Hi,

although I'm not a kernel guru I think I've got something to say to this.


I am wondering if 26sec supports NAT-Traversal for multiple
endpoints behind the same NAT. In looking at xfrm_tmpl it's
not obvious to me that it's supported, ...

You are looking at the rignt place indeed. Just to make you sure, there is really no space to store the port infomation of the tunnel endpoints in the xfrm_tmpl structure. The structure xfrm_state (a kernel structuture for holding SA's) is a bit different story though. Although the port information is not stored directly in the structure either, there is the encap member pointing to a xfrm_encap_tmpl structure which is used to hold the required information.

The consequences of this are:
1) The IKE dameon (or the key manager as it is called in the kernel context) can't get the full infomation from the kernel required to be a successful initiator in the case of multiple peers behind the same NAT. (Though you might be able to get it working with a single peer behind the NAT if you configure the port forwarding at the NAT box carefuly.)

2) If there was an IKE daemon which could be told the required port information by some other means then directly by the kernel it should be possible to make it work despite the deficiencies of the kernel. I don't know if there is any IKE daemon capable of this, but I'm sure racoon can't do that.

3) It is possible to get this working the other way around: If the boxes behind the NAT were the initiators then it should work just fine at least if tunnel mode was used. There are some problems with the transport mode but even that can be made to work for certain scenarios.

Regards,
Michal
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