Re: [mpls-linux-general] packet journey in mpls linux (for experts)

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

On Fri, Mar 28, 2003 at 04:29:44PM +0000, Francesco Oppedisano wrote:
> For my degree thesis i have to understand which is the real path a packet 
> traverses in a linux mpls box.
> Here is what a know:
> when an (e.g.) ethernet frame arrives to the nic, it is stored in a skbuff 
> structure; 
> here a kernel function dermines the protocol field of the frame and calls the 
> code of the corresponding layer; if this code is 0x0800 the frame is passed 
> to the IP layer which in turn calls the first netfilter hook (prerouting)...
> if the code is 0x8847 the frame is passed to the mpls layer; here are  my 
> questions: 
> this  means that no netfilter code is called because the frame is handled by 
> mpls layer? 
> So if i write a kernel module that hooks to the netfilter code, it will be 
> bypassed in the mpls core nodes?  

Are you asking if there are netfilter hooks in MPLS?  Not, not yet.
As far as I know there are only netfilter hook in the IPv4 and IPv6 code.
Remember there are two differnt path a packet can take to get into the
MPLS code:
-packet arrives at ethernet driver with protocol ID of 0x8847
 (LSR or egress LER)
-packet get diverted from IPv4 into MPLS (ingress LER)

May I ask what you are trying to do?  Maybe I can help point you in the
right direction.

> Is there a documentation that explains step by step the funcions that are 
> called by the mpls layer?

No.  Although it seems you are doing a good job reading the kernel source.
I suggest continuing to do that and ask specific question when you need help.

> 
> Thank you very much
> Francesco Oppedisano
> 
> 
> -------------------------------------------------------
> This SF.net email is sponsored by:
> The Definitive IT and Networking Event. Be There!
> NetWorld+Interop Las Vegas 2003 -- Register today!
> http://ads.sourceforge.net/cgi-bin/redirect.pl?keyn0001en
> _______________________________________________
> mpls-linux-general mailing list
> mpl...@li...
> https://lists.sourceforge.net/lists/listinfo/mpls-linux-general

-- 
James R. Leu