[Olsr-dev] SmartGW client side questions

Henning Rogge (spam-protected)
Wed Apr 28 16:55:44 CEST 2010

Am Mittwoch 28 April 2010 14:43:00 schrieb Sven-Ola Tuecke:
> Yes - of course. A question: do we need that tnl_$%abcd name for the
> smargw-client tunnel interface? I only expect one iface (because only one
> default-route-via-tunnel at a time").
The problem is that we cannot have two tunnels towards the same target, even 
if one is ip6_in_ip6 and one ip4_in_ip6.

Because of this you need to use the same tunnel towards a combined ipv4/ipv6 
gateway. And one of them can switch to a different gateway anytimes. That's 
why I designed the "usage_counter" protected tunnel system. You have a 
guarantee that the interface index will not change unless you need a new 

Any plugin can use the system to build additional tunnels for 'multiple 
gateway' sollutions and graceful gateway switching in ipv6.

> A fixed name e.g. "olsr-smartgw" is more easily to handle, e.g. "iptables
> -A FORWARD -o olsr-smartgw -p tcp --tcp-flags SYN,RST SYN -j
> TCPMSS --clamp-mss-to-pmtu" sits in the firewall list and waits for the
> interface to be created. If we use a fixed name, I would omit the mentioned
> "background" job.

Maybe we could add a callback so that you can have a plugin that calls an 
external script when a tunnel is created ?

1) You can't win.
2) You can't break even.
3) You can't leave the game.
— The Laws of Thermodynamics, summarized
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