diff options
author | pjd <pjd@FreeBSD.org> | 2005-08-24 17:21:38 +0000 |
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committer | pjd <pjd@FreeBSD.org> | 2005-08-24 17:21:38 +0000 |
commit | a5fe3401b9f1cc44c8011e8aa5cdbbe2637084e4 (patch) | |
tree | b6de69447d47fffaa83dd6300aab8b56a9a55567 | |
parent | 473f777e4d124b4ed88d3eb95798889f5570e7f4 (diff) | |
download | FreeBSD-src-a5fe3401b9f1cc44c8011e8aa5cdbbe2637084e4.zip FreeBSD-src-a5fe3401b9f1cc44c8011e8aa5cdbbe2637084e4.tar.gz |
Add a family of functions for reliable pidfiles handling.
Idea from: jmg
Discussed on: arch@
-rw-r--r-- | lib/libutil/Makefile | 11 | ||||
-rw-r--r-- | lib/libutil/libutil.h | 17 | ||||
-rw-r--r-- | lib/libutil/pidfile.3 | 227 | ||||
-rw-r--r-- | lib/libutil/pidfile.c | 246 |
4 files changed, 498 insertions, 3 deletions
diff --git a/lib/libutil/Makefile b/lib/libutil/Makefile index 0cab08a..ebbcf55 100644 --- a/lib/libutil/Makefile +++ b/lib/libutil/Makefile @@ -8,15 +8,16 @@ CFLAGS+=-DLIBC_SCCS -I${.CURDIR} -I${.CURDIR}/../libc/gen/ CFLAGS+=-DINET6 SRCS= _secure_path.c auth.c fparseln.c humanize_number.c login.c \ login_auth.c login_cap.c login_class.c login_crypt.c login_ok.c \ - login_times.c login_tty.c logout.c logwtmp.c property.c pty.c \ - pw_util.c realhostname.c stub.c \ + login_times.c login_tty.c logout.c logwtmp.c \ + pidfile.c property.c pty.c pw_util.c realhostname.c stub.c \ trimdomain.c uucplock.c INCS= libutil.h login_cap.h MAN+= login.3 login_auth.3 login_tty.3 logout.3 logwtmp.3 pty.3 \ login_cap.3 login_class.3 login_times.3 login_ok.3 \ _secure_path.3 uucplock.3 property.3 auth.3 realhostname.3 \ - realhostname_sa.3 trimdomain.3 fparseln.3 humanize_number.3 + realhostname_sa.3 trimdomain.3 fparseln.3 humanize_number.3 \ + pidfile.3 MAN+= login.conf.5 auth.conf.5 MLINKS+= property.3 properties_read.3 property.3 properties_free.3 MLINKS+= property.3 property_find.3 @@ -39,5 +40,9 @@ MLINKS+=login_ok.3 auth_ttyok.3 login_ok.3 auth_hostok.3 \ MLINKS+=login_auth.3 auth_checknologin.3 login_auth.3 auth_cat.3 MLINKS+=uucplock.3 uu_lock.3 uucplock.3 uu_lock_txfr.3 \ uucplock.3 uu_unlock.3 uucplock.3 uu_lockerr.3 +MLINKS+=pidfile.3 pidfile_open.3 \ + pidfile.3 pidfile_write.3 \ + pidfile.3 pidfile_close.3 \ + pidfile.3 pidfile_remove.3 .include <bsd.lib.mk> diff --git a/lib/libutil/libutil.h b/lib/libutil/libutil.h index 3042d0f..961fa1b 100644 --- a/lib/libutil/libutil.h +++ b/lib/libutil/libutil.h @@ -49,6 +49,16 @@ typedef struct _property { char *value; } *properties; +#ifdef _SYS_PARAM_H_ +/* for pidfile.c */ +struct pidfh { + int pf_fd; + char pf_path[MAXPATHLEN + 1]; + __dev_t pf_dev; + ino_t pf_ino; +}; +#endif + /* Avoid pulling in all the include files for no need */ struct termios; struct winsize; @@ -102,6 +112,13 @@ struct passwd *pw_scan(const char *_line, int _flags); const char *pw_tempname(void); int pw_tmp(int _mfd); #endif + +#ifdef _SYS_PARAM_H_ +struct pidfh *pidfile_open(const char *path, mode_t mode, pid_t *pidptr); +int pidfile_write(struct pidfh *pfh); +int pidfile_close(struct pidfh *pfh); +int pidfile_remove(struct pidfh *pfh); +#endif __END_DECLS #define UU_LOCK_INUSE (1) diff --git a/lib/libutil/pidfile.3 b/lib/libutil/pidfile.3 new file mode 100644 index 0000000..4ae7067 --- /dev/null +++ b/lib/libutil/pidfile.3 @@ -0,0 +1,227 @@ +.\" Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org> +.\" 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. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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. +.\" +.\" $FreeBSD$ +.\" +.Dd August 22, 2005 +.Dt PIDFILE 3 +.Os +.Sh NAME +.Nm pidfile_open , +.Nm pidfile_write , +.Nm pidfile_close , +.Nm pidfile_remove +.Nd library for PID files handling +.Sh LIBRARY +.Lb libutil +.Sh SYNOPSIS +.In sys/param.h +.In libutil.h +.Ft struct pidfh * +.Fn pidfile_open "const char *path" "mode_t mode" "pid_t *pidptr" +.Ft int +.Fn pidfile_write "struct pidfh *pfh" +.Ft int +.Fn pidfile_close "struct pidfh *pfh" +.Ft int +.Fn pidfile_remove "struct pidfh *pfh" +.Sh DESCRIPTION +The +.Nm libpidfile +library provides functions for daemons to handle file with PID. +It uses +.Xr flock 2 +to lock pidfile and detect already running daemons. +.Pp +The +.Fn pidfile_open +function opens (or creates) a file specified by +.Fa path +argument and locks it with +.Xr flock 2 +syscall. +If file can not be locked, PID of already running daemon is returned in +.Fa pidptr +argument (if it is not NULL). +The function doesn't write process' PID into the file here, so it can be +used before fork()ing and exit with proper error message when needed. +If +.Fa path +argument is NULL, +.Pa /var/run/<progname>.pid +file will be used. +.Pp +The +.Fn pidfile_write +function write process' PID into previously opened file. +.Pp +The +.Fn pidfile_close +function closes pidfile. +It should be used after daemon fork()s to start a child process. +.Pp +The +.Fn pidfile_remove +function closes and removes pidfile. +.Sh RETURN VALUES +The +.Fn pidfile_open +function return a valid pointer to a pidfh structure on success or +.Dv NULL +if an error occurs. +If an error does occur, +.Va errno +will be set. +.Rv -std pidfile_write pidfile_close pidfile_remove +.Sh EXAMPLES +The following example shows in which order those functions should be used. +.Bd -literal +struct pidfh *pfh; +pid_t otherpid, childpid; + +pfh = pidfile_open("/var/run/daemon.pid", 0644, &otherpid); +if (pfh == NULL) { + if (errno == EEXIST) + errx(EXIT_FAILURE, "Daemon already running, pid: %d.", otherpid); + /* If we cannot create pidfile from other reasons, only warn. */ + warn("Cannot open or create pidfile"); +} + +if (daemon(0, 0) == -1) { + warn("Cannot daemonize"); + pidfile_remove(pfh); + exit(EXIT_FAILURE); +} + +pidfile_write(pfh); + +for (;;) { + /* Do work. */ + childpid = fork(); + switch (childpid) { + case -1: + syslog(LOG_ERR, "Cannot fork(): %s.", strerror(errno)); + break; + case 0: + pidfile_close(pfh); + /* Do child work. */ + break; + default: + syslog(LOG_INFO, "Child %d started.", childpid); + break; + } +} + +pidfile_remove(pfh); +exit(EXIT_SUCCESS); +.Ed +.Sh ERRORS +The +.Fn pidfile_open +function will fail if: +.Bl -tag -width Er +.It Bq Er EEXIST +Some process already holds the lock on the given pidfile, which means, +daemon is already running. +.It Bq Er ENAMETOOLONG +Specified pidfile's name is too long. +.It Bq Er EINVAL +Some process already holds the lock on the given pidfile, but PID read +from there is invalid. +.El +.Pp +The +.Fn pidfile_open +function may also fail and set +.Va errno +for any errors specified for the +.Xr fstat 2 , +.Xr open 2 , +.Xr read 2 +routines. +.Pp +The +.Fn pidfile_write +function will fail if: +.Bl -tag -width Er +.It Bq Er EDOOFUS +Inproper function use. +Probably called before +.Fn pidfile_open . +.El +.Pp +The +.Fn pidfile_write +function may also fail and set +.Va errno +for any errors specified for the +.Xr fstat 2 , +.Xr ftruncate 2 , +.Xr write 2 +routines. +.Pp +The +.Fn pidfile_close +function may fail and set +.Va errno +for any errors specified for the +.Xr close 2 , +.Xr fstat 2 +routines. +.Pp +The +.Fn pidfile_remove +function will fail if: +.Bl -tag -width Er +.It Bq Er EDOOFUS +Inproper function use. +Probably called not from the process which made +.Fn pidfile_write . +.El +.Pp +The +.Fn pidfile_remove +function may also fail and set +.Va errno +for any errors specified for the +.Xr close 2 , +.Xr flock 2 , +.Xr fstat 2 , +.Xr write 2 , +.Xr unlink 2 +routines. +.Pp +.Sh SEE ALSO +.Xr flock 2 , +.Xr open 2 , +.Xr daemon 3 +.Sh AUTHORS +.An -nosplit +The +.Xr pidfile 3 +functionality is based on ideas from +.An John-Mark Gurney Aq jmg@FreeBSD.org . +.Pp +The code and manual page was written by +.An Pawel Jakub Dawidek Aq pjd@FreeBSD.org . diff --git a/lib/libutil/pidfile.c b/lib/libutil/pidfile.c new file mode 100644 index 0000000..0b8ade1 --- /dev/null +++ b/lib/libutil/pidfile.c @@ -0,0 +1,246 @@ +/*- + * Copyright (c) 2005 Pawel Jakub Dawidek <pjd@FreeBSD.org> + * 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. + * + * THIS SOFTWARE IS PROVIDED BY THE AUTHORS 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 AUTHORS 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. + */ + +#include <sys/cdefs.h> +__FBSDID("$FreeBSD$"); + +#include <sys/param.h> +#include <sys/file.h> +#include <sys/stat.h> + +#include <stdio.h> +#include <stdlib.h> +#include <unistd.h> +#include <fcntl.h> +#include <string.h> +#include <err.h> +#include <errno.h> +#include <libutil.h> + +static int _pidfile_remove(struct pidfh *pfh, int freeit); + +static int +pidfile_verify(struct pidfh *pfh) +{ + struct stat sb; + int fd; + + if (pfh == NULL || pfh->pf_fd == -1) + return (EDOOFUS); + /* + * Check remembered descriptor. + */ + if (fstat(pfh->pf_fd, &sb) == -1) + return (errno); + if (sb.st_dev != pfh->pf_dev || sb.st_ino != pfh->pf_ino) + return (EDOOFUS); + return (0); +} + +static int +pidfile_read(const char *path, pid_t *pidptr) +{ + char buf[16], *endptr; + int error, fd, i; + + fd = open(path, O_RDONLY); + if (fd == -1) + return (errno); + + i = read(fd, buf, sizeof(buf) - 1); + error = errno; /* Remember errno in case close() wants to change it. */ + close(fd); + if (i == -1) + return (error); + buf[i] = '\0'; + + *pidptr = strtol(buf, &endptr, 10); + if (endptr != &buf[i]) + return (EINVAL); + + return (0); +} + +struct pidfh * +pidfile_open(const char *path, mode_t mode, pid_t *pidptr) +{ + struct pidfh *pfh; + struct stat sb; + int error, fd; + + pfh = malloc(sizeof(*pfh)); + if (pfh == NULL) + return (NULL); + + if (path == NULL) { + snprintf(pfh->pf_path, sizeof(pfh->pf_path), "/var/run/%s.pid", + getprogname()); + } else { + strlcpy(pfh->pf_path, path, sizeof(pfh->pf_path)); + } + if (strlen(pfh->pf_path) == sizeof(pfh->pf_path) - 1) { + free(pfh); + errno = ENAMETOOLONG; + return (NULL); + } + + /* + * Open the PID file and obtain exclusive lock. + * We truncate PID file here only to remove old PID immediatelly, + * PID file will be truncated again in pidfile_write(), so + * pidfile_write() can be called multiple times. + */ + fd = open(pfh->pf_path, + O_WRONLY | O_CREAT | O_EXLOCK | O_TRUNC | O_NONBLOCK, mode); + if (fd == -1) { + if (errno == EWOULDBLOCK && pidptr != NULL) { + errno = pidfile_read(pfh->pf_path, pidptr); + if (errno == 0) + errno = EEXIST; + } + free(pfh); + return (NULL); + } + /* + * Remember file information, so in pidfile_write() we are sure we write + * to the proper descriptor. + */ + if (fstat(fd, &sb) == -1) { + error = errno; + unlink(pfh->pf_path); + close(fd); + free(pfh); + errno = error; + return (NULL); + } + + pfh->pf_fd = fd; + pfh->pf_dev = sb.st_dev; + pfh->pf_ino = sb.st_ino; + + return (pfh); +} + +int +pidfile_write(struct pidfh *pfh) +{ + struct stat sb; + char pidstr[16]; + int error, fd; + + /* + * Check remembered descriptor, so we don't overwrite some other + * file if pidfile was closed and descriptor reused. + */ + errno = pidfile_verify(pfh); + if (errno != 0) { + /* + * Don't close descriptor, because we are not sure if it's ours. + */ + return (-1); + } + fd = pfh->pf_fd; + + /* + * Truncate PID file, so multiple calls of pidfile_write() are allowed. + */ + if (ftruncate(fd, 0) == -1) { + error = errno; + _pidfile_remove(pfh, 0); + errno = error; + return (-1); + } + + snprintf(pidstr, sizeof(pidstr), "%u", getpid()); + if (write(fd, pidstr, strlen(pidstr)) != (ssize_t)strlen(pidstr)) { + error = errno; + _pidfile_remove(pfh, 0); + errno = error; + return (-1); + } + + return (0); +} + +int +pidfile_close(struct pidfh *pfh) +{ + int error; + + error = pidfile_verify(pfh); + if (error != 0) { + errno = error; + return (-1); + } + + if (close(pfh->pf_fd) == -1) + error = errno; + free(pfh); + if (error != 0) { + errno = error; + return (-1); + } + return (0); +} + +static int +_pidfile_remove(struct pidfh *pfh, int freeit) +{ + int error; + + error = pidfile_verify(pfh); + if (error != 0) { + errno = error; + return (-1); + } + + if (unlink(pfh->pf_path) == -1) + error = errno; + if (flock(pfh->pf_fd, LOCK_UN) == -1) { + if (error == 0) + error = errno; + } + if (close(pfh->pf_fd) == -1) { + if (error == 0) + error = errno; + } + if (freeit) + free(pfh); + else + pfh->pf_fd = -1; + if (error != 0) { + errno = error; + return (-1); + } + return (0); +} + +int +pidfile_remove(struct pidfh *pfh) +{ + + return (_pidfile_remove(pfh, 1)); +} |