zebra: implement RFC8781 (NAT64 prefix in RAs)

[eqvinox]

This tells hosts on the subnet if (and which) NAT64 prefix is in use. Useful for things like xlat464, or local dns64.

Updated from the previous -03 draft implementation. (PLC field did not exist before.)

---

This was previously #4741. The option encoding has indeed changed from what it was in draft -03 back then, and the option code (38) was not allocated yet.

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-PULLREQ2-5474/

This is a comment from an automated CI system. For questions and feedback in regards to this CI system, please feel free to email Martin Winter - mwinter (at) opensourcerouting.org.

Warnings Generated during build:

Checkout code: Successful with additional warnings

Report for rtadv.c | 2 issues
===============================================
< WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
< #487: FILE: /tmp/f1-555/rtadv.c:487:

[NetDEF-CI]

Continuous Integration Result: SUCCESSFUL

Congratulations, this patch passed basic tests

Tested-by: NetDEF / OpenSourceRouting.org CI System

CI System Testrun URL: https://ci1.netdef.org/browse/FRR-PULLREQ2-5475/

This is a comment from an automated CI system. For questions and feedback in regards to this CI system, please feel free to email Martin Winter - mwinter (at) opensourcerouting.org.

Warnings Generated during build:

Checkout code: Successful with additional warnings

Report for rtadv.c | 2 issues
===============================================
< WARNING: Prefer 'unsigned int' to bare use of 'unsigned'
< #487: FILE: /tmp/f1-7339/rtadv.c:487:

[donaldsharp]

let's clean up the code warning and I believe we need a topotest too.

[github-actions[bot]]

This pull request has conflicts, please resolve those before we can evaluate the pull request.

[aalmenar]

Any possibility of this being merged for 8.4 and backported to 8.3?

[github-actions[bot]]

This PR is stale because it has been open 180 days with no activity. Comment or remove the autoclose label in order to avoid having this PR closed.

[mruprich]

Hi, can I ask, what is the status of this RFE? Seems like the work has started but was not finished due to some conflicts? Is there an intention to revisit this?

Thanks and regards, Michal Ruprich

[eqvinox]

can I ask, what is the status of this RFE?

Our current test framework doesn't support testing this, so it's stuck due to the test requirement. I'm working on a better test framework…

[ne-vlezay80]

linux kernel is not support nat64

[eqvinox]

linux kernel is not support nat64

@ne-vlezay80 this is irrelevant, the NAT64 system can be somewhere else in the network.