Add UDP encapsulation of ESP in IPv6

[allanjude]

Summary

This patch provides UDP encapsulation of ESP packets over IPv6.
It mostly consist of porting IPv4 code to IPv6 and adding support of IPv6 in udpencap.c
As required by the RFC and unlike in IPv4 encapsulation, UDP checksums are calculated

Sponsored by: Stormshield

Test Plan

After enabling UDP encapsulation, pings are correctly encapsulated in UDP, transfered and decapsulated on the other side of the tunnel

[ae]

sys/netinet6/udp6_usrreq.c

171

I think this won't work if kernel was built without INET support.
I.e. we need to implement per-AF methods.

707

This ifdef looks useless, is it possible udp6_ctloutput() to be called without INET6?

sys/netipsec/ipsec_output.c

778

This also seems unneeded if we have NAT-T support for both AF.

sys/netipsec/udpencap.c

124

Without ifdefs this will lead to build failure for NOINET/NOINET6 builds. I think to reduce number of ifdes we can move ip/ip6 declarations to the switch (af) below.

326

It seems you didn't modified key_setnatt() to handle IPv6 addresses. Does it not needed? :)

[ae]

I'll try to test this and commit with small modifications after weekend. Thanks!

[brueffer]

Is this review still active? Would be useful functionality in some scenarios.

[allanjude]

That was committed as https://reviews.freebsd.org/D42526 / 80044c785cb040a2cf73779d23f9e1e81a00c6c3