On Fri, Nov 19, 2021 at 04:28:39PM +0100, Florian Westphal wrote:
> This series adds 'tcp option mptcp subtype' matching to nft.
LGTM.
> Because the subtype is only 4 bits in size the exthdr
> delinearization needs a fixup to remove the binop added by the
> evaluation step.
By the bitwise operation to take the 4 bits you can infer this refers to
mptcp, but it might be good to store in the rule userdata area that this
expression refers to mptcp as a suggestion to userspace when
delinearizing the rule. I wanted to look into this for a different
usecase.
> One remaining usablility problem is the lack of mnemonics for the
> subtype, i.e. something like:
>
> static const struct symbol_table mptcp_subtype_tbl = {
> .base = BASE_DECIMAL,
> .symbols = {
> SYMBOL("mp-capable", 0),
> SYMBOL("mp-join", 1),
> SYMBOL("dss", 2),
> SYMBOL("add-addr", 3),
> SYMBOL("remove-addr", 4),
> SYMBOL("mp-prio", 5),
> SYMBOL("mp-fail", 6),
> SYMBOL("mp-fastclose", 7),
> SYMBOL("mp-tcprst", 8),
> SYMBOL_LIST_END
> },
>
> ... but this would need addition of yet another data type.
>
> Use of implicit/context-dependent symbol table would
> be preferrable, I will look into this next.
Could you develop your idea?
Thanks.
