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      1 /*	$NetBSD: rumpuser_daemonize.c,v 1.10 2024/04/04 21:19:25 riastradh Exp $	*/
      2 
      3 /*
      4  * Copyright (c) 2010 Antti Kantee.  All Rights Reserved.
      5  *
      6  * Redistribution and use in source and binary forms, with or without
      7  * modification, are permitted provided that the following conditions
      8  * are met:
      9  * 1. Redistributions of source code must retain the above copyright
     10  *    notice, this list of conditions and the following disclaimer.
     11  * 2. Redistributions in binary form must reproduce the above copyright
     12  *    notice, this list of conditions and the following disclaimer in the
     13  *    documentation and/or other materials provided with the distribution.
     14  *
     15  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS
     16  * OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     17  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     18  * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
     19  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     20  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
     21  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     22  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     23  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     24  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     25  * SUCH DAMAGE.
     26  */
     27 
     28 #include "rumpuser_port.h"
     29 
     30 #if !defined(lint)
     31 __RCSID("$NetBSD: rumpuser_daemonize.c,v 1.10 2024/04/04 21:19:25 riastradh Exp $");
     32 #endif /* !lint */
     33 
     34 #include <sys/types.h>
     35 #include <sys/socket.h>
     36 
     37 #include <errno.h>
     38 #include <fcntl.h>
     39 #include <stdint.h>
     40 #include <stdio.h>
     41 #include <unistd.h>
     42 
     43 #include "rumpuser_int.h"
     44 
     45 #if defined(HAVE_PATHS_H)
     46 #include <paths.h>
     47 #else
     48 #define _PATH_DEVNULL "/dev/null"
     49 #endif
     50 
     51 static int isdaemonizing;
     52 static int daemonpipe[2];
     53 
     54 #include <rump/rumpuser.h>
     55 
     56 static int
     57 openstdoutstderr(void)
     58 {
     59 	char path[PATH_MAX];
     60 	int fd;
     61 
     62 	if (getenv_r("RUMP_STDOUT", path, sizeof(path)) == 0) {
     63 		if ((fd = open(path, O_WRONLY|O_CREAT)) == -1)
     64 			return -1;
     65 		dup2(fd, STDOUT_FILENO);
     66 		(void)close(fd);
     67 	}
     68 	if (getenv_r("RUMP_STDERR", path, sizeof(path)) == 0) {
     69 		if ((fd = open(path, O_WRONLY|O_CREAT)) == -1)
     70 			return -1;
     71 		dup2(fd, STDERR_FILENO);
     72 		(void)close(fd);
     73 	}
     74 	return 0;
     75 }
     76 
     77 int
     78 rumpuser_daemonize_begin(void)
     79 {
     80 	ssize_t n;
     81 	int error;
     82 	int rv;
     83 
     84 	if (isdaemonizing) {
     85 		rv = EINPROGRESS;
     86 		goto out;
     87 	}
     88 	isdaemonizing = 1;
     89 
     90 	/*
     91 	 * For daemons we need to fork.  However, since we can't fork
     92 	 * after rump_init (which creates threads), do it now.  Add
     93 	 * a little pipe trickery to make sure we don't exit until the
     94 	 * service is fully inited (i.e. interlocked daemonization).
     95 	 * Actually, use socketpair since that allows to easily steer
     96 	 * clear of the dreaded sigpipe.
     97 	 *
     98 	 * Note: We do *NOT* host chdir("/").  It's up to the caller to
     99 	 * take care of that or not.
    100 	 */
    101 	if (socketpair(PF_LOCAL, SOCK_STREAM, 0, daemonpipe) == -1) {
    102 		rv = errno;
    103 		goto out;
    104 	}
    105 
    106 	if (openstdoutstderr() == -1) {
    107 		rv = errno;
    108 		(void)close(daemonpipe[0]);
    109 		(void)close(daemonpipe[1]);
    110 		goto out;
    111 	}
    112 
    113 	switch (fork()) {
    114 	case 0:
    115 		if (setsid() == -1) {
    116 			rumpuser_daemonize_done(errno);
    117 		}
    118 		rv = 0;
    119 		break;
    120 	case -1:
    121 		rv = errno;
    122 		break;
    123 	default:
    124 		close(daemonpipe[1]);
    125 		n = recv(daemonpipe[0], &error, sizeof(error), MSG_NOSIGNAL);
    126 		if (n == -1)
    127 			error = errno;
    128 		else if (n != sizeof(error))
    129 			error = ESRCH;
    130 		_exit(error);
    131 		/*NOTREACHED*/
    132 	}
    133 
    134  out:
    135 	ET(rv);
    136 }
    137 
    138 int
    139 rumpuser_daemonize_done(int error)
    140 {
    141 	ssize_t n;
    142 	int fd, rv = 0;
    143 
    144 	if (!isdaemonizing) {
    145 		rv = ENOENT;
    146 		goto outout;
    147 	}
    148 
    149 	if (error == 0) {
    150 		fd = open(_PATH_DEVNULL, O_RDWR);
    151 		if (fd == -1) {
    152 			error = errno;
    153 			goto out;
    154 		}
    155 		dup2(fd, STDIN_FILENO);
    156 		if (getenv("RUMP_STDOUT") == NULL)
    157 			dup2(fd, STDOUT_FILENO);
    158 		if (getenv("RUMP_STDERR") == NULL)
    159 			dup2(fd, STDERR_FILENO);
    160 		if (fd > STDERR_FILENO)
    161 			close(fd);
    162 	}
    163 
    164 	fflush(stdout);
    165 	fflush(stderr);
    166 
    167  out:
    168 	n = send(daemonpipe[1], &error, sizeof(error), MSG_NOSIGNAL);
    169 	if (n != sizeof(error)) {
    170 		rv = EPIPE;
    171 	} else if (n == -1) {
    172 		rv = errno;
    173 	} else {
    174 		close(daemonpipe[0]);
    175 		close(daemonpipe[1]);
    176 	}
    177 
    178  outout:
    179 	ET(rv);
    180 }
    181