From mboxrd@z Thu Jan  1 00:00:00 1970
From: Balazs Scheidler <bazsi77@gmail.com>
Subject: Re: Unable to create a chain called "trace"
Date: Fri, 12 Feb 2021 19:02:21 +0100
Message-ID: <20210212180221.GA3914830@bzorp>
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To: Florian Westphal <fw@strlen.de>
Cc: Phil Sutter <phil@nwl.cc>, Martin Gignac <martin.gignac@gmail.com>, netfilter@vger.kernel.org, netfilter-devel <netfilter-devel@vger.kernel.org>

On Fri, Feb 12, 2021 at 01:20:07PM +0100, Florian Westphal wrote:
> Phil Sutter <phil@nwl.cc> wrote:
> > I didn't find a better way to conditionally parse two following args as
> > strings instead of just a single one. Basically I miss an explicit end
> > condition from which to call BEGIN(0).
> 
> Yes, thats part of the problem.
> 
> > > Seems we need allow "{" for "*" and then count the {} nests so
> > > we can pop off a scanner state stack once we make it back to the
> > > same } level that we had at the last state switch.
> > 
> > What is the problem?
> 
> Detect when we need to exit the current start condition.
> 
> We may not even be able to do BEGIN(0) if we have multiple, nested
> start conditionals. flex supports start condition stacks, but that
> still leaves the exit/closure issue.
> 
> Example:
> 
> table chain {
>  chain bla {  /* should start to recognize rules, but
> 		 we did not see 'rule' keyword */
> 	ip saddr { ... } /* can't exit rule start condition on } ... */
> 	ip daddr { ... }
>  }  /* should disable rule keywords again */
> 
>  chain dynamic { /* so 'dynamic' is a string here ... */
>  }
> }
> 
> I don't see a solution, perhaps add dummy bison rule(s)
> to explicitly signal closure of e.g. a rule context?

You can always push/pop the flexer state from bison code blocks, maybe
that's what you mean on "dummy bison rules".

Trigger the state from bison and make sure it ends.

Something like this:

diff --git a/src/parser_bison.y b/src/parser_bison.y
index 11e899ff..d8107181 100644
--- a/src/parser_bison.y
+++ b/src/parser_bison.y
@@ -2397,7 +2397,10 @@ chain_policy             :       ACCEPT          { $$ = NF_ACCEPT; }
 identifier             :       STRING
                        ;
 
-string                 :       STRING
+string                 :       { yy_push_state(scanner, STRING); } __string { yy_pop_state(scanner); }
+                       ;
+
+__string               :       STRING
                        |       QUOTED_STRING
                        |       ASTERISK_STRING
                        ;

-- 
Bazsi