[LARTC] DSCP, ToS and Egress

[Catalin(ux aka Dino) BOIE]

On Tue, 15 Feb 2005, Dan Cox wrote:

> I'm successfully using HTB + GRED to shape traffic based on the DSCP field. I
> would like to strip the DSCP and possibly replace it with normal ToS bits on
> egress traffic leaving my network. Leaving DSCP set is pointless, and could
> potentially cause problems with some ISPs that use DSCP internally I suppose.
> Setting ToS bits would seem ideal as most networks still honor it to varying
> degrees.
>
> The problem is I can see no way of doing this. Since DSCP is needed in the
> qdiscs for shaping, it can't be mangled with iptables. According to the packet
> flow diagram, there doesn't appear to be any other opportunity to mangle the
> packets in this manor. Will I need to insert another router in the chain just
> to do this? :(

You can clone the GRED qdisc code and modify it to overwrite the DSCP 
bits.

>
> -- 
> Dan-
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---
Catalin(ux aka Dino) BOIE
catab at deuroconsult.ro
http://kernel.umbrella.ro/