Re: question about UNDEFINE/REDEFINE

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Hello Pablo,

Dne pátek 26. ledna 2018 14:45:49 CET, Pablo Neira Ayuso napsal(a):
> 2) Probably even cleaner is to look at 'local' scopes like in bash.
> 
>  define local IP1 = 1.1.1.1
> 
> so the symbol is bound to this file - consider the content of a file
> determines a given scope. This can be also useful to the nested
> notation.
> 
> 3) You rework your ruleset to use the notation with nesting :-). But I
> think 2) can be useful for both the flat and nested notation.
> 
> I'm not asking you to do 2), but I would like to see how a patch that
> adds explicit scoping for the flat ruleset representation looks like.

I know about scopes in the code but unfortunately as you said, the flat 
notation only has a single scope. Since we are talking about analogy to bash, 
bash allows me to redefine a variable in the same scope. Variables in nftables 
feel more like constants which is not necessarily bad as it can prevent some 
typos but is hard to work with in scripting as it's not that flexible.

>From those options you listed I would strongly prefer to have an implicit 
scope for each file included in the flat notation. That way, defining a variable 
in one file would not collide with the same variable in a sibling include. 
Variables from outer scopes would still be available in inner scopes. For 
people that would want to have their "global" definitions in a separate 
include, I would recommend creating a new keyword like global or export that 
would tie a variable to the top-level scope and thus make it available to 
everyone. I don't think that would be that hard to implement and I may try to 
if we agree on it.

Anyway there should definitely be a way to de-register (undefine) a variable 
from a scope to prevent a misuse due to typos.

By the way, can we restructure the FW using nesting and still be able to 
retain all per-customer rules in a single file? Wouldn't that require us to 
split prerouting, postrouting, forward and other rules to separate scopes/
table definitions? That would be highly inconvenient.

-- 
S pozdravem,

David Fabian
Cluster Design, s.r.o.
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