Re: [nft v3 PATCH 4/4] py: add Nftables.input_{set,get}_flags() API

[Phil Sutter <phil@nwl.cc>]

On Thu, Jul 20, 2023 at 04:27:03PM +0200, Thomas Haller wrote:
> Add new API to expose the input flags in the Python API.
> 
> Note that the chosen approach differs from the existing
> nft_ctx_output_get_flags() and nft_ctx_output_get_debug()
> API, which themselves are inconsistent approaches.
> 
> The new API directly exposes the underlying C API, that is, the numeric
> flags.

Insisting on forcing users to set input flags differently than output
flags is a bit odd, but once complaints come in we can still follow-up I
guess.

[...]
> diff --git a/py/nftables.py b/py/nftables.py
> index 68fcd7dd103c..e2417b7598c0 100644
> --- a/py/nftables.py
> +++ b/py/nftables.py
[...]
> @@ -152,6 +182,30 @@ class Nftables:
>      def __del__(self):
>          self.nft_ctx_free(self.__ctx)
>  
> +    def input_get_flags(self):
> +        """Query input flags for the nft context.
> +
> +        See input_get_flags() for supported flags.
> +
> +        Returns the currently set input flags as number.
> +        """
> +        return self.nft_ctx_input_get_flags(self.__ctx)
> +
> +    def input_set_flags(self, flags):
> +        """Set input flags for the nft context as number.
> +
> +        By default, a new context objects has flags set to zero.
> +
> +        The following flags are currently supported.
> +        NFT_CTX_INPUT_NO_DNS (0x1) disables blocking address lookup.
> +        NFT_CTX_INPUT_JSON (0x2) enables JSON mode for input.
> +
> +        Unknown flags are silently accepted.
> +
> +        Returns nothing.
> +        """
> +        self.nft_ctx_input_set_flags(self.__ctx, flags)

Please make this return the old flags. It makes temporary flag setting
much easier, see this snippet from tests/py/nft-test.py for instance:

|  # Check for matching ruleset listing
|  numeric_proto_old = nftables.set_numeric_proto_output(True)
|  stateless_old = nftables.set_stateless_output(True)
|  list_cmd = 'list table %s' % table
|  rc, pre_output, err = nftables.cmd(list_cmd)
|  nftables.set_numeric_proto_output(numeric_proto_old)
|  nftables.set_stateless_output(stateless_old)

Thanks, Phil