Merge pull request #34747 from yuwata/busctl-json-fd

busctl: dump passed fd info

8 files changed, 310 insertions, 44 deletions

diff --git a/src/basic/fs-util.c b/src/basic/fs-util.c
index a6b53e7067..9292e567c8 100644
--- a/src/basic/fs-util.c
+++ b/src/basic/fs-util.c
@@ -153,10 +153,6 @@ int readlinkat_malloc(int fd, const char *p, char **ret) {
         }
 }
 
-int readlink_malloc(const char *p, char **ret) {
-        return readlinkat_malloc(AT_FDCWD, p, ret);
-}
-
 int readlink_value(const char *p, char **ret) {
         _cleanup_free_ char *link = NULL, *name = NULL;
         int r;
diff --git a/src/basic/fs-util.h b/src/basic/fs-util.h
index 82e865180b..702b6010e2 100644
--- a/src/basic/fs-util.h
+++ b/src/basic/fs-util.h
@@ -28,9 +28,11 @@ int rmdir_parents(const char *path, const char *stop);
 int rename_noreplace(int olddirfd, const char *oldpath, int newdirfd, const char *newpath);
 
 int readlinkat_malloc(int fd, const char *p, char **ret);
-int readlink_malloc(const char *p, char **r);
+static inline int readlink_malloc(const char *p, char **ret) {
+        return readlinkat_malloc(AT_FDCWD, p, ret);
+}
 int readlink_value(const char *p, char **ret);
-int readlink_and_make_absolute(const char *p, char **r);
+int readlink_and_make_absolute(const char *p, char **ret);
 
 int chmod_and_chown_at(int dir_fd, const char *path, mode_t mode, uid_t uid, gid_t gid);
 static inline int chmod_and_chown(const char *path, mode_t mode, uid_t uid, gid_t gid) {
diff --git a/src/busctl/busctl.c b/src/busctl/busctl.c
index c3e0a3a633..1e352a3729 100644
--- a/src/busctl/busctl.c
+++ b/src/busctl/busctl.c
@@ -21,6 +21,7 @@
 #include "fileio.h"
 #include "format-table.h"
 #include "glyph-util.h"
+#include "json-util.h"
 #include "log.h"
 #include "main-func.h"
 #include "memstream-util.h"
@@ -1728,18 +1729,22 @@ static int message_append_cmdline(sd_bus_message *m, const char *signature, FDSe
 
 static int json_transform_one(sd_bus_message *m, sd_json_variant **ret);
 
-static int json_transform_and_append(sd_bus_message *m, sd_json_variant **ret) {
+static int json_transform_and_append(sd_bus_message *m, sd_json_variant **array) {
         _cleanup_(sd_json_variant_unrefp) sd_json_variant *element = NULL;
         int r;
 
         assert(m);
-        assert(ret);
+        assert(array);
 
         r = json_transform_one(m, &element);
         if (r < 0)
                 return r;
 
-        return sd_json_variant_append_array(ret, element);
+        r = sd_json_variant_append_array(array, element);
+        if (r < 0)
+                return log_error_errno(r, "Failed to append json element to array: %m");
+
+        return 0;
 }
 
 static int json_transform_array_or_struct(sd_bus_message *m, sd_json_variant **ret) {
@@ -1749,6 +1754,10 @@ static int json_transform_array_or_struct(sd_bus_message *m, sd_json_variant **r
         assert(m);
         assert(ret);
 
+        r = sd_json_variant_new_array(&array, NULL, 0);
+        if (r < 0)
+                return log_error_errno(r, "Failed to allocate json empty array: %m");
+
         for (;;) {
                 r = sd_bus_message_at_end(m, false);
                 if (r < 0)
@@ -1761,9 +1770,6 @@ static int json_transform_array_or_struct(sd_bus_message *m, sd_json_variant **r
                         return r;
         }
 
-        if (!array)
-                return sd_json_variant_new_array(ret, NULL, 0);
-
         *ret = TAKE_PTR(array);
         return 0;
 }
@@ -1784,7 +1790,7 @@ static int json_transform_variant(sd_bus_message *m, const char *contents, sd_js
                           SD_JSON_BUILD_PAIR("type", SD_JSON_BUILD_STRING(contents)),
                           SD_JSON_BUILD_PAIR("data", SD_JSON_BUILD_VARIANT(value)));
         if (r < 0)
-                return log_oom();
+                return log_error_errno(r, "Failed to build json object: %m");
 
         return r;
 }
@@ -1811,7 +1817,7 @@ static int json_transform_dict_array(sd_bus_message *m, sd_json_variant **ret) {
 
                 r = sd_bus_message_peek_type(m, &type, &contents);
                 if (r < 0)
-                        return r;
+                        return bus_log_parse_error(r);
 
                 assert(type == 'e');
 
@@ -1839,7 +1845,11 @@ static int json_transform_dict_array(sd_bus_message *m, sd_json_variant **ret) {
                         return bus_log_parse_error(r);
         }
 
-        return sd_json_variant_new_object(ret, elements, n_elements);
+        r = sd_json_variant_new_object(ret, elements, n_elements);
+        if (r < 0)
+                return log_error_errno(r, "Failed to create new json object: %m");
+
+        return 0;
 }
 
 static int json_transform_one(sd_bus_message *m, sd_json_variant **ret) {
@@ -1999,16 +2009,19 @@ static int json_transform_one(sd_bus_message *m, sd_json_variant **ret) {
                 break;
         }
 
-        case SD_BUS_TYPE_UNIX_FD:
-                r = sd_bus_message_read_basic(m, type, NULL);
+        case SD_BUS_TYPE_UNIX_FD: {
+                int fd;
+
+                r = sd_bus_message_read_basic(m, type, &fd);
                 if (r < 0)
                         return bus_log_parse_error(r);
 
-                r = sd_json_variant_new_null(&v);
+                r = json_variant_new_fd_info(&v, fd);
                 if (r < 0)
                         return log_error_errno(r, "Failed to transform fd: %m");
 
                 break;
+        }
 
         case SD_BUS_TYPE_ARRAY:
         case SD_BUS_TYPE_VARIANT:
@@ -2055,10 +2068,10 @@ static int json_transform_message(sd_bus_message *m, sd_json_variant **ret) {
                 return r;
 
         r = sd_json_buildo(ret,
-                          SD_JSON_BUILD_PAIR("type",  SD_JSON_BUILD_STRING(type)),
+                          SD_JSON_BUILD_PAIR("type", SD_JSON_BUILD_STRING(type)),
                           SD_JSON_BUILD_PAIR("data", SD_JSON_BUILD_VARIANT(v)));
         if (r < 0)
-                return log_oom();
+                return log_error_errno(r, "Failed to build json object: %m");
 
         return 0;
 }
@@ -2130,38 +2143,37 @@ static int call(int argc, char **argv, void *userdata) {
         r = sd_bus_message_is_empty(reply);
         if (r < 0)
                 return bus_log_parse_error(r);
+        if (r > 0 || arg_quiet)
+                return 0;
 
-        if (r == 0 && !arg_quiet) {
-
-                if (!FLAGS_SET(arg_json_format_flags, SD_JSON_FORMAT_OFF)) {
-                        _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL;
+        if (!FLAGS_SET(arg_json_format_flags, SD_JSON_FORMAT_OFF)) {
+                _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL;
 
-                        if (arg_json_format_flags & (SD_JSON_FORMAT_PRETTY|SD_JSON_FORMAT_PRETTY_AUTO))
-                                pager_open(arg_pager_flags);
+                if (arg_json_format_flags & (SD_JSON_FORMAT_PRETTY|SD_JSON_FORMAT_PRETTY_AUTO))
+                        pager_open(arg_pager_flags);
 
-                        r = json_transform_message(reply, &v);
-                        if (r < 0)
-                                return r;
+                r = json_transform_message(reply, &v);
+                if (r < 0)
+                        return r;
 
-                        sd_json_variant_dump(v, arg_json_format_flags, NULL, NULL);
+                sd_json_variant_dump(v, arg_json_format_flags, NULL, NULL);
 
-                } else if (arg_verbose) {
-                        pager_open(arg_pager_flags);
+        } else if (arg_verbose) {
+                pager_open(arg_pager_flags);
 
-                        r = sd_bus_message_dump(reply, stdout, 0);
-                        if (r < 0)
-                                return r;
-                } else {
+                r = sd_bus_message_dump(reply, stdout, 0);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to dump dbus message: %m");
+        } else {
 
-                        fputs(sd_bus_message_get_signature(reply, true), stdout);
-                        fputc(' ', stdout);
+                fputs(sd_bus_message_get_signature(reply, true), stdout);
+                fputc(' ', stdout);
 
-                        r = format_cmdline(reply, stdout, false);
-                        if (r < 0)
-                                return bus_log_parse_error(r);
+                r = format_cmdline(reply, stdout, false);
+                if (r < 0)
+                        return bus_log_parse_error(r);
 
-                        fputc('\n', stdout);
-                }
+                fputc('\n', stdout);
         }
 
         return 0;
@@ -2289,7 +2301,6 @@ static int on_bus_signal_impl(sd_bus_message *msg) {
         r = sd_bus_message_is_empty(msg);
         if (r < 0)
                 return bus_log_parse_error(r);
-
         if (r > 0 || arg_quiet)
                 return 0;
 
diff --git a/src/libsystemd/sd-json/json-util.c b/src/libsystemd/sd-json/json-util.c
index 0c1dea566a..4c978850c4 100644
--- a/src/libsystemd/sd-json/json-util.c
+++ b/src/libsystemd/sd-json/json-util.c
@@ -1,10 +1,13 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
 #include "alloc-util.h"
+#include "devnum-util.h"
+#include "fd-util.h"
 #include "glyph-util.h"
 #include "in-addr-util.h"
 #include "iovec-util.h"
 #include "json-util.h"
+#include "mountpoint-util.h"
 #include "parse-util.h"
 #include "path-util.h"
 #include "process-util.h"
@@ -294,3 +297,124 @@ int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dis
 
         return 0;
 }
+
+int json_variant_new_devnum(sd_json_variant **ret, dev_t devnum) {
+        if (devnum == 0)
+                return sd_json_variant_new_null(ret);
+
+        return sd_json_buildo(
+                        ret,
+                        SD_JSON_BUILD_PAIR_UNSIGNED("major", major(devnum)),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("minor", minor(devnum)));
+}
+
+int json_dispatch_devnum(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata) {
+        dev_t *ret = ASSERT_PTR(userdata);
+        int r;
+
+        assert(variant);
+
+        if (sd_json_variant_is_null(variant)) {
+                *ret = 0;
+                return 0;
+        }
+
+        struct {
+                uint32_t major;
+                uint32_t minor;
+        } data;
+
+        static const sd_json_dispatch_field dispatch_table[] = {
+                { "major", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint32, voffsetof(data, major), SD_JSON_MANDATORY },
+                { "minor", _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint32, voffsetof(data, minor), SD_JSON_MANDATORY },
+                {}
+        };
+
+        r = sd_json_dispatch(variant, dispatch_table, flags, &data);
+        if (r < 0)
+                return r;
+
+        if (!DEVICE_MAJOR_VALID(data.major) || !DEVICE_MINOR_VALID(data.minor))
+                return json_log(variant, flags, SYNTHETIC_ERRNO(EINVAL), "JSON field '%s' is not a valid device number.", strna(name));
+
+        *ret = makedev(data.major, data.minor);
+        return 0;
+}
+
+static int json_variant_new_stat(sd_json_variant **ret, const struct stat *st) {
+        char mode[STRLEN("0755")+1];
+
+        assert(st);
+
+        if (!stat_is_set(st))
+                return sd_json_variant_new_null(ret);
+
+        xsprintf(mode, "%04o", st->st_mode & ~S_IFMT);
+
+        return sd_json_buildo(
+                        ret,
+                        JSON_BUILD_PAIR_DEVNUM("dev", st->st_dev),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("inode", st->st_ino),
+                        JSON_BUILD_PAIR_STRING_NON_EMPTY("type", inode_type_to_string(st->st_mode)),
+                        SD_JSON_BUILD_PAIR_STRING("mode", mode),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("linkCount", st->st_nlink),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("uid", st->st_uid),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("gid", st->st_gid),
+                        SD_JSON_BUILD_PAIR_CONDITION(
+                                        S_ISCHR(st->st_mode) || S_ISBLK(st->st_mode),
+                                        "rdev",
+                                        JSON_BUILD_DEVNUM(st->st_rdev)),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("size", st->st_size),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("blockSize", st->st_blksize),
+                        SD_JSON_BUILD_PAIR_UNSIGNED("blocks", st->st_blocks));
+}
+
+static int json_variant_new_file_handle(sd_json_variant **ret, const struct file_handle *fid) {
+        assert(ret);
+
+        if (!fid)
+                return sd_json_variant_new_null(ret);
+
+        return sd_json_buildo(
+                        ret,
+                        SD_JSON_BUILD_PAIR_INTEGER("type", fid->handle_type),
+                        SD_JSON_BUILD_PAIR_BASE64("handle", fid->f_handle, fid->handle_bytes));
+}
+
+int json_variant_new_fd_info(sd_json_variant **ret, int fd) {
+        _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL, *w = NULL;
+        _cleanup_free_ char *path = NULL;
+        _cleanup_free_ struct file_handle *fid = NULL;
+        struct stat st;
+        int mntid = -1, r;
+
+        assert(fd >= 0 || fd == AT_FDCWD);
+
+        r = fd_get_path(fd, &path);
+        if (r < 0)
+                return r;
+
+        /* If AT_FDCWD is specified, show information about the current working directory.  */
+        if (fstatat(fd, "", &st, AT_EMPTY_PATH) < 0)
+                return -errno;
+
+        r = json_variant_new_stat(&v, &st);
+        if (r < 0)
+                return r;
+
+        r = name_to_handle_at_try_fid(fd, "", &fid, &mntid, AT_EMPTY_PATH);
+        if (r < 0 && is_name_to_handle_at_fatal_error(r))
+                return r;
+
+        r = json_variant_new_file_handle(&w, fid);
+        if (r < 0)
+                return r;
+
+        return sd_json_buildo(
+                        ret,
+                        JSON_BUILD_PAIR_INTEGER_NON_NEGATIVE("fd", fd),
+                        SD_JSON_BUILD_PAIR_STRING("path", path),
+                        SD_JSON_BUILD_PAIR_VARIANT("stat", v),
+                        JSON_BUILD_PAIR_INTEGER_NON_NEGATIVE("mountId", mntid),
+                        SD_JSON_BUILD_PAIR_VARIANT("fileHandle", w));
+}
diff --git a/src/libsystemd/sd-json/json-util.h b/src/libsystemd/sd-json/json-util.h
index 6b72d0d93d..2aeb076823 100644
--- a/src/libsystemd/sd-json/json-util.h
+++ b/src/libsystemd/sd-json/json-util.h
@@ -114,6 +114,7 @@ int json_dispatch_const_user_group_name(const char *name, sd_json_variant *varia
 int json_dispatch_in_addr(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_path(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 int json_dispatch_pidref(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
+int json_dispatch_devnum(const char *name, sd_json_variant *variant, sd_json_dispatch_flags_t flags, void *userdata);
 
 static inline int json_variant_unbase64_iovec(sd_json_variant *v, struct iovec *ret) {
         return sd_json_variant_unbase64(v, ret ? &ret->iov_base : NULL, ret ? &ret->iov_len : NULL);
@@ -147,6 +148,7 @@ enum {
         _JSON_BUILD_RATELIMIT,
         _JSON_BUILD_TRISTATE,
         _JSON_BUILD_PIDREF,
+        _JSON_BUILD_DEVNUM,
 
         _JSON_BUILD_PAIR_INTEGER_NON_ZERO,
         _JSON_BUILD_PAIR_INTEGER_NON_NEGATIVE,
@@ -172,6 +174,7 @@ enum {
         _JSON_BUILD_PAIR_OCTESCAPE_NON_EMPTY,
         _JSON_BUILD_PAIR_TRISTATE_NON_NULL,
         _JSON_BUILD_PAIR_PIDREF_NON_NULL,
+        _JSON_BUILD_PAIR_DEVNUM,
 
         _SD_JSON_BUILD_REALLYMAX,
 };
@@ -192,6 +195,7 @@ enum {
 #define JSON_BUILD_RATELIMIT(rl) _JSON_BUILD_RATELIMIT, (const RateLimit*) { rl }
 #define JSON_BUILD_TRISTATE(i) _JSON_BUILD_TRISTATE, (int) { i }
 #define JSON_BUILD_PIDREF(p) _JSON_BUILD_PIDREF, (const PidRef*) { p }
+#define JSON_BUILD_DEVNUM(d) _JSON_BUILD_DEVNUM, (dev_t) { d }
 
 #define JSON_BUILD_PAIR_INTEGER_NON_ZERO(name, i) _JSON_BUILD_PAIR_INTEGER_NON_ZERO, (const char*) { name }, (int64_t) { i }
 #define JSON_BUILD_PAIR_INTEGER_NON_NEGATIVE(name, i) _JSON_BUILD_PAIR_INTEGER_NON_NEGATIVE, (const char*) { name }, (int64_t) { i }
@@ -230,5 +234,8 @@ enum {
 #define JSON_BUILD_PAIR_RATELIMIT(name, rl) SD_JSON_BUILD_PAIR(name, JSON_BUILD_RATELIMIT(rl))
 #define JSON_BUILD_PAIR_TRISTATE(name, i) SD_JSON_BUILD_PAIR(name, JSON_BUILD_TRISTATE(i))
 #define JSON_BUILD_PAIR_PIDREF(name, p) SD_JSON_BUILD_PAIR(name, JSON_BUILD_PIDREF(p))
+#define JSON_BUILD_PAIR_DEVNUM(name, d) SD_JSON_BUILD_PAIR(name, JSON_BUILD_DEVNUM(d))
 
 int json_variant_new_pidref(sd_json_variant **ret, PidRef *pidref);
+int json_variant_new_devnum(sd_json_variant **ret, dev_t devnum);
+int json_variant_new_fd_info(sd_json_variant **ret, int fd);
diff --git a/src/libsystemd/sd-json/sd-json.c b/src/libsystemd/sd-json/sd-json.c
index 2028f222cb..297052bdb4 100644
--- a/src/libsystemd/sd-json/sd-json.c
+++ b/src/libsystemd/sd-json/sd-json.c
@@ -4224,6 +4224,34 @@ _public_ int sd_json_buildv(sd_json_variant **ret, va_list ap) {
                         break;
                 }
 
+                case _JSON_BUILD_DEVNUM: {
+                        dev_t devnum;
+
+                        if (!IN_SET(current->expect, EXPECT_TOPLEVEL, EXPECT_OBJECT_VALUE, EXPECT_ARRAY_ELEMENT)) {
+                                r = -EINVAL;
+                                goto finish;
+                        }
+
+                        devnum = va_arg(ap, dev_t);
+
+                        if (current->n_suppress == 0) {
+                                r = json_variant_new_devnum(&add, devnum);
+                                if (r < 0)
+                                        goto finish;
+                        }
+
+                        n_subtract = 1;
+
+                        if (current->expect == EXPECT_TOPLEVEL)
+                                current->expect = EXPECT_END;
+                        else if (current->expect == EXPECT_OBJECT_VALUE)
+                                current->expect = EXPECT_OBJECT_KEY;
+                        else
+                                assert(current->expect == EXPECT_ARRAY_ELEMENT);
+
+                        break;
+                }
+
                 case _JSON_BUILD_TRISTATE: {
                         int tristate;
 
diff --git a/src/test/test-json.c b/src/test/test-json.c
index 32cd285841..75dff429d5 100644
--- a/src/test/test-json.c
+++ b/src/test/test-json.c
@@ -17,6 +17,7 @@
 #include "string-util.h"
 #include "strv.h"
 #include "tests.h"
+#include "tmpfile-util.h"
 
 static void test_tokenizer_one(const char *data, ...) {
         unsigned line = 0, column = 0;
@@ -1307,4 +1308,97 @@ TEST(pidref) {
         pidref_done(&data.pid1);
 }
 
+TEST(devnum) {
+        _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL;
+        dev_t dev = makedev(123, 456), parsed;
+
+        ASSERT_OK(json_variant_new_devnum(&v, dev));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        ASSERT_OK(json_dispatch_devnum("devnum", v, /* flags= */ 0, &parsed));
+        ASSERT_EQ(major(parsed), major(dev));
+        ASSERT_EQ(minor(parsed), minor(dev));
+        v = sd_json_variant_unref(v);
+
+        dev = makedev(1 << 12, 456);
+        ASSERT_OK(json_variant_new_devnum(&v, dev));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        ASSERT_FAIL(json_dispatch_devnum("devnum", v, /* flags= */ 0, &parsed));
+        v = sd_json_variant_unref(v);
+
+        dev = makedev(123, 1 << 20);
+        ASSERT_OK(json_variant_new_devnum(&v, dev));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        ASSERT_FAIL(json_dispatch_devnum("devnum", v, /* flags= */ 0, &parsed));
+}
+
+TEST(fd_info) {
+        _cleanup_(sd_json_variant_unrefp) sd_json_variant *v = NULL;
+        _cleanup_(pidref_done) PidRef pidref = PIDREF_NULL;
+        _cleanup_close_ int fd = -EBADF;
+
+        /* directories */
+        ASSERT_OK(json_variant_new_fd_info(&v, AT_FDCWD));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        v = sd_json_variant_unref(v);
+
+        ASSERT_OK_ERRNO(fd = openat(AT_FDCWD, ".", O_CLOEXEC | O_DIRECTORY | O_PATH));
+        ASSERT_OK(json_variant_new_fd_info(&v, fd));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        v = sd_json_variant_unref(v);
+        fd = safe_close(fd);
+
+        /* regular file */
+        ASSERT_OK(fd = open_tmpfile_unlinkable(NULL, O_RDWR));
+        ASSERT_OK(json_variant_new_fd_info(&v, fd));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        v = sd_json_variant_unref(v);
+        fd = safe_close(fd);
+
+        if (access("/sys/class/net/lo/uevent", F_OK) >= 0) {
+                ASSERT_OK_ERRNO(fd = open("/sys/class/net/lo/uevent", O_CLOEXEC | O_PATH));
+                ASSERT_OK(json_variant_new_fd_info(&v, fd));
+                ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+                v = sd_json_variant_unref(v);
+                fd = safe_close(fd);
+        }
+
+        /* block device */
+        if (access("/dev/sda", F_OK) >= 0) {
+                ASSERT_OK_ERRNO(fd = open("/dev/sda", O_CLOEXEC | O_PATH));
+                ASSERT_OK(json_variant_new_fd_info(&v, fd));
+                ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+                v = sd_json_variant_unref(v);
+                fd = safe_close(fd);
+        }
+
+        /* stream */
+        ASSERT_OK(json_variant_new_fd_info(&v, fileno(stdout)));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        v = sd_json_variant_unref(v);
+
+        /* socket */
+        ASSERT_OK_ERRNO(fd = socket(AF_INET, SOCK_DGRAM, 0));
+        ASSERT_OK(json_variant_new_fd_info(&v, fd));
+        ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+        v = sd_json_variant_unref(v);
+        fd = safe_close(fd);
+
+        /* pidfd */
+        ASSERT_OK(pidref_set_pid(&pidref, 0));
+        if (pidref.fd >= 0) {
+                ASSERT_OK(json_variant_new_fd_info(&v, pidref.fd));
+                ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+                v = sd_json_variant_unref(v);
+        }
+        pidref_done(&pidref);
+
+        ASSERT_OK(pidref_set_pid(&pidref, 1));
+        if (pidref.fd >= 0) {
+                ASSERT_OK(json_variant_new_fd_info(&v, pidref.fd));
+                ASSERT_OK(sd_json_variant_dump(v, SD_JSON_FORMAT_PRETTY_AUTO | SD_JSON_FORMAT_COLOR_AUTO, NULL, NULL));
+                v = sd_json_variant_unref(v);
+        }
+        pidref_done(&pidref);
+}
+
 DEFINE_TEST_MAIN(LOG_DEBUG);
diff --git a/test/units/TEST-74-AUX-UTILS.busctl.sh b/test/units/TEST-74-AUX-UTILS.busctl.sh
index eb1f9e265d..4949f4bac7 100755
--- a/test/units/TEST-74-AUX-UTILS.busctl.sh
+++ b/test/units/TEST-74-AUX-UTILS.busctl.sh
@@ -46,6 +46,10 @@ busctl call -j \
 busctl call --verbose --timeout=60 --expect-reply=yes \
             org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager \
             ListUnitsByPatterns asas 1 "active" 2 "systemd-*.socket" "*.mount"
+# show information passed fd
+busctl call --json=pretty \
+            org.freedesktop.systemd1 /org/freedesktop/systemd1 org.freedesktop.systemd1.Manager \
+            DumpByFileDescriptor | jq
 
 busctl emit /org/freedesktop/login1 org.freedesktop.login1.Manager \
             PrepareForSleep b false