test: add tests for the file watcher

tests/Makefile.am

@@ -8,10 +8,11 @@
 
 EXTRA_DIST = package.m4 testsuite.at $(TESTSUITE) $(TESTS_)
 
-TESTS_ = lib_hash.at lib_prng.at
+TESTS_ = lib_hash.at lib_prng.at lib_watcher.at
 
 # Helper programs for testing
 
+check_HEADERS  = check_lib.h
 check_PROGRAMS =
 
 if BOOKMARKFS_UTIL
@@ -19,7 +20,7 @@ if BOOKMARKFS_UTIL
 
   check_bookmarkfs_util_CPPFLAGS = -I$(top_srcdir)/src
   check_bookmarkfs_util_LDADD    = $(top_builddir)/src/libbookmarkfs_util.la
-  check_bookmarkfs_util_SOURCES  = check_lib.c
+  check_bookmarkfs_util_SOURCES  = check_lib.c check_watcher.c
 endif  # BOOKMARKFS_UTIL
 
 # Autotest setup

tests/check_lib.c

@@ -22,6 +22,8 @@
 #  include "config.h"
 #endif
 
+#include "check_lib.h"
+
 #include <inttypes.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -55,6 +57,8 @@ dispatch_subcmds (
         status = subcmd_hash(argc, argv);
     } else if (0 == strcmp("prng", cmd)) {
         status = subcmd_prng(argc, argv);
+    } else if (0 == strcmp("watcher", cmd)) {
+        status = check_watcher(argc, argv);
     }
     return status;
 }

tests/check_lib.h

@@ -0,0 +1,38 @@
+/**
+ * bookmarkfs/tests/check_lib.h
+ * ----
+ *
+ * Copyright (C) 2025  CismonX <admin@cismon.net>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#ifndef BOOKMARKFS_CHECK_LIB_H_
+#define BOOKMARKFS_CHECK_LIB_H_
+
+#include "xstd.h"
+
+#define ASSERT_EXPR(cond, action_if_false)           \
+    if (!(cond)) {                                   \
+        log_printf("assertion (%s) failed", #cond);  \
+        action_if_false                              \
+    }
+
+int
+check_watcher (
+    int   argc,
+    char *argv[]
+);
+
+#endif  /* !defined(BOOKMARKFS_CHECK_LIB_H_) */

tests/check_watcher.c

@@ -0,0 +1,184 @@
+/**
+* bookmarkfs/tests/check_watcher.c
+* ----
+*
+* Copyright (C) 2025  CismonX <admin@cismon.net>
+*
+* This program is free software: you can redistribute it and/or modify
+* it under the terms of the GNU General Public License as published by
+* the Free Software Foundation, either version 3 of the License, or
+* (at your option) any later version.
+*
+* This program 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 copy of the GNU General Public License
+* along with this program.  If not, see <https://www.gnu.org/licenses/>.
+*/
+
+#ifdef HAVE_CONFIG_H
+#  include "config.h"
+#endif
+
+#include <errno.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <time.h>
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "check_lib.h"
+#include "frontend_util.h"
+#include "sandbox.h"
+#include "watcher.h"
+
+// Forward declaration start
+static int  do_check_watcher  (int, uint32_t);
+static void msecs_to_timespec (struct timespec *, unsigned long);
+static int  wait_for_watcher  (struct watcher *, struct timespec const *, int);
+// Forward declaration end
+
+static int
+do_check_watcher (
+    int      dirfd,
+    uint32_t flags
+) {
+#define FILE1_NAME  "foo.tmp"
+#define FILE2_NAME  "bar.tmp"
+
+#define ASSERT_EQ(val, expr)  ASSERT_EXPR((val) == (expr), goto end;)
+#define ASSERT_NE(val, expr)  ASSERT_EXPR((val) != (expr), goto end;)
+
+    struct watcher *w = watcher_create(dirfd, FILE1_NAME, flags);
+    if (w == NULL) {
+        return -1;
+    }
+
+    unsigned long msecs = 100;
+    int           tries = 5;
+    if (flags & WATCHER_FALLBACK) {
+        msecs = 2500;
+        tries = 2;
+    }
+    struct timespec ts;
+    msecs_to_timespec(&ts, msecs);
+
+    int status = -1;
+    int fd     = -1;
+
+    fd = openat(dirfd, FILE1_NAME, O_WRONLY | O_CREAT, 0600);
+    ASSERT_NE(-1, fd);
+    // Lazy-init watcher.
+    ASSERT_EQ(0, wait_for_watcher(w, &ts, tries));
+
+    ASSERT_NE(-1, write(fd, "foo", 3));
+    ASSERT_EQ(0, wait_for_watcher(w, &ts, tries));
+
+    bool check_truncate = true;
+#if defined(__FreeBSD__)
+    // For kevent() EVFILT_VNODE, ftruncate() only triggers NOTE_ATTRIB,
+    // which we don't want to watch.
+    check_truncate = flags & WATCHER_FALLBACK;
+#endif
+    if (check_truncate) {
+        ASSERT_EQ(0, ftruncate(fd, 0));
+        ASSERT_EQ(0, wait_for_watcher(w, &ts, tries));
+    }
+
+    int fd2 = openat(dirfd, FILE2_NAME, O_WRONLY | O_CREAT, 0600);
+    ASSERT_NE(-1, fd2);
+    close(fd2);
+
+    // FAN_DELETE_SELF won't fire if the watched file
+    // is still opened somewhere.
+    close(fd);
+    fd = -1;
+    ASSERT_EQ(0, renameat(dirfd, FILE2_NAME, dirfd, FILE1_NAME));
+    ASSERT_EQ(0, wait_for_watcher(w, &ts, tries));
+
+    ASSERT_EQ(0, renameat(dirfd, FILE1_NAME, dirfd, FILE2_NAME));
+    ASSERT_EQ(-ENOENT, wait_for_watcher(w, &ts, tries));
+
+    // If the watched file has gone, but managed to come back,
+    // the watcher should continue to work.
+    ASSERT_EQ(0, renameat(dirfd, FILE2_NAME, dirfd, FILE1_NAME));
+    ASSERT_EQ(0, wait_for_watcher(w, &ts, tries));
+
+    ASSERT_EQ(0, unlinkat(dirfd, FILE1_NAME, 0));
+    ASSERT_EQ(-ENOENT, wait_for_watcher(w, &ts, tries));
+
+    status = 0;
+
+  end:
+    if (fd >= 0) {
+        close(fd);
+    }
+    unlinkat(dirfd, FILE1_NAME, 0);
+    unlinkat(dirfd, FILE2_NAME, 0);
+    watcher_destroy(w);
+    return status;
+}
+
+static void
+msecs_to_timespec (
+    struct timespec *ts_buf,
+    unsigned long    millisecs
+) {
+    ts_buf->tv_sec  = millisecs / 1000;
+    ts_buf->tv_nsec = (millisecs % 1000) * 1000000;
+}
+
+static int
+wait_for_watcher (
+    struct watcher        *w,
+    struct timespec const *ts,
+    int                    retry
+) {
+    for (int i = 0; i < retry; ++i) {
+        clock_nanosleep(CLOCK_MONOTONIC, 0, ts, NULL);
+
+        int status = watcher_poll(w);
+        if (status != -EAGAIN) {
+            return status;
+        }
+    }
+    return -ETIMEDOUT;
+}
+
+int
+check_watcher (
+    int   argc,
+    char *argv[]
+) {
+    uint32_t flags = 0;
+#if defined(__FreeBSD__)
+    // Do not enable sandbox on FreeBSD,
+    // since the watcher sandbox only grants read access to dirfd,
+    // and cap_enter() applies to the entire process.
+    flags |= SANDBOX_NOOP << WATCHER_SANDBOX_FLAGS_OFFSET;
+#endif
+
+    getopt_foreach(argc, argv, ":f") {
+      case 'f':
+        flags |= WATCHER_FALLBACK;
+        break;
+
+      default:
+        return -1;
+    }
+    if (argc < 1) {
+        return -1;
+    }
+    argv += optind;
+
+    int dirfd = open(argv[0], O_RDONLY | O_DIRECTORY);
+    if (dirfd < 0) {
+        return -1;
+    }
+    int status = do_check_watcher(dirfd, flags);
+    close(dirfd);
+    return status;
+}

tests/lib_watcher.at

@@ -0,0 +1,25 @@
+dnl
+dnl  Copyright (C) 2025  CismonX <admin@cismon.net>
+dnl
+dnl  Copying and distribution of this file, with or without modification,
+dnl  are permitted in any medium without royalty,
+dnl  provided the copyright notice and this notice are preserved.
+dnl  This file is offered as-is, without any warranty.
+dnl
+
+AT_SETUP([util lib: file watcher])
+AT_KEYWORDS([lib watcher])
+
+ATX_CHECK_LIB([
+    args=
+    ATX_FEAT_IF([native-watcher], , [
+        args="$args -f"
+    ])
+
+    tmpdir=./$(ath_fn_rand_u64_hex).tmp.d
+
+    mkdir $tmpdir
+    check-bookmarkfs-util watcher $args $tmpdir
+])
+
+AT_CLEANUP

tests/testsuite.at

@@ -28,9 +28,9 @@ dnl
 dnl  Conditionally run script depending on whether a feature is enabled.
 dnl
 m4_define([ATX_FEAT_IF], [
-    if test -n "$ATX_FEAT_NAME($1)"; then
+    if test -n "$ATX_FEAT_NAME($1)"; then :
         $2
-    else
+    else :
         $3
     fi
 ])
@@ -47,7 +47,11 @@ m4_define([ATX_FEAT_PREREQ], [
 ])
 
 m4_define([ATX_CHECK_SIMPLE], [
-    AT_CHECK([$1], , [ignore], [ignore])
+    AT_CHECK([
+        atx_line_start=$LINENO
+        trap 'echo "Error $? at line $(($LINENO-$atx_line_start))"; exit 1' ERR
+        $1
+    ], , [ignore], [ignore])
 ])
 
 m4_define([ATX_CHECK_LIB], [
@@ -70,3 +74,4 @@ AT_TEST_HELPER_FN([rand_base64], , , [
 AT_BANNER([The Utility Library])
 m4_include([lib_hash.at])
 m4_include([lib_prng.at])
+m4_include([lib_watcher.at])