Re: [PATCH v2] migration/multifd: close TLS channel before socket finalize

[Daniel P . Berrangé]

On Fri, Nov 06, 2020 at 06:54:54PM +0800, Chuan Zheng wrote:
> Since we now support tls multifd, when we cancel migration, the TLS
> sockets will be left as CLOSE-WAIT On Src which results in socket
> leak.
> Fix it by closing TLS channel before socket finalize.
> 
> Signed-off-by: Chuan Zheng <zhengchuan@huawei.com>
> ---
>  migration/multifd.c | 14 ++++++++++++++
>  1 file changed, 14 insertions(+)
> 
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 68b171f..a6838dc 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -523,6 +523,19 @@ static void multifd_send_terminate_threads(Error *err)
>      }
>  }
>  
> +static void multifd_tls_socket_close(QIOChannel *ioc, Error *err)
> +{
> +    if (ioc &&
> +        object_dynamic_cast(OBJECT(ioc),
> +                            TYPE_QIO_CHANNEL_TLS)) {
> +        /*
> +         * TLS channel is special, we need close it before
> +         * socket finalize.
> +         */
> +        qio_channel_close(ioc, &err);
> +    }
> +}

This doesn't feel quite right to me.  Calling qio_channel_close will close
both the TLS layer, and the underlying QIOChannelSocket. If the latter
is safe to do, then we don't need the object_dynamic_cast() check, we can
do it unconditionally whether we're using TLS or not.

Having said that, I'm not sure if we actually want to be using
qio_channel_close or not ?

I would have expected that there is already code somewhere else in the
migration layer that is closing these multifd channels, but I can't
actually find where that happens right now.  Assuming that code does
exist though, qio_channel_shutdown(ioc, BOTH) feels like the right
answer to unblock waiting I/O ops.

> +
>  void multifd_save_cleanup(void)
>  {
>      int i;
> @@ -542,6 +555,7 @@ void multifd_save_cleanup(void)
>          MultiFDSendParams *p = &multifd_send_state->params[i];
>          Error *local_err = NULL;
>  
> +        multifd_tls_socket_close(p->c, NULL);
>          socket_send_channel_destroy(p->c);
>          p->c = NULL;
>          qemu_mutex_destroy(&p->mutex);
> -- 
> 1.8.3.1
> 

Regards,
Daniel
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