varlinkctl: when operating in --more mode, fail correcly on Varlink method error

In varlink.c we generally do not make failing callback functions fatal,
since that should be up to the app. Hence, in case of varlinkctl (where
we want failures to be fatal), make sure to propagate the error back
explicitly.

Before this change a failing call to "varlinkctl --more call …" would result in
a zero exit code. With this it will correctly exit with a non-zero exit
code.

Author: poettering

src/varlinkctl/varlinkctl.c

@@ -350,15 +350,15 @@ static int reply_callback(
                 VarlinkReplyFlags flags,
                 void *userdata)  {
 
-        int r;
+        int *ret = ASSERT_PTR(userdata), r;
 
         assert(link);
 
         if (error) {
                 /* Propagate the error we received via sd_notify() */
                 (void) sd_notifyf(/* unset_environment= */ false, "VARLINKERROR=%s", error);
 
-                r = log_error_errno(SYNTHETIC_ERRNO(EBADE), "Method call failed: %s", error);
+                r = *ret = log_error_errno(SYNTHETIC_ERRNO(EBADE), "Method call failed: %s", error);
         } else
                 r = 0;
 
@@ -432,7 +432,8 @@ static int verb_call(int argc, char *argv[], void *userdata) {
 
         } else if (arg_method_flags & VARLINK_METHOD_MORE) {
 
-                varlink_set_userdata(vl, (void*) method);
+                int ret = 0;
+                varlink_set_userdata(vl, &ret);
 
                 r = varlink_bind_reply(vl, reply_callback);
                 if (r < 0)
@@ -459,6 +460,8 @@ static int verb_call(int argc, char *argv[], void *userdata) {
                         if (r < 0)
                                 return log_error_errno(r, "Failed to wait for varlink connection events: %m");
                 }
+
+                return ret;
         } else {
                 JsonVariant *reply = NULL;
                 const char *error = NULL;

test/units/TEST-74-AUX-UTILS.varlinkctl.sh

@@ -32,8 +32,9 @@ if command -v userdbctl >/dev/null; then
     systemctl start systemd-userdbd
     varlinkctl call /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetUserRecord '{ "userName" : "testuser", "service" : "io.systemd.Multiplexer" }'
     varlinkctl call -j /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetUserRecord '{ "userName" : "testuser", "service" : "io.systemd.Multiplexer" }' | jq .
-    varlinkctl call --more /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetMemberships '{ "service" : "io.systemd.Multiplexer" }'
-    varlinkctl call --more -j /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetMemberships '{ "service" : "io.systemd.Multiplexer" }' | jq --seq .
+    # We ignore the return value of the following two calls, since if no memberships are defined at all this will return a NotFound error, which is OK
+    (varlinkctl call --more /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetMemberships '{ "service" : "io.systemd.Multiplexer" }' ||:)
+    (varlinkctl call --more -j /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetMemberships '{ "service" : "io.systemd.Multiplexer" }' ||:) | jq --seq .
     varlinkctl call --oneway /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetMemberships '{ "service" : "io.systemd.Multiplexer" }'
     (! varlinkctl call --oneway /run/systemd/userdb/io.systemd.Multiplexer io.systemd.UserDatabase.GetMemberships '{ "service" : "io.systemd.Multiplexer" }' | grep .)
 fi