[PATCH 11/18] nvme-tcp: enable TLS handshake upcall

[Daniel Wagner]

On Mon, Apr 17, 2023 at 03:02:55PM +0200, Hannes Reinecke wrote:
 --- a/drivers/nvme/host/fabrics.c
> +++ b/drivers/nvme/host/fabrics.c
> @@ -609,6 +609,7 @@ static const match_table_t opt_tokens = {
>  	{ NVMF_OPT_DISCOVERY,		"discovery"		},
>  	{ NVMF_OPT_DHCHAP_SECRET,	"dhchap_secret=%s"	},
>  	{ NVMF_OPT_DHCHAP_CTRL_SECRET,	"dhchap_ctrl_secret=%s"	},
> +	{ NVMF_OPT_TLS,			"tls"			},
>  	{ NVMF_OPT_ERR,			NULL			}
>  };

Coming back to your previous discussion about this. 'tls' is always announced
but not always supported. This renders the unsupported option filtering added to
libnvme useles:

  https://github.com/linux-nvme/libnvme/issues/612

Let's assume we go ahead with this patch. The user set explicit the tls option
via 'nvme connect ... --tls' and the kernel will return EINVAL, but userland
can't really know what it was and drop --tls and retry again (or print some
useful information). It could be any other parameter provided by the user.

How is userland supposed to do any feature detection?