From 968f2f3f5a76b05142e1de447bb79f4f97868721 Mon Sep 17 00:00:00 2001
From: Lennart Poettering <lennart@poettering.net>
Date: Thu, 21 Oct 2021 17:29:48 +0200
Subject: [PATCH] varlink: disconnect varlink link in one more case

Previously we'd possibly see POLLHUP on a varlink link, and continue to
run epoll on it even though we have nothing to read nor write anymore.

Let's fix that, and once we know that there's nothing to write anymore
(or we saw a write error already) we'll disconnect after POLLHUP.

Fixes: #20062
(cherry picked from commit 7c26a631ad8bf91016db156b7d299ca68fd7866e)

Conflict:NA
Reference:https://github.com/systemd/systemd/commit/968f2f3f5a76b05142e1de447bb79f4f97868721
---
 src/shared/varlink.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/src/shared/varlink.c b/src/shared/varlink.c
index 8da568e208..a57475b5ba 100644
--- a/src/shared/varlink.c
+++ b/src/shared/varlink.c
@@ -417,9 +417,10 @@ static int varlink_test_disconnect(Varlink *v) {
         if (IN_SET(v->state, VARLINK_IDLE_CLIENT) && (v->write_disconnected || v->got_pollhup))
                 goto disconnect;
 
-        /* The server is still expecting to write more, but its write end is disconnected and it got a POLLHUP
-         * (i.e. from a disconnected client), so disconnect. */
-        if (IN_SET(v->state, VARLINK_PENDING_METHOD, VARLINK_PENDING_METHOD_MORE) && v->write_disconnected && v->got_pollhup)
+        /* We are on the server side and still want to send out more replies, but we saw POLLHUP already, and
+         * either got no buffered bytes to write anymore or already saw a write error. In that case we should
+         * shut down the varlink link. */
+        if (IN_SET(v->state, VARLINK_PENDING_METHOD, VARLINK_PENDING_METHOD_MORE) && (v->write_disconnected || v->output_buffer_size == 0) && v->got_pollhup)
                 goto disconnect;
 
         return 0;
-- 
2.33.0