test: Add a test for Type=dbus services surviving a broker restart

mkosi/mkosi.extra/usr/share/dbus-1/system.d/systemd.test.DBusReconnect.conf

@@ -0,0 +1,13 @@
+<?xml version="1.0"?>
+<!DOCTYPE busconfig PUBLIC "-//freedesktop//DTD D-BUS Bus Configuration 1.0//EN"
+        "http://www.freedesktop.org/standards/dbus/1.0/busconfig.dtd">
+
+<!--
+  SPDX-License-Identifier: LGPL-2.1-or-later
+-->
+
+<busconfig>
+    <policy user="root">
+        <allow own="systemd.test.DBusReconnect"/>
+    </policy>
+</busconfig>

src/test/meson.build

@@ -315,6 +315,10 @@ executables += [
                 'dependencies' : libopenssl_cflags,
                 'conditions' : ['HAVE_OPENSSL'],
         },
+        test_template + {
+                'sources' : files('test-dbus-name-holder.c'),
+                'type' : 'manual',
+        },
         test_template + {
                 'sources' : files('test-display-quota.c'),
                 'type' : 'manual',

src/test/test-dbus-name-holder.c

@@ -0,0 +1,77 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <unistd.h>
+
+#include "sd-bus.h"
+#include "sd-daemon.h"
+
+#include "log.h"
+#include "main-func.h"
+#include "time-util.h"
+
+static int run(int argc, char *argv[]) {
+        int r;
+
+        if (argc < 3 || argc > 5)
+                return log_error_errno(SYNTHETIC_ERRNO(EINVAL),
+                                       "Usage: %s BUSNAME READY_MARKER [RELEASE_MARKER] [NOTIFY_MARKER]",
+                                       program_invocation_short_name);
+
+        const char
+                *name = argv[1],
+                *marker = argv[2],
+                *release_marker = argc > 3 ? argv[3] : NULL,
+                *notify_marker = argc > 4 ? argv[4] : NULL;
+
+        for (;;) {
+                _cleanup_(sd_bus_flush_close_unrefp) sd_bus *bus = NULL;
+
+                r = sd_bus_open_system(&bus);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to open system bus: %m");
+
+                r = sd_bus_request_name(bus, name, /* flags= */ 0);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to acquire dbus name '%s': %m", name);
+
+                log_info("Acquired dbus name '%s'.", name);
+
+                for (;;) {
+                        r = sd_bus_process(bus, /* ret= */ NULL);
+                        if (r < 0)
+                                break;
+                        if (r > 0)
+                                continue;
+
+                        if (release_marker && access(release_marker, F_OK) >= 0) {
+                                r = sd_bus_release_name(bus, name);
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to release dbus name '%s': %m", name);
+
+                                log_info("Released dbus name '%s'.", name);
+                                release_marker = NULL; /* go back to blocking until we're killed */
+                        }
+
+                        r = sd_bus_wait(bus, release_marker ? 100 * USEC_PER_MSEC : USEC_INFINITY);
+                        if (r < 0)
+                                break;
+                }
+
+                log_info("Disconnected from bus, reconnecting...");
+
+                while (access(marker, F_OK) < 0) {
+                        if (notify_marker && access(notify_marker, F_OK) >= 0) {
+                                r = sd_notify(/* unset_environment= */ false, "RELOADING=1\nREADY=1");
+                                if (r < 0)
+                                        return log_error_errno(r, "Failed to send reload notification: %m");
+
+                                log_info("Sent reload notification.");
+                                notify_marker = NULL;
+                        }
+
+                        usleep_safe(50 * USEC_PER_MSEC);
+                }
+        }
+}
+
+DEFINE_MAIN_FUNCTION(run);

test/units/TEST-23-UNIT-FILE.dbus-reconnect.sh

@@ -0,0 +1,161 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -eux
+set -o pipefail
+
+# shellcheck source=test/units/util.sh
+. "$(dirname "$0")"/util.sh
+
+holder=/usr/lib/systemd/tests/unit-tests/manual/test-dbus-name-holder
+name=systemd.test.DBusReconnect
+marker=/run/dbus-reconnect-go
+release=/run/dbus-reconnect-release
+notify=/run/dbus-reconnect-notify
+reloaded=/run/dbus-reconnect-reloaded
+
+at_exit() {
+    rm -f "$marker" "$release" "$notify" "$reloaded"
+    systemctl stop \
+              dbus-reconnect-recover.service \
+              dbus-reconnect-stop.service \
+              dbus-reconnect-exit.service \
+              dbus-reconnect-drop.service \
+              dbus-reconnect-notify.service \
+              dbus-reconnect-notify-target.service \
+              dbus-reconnect-reexec.service 2>/dev/null || :
+}
+
+trap at_exit EXIT
+
+# Poll until property $2 of unit $1 reaches value $3
+poll() {
+    local unit="${1:?}" prop="${2:?}" want="${3:?}" got i
+    for ((i = 0; i < 150; i++)); do
+        got="$(systemctl show -p "$prop" --value "$unit")"
+        if [[ "$got" == "$want" ]]; then
+            return 0
+        fi
+        sleep 0.2
+    done
+    echo "poll: timed out waiting for $unit $prop=$want (last: $got)" >&2
+    return 1
+}
+
+reset_failed() {
+    local unit="${1:?}"
+
+    systemctl reset-failed "$unit" 2>/dev/null || :
+}
+
+restart_broker() {
+    systemctl kill --signal=KILL dbus.service
+    timeout 90 bash -c '
+        until busctl --system status >/dev/null 2>&1; do
+            systemctl reset-failed dbus.service dbus.socket 2>/dev/null
+            systemctl start dbus.socket 2>/dev/null
+            sleep 0.2
+        done'
+}
+
+enter_revalidation() {
+    local unit="${1:?}"
+
+    shift
+    reset_failed "$unit"
+    rm -f "$marker"
+    systemd-run \
+        --unit="$unit" \
+        -p Type=dbus \
+        -p BusName="$name" \
+        -p Restart=no \
+        "$@" \
+        "$holder" "$name" "$marker"
+    restart_broker
+    poll "$unit" SubState running-revalidating
+}
+
+# the name comes back within the grace window
+unit=dbus-reconnect-recover.service
+enter_revalidation "$unit"
+main_pid="$(systemctl show -p MainPID --value "$unit")"
+assert_neq "$main_pid" "0"
+touch "$marker"
+poll "$unit" SubState running
+assert_eq "$(systemctl show -p MainPID --value "$unit")" "$main_pid"
+systemctl stop "$unit"
+
+# the name never comes back
+unit=dbus-reconnect-stop.service
+enter_revalidation "$unit"
+poll "$unit" ActiveState inactive
+
+# ditto with RemainAfterExit=yes
+unit=dbus-reconnect-exit.service
+enter_revalidation "$unit" -p RemainAfterExit=yes
+poll "$unit" SubState exited
+systemctl stop "$unit"
+
+# the name is dropped on a live connection and we action it at once
+unit=dbus-reconnect-drop.service
+reset_failed "$unit"
+rm -f "$release"
+systemd-run \
+    --unit="$unit" \
+    -p Type=dbus \
+    -p BusName="$name" \
+    -p Restart=no \
+    "$holder" "$name" "$marker" "$release"
+poll "$unit" SubState running
+touch "$release"
+for ((i = 0; i < 150; i++)); do
+    sub_state="$(systemctl show -p SubState --value "$unit")"
+    if [[ "$sub_state" == running-revalidating ]]; then
+        echo "live drop entered the revalidation window" >&2
+        exit 1
+    fi
+
+    active_state="$(systemctl show -p ActiveState --value "$unit")"
+    if [[ "$active_state" == inactive ]]; then
+        break
+    fi
+
+    sleep 0.2
+done
+assert_eq "$(systemctl show -p ActiveState --value "$unit")" inactive
+
+# a reload notification is propagated even while the name is absent (revalidating)
+target=dbus-reconnect-notify-target.service
+reset_failed "$target"
+systemd-run \
+    --unit="$target" \
+    -p Type=oneshot \
+    -p RemainAfterExit=yes \
+    -p "ExecReload=/usr/bin/touch $reloaded" \
+    /usr/bin/true
+
+unit=dbus-reconnect-notify.service
+reset_failed "$unit"
+rm -f "$marker" "$release" "$notify" "$reloaded"
+systemd-run \
+    --unit="$unit" \
+    -p Type=dbus \
+    -p BusName="$name" \
+    -p Restart=no \
+    -p NotifyAccess=main \
+    -p PropagatesReloadTo="$target" \
+    "$holder" "$name" "$marker" "$release" "$notify"
+restart_broker
+poll "$unit" SubState running-revalidating
+touch "$notify"
+timeout 30 bash -c "until [[ -e '$reloaded' ]]; do sleep 0.2; done"
+touch "$marker"
+poll "$unit" SubState running
+systemctl stop "$unit" "$target"
+
+# the revalidation state survives a daemon-reexec and still recovers afterwards
+unit=dbus-reconnect-reexec.service
+enter_revalidation "$unit"
+systemctl daemon-reexec
+touch "$marker"
+poll "$unit" SubState running
+systemctl stop "$unit"