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Date: Wed, 24 Jan 2024 16:42:16 +0100
From: Florian Westphal <fw@strlen.de>
To: Phil Sutter <phil@nwl.cc>, Florian Westphal <fw@strlen.de>,
	netfilter-devel@vger.kernel.org
Subject: Re: [PATCH iptables] extensions: libebt_stp: fix range checking
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Phil Sutter <phil@nwl.cc> wrote:
> While you correctly hate the game instead of its player, you probably
> hate the wrong game: The code above indeed is confusing. Maybe one
> should move that monotonicity check into libxtables which should
> simplify it quite a bit. I'll have a look. :)

Something IS broken.  Still not working on FC 39 test machine
even after fresh clone.

On a "working" VM:
export XTABLES_LIBDIR=$(pwd)/extensions
iptables/xtables-nft-multi ebtables -A INPUT --stp-root-cost 1
have 1 32765

@@ -150,7 +151,9 @@ static void brstp_parse(struct xt_option_call *cb)
                RANGE_ASSIGN("root-prio", root_prio, cb->val.u16_range);
                break;
        case O_RCOST:
+               fprintf(stderr, "have %u %u\n", cb->val.u32_range[0], cb->val.u32_range[1]);

I can't even figure out where the correct max value is supposed to be set.

Varying the input:

xtables-nft-multi ebtables -A INPUT --stp-root-cost 1
have 1 32764

Looks to me as if the upper value is undefined.

Other users of *RC versions handle it in .parse, e.g. libxt_length.
No idea how this is working.