Hello Brian, On 18.10.2016 21:05, Brian O'Connor wrote: > 1. Where in the diagram is NAT-T de-capsulation performed? XFRM lookup. > > 2. Where in the diagram is NAT-T encapsulation performed? XFRM lookup. > > 3. Does the NAT-T UDP header have to be removed so the iptables IPsec > policy module can operate? Nope. This question sound suspiciously like you want to check if an ESP/NAT-T packet has a matching policy. XFRM does that for you. IPsec policies also work the other way around. They don't just only allow protected traffic to or from an IP address, they also implicitely drop unprotected matching datagrams. The kernel will and does also efficiently drop spoofed ESP packets. The system design is sound. There's no reason to try to protect the kernel from invalid ESP packets.
> > 4. Traffic from the topmost "local process" block flows to a "routing > decision" block. Is this to prevent > a local IPsec connection (to loopback address, possibly ) from being > encrypted? No, it's just there to fill in required routing information into the skb in the kernel. XFRM is disabled on loopback via a sysctl value. You can enable it, if you want, but that makes no sense and there's no need for that. > >  http://inai.de/images/nf-packet-flow.png > > TIA, > Brian -- Mit freundlichen Grüßen/Kind Regards, Noel Kuntze GPG Key ID: 0x63EC6658 Fingerprint: 23CA BB60 2146 05E7 7278 6592 3839 298F 63EC 6658
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