sd-bus: Add sd_bus_reply()

While sd-bus already provides sd_bus_call() for calling a method
from a complete bus message object, We don't have an equivalent
function for replying from a method with a complete bus message
object.

Currently, we use sd_bus_send(call->bus, m, NULL) instead. Let's
add a shorthand for this pattern and name it sd_bus_reply().

man/rules/meson.build

@@ -11,7 +11,6 @@ manpages = [
  ['coredump.conf', '5', ['coredump.conf.d'], 'ENABLE_COREDUMP'],
  ['coredumpctl', '1', [], 'ENABLE_COREDUMP'],
  ['crypttab', '5', [], 'HAVE_LIBCRYPTSETUP'],
- ['veritytab', '5', [], 'HAVE_LIBCRYPTSETUP'],
  ['daemon', '7', [], ''],
  ['dnssec-trust-anchors.d',
   '5',
@@ -405,7 +404,10 @@ manpages = [
    'sd_bus_reply_method_errorf',
    'sd_bus_reply_method_errorfv'],
   ''],
- ['sd_bus_reply_method_return', '3', ['sd_bus_reply_method_returnv'], ''],
+ ['sd_bus_reply_method_return',
+  '3',
+  ['sd_bus_reply', 'sd_bus_reply_method_returnv'],
+  ''],
  ['sd_bus_request_name',
   '3',
   ['sd_bus_release_name',
@@ -1128,6 +1130,7 @@ manpages = [
   ['systemd-user-runtime-dir', 'user-runtime-dir@.service'],
   ''],
  ['userdbctl', '1', [], 'ENABLE_USERDB'],
- ['vconsole.conf', '5', [], 'ENABLE_VCONSOLE']
+ ['vconsole.conf', '5', [], 'ENABLE_VCONSOLE'],
+ ['veritytab', '5', [], 'HAVE_LIBCRYPTSETUP']
 ]
 # Really, do not edit.

man/sd-bus.xml

@@ -144,6 +144,7 @@
 <citerefentry><refentrytitle>sd_bus_query_sender_privilege</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 <citerefentry><refentrytitle>sd_bus_reply_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 <citerefentry><refentrytitle>sd_bus_reply_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
+<citerefentry><refentrytitle>sd_bus_reply</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 <citerefentry><refentrytitle>sd_bus_request_name</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 <citerefentry><refentrytitle>sd_bus_send</refentrytitle><manvolnum>3</manvolnum></citerefentry>,
 <citerefentry><refentrytitle>sd_bus_send_to</refentrytitle><manvolnum>3</manvolnum></citerefentry>,

man/sd_bus_reply_method_return.xml

@@ -19,6 +19,7 @@
   <refnamediv>
     <refname>sd_bus_reply_method_return</refname>
     <refname>sd_bus_reply_method_returnv</refname>
+    <refname>sd_bus_reply</refname>
 
     <refpurpose>Reply to a D-Bus method call</refpurpose>
   </refnamediv>
@@ -40,6 +41,12 @@
         <paramdef>const char *<parameter>types</parameter></paramdef>
         <paramdef>va_list <parameter>ap</parameter></paramdef>
       </funcprototype>
+
+      <funcprototype>
+        <funcdef>int sd_bus_reply</funcdef>
+        <paramdef>const sd_bus_message *<parameter>call</parameter></paramdef>
+        <paramdef>sd_bus_message *<parameter>m</parameter></paramdef>
+      </funcprototype>
     </funcsynopsis>
   </refsynopsisdiv>
 
@@ -52,6 +59,11 @@
     <citerefentry><refentrytitle>sd_bus_message_append</refentrytitle><manvolnum>3</manvolnum></citerefentry>.
     If no reply is expected to <parameter>call</parameter>, this function succeeds without sending a
     reply.</para>
+
+    <para><function>sd_bus_reply()</function> takes a complete bus message object created with either
+    <citerefentry><refentrytitle>sd_bus_new_method_return</refentrytitle><manvolnum>3</manvolnum></citerefentry> or
+    <citerefentry><refentrytitle>sd_bus_new_method_error</refentrytitle><manvolnum>3</manvolnum></citerefentry>
+    and sends it as a reply to the <parameter>call</parameter> message.</para>
   </refsect1>
 
   <refsect1>
@@ -76,6 +88,8 @@
           </para>
 
           <para>Message <parameter>call</parameter> is not attached to a bus.</para>
+
+          <para>Message <parameter>m</parameter> is not a method reply message.</para>
           </listitem>
         </varlistentry>
 

src/libsystemd/libsystemd.sym

@@ -740,6 +740,7 @@ global:
 LIBSYSTEMD_248 {
 global:
         sd_bus_open_user_machine;
+        sd_bus_reply;
 
         sd_event_source_set_ratelimit;
         sd_event_source_get_ratelimit;

src/libsystemd/sd-bus/bus-convenience.c

@@ -198,7 +198,7 @@ _public_ int sd_bus_reply_method_returnv(
                         return r;
         }
 
-        return sd_bus_send(call->bus, m, NULL);
+        return sd_bus_reply(call, m);
 }
 
 _public_ int sd_bus_reply_method_return(
@@ -239,7 +239,7 @@ _public_ int sd_bus_reply_method_error(
         if (r < 0)
                 return r;
 
-        return sd_bus_send(call->bus, m, NULL);
+        return sd_bus_reply(call, m);
 }
 
 _public_ int sd_bus_reply_method_errorfv(

src/libsystemd/sd-bus/sd-bus.c

@@ -2604,6 +2604,20 @@ _public_ int sd_bus_get_timeout(sd_bus *bus, uint64_t *timeout_usec) {
         }
 }
 
+int sd_bus_reply(const sd_bus_message *call, sd_bus_message *reply) {
+        assert_return(call, -EINVAL);
+        assert_return(call->sealed, -EPERM);
+        assert_return(call->header->type == SD_BUS_MESSAGE_METHOD_CALL, -EINVAL);
+        assert_return(call->bus, -EINVAL);
+        assert_return(!bus_pid_changed(call->bus), -ECHILD);
+        assert_return(reply, -EINVAL);
+        assert_return(
+                IN_SET(reply->header->type, SD_BUS_MESSAGE_METHOD_RETURN, SD_BUS_MESSAGE_METHOD_ERROR),
+                -EINVAL);
+
+        return sd_bus_send(call->bus, reply, NULL);
+}
+
 static int process_timeout(sd_bus *bus) {
         _cleanup_(sd_bus_error_free) sd_bus_error error_buffer = SD_BUS_ERROR_NULL;
         _cleanup_(sd_bus_message_unrefp) sd_bus_message* m = NULL;

src/systemd/sd-bus.h

@@ -201,6 +201,7 @@ int sd_bus_send(sd_bus *bus, sd_bus_message *m, uint64_t *cookie);
 int sd_bus_send_to(sd_bus *bus, sd_bus_message *m, const char *destination, uint64_t *cookie);
 int sd_bus_call(sd_bus *bus, sd_bus_message *m, uint64_t usec, sd_bus_error *ret_error, sd_bus_message **reply);
 int sd_bus_call_async(sd_bus *bus, sd_bus_slot **slot, sd_bus_message *m, sd_bus_message_handler_t callback, void *userdata, uint64_t usec);
+int sd_bus_reply(const sd_bus_message *call, sd_bus_message *reply);
 
 int sd_bus_get_fd(sd_bus *bus);
 int sd_bus_get_events(sd_bus *bus);