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Date: Mon, 31 Mar 2025 18:15:30 +0200
From: Florian Westphal <fw@strlen.de>
To: Florian Westphal <fw@strlen.de>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH nft 2/2] evaluate: only allow stateful statements in set
 and map definitions
Message-ID: <20250331161530.GA19247@breakpoint.cc>
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 <20250331152323.31093-2-fw@strlen.de>
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Florian Westphal <fw@strlen.de> wrote:
> The bison parser doesn't allow this to happen due to grammar
> restrictions, but the json input has no such issues.
> 
> The bogon input assigns 'notrack' which triggers:
> BUG: unknown stateful statement type 19
> nft: src/netlink_linearize.c:1061: netlink_gen_stmt_stateful: Assertion `0' failed.
> 
> After patch, we get:
> Error: map statement must be stateful

On the same subject of 'do I fix this in evaluate.c or parser_json.c':

cat bla
table t {
        set sc {
                type inet_service . ifname
        }

        chain c {
                tcp dport . bla* @sc accept
        }
}
nft -f bla
BUG: unknown expression type prefix
nft: src/netlink_linearize.c:914: netlink_gen_expr: Assertion `0' failed.
Aborted (core dumped)

I can either fix this in evaluate.c, or I try to rework both
parser_bison.y and parser_json.c to no longer allow prefix expressions
when specifying the lookup key.

I suspect that fixing it in evaluate.c is going to be a lot simpler.

We can't disable prefixes in concatenations, its valid for set element
keys, but I suspect that we can use recursion counter to figure out if
the concatenation is on the RHS of something else (such as part of
EXPR_SET_ELEM).

I'll work on it tomorrow.