From 516dfbb783484959cf33f051864f2e44cbed45ca Mon Sep 17 00:00:00 2001
From: Stefano Garzarella <sgarzare@redhat.com>
Date: Tue, 18 Jun 2024 12:00:32 +0200
Subject: [PATCH] libvhost-user: set msg.msg_control to NULL when it is empty
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On some OS (e.g. macOS) sendmsg() returns -1 (errno EINVAL) if
the `struct msghdr` has the field `msg_controllen` set to 0, but
`msg_control` is not NULL.

Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Tested-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Message-Id: <20240618100043.144657-3-sgarzare@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 subprojects/libvhost-user/libvhost-user.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/subprojects/libvhost-user/libvhost-user.c b/subprojects/libvhost-user/libvhost-user.c
index 8adb277d54..53bf1adda6 100644
--- a/subprojects/libvhost-user/libvhost-user.c
+++ b/subprojects/libvhost-user/libvhost-user.c
@@ -632,6 +632,7 @@ vu_message_write(VuDev *dev, int conn_fd, VhostUserMsg *vmsg)
         memcpy(CMSG_DATA(cmsg), vmsg->fds, fdsize);
     } else {
         msg.msg_controllen = 0;
+        msg.msg_control = NULL;
     }
 
     do {