From 9667055264d5c60d857fd6c525793c083c1aad06 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Dag-Erling=20Sm=C3=B8rgrav?= Date: Thu, 10 May 2007 14:43:31 +0000 Subject: [PATCH] I'm tired of seeing this done incorrectly and non-portably, so add a flopen(3) function which reliably opens and locks a file. MFC after: 3 weeks --- lib/libutil/Makefile | 12 +++--- lib/libutil/flopen.3 | 79 +++++++++++++++++++++++++++++++++++++ lib/libutil/flopen.c | 91 +++++++++++++++++++++++++++++++++++++++++++ lib/libutil/libutil.h | 1 + 4 files changed, 177 insertions(+), 6 deletions(-) create mode 100644 lib/libutil/flopen.3 create mode 100644 lib/libutil/flopen.c diff --git a/lib/libutil/Makefile b/lib/libutil/Makefile index 9ce21c0aca58..ce641538498b 100644 --- a/lib/libutil/Makefile +++ b/lib/libutil/Makefile @@ -8,11 +8,11 @@ SHLIBDIR?= /lib LIB= util SHLIB_MAJOR= 6 -SRCS= _secure_path.c auth.c fparseln.c humanize_number.c kld.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 \ - pidfile.c property.c pty.c pw_util.c realhostname.c stub.c \ - trimdomain.c uucplock.c +SRCS= _secure_path.c auth.c flopen.c fparseln.c humanize_number.c \ + kld.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 pidfile.c property.c pty.c pw_util.c realhostname.c \ + stub.c trimdomain.c uucplock.c INCS= libutil.h login_cap.h CFLAGS+= -DLIBC_SCCS @@ -27,7 +27,7 @@ MAN+= kld.3 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 \ - pidfile.3 + pidfile.3 flopen.3 MAN+= login.conf.5 auth.conf.5 MLINKS+= kld.3 kld_isloaded.3 kld.3 kld_load.3 MLINKS+= property.3 properties_read.3 property.3 properties_free.3 diff --git a/lib/libutil/flopen.3 b/lib/libutil/flopen.3 new file mode 100644 index 000000000000..53a2132aec4b --- /dev/null +++ b/lib/libutil/flopen.3 @@ -0,0 +1,79 @@ +.\"- +.\" Copyright (c) 2007 Dag-Erling Coïdan Smørgrav +.\" 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 AUTHOR 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 AUTHOR 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 May 10, 2007 +.Dt FLOPEN 3 +.Os +.Sh NAME +.Nm flopen +.Nd "Reliably open and lock a file" +.Sh LIBRARY +.Lb libutil +.Sh SYNOPSIS +.In sys/fcntl.h +.In libutil.h +.Ft int +.Fn flopen "const char *path" "int flags" +.Ft int +.Fn flopen "const char *path" "int flags" "mode_t mode" +.Sh DESCRIPTION +The +.Fn flopen +function opens or creates a file and acquires an exclusive lock on it. +It is essentially equivalent with calling +.Fn open +with the same parameters followed by +.Fn flock +with an +.Va operation +argument of +.Dv LOCK_EX , +except that +.Fn flopen +will attempt to detect and handle races that may occur between opening +/ creating the file and locking it. +Thus, it is well suited for opening lock files, PID files, spool +files, mailboxes and other kinds of files which are used for +synchronization between processes. +.Pp +As with +.Fn flopen , +the additional +.Va mode +argument is required if +.Va flags +includes +.Dv O_CREAT . +.Sh SEE ALSO +.Xr flock 2 , +.Xr open 2 +.Sh AUTHORS +.An -nosplit +The +.Nm +function and this manual page were written by +.An Dag-Erling Sm\(/orgrav Aq des@FreeBSD.org . diff --git a/lib/libutil/flopen.c b/lib/libutil/flopen.c new file mode 100644 index 000000000000..66d4e470f901 --- /dev/null +++ b/lib/libutil/flopen.c @@ -0,0 +1,91 @@ +/*- + * Copyright (c) 2007 Dag-Erling Coïdan Smørgrav + * 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 + * in this position and unchanged. + * 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 AUTHOR 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 AUTHOR 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. + * + * $Id$ + */ + +#include +__FBSDID("$FreeBSD$"); + +#include + +#include +#include +#include + +int +flopen(const char *path, int flags, ...) +{ + struct stat sb, fsb; + mode_t mode; + int fd, serrno; + +#ifdef O_EXLOCK + flags &= ~O_EXLOCK; +#endif + + if (flags & O_CREAT) { + va_list ap; + + va_start(ap, flags); + mode = va_arg(ap, int); /* mode_t promoted to int */ + va_end(ap); + } else { + mode = 0; + } + + for (;;) { + if ((fd = open(path, flags, mode)) == -1) + /* non-existent or no access */ + return (-1); + if (flock(fd, LOCK_EX) == -1) { + /* unsupported or interrupted */ + serrno = errno; + close(fd); + errno = serrno; + return (-1); + } + if (stat(path, &sb) == -1) { + /* disappeared from under our feet */ + close(fd); + continue; + } + if (fstat(fd, &fsb) == -1) { + /* can't happen [tm] */ + serrno = errno; + close(fd); + errno = serrno; + return (-1); + } + if (sb.st_dev != fsb.st_dev || + sb.st_ino != fsb.st_ino) { + /* changed under our feet */ + close(fd); + continue; + } + return (fd); + } +} diff --git a/lib/libutil/libutil.h b/lib/libutil/libutil.h index aefff0c609c9..4a89856aaf11 100644 --- a/lib/libutil/libutil.h +++ b/lib/libutil/libutil.h @@ -70,6 +70,7 @@ void clean_environment(const char * const *_white, const char * const *_more_white); int extattr_namespace_to_string(int _attrnamespace, char **_string); int extattr_string_to_namespace(const char *_string, int *_attrnamespace); +int flopen(const char *_path, int _flags, mode_t _mode); void login(struct utmp *_ut); int login_tty(int _fd); int logout(const char *_line);