Re: [PATCH libnftnl 1/5] expr: add and use incomplete tag

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Mon, Oct 07, 2024 at 11:49:34AM +0200, Florian Westphal wrote:
> Extend netlink dump decoder functions to set
> expr->incomplete marker if there are unrecognized attributes
> set in the kernel dump.
>
> This can be used by frontend tools to provide a warning to the user
> that the rule dump might be incomplete.

This is to handle old binary and new kernel scenario, correct?

I think it is hard to know if this attribute is fundamental to rise a
warning from libnftnl. It could be just an new attribute that can be
ignored by userspace or not? I think libnftables (higher layer) knows
better what to do in this case, if such new attribute is required or
not.

Or maybe this is a different issue?

> diff --git a/src/expr/bitwise.c b/src/expr/bitwise.c
> index e99131a090ed..46346712e462 100644
> --- a/src/expr/bitwise.c
> +++ b/src/expr/bitwise.c
> @@ -97,9 +97,6 @@ static int nftnl_expr_bitwise_cb(const struct nlattr *attr, void *data)
>  	const struct nlattr **tb = data;
>  	int type = mnl_attr_get_type(attr);

Why not simplify with:

	if (mnl_attr_type_valid(attr, NFTA_BITWISE_MAX) < 0) {
		tb[NFTA_BITWISE_UNSPEC] = attr;
		return MNL_CB_OK;
        }

I think it is intentional you are doing this at a later stage.

> -	if (mnl_attr_type_valid(attr, NFTA_BITWISE_MAX) < 0)
> -		return MNL_CB_OK;
> -
>  	switch(type) {
>  	case NFTA_BITWISE_SREG:
>  	case NFTA_BITWISE_DREG: