Re: [mpls-linux-general] What does the RADIX_* do?

[James R. L. <jl...@mi...>]

On Mon, Jan 21, 2002 at 04:34:44AM -0800, Cheng Zhengchao wrote:
> Hi,All,
> 
>   When I read the codes of mpls*.c in the
> /usr/src/linux/net/mpls,I find I can not catch what
> the RADIX_* do.Can anyone help me to understand

The corect name is a radix trie.  Which is basically a tree (binary or
otherwise) that can support variable length keys.  I wrote the RADIX* macros
when I was studying differnt way to optimize the storage of the internet
routing table.

I use it now because I'm lazy :-) It provides a pretty speedy look up, but I
never fully take advantage of the trie, the keys I store in it are always
32 bits in length.  Someday I'll replace RADIX* with some sort of multilevel
hash.  You don't need to understand RADIX* to understand the MPLS
implementation.  Just think of them as easy ways to save and retireve info
by a 32 bit key.

> it?What do them to do?
>   At the same time,mpls_label2key() is used to get the
> key,but I wonder how can it get the mark?and what is

The structure mpls_key is a union.  If you understand how a union works
it becomes quit evident how I get 'mark' from it.

> the role of key in the RADIX_*?
>  Thanks for your help in advance.
> 
> Yours Sincerely
> Cheng
> 
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-- 
James R. Leu