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+/* dotlock.c - dotfile locking
+ * Copyright (C) 1998, 2000, 2001, 2003, 2004,
+ * 2005, 2006, 2008, 2010, 2011 Free Software Foundation, Inc.
+ *
+ * This file is part of GnuPG.
+ *
+ * GnuPG is free software; you can redistribute and/or modify this
+ * part of GnuPG under the terms of either
+ *
+ * - the GNU Lesser General Public License as published by the Free
+ * Software Foundation; either version 3 of the License, or (at
+ * your option) any later version.
+ *
+ * or
+ *
+ * - the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at
+ * your option) any later version.
+ *
+ * or both in parallel, as here.
+ *
+ * GnuPG is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copies of the GNU General Public License
+ * and the GNU Lesser General Public License along with this program;
+ * if not, see <https://www.gnu.org/licenses/>.
+ *
+ * ALTERNATIVELY, this file may be distributed under the terms of the
+ * following license, in which case the provisions of this license are
+ * required INSTEAD OF the GNU Lesser General License or the GNU
+ * General Public License. If you wish to allow use of your version of
+ * this file only under the terms of the GNU Lesser General License or
+ * the GNU General Public License, and not to allow others to use your
+ * version of this file under the terms of the following license,
+ * indicate your decision by deleting this paragraph and the license
+ * below.
+ *
+ * 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, and the entire permission notice in its entirety,
+ * including the disclaimer of warranties.
+ * 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. The name of the author may not be used to endorse or promote
+ * products derived from this software without specific prior
+ * written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED "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 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.
+ */
+
+/*
+ Overview:
+ =========
+
+ This module implements advisory file locking in a portable way.
+ Due to the problems with POSIX fcntl locking a separate lock file
+ is used. It would be possible to use fcntl locking on this lock
+ file and thus avoid the weird auto unlock bug of POSIX while still
+ having an unproved better performance of fcntl locking. However
+ there are still problems left, thus we resort to use a hardlink
+ which has the well defined property that a link call will fail if
+ the target file already exists.
+
+ Given that hardlinks are also available on NTFS file systems since
+ Windows XP; it will be possible to enhance this module to use
+ hardlinks even on Windows and thus allow Windows and Posix clients
+ to use locking on the same directory. This is not yet implemented;
+ instead we use a lockfile on Windows along with W32 style file
+ locking.
+
+ On FAT file systems hardlinks are not supported. Thus this method
+ does not work. Our solution is to use a O_EXCL locking instead.
+ Querying the type of the file system is not easy to do in a
+ portable way (e.g. Linux has a statfs, BSDs have a the same call
+ but using different structures and constants). What we do instead
+ is to check at runtime whether link(2) works for a specific lock
+ file.
+
+
+ How to use:
+ ===========
+
+ At program initialization time, the module should be explicitly
+ initialized:
+
+ dotlock_create (NULL, 0);
+
+ This installs an atexit handler and may also initialize mutex etc.
+ It is optional for non-threaded applications. Only the first call
+ has an effect. This needs to be done before any extra threads are
+ started.
+
+ To create a lock file (which prepares it but does not take the
+ lock) you do:
+
+ dotlock_t h
+
+ h = dotlock_create (fname, 0);
+ if (!h)
+ error ("error creating lock file: %s\n", strerror (errno));
+
+ It is important to handle the error. For example on a read-only
+ file system a lock can't be created (but is usually not needed).
+ FNAME is the file you want to lock; the actual lockfile is that
+ name with the suffix ".lock" appended. On success a handle to be
+ used with the other functions is returned or NULL on error. Note
+ that the handle shall only be used by one thread at a time. This
+ function creates a unique file temporary file (".#lk*") in the same
+ directory as FNAME and returns a handle for further operations.
+ The module keeps track of theses unique files so that they will be
+ unlinked using the atexit handler. If you don't need the lock file
+ anymore, you may also explicitly remove it with a call to:
+
+ dotlock_destroy (h);
+
+ To actually lock the file, you use:
+
+ if (dotlock_take (h, -1))
+ error ("error taking lock: %s\n", strerror (errno));
+
+ This function will wait until the lock is acquired. If an
+ unexpected error occurs if will return non-zero and set ERRNO. If
+ you pass (0) instead of (-1) the function does not wait in case the
+ file is already locked but returns -1 and sets ERRNO to EACCES.
+ Any other positive value for the second parameter is considered a
+ timeout valuie in milliseconds.
+
+ To release the lock you call:
+
+ if (dotlock_release (h))
+ error ("error releasing lock: %s\n", strerror (errno));
+
+ or, if the lock file is not anymore needed, you may just call
+ dotlock_destroy. However dotlock_release does some extra checks
+ before releasing the lock and prints diagnostics to help detecting
+ bugs.
+
+ If you want to explicitly destroy all lock files you may call
+
+ dotlock_remove_lockfiles ();
+
+ which is the core of the installed atexit handler. In case your
+ application wants to disable locking completely it may call
+
+ disable_locking ()
+
+ before any locks are created.
+
+ There are two convenience functions to store an integer (e.g. a
+ file descriptor) value with the handle:
+
+ void dotlock_set_fd (dotlock_t h, int fd);
+ int dotlock_get_fd (dotlock_t h);
+
+ If nothing has been stored dotlock_get_fd returns -1.
+
+
+
+ How to build:
+ =============
+
+ This module was originally developed for GnuPG but later changed to
+ allow its use without any GnuPG dependency. If you want to use it
+ with you application you may simply use it and it should figure out
+ most things automagically.
+
+ You may use the common config.h file to pass macros, but take care
+ to pass -DHAVE_CONFIG_H to the compiler. Macros used by this
+ module are:
+
+ DOTLOCK_USE_PTHREAD - Define if POSIX threads are in use.
+
+ DOTLOCK_GLIB_LOGGING - Define this to use Glib logging functions.
+
+ DOTLOCK_EXT_SYM_PREFIX - Prefix all external symbols with the
+ string to which this macro evaluates.
+
+ GNUPG_MAJOR_VERSION - Defined when used by GnuPG.
+
+ HAVE_DOSISH_SYSTEM - Defined for Windows etc. Will be
+ automatically defined if a the target is
+ Windows.
+
+ HAVE_POSIX_SYSTEM - Internally defined to !HAVE_DOSISH_SYSTEM.
+
+ HAVE_SIGNAL_H - Should be defined on Posix systems. If config.h
+ is not used defaults to defined.
+
+ DIRSEP_C - Separation character for file name parts.
+ Usually not redefined.
+
+ EXTSEP_S - Separation string for file name suffixes.
+ Usually not redefined.
+
+ HAVE_W32CE_SYSTEM - Currently only used by GnuPG.
+
+ Note that there is a test program t-dotlock which has compile
+ instructions at its end. At least for SMBFS and CIFS it is
+ important that 64 bit versions of stat are used; most programming
+ environments do this these days, just in case you want to compile
+ it on the command line, remember to pass -D_FILE_OFFSET_BITS=64
+
+
+ Bugs:
+ =====
+
+ On Windows this module is not yet thread-safe.
+
+
+ Miscellaneous notes:
+ ====================
+
+ On hardlinks:
+ - Hardlinks are supported under Windows with NTFS since XP/Server2003.
+ - In Linux 2.6.33 both SMBFS and CIFS seem to support hardlinks.
+ - NFS supports hard links. But there are solvable problems.
+ - FAT does not support links
+
+ On the file locking API:
+ - CIFS on Linux 2.6.33 supports several locking methods.
+ SMBFS seems not to support locking. No closer checks done.
+ - NFS supports Posix locks. flock is emulated in the server.
+ However there are a couple of problems; see below.
+ - FAT does not support locks.
+ - An advantage of fcntl locking is that R/W locks can be
+ implemented which is not easy with a straight lock file.
+
+ On O_EXCL:
+ - Does not work reliable on NFS
+ - Should work on CIFS and SMBFS but how can we delete lockfiles?
+
+ On NFS problems:
+ - Locks vanish if the server crashes and reboots.
+ - Client crashes keep the lock in the server until the client
+ re-connects.
+ - Communication problems may return unreliable error codes. The
+ MUA Postfix's workaround is to compare the link count after
+ seeing an error for link. However that gives a race. If using a
+ unique file to link to a lockfile and using stat to check the
+ link count instead of looking at the error return of link(2) is
+ the best solution.
+ - O_EXCL seems to have a race and may re-create a file anyway.
+
+*/
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+/* Some quick replacements for stuff we usually expect to be defined
+ in config.h. Define HAVE_POSIX_SYSTEM for better readability. */
+#if !defined (HAVE_DOSISH_SYSTEM) && defined(_WIN32)
+# define HAVE_DOSISH_SYSTEM 1
+#endif
+#if !defined (HAVE_DOSISH_SYSTEM) && !defined (HAVE_POSIX_SYSTEM)
+# define HAVE_POSIX_SYSTEM 1
+#endif
+
+/* With no config.h assume that we have sitgnal.h. */
+#if !defined (HAVE_CONFIG_H) && defined (HAVE_POSIX_SYSTEM)
+# define HAVE_SIGNAL_H 1
+#endif
+
+/* Standard headers. */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <ctype.h>
+#include <errno.h>
+#include <unistd.h>
+#ifdef HAVE_DOSISH_SYSTEM
+# define WIN32_LEAN_AND_MEAN /* We only need the OS core stuff. */
+# include <windows.h>
+#else
+# include <sys/types.h>
+# include <sys/stat.h>
+# include <sys/utsname.h>
+#endif
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#ifdef HAVE_SIGNAL_H
+# include <signal.h>
+#endif
+#ifdef DOTLOCK_USE_PTHREAD
+# include <pthread.h>
+#endif
+
+#ifdef DOTLOCK_GLIB_LOGGING
+# include <glib.h>
+#endif
+
+#ifdef GNUPG_MAJOR_VERSION
+# include "util.h"
+# include "common-defs.h"
+# include "stringhelp.h" /* For stpcpy and w32_strerror. */
+#endif
+#ifdef HAVE_W32CE_SYSTEM
+# include "utf8conv.h" /* WindowsCE requires filename conversion. */
+#endif
+
+#include "dotlock.h"
+
+
+/* Define constants for file name construction. */
+#if !defined(DIRSEP_C) && !defined(EXTSEP_S)
+# ifdef HAVE_DOSISH_SYSTEM
+# define DIRSEP_C '\\'
+# define EXTSEP_S "."
+#else
+# define DIRSEP_C '/'
+# define EXTSEP_S "."
+# endif
+#endif
+
+/* In GnuPG we use wrappers around the malloc functions. If they are
+ not defined we assume that this code is used outside of GnuPG and
+ fall back to the regular malloc functions. */
+#ifndef xtrymalloc
+# define xtrymalloc(a) malloc ((a))
+# define xtrycalloc(a,b) calloc ((a), (b))
+# define xfree(a) free ((a))
+#endif
+
+/* Wrapper to set ERRNO (required for W32CE). */
+#ifdef GPG_ERROR_VERSION
+# define my_set_errno(e) gpg_err_set_errno ((e))
+#else
+# define my_set_errno(e) do { errno = (e); } while (0)
+#endif
+
+/* Gettext macro replacement. */
+#ifndef _
+# define _(a) (a)
+#endif
+
+#ifdef GNUPG_MAJOR_VERSION
+# define my_info_0(a) log_info ((a))
+# define my_info_1(a,b) log_info ((a), (b))
+# define my_info_2(a,b,c) log_info ((a), (b), (c))
+# define my_info_3(a,b,c,d) log_info ((a), (b), (c), (d))
+# define my_error_0(a) log_error ((a))
+# define my_error_1(a,b) log_error ((a), (b))
+# define my_error_2(a,b,c) log_error ((a), (b), (c))
+# define my_debug_1(a,b) log_debug ((a), (b))
+# define my_fatal_0(a) log_fatal ((a))
+#elif defined (DOTLOCK_GLIB_LOGGING)
+# define my_info_0(a) g_message ((a))
+# define my_info_1(a,b) g_message ((a), (b))
+# define my_info_2(a,b,c) g_message ((a), (b), (c))
+# define my_info_3(a,b,c,d) g_message ((a), (b), (c), (d))
+# define my_error_0(a) g_warning ((a))
+# define my_error_1(a,b) g_warning ((a), (b))
+# define my_error_2(a,b,c) g_warning ((a), (b), (c))
+# define my_debug_1(a,b) g_debug ((a), (b))
+# define my_fatal_0(a) g_error ((a))
+#else
+# define my_info_0(a) fprintf (stderr, (a))
+# define my_info_1(a,b) fprintf (stderr, (a), (b))
+# define my_info_2(a,b,c) fprintf (stderr, (a), (b), (c))
+# define my_info_3(a,b,c,d) fprintf (stderr, (a), (b), (c), (d))
+# define my_error_0(a) fprintf (stderr, (a))
+# define my_error_1(a,b) fprintf (stderr, (a), (b))
+# define my_error_2(a,b,c) fprintf (stderr, (a), (b), (c))
+# define my_debug_1(a,b) fprintf (stderr, (a), (b))
+# define my_fatal_0(a) do { fprintf (stderr,(a)); fflush (stderr); \
+ abort (); } while (0)
+#endif
+
+
+
+
+
+/* The object describing a lock. */
+struct dotlock_handle
+{
+ struct dotlock_handle *next;
+ char *lockname; /* Name of the actual lockfile. */
+ unsigned int locked:1; /* Lock status. */
+ unsigned int disable:1; /* If true, locking is disabled. */
+ unsigned int use_o_excl:1; /* Use open (O_EXCL) for locking. */
+
+ int extra_fd; /* A place for the caller to store an FD. */
+
+#ifdef HAVE_DOSISH_SYSTEM
+ HANDLE lockhd; /* The W32 handle of the lock file. */
+#else /*!HAVE_DOSISH_SYSTEM */
+ char *tname; /* Name of the lockfile template. */
+ size_t nodename_off; /* Offset in TNAME of the nodename part. */
+ size_t nodename_len; /* Length of the nodename part. */
+#endif /*!HAVE_DOSISH_SYSTEM */
+};
+
+
+/* A list of all lock handles. The volatile attribute might help
+ if used in an atexit handler. Note that [UN]LOCK_all_lockfiles
+ must not change ERRNO. */
+static volatile dotlock_t all_lockfiles;
+#ifdef DOTLOCK_USE_PTHREAD
+static pthread_mutex_t all_lockfiles_mutex = PTHREAD_MUTEX_INITIALIZER;
+# define LOCK_all_lockfiles() do { \
+ if (pthread_mutex_lock (&all_lockfiles_mutex)) \
+ my_fatal_0 ("locking all_lockfiles_mutex failed\n"); \
+ } while (0)
+# define UNLOCK_all_lockfiles() do { \
+ if (pthread_mutex_unlock (&all_lockfiles_mutex)) \
+ my_fatal_0 ("unlocking all_lockfiles_mutex failed\n"); \
+ } while (0)
+#else /*!DOTLOCK_USE_PTHREAD*/
+# define LOCK_all_lockfiles() do { } while (0)
+# define UNLOCK_all_lockfiles() do { } while (0)
+#endif /*!DOTLOCK_USE_PTHREAD*/
+
+/* If this has the value true all locking is disabled. */
+static int never_lock;
+
+
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* FIXME: For use in GnuPG this can be replaced by
+ * gnupg_w32_set_errno. */
+static int
+map_w32_to_errno (DWORD w32_err)
+{
+ switch (w32_err)
+ {
+ case 0:
+ return 0;
+
+ case ERROR_FILE_NOT_FOUND:
+ return ENOENT;
+
+ case ERROR_PATH_NOT_FOUND:
+ return ENOENT;
+
+ case ERROR_ACCESS_DENIED:
+ return EPERM;
+
+ case ERROR_INVALID_HANDLE:
+ case ERROR_INVALID_BLOCK:
+ return EINVAL;
+
+ case ERROR_NOT_ENOUGH_MEMORY:
+ return ENOMEM;
+
+ case ERROR_NO_DATA:
+ case ERROR_BROKEN_PIPE:
+ return EPIPE;
+
+ default:
+ return EIO;
+ }
+}
+#endif /*HAVE_DOSISH_SYSTEM*/
+
+
+#ifdef HAVE_W32_SYSTEM
+static int
+any8bitchar (const char *string)
+{
+ if (string)
+ for ( ; *string; string++)
+ if ((*string & 0x80))
+ return 1;
+ return 0;
+}
+#endif /*HAVE_W32_SYSTEM*/
+
+
+
+
+/* Entirely disable all locking. This function should be called
+ before any locking is done. It may be called right at startup of
+ the process as it only sets a global value. */
+void
+dotlock_disable (void)
+{
+ never_lock = 1;
+}
+
+
+#ifdef HAVE_POSIX_SYSTEM
+static int
+maybe_deadlock (dotlock_t h)
+{
+ dotlock_t r;
+ int res = 0;
+
+ LOCK_all_lockfiles ();
+ for (r=all_lockfiles; r; r = r->next)
+ {
+ if ( r != h && r->locked )
+ {
+ res = 1;
+ break;
+ }
+ }
+ UNLOCK_all_lockfiles ();
+ return res;
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+/* Read the lock file and return the pid, returns -1 on error. True
+ will be stored in the integer at address SAME_NODE if the lock file
+ has been created on the same node. */
+#ifdef HAVE_POSIX_SYSTEM
+static int
+read_lockfile (dotlock_t h, int *same_node )
+{
+ char buffer_space[10+1+70+1]; /* 70 is just an estimated value; node
+ names are usually shorter. */
+ int fd;
+ int pid = -1;
+ char *buffer, *p;
+ size_t expected_len;
+ int res, nread;
+
+ *same_node = 0;
+ expected_len = 10 + 1 + h->nodename_len + 1;
+ if ( expected_len >= sizeof buffer_space)
+ {
+ buffer = xtrymalloc (expected_len);
+ if (!buffer)
+ return -1;
+ }
+ else
+ buffer = buffer_space;
+
+ if ( (fd = open (h->lockname, O_RDONLY)) == -1 )
+ {
+ int e = errno;
+ my_info_2 ("error opening lockfile '%s': %s\n",
+ h->lockname, strerror(errno) );
+ if (buffer != buffer_space)
+ xfree (buffer);
+ my_set_errno (e); /* Need to return ERRNO here. */
+ return -1;
+ }
+
+ p = buffer;
+ nread = 0;
+ do
+ {
+ res = read (fd, p, expected_len - nread);
+ if (res == -1 && errno == EINTR)
+ continue;
+ if (res < 0)
+ {
+ int e = errno;
+ my_info_1 ("error reading lockfile '%s'\n", h->lockname );
+ close (fd);
+ if (buffer != buffer_space)
+ xfree (buffer);
+ my_set_errno (e);
+ return -1;
+ }
+ p += res;
+ nread += res;
+ }
+ while (res && nread != expected_len);
+ close(fd);
+
+ if (nread < 11)
+ {
+ my_info_1 ("invalid size of lockfile '%s'\n", h->lockname);
+ if (buffer != buffer_space)
+ xfree (buffer);
+ my_set_errno (EINVAL);
+ return -1;
+ }
+
+ if (buffer[10] != '\n'
+ || (buffer[10] = 0, pid = atoi (buffer)) == -1
+ || !pid )
+ {
+ my_error_2 ("invalid pid %d in lockfile '%s'\n", pid, h->lockname);
+ if (buffer != buffer_space)
+ xfree (buffer);
+ my_set_errno (EINVAL);
+ return -1;
+ }
+
+ if (nread == expected_len
+ && !memcmp (h->tname+h->nodename_off, buffer+11, h->nodename_len)
+ && buffer[11+h->nodename_len] == '\n')
+ *same_node = 1;
+
+ if (buffer != buffer_space)
+ xfree (buffer);
+ return pid;
+}
+#endif /*HAVE_POSIX_SYSTEM */
+
+
+/* Check whether the file system which stores TNAME supports
+ hardlinks. Instead of using the non-portable statsfs call which
+ differs between various Unix versions, we do a runtime test.
+ Returns: 0 supports hardlinks; 1 no hardlink support, -1 unknown
+ (test error). */
+#ifdef HAVE_POSIX_SYSTEM
+static int
+use_hardlinks_p (const char *tname)
+{
+ char *lname;
+ struct stat sb;
+ unsigned int nlink;
+ int res;
+
+ if (stat (tname, &sb))
+ return -1;
+ nlink = (unsigned int)sb.st_nlink;
+
+ lname = xtrymalloc (strlen (tname) + 1 + 1);
+ if (!lname)
+ return -1;
+ strcpy (lname, tname);
+ strcat (lname, "x");
+
+ /* We ignore the return value of link() because it is unreliable. */
+ (void) link (tname, lname);
+
+ if (stat (tname, &sb))
+ res = -1; /* Ooops. */
+ else if (sb.st_nlink == nlink + 1)
+ res = 0; /* Yeah, hardlinks are supported. */
+ else
+ res = 1; /* No hardlink support. */
+
+ unlink (lname);
+ xfree (lname);
+ return res;
+}
+#endif /*HAVE_POSIX_SYSTEM */
+
+
+
+#ifdef HAVE_POSIX_SYSTEM
+/* Locking core for Unix. It used a temporary file and the link
+ system call to make locking an atomic operation. */
+static dotlock_t
+dotlock_create_unix (dotlock_t h, const char *file_to_lock)
+{
+ int fd = -1;
+ char pidstr[16];
+ const char *nodename;
+ const char *dirpart;
+ int dirpartlen;
+ struct utsname utsbuf;
+ size_t tnamelen;
+
+ snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid() );
+
+ /* Create a temporary file. */
+ if ( uname ( &utsbuf ) )
+ nodename = "unknown";
+ else
+ nodename = utsbuf.nodename;
+
+ if ( !(dirpart = strrchr (file_to_lock, DIRSEP_C)) )
+ {
+ dirpart = EXTSEP_S;
+ dirpartlen = 1;
+ }
+ else
+ {
+ dirpartlen = dirpart - file_to_lock;
+ dirpart = file_to_lock;
+ }
+
+ LOCK_all_lockfiles ();
+ h->next = all_lockfiles;
+ all_lockfiles = h;
+
+ tnamelen = dirpartlen + 6 + 30 + strlen(nodename) + 10 + 1;
+ h->tname = xtrymalloc (tnamelen + 1);
+ if (!h->tname)
+ {
+ all_lockfiles = h->next;
+ UNLOCK_all_lockfiles ();
+ xfree (h);
+ return NULL;
+ }
+ h->nodename_len = strlen (nodename);
+
+ snprintf (h->tname, tnamelen, "%.*s/.#lk%p.", dirpartlen, dirpart, h );
+ h->nodename_off = strlen (h->tname);
+ snprintf (h->tname+h->nodename_off, tnamelen - h->nodename_off,
+ "%s.%d", nodename, (int)getpid ());
+
+ do
+ {
+ my_set_errno (0);
+ fd = open (h->tname, O_WRONLY|O_CREAT|O_EXCL,
+ S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR );
+ }
+ while (fd == -1 && errno == EINTR);
+
+ if ( fd == -1 )
+ {
+ int saveerrno = errno;
+ all_lockfiles = h->next;
+ UNLOCK_all_lockfiles ();
+ my_error_2 (_("failed to create temporary file '%s': %s\n"),
+ h->tname, strerror (errno));
+ xfree (h->tname);
+ xfree (h);
+ my_set_errno (saveerrno);
+ return NULL;
+ }
+ if ( write (fd, pidstr, 11 ) != 11 )
+ goto write_failed;
+ if ( write (fd, nodename, strlen (nodename) ) != strlen (nodename) )
+ goto write_failed;
+ if ( write (fd, "\n", 1 ) != 1 )
+ goto write_failed;
+ if ( close (fd) )
+ {
+ if ( errno == EINTR )
+ fd = -1;
+ goto write_failed;
+ }
+ fd = -1;
+
+ /* Check whether we support hard links. */
+ switch (use_hardlinks_p (h->tname))
+ {
+ case 0: /* Yes. */
+ break;
+ case 1: /* No. */
+ unlink (h->tname);
+ h->use_o_excl = 1;
+ break;
+ default:
+ {
+ int saveerrno = errno;
+ my_error_2 ("can't check whether hardlinks are supported for '%s': %s\n"
+ , h->tname, strerror (saveerrno));
+ my_set_errno (saveerrno);
+ }
+ goto write_failed;
+ }
+
+ h->lockname = xtrymalloc (strlen (file_to_lock) + 6 );
+ if (!h->lockname)
+ {
+ int saveerrno = errno;
+ all_lockfiles = h->next;
+ UNLOCK_all_lockfiles ();
+ unlink (h->tname);
+ xfree (h->tname);
+ xfree (h);
+ my_set_errno (saveerrno);
+ return NULL;
+ }
+ strcpy (stpcpy (h->lockname, file_to_lock), EXTSEP_S "lock");
+ UNLOCK_all_lockfiles ();
+
+ return h;
+
+ write_failed:
+ {
+ int saveerrno = errno;
+ all_lockfiles = h->next;
+ UNLOCK_all_lockfiles ();
+ my_error_2 (_("error writing to '%s': %s\n"), h->tname, strerror (errno));
+ if ( fd != -1 )
+ close (fd);
+ unlink (h->tname);
+ xfree (h->tname);
+ xfree (h);
+ my_set_errno (saveerrno);
+ }
+ return NULL;
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Locking core for Windows. This version does not need a temporary
+ file but uses the plain lock file along with record locking. We
+ create this file here so that we later only need to do the file
+ locking. For error reporting it is useful to keep the name of the
+ file in the handle. */
+static dotlock_t
+dotlock_create_w32 (dotlock_t h, const char *file_to_lock)
+{
+ LOCK_all_lockfiles ();
+ h->next = all_lockfiles;
+ all_lockfiles = h;
+
+ h->lockname = strconcat (file_to_lock, EXTSEP_S "lock", NULL);
+ if (!h->lockname)
+ {
+ all_lockfiles = h->next;
+ UNLOCK_all_lockfiles ();
+ xfree (h);
+ return NULL;
+ }
+
+ /* If would be nice if we would use the FILE_FLAG_DELETE_ON_CLOSE
+ along with FILE_SHARE_DELETE but that does not work due to a race
+ condition: Despite the OPEN_ALWAYS flag CreateFile may return an
+ error and we can't reliable create/open the lock file unless we
+ would wait here until it works - however there are other valid
+ reasons why a lock file can't be created and thus the process
+ would not stop as expected but spin until Windows crashes. Our
+ solution is to keep the lock file open; that does not harm. */
+ if (any8bitchar (h->lockname))
+ {
+ wchar_t *wname = utf8_to_wchar (h->lockname);
+
+ if (wname)
+ h->lockhd = CreateFileW (wname,
+ GENERIC_READ|GENERIC_WRITE,
+ FILE_SHARE_READ|FILE_SHARE_WRITE,
+ NULL, OPEN_ALWAYS, 0, NULL);
+ else
+ h->lockhd = INVALID_HANDLE_VALUE;
+ xfree (wname);
+ }
+ else
+ h->lockhd = CreateFileA (h->lockname,
+ GENERIC_READ|GENERIC_WRITE,
+ FILE_SHARE_READ|FILE_SHARE_WRITE,
+ NULL, OPEN_ALWAYS, 0, NULL);
+ if (h->lockhd == INVALID_HANDLE_VALUE)
+ {
+ int saveerrno = map_w32_to_errno (GetLastError ());
+ all_lockfiles = h->next;
+ UNLOCK_all_lockfiles ();
+ my_error_2 (_("can't create '%s': %s\n"), h->lockname, w32_strerror (-1));
+ xfree (h->lockname);
+ xfree (h);
+ my_set_errno (saveerrno);
+ return NULL;
+ }
+ return h;
+}
+#endif /*HAVE_DOSISH_SYSTEM*/
+
+
+/* Create a lockfile for a file name FILE_TO_LOCK and returns an
+ object of type dotlock_t which may be used later to actually acquire
+ the lock. A cleanup routine gets installed to cleanup left over
+ locks or other files used internally by the lock mechanism.
+
+ Calling this function with NULL does only install the atexit
+ handler and may thus be used to assure that the cleanup is called
+ after all other atexit handlers.
+
+ This function creates a lock file in the same directory as
+ FILE_TO_LOCK using that name and a suffix of ".lock". Note that on
+ POSIX systems a temporary file ".#lk.<hostname>.pid[.threadid] is
+ used.
+
+ FLAGS must be 0.
+
+ The function returns an new handle which needs to be released using
+ destroy_dotlock but gets also released at the termination of the
+ process. On error NULL is returned.
+ */
+
+dotlock_t
+dotlock_create (const char *file_to_lock, unsigned int flags)
+{
+ static int initialized;
+ dotlock_t h;
+
+ if ( !initialized )
+ {
+ atexit (dotlock_remove_lockfiles);
+ initialized = 1;
+ }
+
+ if ( !file_to_lock )
+ return NULL; /* Only initialization was requested. */
+
+ if (flags)
+ {
+ my_set_errno (EINVAL);
+ return NULL;
+ }
+
+ h = xtrycalloc (1, sizeof *h);
+ if (!h)
+ return NULL;
+ h->extra_fd = -1;
+
+ if (never_lock)
+ {
+ h->disable = 1;
+ LOCK_all_lockfiles ();
+ h->next = all_lockfiles;
+ all_lockfiles = h;
+ UNLOCK_all_lockfiles ();
+ return h;
+ }
+
+#ifdef HAVE_DOSISH_SYSTEM
+ return dotlock_create_w32 (h, file_to_lock);
+#else /*!HAVE_DOSISH_SYSTEM */
+ return dotlock_create_unix (h, file_to_lock);
+#endif /*!HAVE_DOSISH_SYSTEM*/
+}
+
+
+
+/* Convenience function to store a file descriptor (or any other
+ integer value) in the context of handle H. */
+void
+dotlock_set_fd (dotlock_t h, int fd)
+{
+ h->extra_fd = fd;
+}
+
+/* Convenience function to retrieve a file descriptor (or any other
+ integer value) stored in the context of handle H. */
+int
+dotlock_get_fd (dotlock_t h)
+{
+ return h->extra_fd;
+}
+
+
+
+#ifdef HAVE_POSIX_SYSTEM
+/* Unix specific code of destroy_dotlock. */
+static void
+dotlock_destroy_unix (dotlock_t h)
+{
+ if (h->locked && h->lockname)
+ unlink (h->lockname);
+ if (h->tname && !h->use_o_excl)
+ unlink (h->tname);
+ xfree (h->tname);
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Windows specific code of destroy_dotlock. */
+static void
+dotlock_destroy_w32 (dotlock_t h)
+{
+ if (h->locked)
+ {
+ OVERLAPPED ovl;
+
+ memset (&ovl, 0, sizeof ovl);
+ UnlockFileEx (h->lockhd, 0, 1, 0, &ovl);
+ }
+ CloseHandle (h->lockhd);
+}
+#endif /*HAVE_DOSISH_SYSTEM*/
+
+
+/* Destroy the lock handle H and release the lock. */
+void
+dotlock_destroy (dotlock_t h)
+{
+ dotlock_t hprev, htmp;
+
+ if ( !h )
+ return;
+
+ /* First remove the handle from our global list of all locks. */
+ LOCK_all_lockfiles ();
+ for (hprev=NULL, htmp=all_lockfiles; htmp; hprev=htmp, htmp=htmp->next)
+ if (htmp == h)
+ {
+ if (hprev)
+ hprev->next = htmp->next;
+ else
+ all_lockfiles = htmp->next;
+ h->next = NULL;
+ break;
+ }
+ UNLOCK_all_lockfiles ();
+
+ /* Then destroy the lock. */
+ if (!h->disable)
+ {
+#ifdef HAVE_DOSISH_SYSTEM
+ dotlock_destroy_w32 (h);
+#else /* !HAVE_DOSISH_SYSTEM */
+ dotlock_destroy_unix (h);
+#endif /* HAVE_DOSISH_SYSTEM */
+ xfree (h->lockname);
+ }
+ xfree(h);
+}
+
+
+
+#ifdef HAVE_POSIX_SYSTEM
+/* Unix specific code of make_dotlock. Returns 0 on success and -1 on
+ error. */
+static int
+dotlock_take_unix (dotlock_t h, long timeout)
+{
+ int wtime = 0;
+ int sumtime = 0;
+ int pid;
+ int lastpid = -1;
+ int ownerchanged;
+ const char *maybe_dead="";
+ int same_node;
+ int saveerrno;
+
+ again:
+ if (h->use_o_excl)
+ {
+ /* No hardlink support - use open(O_EXCL). */
+ int fd;
+
+ do
+ {
+ my_set_errno (0);
+ fd = open (h->lockname, O_WRONLY|O_CREAT|O_EXCL,
+ S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR );
+ }
+ while (fd == -1 && errno == EINTR);
+
+ if (fd == -1 && errno == EEXIST)
+ ; /* Lock held by another process. */
+ else if (fd == -1)
+ {
+ saveerrno = errno;
+ my_error_2 ("lock not made: open(O_EXCL) of '%s' failed: %s\n",
+ h->lockname, strerror (saveerrno));
+ my_set_errno (saveerrno);
+ return -1;
+ }
+ else
+ {
+ char pidstr[16];
+
+ snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid());
+ if (write (fd, pidstr, 11 ) == 11
+ && write (fd, h->tname + h->nodename_off,h->nodename_len)
+ == h->nodename_len
+ && write (fd, "\n", 1) == 1
+ && !close (fd))
+ {
+ h->locked = 1;
+ return 0;
+ }
+ /* Write error. */
+ saveerrno = errno;
+ my_error_2 ("lock not made: writing to '%s' failed: %s\n",
+ h->lockname, strerror (errno));
+ close (fd);
+ unlink (h->lockname);
+ my_set_errno (saveerrno);
+ return -1;
+ }
+ }
+ else /* Standard method: Use hardlinks. */
+ {
+ struct stat sb;
+
+ /* We ignore the return value of link() because it is unreliable. */
+ (void) link (h->tname, h->lockname);
+
+ if (stat (h->tname, &sb))
+ {
+ saveerrno = errno;
+ my_error_1 ("lock not made: Oops: stat of tmp file failed: %s\n",
+ strerror (errno));
+ /* In theory this might be a severe error: It is possible
+ that link succeeded but stat failed due to changed
+ permissions. We can't do anything about it, though. */
+ my_set_errno (saveerrno);
+ return -1;
+ }
+
+ if (sb.st_nlink == 2)
+ {
+ h->locked = 1;
+ return 0; /* Okay. */
+ }
+ }
+
+ /* Check for stale lock files. */
+ if ( (pid = read_lockfile (h, &same_node)) == -1 )
+ {
+ if ( errno != ENOENT )
+ {
+ saveerrno = errno;
+ my_info_0 ("cannot read lockfile\n");
+ my_set_errno (saveerrno);
+ return -1;
+ }
+ my_info_0 ("lockfile disappeared\n");
+ goto again;
+ }
+ else if ( pid == getpid() && same_node )
+ {
+ my_info_0 ("Oops: lock already held by us\n");
+ h->locked = 1;
+ return 0; /* okay */
+ }
+ else if ( same_node && kill (pid, 0) && errno == ESRCH )
+ {
+ /* Note: It is unlikley that we get a race here unless a pid is
+ reused too fast or a new process with the same pid as the one
+ of the stale file tries to lock right at the same time as we. */
+ my_info_1 (_("removing stale lockfile (created by %d)\n"), pid);
+ unlink (h->lockname);
+ goto again;
+ }
+
+ if (lastpid == -1)
+ lastpid = pid;
+ ownerchanged = (pid != lastpid);
+
+ if (timeout)
+ {
+ struct timeval tv;
+
+ /* Wait until lock has been released. We use increasing retry
+ intervals of 50ms, 100ms, 200ms, 400ms, 800ms, 2s, 4s and 8s
+ but reset it if the lock owner meanwhile changed. */
+ if (!wtime || ownerchanged)
+ wtime = 50;
+ else if (wtime < 800)
+ wtime *= 2;
+ else if (wtime == 800)
+ wtime = 2000;
+ else if (wtime < 8000)
+ wtime *= 2;
+
+ if (timeout > 0)
+ {
+ if (wtime > timeout)
+ wtime = timeout;
+ timeout -= wtime;
+ }
+
+ sumtime += wtime;
+ if (sumtime >= 1500)
+ {
+ sumtime = 0;
+ my_info_3 (_("waiting for lock (held by %d%s) %s...\n"),
+ pid, maybe_dead, maybe_deadlock(h)? _("(deadlock?) "):"");
+ }
+
+
+ tv.tv_sec = wtime / 1000;
+ tv.tv_usec = (wtime % 1000) * 1000;
+ select (0, NULL, NULL, NULL, &tv);
+ goto again;
+ }
+
+ my_set_errno (EACCES);
+ return -1;
+}
+#endif /*HAVE_POSIX_SYSTEM*/
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Windows specific code of make_dotlock. Returns 0 on success and -1 on
+ error. */
+static int
+dotlock_take_w32 (dotlock_t h, long timeout)
+{
+ int wtime = 0;
+ int w32err;
+ OVERLAPPED ovl;
+
+ again:
+ /* Lock one byte at offset 0. The offset is given by OVL. */
+ memset (&ovl, 0, sizeof ovl);
+ if (LockFileEx (h->lockhd, (LOCKFILE_EXCLUSIVE_LOCK
+ | LOCKFILE_FAIL_IMMEDIATELY), 0, 1, 0, &ovl))
+ {
+ h->locked = 1;
+ return 0; /* okay */
+ }
+
+ w32err = GetLastError ();
+ if (w32err != ERROR_LOCK_VIOLATION)
+ {
+ my_error_2 (_("lock '%s' not made: %s\n"),
+ h->lockname, w32_strerror (w32err));
+ my_set_errno (map_w32_to_errno (w32err));
+ return -1;
+ }
+
+ if (timeout)
+ {
+ /* Wait until lock has been released. We use retry intervals of
+ 50ms, 100ms, 200ms, 400ms, 800ms, 2s, 4s and 8s. */
+ if (!wtime)
+ wtime = 50;
+ else if (wtime < 800)
+ wtime *= 2;
+ else if (wtime == 800)
+ wtime = 2000;
+ else if (wtime < 8000)
+ wtime *= 2;
+
+ if (timeout > 0)
+ {
+ if (wtime > timeout)
+ wtime = timeout;
+ timeout -= wtime;
+ }
+
+ if (wtime >= 800)
+ my_info_1 (_("waiting for lock %s...\n"), h->lockname);
+
+ Sleep (wtime);
+ goto again;
+ }
+
+ my_set_errno (EACCES);
+ return -1;
+}
+#endif /*HAVE_DOSISH_SYSTEM*/
+
+
+/* Take a lock on H. A value of 0 for TIMEOUT returns immediately if
+ the lock can't be taked, -1 waits forever (hopefully not), other
+ values wait for TIMEOUT milliseconds. Returns: 0 on success */
+int
+dotlock_take (dotlock_t h, long timeout)
+{
+ int ret;
+
+ if ( h->disable )
+ return 0; /* Locks are completely disabled. Return success. */
+
+ if ( h->locked )
+ {
+ my_debug_1 ("Oops, '%s' is already locked\n", h->lockname);
+ return 0;
+ }
+
+#ifdef HAVE_DOSISH_SYSTEM
+ ret = dotlock_take_w32 (h, timeout);
+#else /*!HAVE_DOSISH_SYSTEM*/
+ ret = dotlock_take_unix (h, timeout);
+#endif /*!HAVE_DOSISH_SYSTEM*/
+
+ return ret;
+}
+
+
+
+#ifdef HAVE_POSIX_SYSTEM
+/* Unix specific code of release_dotlock. */
+static int
+dotlock_release_unix (dotlock_t h)
+{
+ int pid, same_node;
+ int saveerrno;
+
+ pid = read_lockfile (h, &same_node);
+ if ( pid == -1 )
+ {
+ saveerrno = errno;
+ my_error_0 ("release_dotlock: lockfile error\n");
+ my_set_errno (saveerrno);
+ return -1;
+ }
+ if ( pid != getpid() || !same_node )
+ {
+ my_error_1 ("release_dotlock: not our lock (pid=%d)\n", pid);
+ my_set_errno (EACCES);
+ return -1;
+ }
+
+ if ( unlink( h->lockname ) )
+ {
+ saveerrno = errno;
+ my_error_1 ("release_dotlock: error removing lockfile '%s'\n",
+ h->lockname);
+ my_set_errno (saveerrno);
+ return -1;
+ }
+ /* Fixme: As an extra check we could check whether the link count is
+ now really at 1. */
+ return 0;
+}
+#endif /*HAVE_POSIX_SYSTEM */
+
+
+#ifdef HAVE_DOSISH_SYSTEM
+/* Windows specific code of release_dotlock. */
+static int
+dotlock_release_w32 (dotlock_t h)
+{
+ OVERLAPPED ovl;
+
+ memset (&ovl, 0, sizeof ovl);
+ if (!UnlockFileEx (h->lockhd, 0, 1, 0, &ovl))
+ {
+ int saveerrno = map_w32_to_errno (GetLastError ());
+ my_error_2 ("release_dotlock: error removing lockfile '%s': %s\n",
+ h->lockname, w32_strerror (-1));
+ my_set_errno (saveerrno);
+ return -1;
+ }
+
+ return 0;
+}
+#endif /*HAVE_DOSISH_SYSTEM */
+
+
+/* Release a lock. Returns 0 on success. */
+int
+dotlock_release (dotlock_t h)
+{
+ int ret;
+
+ /* To avoid atexit race conditions we first check whether there are
+ any locks left. It might happen that another atexit handler
+ tries to release the lock while the atexit handler of this module
+ already ran and thus H is undefined. */
+ LOCK_all_lockfiles ();
+ ret = !all_lockfiles;
+ UNLOCK_all_lockfiles ();
+ if (ret)
+ return 0;
+
+ if ( h->disable )
+ return 0;
+
+ if ( !h->locked )
+ {
+ my_debug_1 ("Oops, '%s' is not locked\n", h->lockname);
+ return 0;
+ }
+
+#ifdef HAVE_DOSISH_SYSTEM
+ ret = dotlock_release_w32 (h);
+#else
+ ret = dotlock_release_unix (h);
+#endif
+
+ if (!ret)
+ h->locked = 0;
+ return ret;
+}
+
+
+
+/* Remove all lockfiles. This is called by the atexit handler
+ installed by this module but may also be called by other
+ termination handlers. */
+void
+dotlock_remove_lockfiles (void)
+{
+ dotlock_t h, h2;
+
+ /* First set the lockfiles list to NULL so that for example
+ dotlock_release is aware that this function is currently
+ running. */
+ LOCK_all_lockfiles ();
+ h = all_lockfiles;
+ all_lockfiles = NULL;
+ UNLOCK_all_lockfiles ();
+
+ while ( h )
+ {
+ h2 = h->next;
+ dotlock_destroy (h);
+ h = h2;
+ }
+}