Re: [Qemu-devel] [PATCH 1.5/6] nbd/server: Ignore write errors when replying to NBD_OPT_ABORT

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

On Sat, Nov 17, 2018 at 04:32:21PM -0600, Eric Blake wrote:
> Commit 37ec36f6 intentionally ignores errors when trying to reply
> to an NBD_OPT_ABORT request for plaintext clients, but did not make
> the same change for a TLS server.  Since NBD_OPT_ABORT is
> documented as being a potential for an EPIPE when the client hangs
> up without waiting for our reply, we don't need to pollute the
> server's output with that failure.
> 
> Signed-off-by: Eric Blake <eblake@redhat.com>
> ---
>  nbd/server.c | 12 ++++++++----
>  1 file changed, 8 insertions(+), 4 deletions(-)
> 
> diff --git a/nbd/server.c b/nbd/server.c
> index 056cfa5ad47..dc04513de70 100644
> --- a/nbd/server.c
> +++ b/nbd/server.c
> @@ -1134,12 +1134,16 @@ static int nbd_negotiate_options(NBDClient *client, uint16_t myflags,
>                  return -EINVAL;
> 
>              default:
> -                ret = nbd_opt_drop(client, NBD_REP_ERR_TLS_REQD, errp,
> +                /* Let the client keep trying, unless they asked to
> +                 * quit. Always try to give an error back to the
> +                 * client; but when replying to OPT_ABORT, be aware
> +                 * that the client may hang up before receiving the
> +                 * error, in which case we are fine ignoring the
> +                 * resulting EPIPE. */
> +                ret = nbd_opt_drop(client, NBD_REP_ERR_TLS_REQD,
> +                                   option == NBD_OPT_ABORT ? NULL : errp,
>                                     "Option 0x%" PRIx32
>                                     " not permitted before TLS", option);
> -                /* Let the client keep trying, unless they asked to
> -                 * quit. In this mode, we've already sent an error, so
> -                 * we can't ack the abort.  */
>                  if (option == NBD_OPT_ABORT) {
>                      return 1;
>                  }

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


Regards,
Daniel
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