Re: [PATCH 06/12] net/slirp: Clean up error reporting

["Daniel P. Berrangé" <berrange@redhat.com>]

On Fri, Aug 08, 2025 at 10:08:17AM +0200, Markus Armbruster wrote:
> net_slirp_register_poll_sock() and net_slirp_unregister_poll_sock()
> report WSAEventSelect() failure with error_setg(&error_warn, ...).
> 
> I'm not familiar with liblirp, so I can't say whether the network

                       ^^^^^^^^^ 'libslirp'


> backend will work after such a failure.  If it doesn't, then this
> should be an error.  If it does, then why bother the user with a
> warning that isn't actionable, and likely confusing?
> 
> Regardless of that, error_setg_win32(&error_warn, ...) is undesirable
> just like error_setg(&error_fatal, ...) and error_setg(&error_abort,
> ...)  are.  Replace by warn_report().
> 
> Cc: Marc-André Lureau <marcandre.lureau@redhat.com>
> Signed-off-by: Markus Armbruster <armbru@redhat.com>
> --->
  net/slirp.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)

Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

> diff --git a/net/slirp.c b/net/slirp.c
> index 9657e86a84..d75b09f16b 100644
> --- a/net/slirp.c
> +++ b/net/slirp.c
> @@ -262,7 +262,8 @@ static void net_slirp_register_poll_sock(slirp_os_socket fd, void *opaque)
>      if (WSAEventSelect(fd, event_notifier_get_handle(&ctxt->notifier),
>                         FD_READ | FD_ACCEPT | FD_CLOSE |
>                         FD_CONNECT | FD_WRITE | FD_OOB) != 0) {
> -        error_setg_win32(&error_warn, WSAGetLastError(), "failed to WSAEventSelect()");
> +        warn_report("failed to WSAEventSelect(): %s",
> +                    g_win32_error_message(WSAGetLastError()));
>      }
>  #endif

IMHO this one ought to be considered fatal. If we can't select the
right events on the socket, then we're not going to have a good time
trying to poll on events. The libslirp callback API doesn't allow
us to return a success/failure code from this function, and IMHO it
is not appropriate to use error_fatal here because a fault with slirp
should not take down the whole of QEMU. So warn_report is the least
worst option I guess. At least it is a hint to the user that all is
not well - even if they can't action it, it might alert them if they
see network problems in their guest.


>  }
> @@ -271,7 +272,8 @@ static void net_slirp_unregister_poll_sock(slirp_os_socket fd, void *opaque)
>  {
>  #ifdef WIN32
>      if (WSAEventSelect(fd, NULL, 0) != 0) {
> -        error_setg_win32(&error_warn, WSAGetLastError(), "failed to WSAEventSelect()");
> +        warn_report("failed to WSAEventSelect()",
> +                    g_win32_error_message(WSAGetLastError()));
>      }

This one is reasonable to treat as non-fatal, since once we've
unregistered the socket for polling

>  #endif
>  }
> -- 
> 2.49.0
> 
> 

With regards,
Daniel
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