CentOS - Apr 2015 - unsetting/erasing an iptables mark

Hello all,

iptables provides a way to mark/tag packets for future
identification/accounting, etc. A brief discussion of it is offered here:

https://wiki.archlinux.org/index.php/Advanced_traffic_control

Here is a more detailed description of the issue I am working on:

http://lists.centos.org/pipermail/centos/2015-April/151245.html

Getting to the crux of the issue as it stands now.

I need to get rid of the mark on the packets after they have been processed
by tc and sent on. That can be done by a VM down the line, too.

Basic logic of the process should be: "anything that comes with a mark,
erase that mark, send it on".

Effectively, going off this syntax:

iptables -A FORWARD -t mangle -i eth0 -j MARK --set-mark 6

I would need to be able to come up with something like --erase-mark or
functional equivalent thereof.

Any suggestions much appreciated.

Cheers,

Boris.