Re: [PATCH 2/5] qemu-nbd: fix regression with qemu-nbd --fork run over ssh

[Kevin Wolf <kwolf@redhat.com>]

Am 17.07.2023 um 16:55 hat Denis V. Lunev geschrieben:
> Commit e6df58a5578fee7a50bbf36f4a50a2781cff855d
>     Author: Hanna Reitz <hreitz@redhat.com>
>     Date:   Wed May 8 23:18:18 2019 +0200
>     qemu-nbd: Do not close stderr
> has introduced an interesting regression. Original behavior of
>     ssh somehost qemu-nbd /home/den/tmp/file -f raw --fork
> was the following:
>  * qemu-nbd was started as a daemon
>  * the command execution is done and ssh exited with success
> 
> The patch has changed this behavior and 'ssh' command now hangs forever.
> 
> According to the normal specification of the daemon() call, we should
> endup with STDERR pointing to /dev/null. That should be done at the
> very end of the successful startup sequence when the pipe to the
> bootstrap process (used for diagnostics) is no longer needed.
> 
> This could be achived in the same way as done for 'qemu-nbd -c' case.
> That was commit 0eaf453e, also fixing up e6df58a5. STDOUT copying to
> STDERR does the trick.
> 
> This also leads to proper 'ssh' connection closing which fixes my
> original problem.
> 
> Signed-off-by: Denis V. Lunev <den@openvz.org>
> CC: Eric Blake <eblake@redhat.com>
> CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
> CC: Hanna Reitz <hreitz@redhat.com>
> CC: <qemu-stable@nongnu.org>

This broke qemu-iotests 233 (Eric, please make sure to run the full
qemu-iotests suite before sending block related pull requests):

--- /home/kwolf/source/qemu/tests/qemu-iotests/233.out
+++ /home/kwolf/source/qemu/build-clang/scratch/raw-file-233/233.out.bad
@@ -99,14 +99,4 @@
 qemu-nbd: TLS handshake failed: The TLS connection was non-properly terminated.

 == final server log ==
-qemu-nbd: option negotiation failed: Failed to read opts magic: Cannot read from TLS channel: Software caused connection abort
-qemu-nbd: option negotiation failed: Failed to read opts magic: Cannot read from TLS channel: Software caused connection abort
-qemu-nbd: option negotiation failed: Verify failed: No certificate was found.
-qemu-nbd: option negotiation failed: Verify failed: No certificate was found.
-qemu-nbd: option negotiation failed: TLS x509 authz check for DISTINGUISHED-NAME is denied
-qemu-nbd: option negotiation failed: TLS x509 authz check for DISTINGUISHED-NAME is denied
-qemu-nbd: option negotiation failed: Failed to read opts magic: Cannot read from TLS channel: Software caused connection abort
-qemu-nbd: option negotiation failed: Failed to read opts magic: Cannot read from TLS channel: Software caused connection abort
-qemu-nbd: option negotiation failed: TLS handshake failed: An illegal parameter has been received.
-qemu-nbd: option negotiation failed: TLS handshake failed: An illegal parameter has been received.
 *** done

Do we really want to lose these error messages? This looks wrong to me.

Kevin