Skip to content

Add AdvSNACRouterFlag option to set the SNAC router bit #271

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 2 commits into
base: master
Choose a base branch
from

Conversation

arkku
Copy link

@arkku arkku commented May 19, 2025

Adds a new option: AdvSNACRouterFlag. When enabled, this sets RA option bit 6, a formerly reserved bit, that is seems to be now allocated to "SNAC router".

The reason for this addition is that I noticed Apple's HomeKit devices setting this flag to 1 when advertising themselves as a Thread border router. I have multiple VLANs, and I wanted to use radvd to re-advertise the route with identical options (but different router address).

In 2019 this same bit has been proposed to stand for IPv6 only, but that does not seem to have been adopted as standard. However, tcpdump still decodes the bit as "ipv6 only". These two uses aren't necessarily contradictory, since the Stub Network advertised as such is indeed IPv6 only.

Comment on lines +534 to +535
When set, indicates the router is a SNAC router (stub network auto
configuration, e.g., for IPv6-only stub networks).
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Please link to the RFC here

Copy link
Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I don't think there is an official RFC yet, even though the bit has been assigned (ietf-wg-snac/draft-ietf-snac-simple#54)

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

@stappersg
Copy link
Member

stappersg commented May 20, 2025 via email

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
Labels
None yet
Development

Successfully merging this pull request may close these issues.

3 participants