RE: Multipath Routing
> I see. My gateway establishes PPP links in random order too, so I cannot
> rely on predictable interface names to set up routes and iptables rules.
At the minute I have a set of scripts taking care of this form ip-up /
ip-down. It seems the only sane way todo it.
> > This looks like what is happening. Is there a way to do nat before the
> > POSTROUTING chain ? Or is there a way to force it to recalculate the
> route
> > after the address translation takes place ?
>
> If you mean source NAT, the short answer is no. As you can see in the
> map, source NAT can only take place in the POSTROUTING chain, and
> rerouting can only occur on locally generated packets after destination
> NAT and/or mangling in the OUTPUT chain.
>
> So you have to decide at routing time what the output interface will be.
> Later, it is too late. I cannot be more precise without knowing your
> routing policy. Then you can do source NAT based on the output interface
> in the POSTROUTING chain.
I don't yet really have a routing policy as such. Its kind of open for
anything. But the ideal way for this to work would be for any outbound tcp /
udp to use either connection on a ratio bases initially 50 / 50 to make
things simple.
I have been able to get it to work off certain ip address by selecting the
route by source ip address before the port routing table. But I cannot get
it to work for all connections.
I was possibly thinking of a way todo this by using a dummy interface and
setting it to be the default route then writing a small program to read
outbound packets on this interface and re-injecting them into the kernel
after the SNAT has been applied. This seems a bit of over kill though.
I did find some linux routing patches at http://www.ssi.bg/~ja/#routes
It makes it work. But it does have some side effect like the first packet of
a connection can go out the wrong interface.
James
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