From 19ea126e0a3d8811fc2b05372c6bd5b760f45dc6 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Wed, 17 Jan 2024 10:57:56 +0100
Subject: [PATCH] varlink: if varlink_call() is called with ret_error_id=NULL
 propagate error via return value

It's OK if callers don't want to know the varlink error string. But in
that case return the fact the call failed via the return value, as a
negative errno as usual, to make sure it's not accidentally ignored.

Similar for varlink_observe()
---
 src/shared/varlink.c | 22 +++++++++++++++++++---
 1 file changed, 19 insertions(+), 3 deletions(-)

diff --git a/src/shared/varlink.c b/src/shared/varlink.c
index ce9cf73646..d39db5382d 100644
--- a/src/shared/varlink.c
+++ b/src/shared/varlink.c
@@ -2211,21 +2211,29 @@ int varlink_call(
 
         switch (v->state) {
 
-        case VARLINK_CALLED:
+        case VARLINK_CALLED: {
                 assert(v->current);
 
                 varlink_set_state(v, VARLINK_IDLE_CLIENT);
                 assert(v->n_pending == 1);
                 v->n_pending--;
 
+                JsonVariant *e = json_variant_by_key(v->current, "error"),
+                        *p = json_variant_by_key(v->current, "parameters");
+
+                /* If caller doesn't ask for the error string, then let's return an error code in case of failure */
+                if (!ret_error_id && e)
+                        return varlink_error_to_errno(json_variant_string(e), p);
+
                 if (ret_parameters)
-                        *ret_parameters = json_variant_by_key(v->current, "parameters");
+                        *ret_parameters = p;
                 if (ret_error_id)
-                        *ret_error_id = json_variant_string(json_variant_by_key(v->current, "error"));
+                        *ret_error_id = e ? json_variant_string(e) : NULL;
                 if (ret_flags)
                         *ret_flags = 0;
 
                 return 1;
+        }
 
         case VARLINK_PENDING_DISCONNECT:
         case VARLINK_DISCONNECTED:
@@ -2341,6 +2349,11 @@ int varlink_collect(
 
                 /* If we get an error from any of the replies, return immediately with just the error_id and flags*/
                 if (context.error_id) {
+
+                        /* If caller doesn't ask for the error string, then let's return an error code in case of failure */
+                        if (!ret_error_id)
+                                return varlink_error_to_errno(context.error_id, context.parameters);
+
                         if (ret_parameters)
                                 *ret_parameters = TAKE_PTR(context.parameters);
                         if (ret_error_id)
@@ -2374,6 +2387,9 @@ int varlink_collect(
                 assert_not_reached();
         }
 
+        if (!ret_error_id && context.error_id)
+                return varlink_error_to_errno(context.error_id, context.parameters);
+
         if (ret_parameters)
                 *ret_parameters = TAKE_PTR(context.parameters);
         if (ret_error_id)