I saw that strongSwan had already supported two post-quantum key exchange algorithms (NTRU and NewHope) for IPSec IKEv2. Good.
https://wiki.strongswan.org/projects/strongswan/wiki/IKEv2Ci...
https://wiki.strongswan.org/projects/strongswan/wiki/IKEv2Ci...
http://www.mail-archive.com/cryptography@metzdowd.com/msg123...
https://www.schneier.com/academic/paperfiles/paper-ipsec.pdf
Conclusions
We are of two minds about IPsec. On the one hand, IPsec is far better than any IP security protocol that has come before: Microsoft PPTP, L2TP, etc.
On the other hand, we do not believe that it will ever result in a secure operational system.
It is far too complex, and the complexity has lead to a large number of ambiguities, contradictions, inefficiencies, and weaknesses.
It has been very hard work to perform any kind of security analysis; we do not feel that we fully understand the system, let alone have fully analyzed it.