[PATCH v3 4/5] util/qemu-sockets: Add support for keep-alive flag to passive sockets

[Juraj Marcin <jmarcin@redhat.com>]

From: Juraj Marcin <jmarcin@redhat.com>

Commit aec21d3175 (qapi: Add InetSocketAddress member keep-alive)
introduces the keep-alive flag, which enables the SO_KEEPALIVE socket
option, but only on client-side sockets. However, this option is also
useful for server-side sockets, so they can check if a client is still
reachable or drop the connection otherwise.

This patch enables the SO_KEEPALIVE socket option on passive server-side
sockets if the keep-alive flag is enabled. This socket option is then
inherited by active server-side sockets communicating with connected
clients.

Signed-off-by: Juraj Marcin <jmarcin@redhat.com>
---
 qapi/sockets.json   | 4 ++--
 util/qemu-sockets.c | 9 +++------
 2 files changed, 5 insertions(+), 8 deletions(-)

diff --git a/qapi/sockets.json b/qapi/sockets.json
index 6a95023315..62797cd027 100644
--- a/qapi/sockets.json
+++ b/qapi/sockets.json
@@ -56,8 +56,8 @@
 # @ipv6: whether to accept IPv6 addresses, default try both IPv4 and
 #     IPv6
 #
-# @keep-alive: enable keep-alive when connecting to this socket.  Not
-#     supported for passive sockets.  (Since 4.2)
+# @keep-alive: enable keep-alive when connecting to/listening on this socket.
+#     (Since 4.2, not supported for listening sockets until 10.1)
 #
 # @mptcp: enable multi-path TCP.  (Since 6.1)
 #
diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
index a86964786a..fed17a1ffb 100644
--- a/util/qemu-sockets.c
+++ b/util/qemu-sockets.c
@@ -236,12 +236,6 @@ static int inet_listen_saddr(InetSocketAddress *saddr,
     int saved_errno = 0;
     bool socket_created = false;
 
-    if (saddr->keep_alive) {
-        error_setg(errp, "keep-alive option is not supported for passive "
-                   "sockets");
-        return -1;
-    }
-
     memset(&ai,0, sizeof(ai));
     ai.ai_flags = AI_PASSIVE;
     if (saddr->has_numeric && saddr->numeric) {
@@ -349,6 +343,9 @@ static int inet_listen_saddr(InetSocketAddress *saddr,
                 goto fail;
             }
             /* We have a listening socket */
+            if (inet_set_sockopts(slisten, saddr, errp)) {
+                goto fail;
+            }
             freeaddrinfo(res);
             return slisten;
         }
-- 
2.48.1