep->se_max, sep->se_count, sep->se_time, sep->se_user, sep->se_group, sep->se_program);

        /* check if the hostname specifier is a comma separated list
         * of hostnames. we'll make new entries for each address. */
        while ((hostdelim = strrchr(sep->se_local_hostname, ',')) != NULL) {
                nsep = dup_servtab(sep);
                /* NUL terminate the hostname field of the existing entry,
                 * and make a dup for the new entry. */
                *hostdelim++ = '\0';
                nsep->se_local_hostname = xstrdup(hostdelim);
                nsep->se_next = sep->se_next;
                sep->se_next = nsep;
        }

        /* was doing it here: */
        /* DNS resolution, create copies for each IP address */
        /* IPv6-ization destroyed it :( */

        return sep;
}

static servtab_t *insert_in_servlist(servtab_t *cp)
{
        servtab_t *sep;
        sigset_t omask;

        sep = new_servtab();
        *sep = *cp; /* struct copy */
        sep->se_fd = -1;
#if ENABLE_FEATURE_INETD_RPC
        sep->se_rpcprog = -1;
#endif
        block_CHLD_HUP_ALRM(&omask);
        sep->se_next = serv_list;
        serv_list = sep;
        restore_sigmask(&omask);
        return sep;
}

static int same_serv_addr_proto(servtab_t *old, servtab_t *new)
{
        if (strcmp(old->se_local_hostname, new->se_local_hostname) != 0)
                return 0;
        if (strcmp(old->se_service, new->se_service) != 0)
                return 0;
        if (strcmp(old->se_proto, new->se_proto) != 0)
                return 0;
        return 1;
}

static void reread_config_file(int sig UNUSED_PARAM)
{
        servtab_t *sep, *cp, **sepp;
        len_and_sockaddr *lsa;
        sigset_t omask;
        unsigned n;
        uint16_t port;
        int save_errno = errno;

        if (!reopen_config_file())
                goto ret;
        for (sep = serv_list; sep; sep = sep->se_next)
                sep->se_checked = 0;

        goto first_line;
        while (1) {
                if (cp == NULL) {
 first_line:
                        cp = parse_one_line();
                        if (cp == NULL)
                                break;
                }
                for (sep = serv_list; sep; sep = sep->se_next)
                        if (same_serv_addr_proto(sep, cp))
                                goto equal_servtab;
                /* not an "equal" servtab */
                sep = insert_in_servlist(cp);
                goto after_check;
 equal_servtab:
                {
                        int i;

                        block_CHLD_HUP_ALRM(&omask);
#if ENABLE_FEATURE_INETD_RPC
                        if (is_rpc_service(sep))
                                unregister_rpc(sep);
                        sep->se_rpcver_lo = cp->se_rpcver_lo;
                        sep->se_rpcver_hi = cp->se_rpcver_hi;
#endif
                        if (cp->se_wait == 0) {
                                /* New config says "nowait". If old one
                                 * was "wait", we currently may be waiting
                                 * for a child (and not accepting connects).
                                 * Stop waiting, start listening again.
                                 * (if it's not true, this op is harmless) */
                                add_fd_to_set(sep->se_fd);
                        }
                        sep->se_wait = cp->se_wait;
                        sep->se_max = cp->se_max;
                        /* string fields need more love - we don't want to leak them */
#define SWAP(type, a, b) do { type c = (type)a; a = (type)b; b = (type)c; } while (0)
                        SWAP(char*, sep->se_user, cp->se_user);
                        SWAP(char*, sep->se_group, cp->se_group);
                        SWAP(char*, sep->se_program, cp->se_program);
                        for (i = 0; i < MAXARGV; i++)
                                SWAP(char*, sep->se_argv[i], cp->se_argv[i]);
#undef SWAP
                        restore_sigmask(&omask);
                        free_servtab_strings(cp);
                }
 after_check:
                /* cp->string_fields are consumed by insert_in_servlist()
                 * or freed at this point, cp itself is not yet freed. */
                sep->se_checked = 1;

                /* create new len_and_sockaddr */
                switch (sep->se_family) {
                        struct sockaddr_un *sun;
                case AF_UNIX:
                        lsa = xzalloc_lsa(AF_UNIX);
                        sun = (struct sockaddr_un*)&lsa->u.sa;
                        safe_strncpy(sun->sun_path, sep->se_service, sizeof(sun->sun_path));
                        break;

                default: /* case AF_INET, case AF_INET6 */
                        n = bb_strtou(sep->se_service, NULL, 10);
#if ENABLE_FEATURE_INETD_RPC
                        if (is_rpc_service(sep)) {
                                sep->se_rpcprog = n;
                                if (errno) { /* se_service is not numeric */
                                        struct rpcent *rp = getrpcbyname(sep->se_service);
                                        if (rp == NULL) {
                                                bb_error_msg("%s: unknown rpc service", sep->se_service);
                                                goto next_cp;
                                        }
                                        sep->se_rpcprog = rp->r_number;
                                }
                                if (sep->se_fd == -1)
                                        prepare_socket_fd(sep);
                                if (sep->se_fd != -1)
                                        register_rpc(sep);
                                goto next_cp;
                        }
#endif
                        /* what port to listen on? */
                        port = htons(n);
                        if (errno || n > 0xffff) { /* se_service is not numeric */
                                char protoname[4];
                                struct servent *sp;
                                /* can result only in "tcp" or "udp": */
                                safe_strncpy(protoname, sep->se_proto, 4);
                                sp = getservbyname(sep->se_service, protoname);
                                if (sp == NULL) {
                                        bb_error_msg("%s/%s: unknown service",
                                                        sep->se_service, sep->se_proto);
                                        goto next_cp;
                                }
                                port = sp->s_port;
                        }
                        if (LONE_CHAR(sep->se_local_hostname, '*')) {
                                lsa = xzalloc_lsa(sep->se_family);

                                set_nport(&lsa->u.sa, port);
                        } else {
                                lsa = host_and_af2sockaddr(sep->se_local_hostname,
                                                ntohs(port), sep->se_family);
                                if (!lsa) {
                                        bb_error_msg("%s/%s: unknown host '%s'",
                                                sep->se_service, sep->se_proto,
                                                sep->se_local_hostname);
                                        goto next_cp;
                                }
                        }
                        break;
                } /* end of "switch (sep->se_family)" */

                /* did lsa change? Then close/open */
                if (sep->se_lsa == NULL
                 || lsa->len != sep->se_lsa->len
                 || memcmp(&lsa->u.sa, &sep->se_lsa->u.sa, lsa->len) != 0
                ) {
                        remove_fd_from_set(sep->se_fd);
                        maybe_close(sep->se_fd);
                        free(sep->se_lsa);
                        sep->se_lsa = lsa;
                        sep->se_fd = -1;
                } else {
                        free(lsa);
                }
                if (sep->se_fd == -1)
                        prepare_socket_fd(sep);
 next_cp:
                sep = cp->se_next;
                free(cp);
                cp = sep;
        } /* end of "while (1) parse lines" */
        close_config_file();

        /* Purge anything not looked at above - these are stale entries,
         * new config file doesnt have them. */
        block_CHLD_HUP_ALRM(&omask);
        sepp = &serv_list;
        while ((sep = *sepp) != NULL) {
                if (sep->se_checked) {
                        sepp = &sep->se_next;
                        continue;
                }
                *sepp = sep->se_next;
                remove_fd_from_set(sep->se_fd);
                maybe_close(sep->se_fd);
#if ENABLE_FEATURE_INETD_RPC
                if (is_rpc_service(sep))
                        unregister_rpc(sep);
#endif
                if (sep->se_family == AF_UNIX)
                        unlink(sep->se_service);
                free_servtab_strings(sep);
                free(sep);
        }
        restore_sigmask(&omask);
 ret:
        errno = save_errno;
}

static void reap_child(int sig UNUSED_PARAM)
{
        pid_t pid;
        int status;
        servtab_t *sep;
        int save_errno = errno;

        for (;;) {
                pid = wait_any_nohang(&status);
                if (pid <= 0)
                        break;
                for (sep = serv_list; sep; sep = sep->se_next) {
                        if (sep->se_wait != pid)
                                continue;
                        /* One of our "wait" services */
                        if (WIFEXITED(status) && WEXITSTATUS(status))
                                bb_error_msg("%s: exit status %u",
                                                sep->se_program, WEXITSTATUS(status));
                        else if (WIFSIGNALED(status))
                                bb_error_msg("%s: exit signal %u",
                                                sep->se_program, WTERMSIG(status));
                        sep->se_wait = 1;
                        add_fd_to_set(sep->se_fd);
                        break;
                }
        }
        errno = save_errno;
}

static void retry_network_setup(int sig UNUSED_PARAM)
{
        int save_errno = errno;
        servtab_t *sep;

        alarm_armed = 0;
        for (sep = serv_list; sep; sep = sep->se_next) {
                if (sep->se_fd == -1) {
                        prepare_socket_fd(sep);
#if ENABLE_FEATURE_INETD_RPC
                        if (sep->se_fd != -1 && is_rpc_service(sep))
                                register_rpc(sep);
#endif
                }
        }
        errno = save_errno;
}

static void clean_up_and_exit(int sig UNUSED_PARAM)
{
        servtab_t *sep;

        /* XXX signal race walking sep list */
        for (sep = serv_list; sep; sep = sep->se_next) {
                if (sep->se_fd == -1)
                        continue;

                switch (sep->se_family) {
                case AF_UNIX:
                        unlink(sep->se_service);
                        break;
                default: /* case AF_INET, AF_INET6 */
#if ENABLE_FEATURE_INETD_RPC
                        if (sep->se_wait == 1 && is_rpc_service(sep))
                                unregister_rpc(sep);   /* XXX signal race */
#endif
                        break;
                }
                if (ENABLE_FEATURE_CLEAN_UP)
                        close(sep->se_fd);
        }
        remove_pidfile(CONFIG_PID_FILE_PATH "/inetd.pid");
        exit(EXIT_SUCCESS);
}

int inetd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int inetd_main(int argc UNUSED_PARAM, char **argv)
{
        struct sigaction sa, saved_pipe_handler;
        servtab_t *sep, *sep2;
        struct passwd *pwd;
        struct group *grp = grp; /* for compiler */
        int opt;
        pid_t pid;
        sigset_t omask;

        INIT_G();

        real_uid = getuid();
        if (real_uid != 0) /* run by non-root user */
                config_filename = NULL;

        opt_complementary = "R+:q+"; /* -q N, -R N */
        opt = getopt32(argv, "R:feq:", &max_concurrency, &global_queuelen);
        argv += optind;
        //argc -= optind;
        if (argv[0])
                config_filename = argv[0];
        if (config_filename == NULL)
                bb_error_msg_and_die("non-root must specify config file");
        if (!(opt & 2))
                bb_daemonize_or_rexec(0, argv - optind);
        else
                bb_sanitize_stdio();
        if (!(opt & 4)) {
                /* LOG_NDELAY: connect to syslog daemon NOW.
                 * Otherwise, we may open syslog socket
                 * in vforked child, making opened fds and syslog()
                 * internal state inconsistent.
                 * This was observed to leak file descriptors. */
                openlog(applet_name, LOG_PID | LOG_NDELAY, LOG_DAEMON);
                logmode = LOGMODE_SYSLOG;
        }

        if (real_uid == 0) {
                /* run by root, ensure groups vector gets trashed */
                gid_t gid = getgid();
                setgroups(1, &gid);
        }

        write_pidfile(CONFIG_PID_FILE_PATH "/inetd.pid");

        /* never fails under Linux (except if you pass it bad arguments) */
        getrlimit(RLIMIT_NOFILE, &rlim_ofile);
        rlim_ofile_cur = rlim_ofile.rlim_cur;
        if (rlim_ofile_cur == RLIM_INFINITY)    /* ! */
                rlim_ofile_cur = OPEN_MAX;

        memset(&sa, 0, sizeof(sa));
        /*sigemptyset(&sa.sa_mask); - memset did it */
        sigaddset(&sa.sa_mask, SIGALRM);
        sigaddset(&sa.sa_mask, SIGCHLD);
        sigaddset(&sa.sa_mask, SIGHUP);
//FIXME: explain why no SA_RESTART
//FIXME: retry_network_setup is unsafe to run in signal handler (many reasons)!
        sa.sa_handler = retry_network_setup;
        sigaction_set(SIGALRM, &sa);
//FIXME: reread_config_file is unsafe to run in signal handler(many reasons)!
        sa.sa_handler = reread_config_file;
        sigaction_set(SIGHUP, &sa);
//FIXME: reap_child is unsafe to run in signal handler (uses stdio)!
        sa.sa_handler = reap_child;
        sigaction_set(SIGCHLD, &sa);
//FIXME: clean_up_and_exit is unsafe to run in signal handler (uses stdio)!
        sa.sa_handler = clean_up_and_exit;
        sigaction_set(SIGTERM, &sa);
        sa.sa_handler = clean_up_and_exit;
        sigaction_set(SIGINT, &sa);
        sa.sa_handler = SIG_IGN;
        sigaction(SIGPIPE, &sa, &saved_pipe_handler);

        reread_config_file(SIGHUP); /* load config from file */

        for (;;) {
                int ready_fd_cnt;
                int ctrl, accepted_fd, new_udp_fd;
                fd_set readable;

                if (maxsock < 0)
                        recalculate_maxsock();

                readable = allsock; /* struct copy */
                /* if there are no fds to wait on, we will block
                 * until signal wakes us up (maxsock == 0, but readable
                 * never contains fds 0 and 1...) */
                ready_fd_cnt = select(maxsock + 1, &readable, NULL, NULL, NULL);
                if (ready_fd_cnt < 0) {
                        if (errno != EINTR) {
                                bb_perror_msg("select");
                                sleep(1);
                        }
                        continue;
                }
                dbg("ready_fd_cnt:%d\n", ready_fd_cnt);

                for (sep = serv_list; ready_fd_cnt && sep; sep = sep->se_next) {
                        if (sep->se_fd == -1 || !FD_ISSET(sep->se_fd, &readable))
                                continue;

                        dbg("ready fd:%d\n", sep->se_fd);
                        ready_fd_cnt--;
                        ctrl = sep->se_fd;
                        accepted_fd = -1;
                        new_udp_fd = -1;
                        if (!sep->se_wait) {
                                if (sep->se_socktype == SOCK_STREAM) {
                                        ctrl = accepted_fd = accept(sep->se_fd, NULL, NULL);
                                        dbg("accepted_fd:%d\n", accepted_fd);
                                        if (ctrl < 0) {
                                                if (errno != EINTR)
                                                        bb_perror_msg("accept (for %s)", sep->se_service);
                                                continue;
                                        }
                                }
                                /* "nowait" udp */
                                if (sep->se_socktype == SOCK_DGRAM
                                 && sep->se_family != AF_UNIX
                                ) {
/* How udp "nowait" works:
 * child peeks at (received and buffered by kernel) UDP packet,
 * performs connect() on the socket so that it is linked only
 * to this peer. But this also affects parent, because descriptors
 * are shared after fork() a-la dup(). When parent performs
 * select(), it will see this descriptor connected to the peer (!)
 * and still readable, will act on it and mess things up
 * (can create many copies of same child, etc).
 * Parent must create and use new socket instead. */
                                        new_udp_fd = socket(sep->se_family, SOCK_DGRAM, 0);
                                        dbg("new_udp_fd:%d\n", new_udp_fd);
                                        if (new_udp_fd < 0) { /* error: eat packet, forget about it */
 udp_err:
                                                recv(sep->se_fd, line, LINE_SIZE, MSG_DONTWAIT);
                                                continue;
                                        }
                                        setsockopt_reuseaddr(new_udp_fd);
                                        /* TODO: better do bind after fork in parent,
                                         * so that we don't have two wildcard bound sockets
                                         * even for a brief moment? */
                                        if (bind(new_udp_fd, &sep->se_lsa->u.sa, sep->se_lsa->len) < 0) {
                                                dbg("bind(new_udp_fd) failed\n");
                                                close(new_udp_fd);
                                                goto udp_err;
                                        }
                                        dbg("bind(new_udp_fd) succeeded\n");
                                }
                        }

                        block_CHLD_HUP_ALRM(&omask);
                        pid = 0;
#ifdef INETD_BUILTINS_ENABLED
                        /* do we need to fork? */
                        if (sep->se_builtin == NULL
                         || (sep->se_socktype == SOCK_STREAM
                             && sep->se_builtin->bi_fork))
#endif
                        {
                                if (sep->se_max != 0) {
                                        if (++sep->se_count == 1)
                                                sep->se_time = monotonic_sec();
                                        else if (sep->se_count >= sep->se_max) {
                                                unsigned now = monotonic_sec();
                                                /* did we accumulate se_max connects too quickly? */
                                                if (now - sep->se_time <= CNT_INTERVAL) {
                                                        bb_error_msg("%s/%s: too many connections, pausing",
                                                                        sep->se_service, sep->se_proto);
                                                        remove_fd_from_set(sep->se_fd);
                                                        close(sep->se_fd);
                                                        sep->se_fd = -1;
                                                        sep->se_count = 0;
                                                        rearm_alarm(); /* will revive it in RETRYTIME sec */
                                                        restore_sigmask(&omask);
                                                        maybe_close(new_udp_fd);
                                                        maybe_close(accepted_fd);
                                                        continue; /* -> check next fd in fd set */
                                                }
                                                sep->se_count = 0;
                                        }
                                }
                                /* on NOMMU, streamed chargen
                                 * builtin wouldn't work, but it is
                                 * not allowed on NOMMU (ifdefed out) */
#ifdef INETD_BUILTINS_ENABLED
                                if (BB_MMU && sep->se_builtin)
                                        pid = fork();
                                else
#endif
                                        pid = vfork();

                                if (pid < 0) { /* fork error */
                                        bb_perror_msg("vfork"+1);
                                        sleep(1);
                                        restore_sigmask(&omask);
                                        maybe_close(new_udp_fd);
                                        maybe_close(accepted_fd);
                                        continue; /* -> check next fd in fd set */
                                }
                                if (pid == 0)
                                        pid--; /* -1: "we did fork and we are child" */
                        }
                        /* if pid == 0 here, we didn't fork */

                        if (pid > 0) { /* parent */
                                if (sep->se_wait) {
                                        /* wait: we passed socket to child,
                                         * will wait for child to terminate */
                                        sep->se_wait = pid;
                                        remove_fd_from_set(sep->se_fd);
                                }
                                if (new_udp_fd >= 0) {
                                        /* udp nowait: child connected the socket,
                                         * we created and will use new, unconnected one */
                                        xmove_fd(new_udp_fd, sep->se_fd);
                                        dbg("moved new_udp_fd:%d to sep->se_fd:%d\n", new_udp_fd, sep->se_fd);
                                }
                                restore_sigmask(&omask);
                                maybe_close(accepted_fd);
                                continue; /* -> check next fd in fd set */
                        }

                        /* we are either child or didn't fork at all */
#ifdef INETD_BUILTINS_ENABLED
                        if (sep->se_builtin) {
                                if (pid) { /* "pid" is -1: we did fork */
                                        close(sep->se_fd); /* listening socket */
                                        dbg("closed sep->se_fd:%d\n", sep->se_fd);
                                        logmode = LOGMODE_NONE; /* make xwrite etc silent */
                                }
                                restore_sigmask(&omask);
                                if (sep->se_socktype == SOCK_STREAM)
                                        sep->se_builtin->bi_stream_fn(ctrl, sep);
                                else
                                        sep->se_builtin->bi_dgram_fn(ctrl, sep);
                                if (pid) /* we did fork */
                                        _exit(EXIT_FAILURE);
                                maybe_close(accepted_fd);
                                continue; /* -> check next fd in fd set */
                        }
#endif
                        /* child */
                        setsid();
                        /* "nowait" udp */
                        if (new_udp_fd >= 0) {
                                len_and_sockaddr *lsa;
                                int r;

                                close(new_udp_fd);
                                dbg("closed new_udp_fd:%d\n", new_udp_fd);
                                lsa = xzalloc_lsa(sep->se_family);
                                /* peek at the packet and remember peer addr */
                                r = recvfrom(ctrl, NULL, 0, MSG_PEEK|MSG_DONTWAIT,
                                        &lsa->u.sa, &lsa->len);
                                if (r < 0)
                                        goto do_exit1;
                                /* make this socket "connected" to peer addr:
                                 * only packets from this peer will be recv'ed,
                                 * and bare write()/send() will work on it */
                                connect(ctrl, &lsa->u.sa, lsa->len);
                                dbg("connected ctrl:%d to remote peer\n", ctrl);
                                free(lsa);
                        }
                        /* prepare env and exec program */
                        pwd = getpwnam(sep->se_user);
                        if (pwd == NULL) {
                                bb_error_msg("%s: no such %s", sep->se_user, "user");
                                goto do_exit1;
                        }
                        if (sep->se_group && (grp = getgrnam(sep->se_group)) == NULL) {
                                bb_error_msg("%s: no such %s", sep->se_group, "group");
                                goto do_exit1;
                        }
                        if (real_uid != 0 && real_uid != pwd->pw_uid) {
                                /* a user running private inetd */
                                bb_error_msg("non-root must run services as himself");
                                goto do_exit1;
                        }
                        if (pwd->pw_uid != 0) {
                                if (sep->se_group)
                                        pwd->pw_gid = grp->gr_gid;
                                /* initgroups, setgid, setuid: */
                                change_identity(pwd);
                        } else if (sep->se_group) {
                                xsetgid(grp->gr_gid);
                                setgroups(1, &grp->gr_gid);
                        }
                        if (rlim_ofile.rlim_cur != rlim_ofile_cur)
                                if (setrlimit(RLIMIT_NOFILE, &rlim_ofile) < 0)
                                        bb_perror_msg("setrlimit");

                        /* closelog(); - WRONG. we are after vfork,
                         * this may confuse syslog() internal state.
                         * Let's hope libc sets syslog fd to CLOEXEC...
                         */
                        xmove_fd(ctrl, STDIN_FILENO);
                        xdup2(STDIN_FILENO, STDOUT_FILENO);
                        dbg("moved ctrl:%d to fd 0,1[,2]\n", ctrl);
                        /* manpages of inetd I managed to find either say
                         * that stderr is also redirected to the network,
                         * or do not talk about redirection at all (!) */
                        if (!sep->se_wait) /* only for usual "tcp nowait" */
                                xdup2(STDIN_FILENO, STDERR_FILENO);
                        /* NB: among others, this loop closes listening sockets
                         * for nowait stream children */
                        for (sep2 = serv_list; sep2; sep2 = sep2->se_next)
                                if (sep2->se_fd != ctrl)
                                        maybe_close(sep2->se_fd);
                        sigaction_set(SIGPIPE, &saved_pipe_handler);
                        restore_sigmask(&omask);
                        dbg("execing:'%s'\n", sep->se_program);
                        BB_EXECVP(sep->se_program, sep->se_argv);
                        bb_perror_msg("can't execute '%s'", sep->se_program);
 do_exit1:
                        /* eat packet in udp case */
                        if (sep->se_socktype != SOCK_STREAM)
                                recv(0, line, LINE_SIZE, MSG_DONTWAIT);
                        _exit(EXIT_FAILURE);
                } /* for (sep = servtab...) */
        } /* for (;;) */
}

#if !BB_MMU
static const char *const cat_args[] = { "cat", NULL };
#endif

/*
 * Internet services provided internally by inetd:
 */
#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_ECHO
/* Echo service -- echo data back. */
/* ARGSUSED */
static void FAST_FUNC echo_stream(int s, servtab_t *sep UNUSED_PARAM)
{
#if BB_MMU
        while (1) {
                ssize_t sz = safe_read(s, line, LINE_SIZE);
                if (sz <= 0)
                        break;
                xwrite(s, line, sz);
        }
#else
        /* We are after vfork here! */
        /* move network socket to stdin/stdout */
        xmove_fd(s, STDIN_FILENO);
        xdup2(STDIN_FILENO, STDOUT_FILENO);
        /* no error messages please... */
        close(STDERR_FILENO);
        xopen(bb_dev_null, O_WRONLY);
        BB_EXECVP("cat", (char**)cat_args);
        /* on failure we return to main, which does exit(EXIT_FAILURE) */
#endif
}
static void FAST_FUNC echo_dg(int s, servtab_t *sep)
{
        enum { BUFSIZE = 12*1024 }; /* for jumbo sized packets! :) */
        char *buf = xmalloc(BUFSIZE); /* too big for stack */
        int sz;
        len_and_sockaddr *lsa = alloca(LSA_LEN_SIZE + sep->se_lsa->len);

        lsa->len = sep->se_lsa->len;
        /* dgram builtins are non-forking - DONT BLOCK! */
        sz = recvfrom(s, buf, BUFSIZE, MSG_DONTWAIT, &lsa->u.sa, &lsa->len);
        if (sz > 0)
                sendto(s, buf, sz, 0, &lsa->u.sa, lsa->len);
        free(buf);
}
#endif  /* FEATURE_INETD_SUPPORT_BUILTIN_ECHO */


#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DISCARD
/* Discard service -- ignore data. */
/* ARGSUSED */
static void FAST_FUNC discard_stream(int s, servtab_t *sep UNUSED_PARAM)
{
#if BB_MMU
        while (safe_read(s, line, LINE_SIZE) > 0)
                continue;
#else
        /* We are after vfork here! */
        /* move network socket to stdin */
        xmove_fd(s, STDIN_FILENO);
        /* discard output */
        close(STDOUT_FILENO);
        xopen(bb_dev_null, O_WRONLY);
        /* no error messages please... */
        xdup2(STDOUT_FILENO, STDERR_FILENO);
        BB_EXECVP("cat", (char**)cat_args);
        /* on failure we return to main, which does exit(EXIT_FAILURE) */
#endif
}
/* ARGSUSED */
static void FAST_FUNC discard_dg(int s, servtab_t *sep UNUSED_PARAM)
{
        /* dgram builtins are non-forking - DONT BLOCK! */
        recv(s, line, LINE_SIZE, MSG_DONTWAIT);
}
#endif /* FEATURE_INETD_SUPPORT_BUILTIN_DISCARD */


#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN
#define LINESIZ 72
static void init_ring(void)
{
        int i;

        end_ring = ring;
        for (i = ' '; i < 127; i++)
                *end_ring++ = i;
}
/* Character generator. MMU arches only. */
/* ARGSUSED */
static void FAST_FUNC chargen_stream(int s, servtab_t *sep UNUSED_PARAM)
{
        char *rs;
        int len;
        char text[LINESIZ + 2];

        if (!end_ring) {
                init_ring();
                rs = ring;
        }

        text[LINESIZ] = '\r';
        text[LINESIZ + 1] = '\n';
        rs = ring;
        for (;;) {
                len = end_ring - rs;
                if (len >= LINESIZ)
                        memmove(text, rs, LINESIZ);
                else {
                        memmove(text, rs, len);
                        memmove(text + len, ring, LINESIZ - len);
                }
                if (++rs == end_ring)
                        rs = ring;
                xwrite(s, text, sizeof(text));
        }
}
/* ARGSUSED */
static void FAST_FUNC chargen_dg(int s, servtab_t *sep)
{
        int len;
        char text[LINESIZ + 2];
        len_and_sockaddr *lsa = alloca(LSA_LEN_SIZE + sep->se_lsa->len);

        /* Eat UDP packet which started it all */
        /* dgram builtins are non-forking - DONT BLOCK! */
        lsa->len = sep->se_lsa->len;
        if (recvfrom(s, text, sizeof(text), MSG_DONTWAIT, &lsa->u.sa, &lsa->len) < 0)
                return;

        if (!end_ring) {
                init_ring();
                ring_pos = ring;
        }

        len = end_ring - ring_pos;
        if (len >= LINESIZ)
                memmove(text, ring_pos, LINESIZ);
        else {
                memmove(text, ring_pos, len);
                memmove(text + len, ring, LINESIZ - len);
        }
        if (++ring_pos == end_ring)
                ring_pos = ring;
        text[LINESIZ] = '\r';
        text[LINESIZ + 1] = '\n';
        sendto(s, text, sizeof(text), 0, &lsa->u.sa, lsa->len);
}
#endif /* FEATURE_INETD_SUPPORT_BUILTIN_CHARGEN */


#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_TIME
/*
 * Return a machine readable date and time, in the form of the
 * number of seconds since midnight, Jan 1, 1900.  Since gettimeofday
 * returns the number of seconds since midnight, Jan 1, 1970,
 * we must add 2208988800 seconds to this figure to make up for
 * some seventy years Bell Labs was asleep.
 */
static uint32_t machtime(void)
{
        struct timeval tv;

        gettimeofday(&tv, NULL);
        return htonl((uint32_t)(tv.tv_sec + 2208988800));
}
/* ARGSUSED */
static void FAST_FUNC machtime_stream(int s, servtab_t *sep UNUSED_PARAM)
{
        uint32_t result;

        result = machtime();
        full_write(s, &result, sizeof(result));
}
static void FAST_FUNC machtime_dg(int s, servtab_t *sep)
{
        uint32_t result;
        len_and_sockaddr *lsa = alloca(LSA_LEN_SIZE + sep->se_lsa->len);

        lsa->len = sep->se_lsa->len;
        if (recvfrom(s, line, LINE_SIZE, MSG_DONTWAIT, &lsa->u.sa, &lsa->len) < 0)
                return;

        result = machtime();
        sendto(s, &result, sizeof(result), 0, &lsa->u.sa, lsa->len);
}
#endif /* FEATURE_INETD_SUPPORT_BUILTIN_TIME */


#if ENABLE_FEATURE_INETD_SUPPORT_BUILTIN_DAYTIME
/* Return human-readable time of day */
/* ARGSUSED */
static void FAST_FUNC daytime_stream(int s, servtab_t *sep UNUSED_PARAM)
{
        time_t t;

        t = time(NULL);
        fdprintf(s, "%.24s\r\n", ctime(&t));
}
static void FAST_FUNC daytime_dg(int s, servtab_t *sep)
{
        time_t t;
        len_and_sockaddr *lsa = alloca(LSA_LEN_SIZE + sep->se_lsa->len);

        lsa->len = sep->se_lsa->len;
        if (recvfrom(s, line, LINE_SIZE, MSG_DONTWAIT, &lsa->u.sa, &lsa->len) < 0)
                return;

        t = time(NULL);
        sprintf(line, "%.24s\r\n", ctime(&t));
        sendto(s, line, strlen(line), 0, &lsa->u.sa, lsa->len);
}
#endif /* FEATURE_INETD_SUPPORT_BUILTIN_DAYTIME */