allow creating offers with blinded paths when you have public channels

[AndySchroder]

https://blog.blockstream.com/core-lightning-v24-08-steel-backed-up-channels/ says "The offers plugin now automatically adds a blinded path from a peer when there are no public channels available, enabling unannounced nodes to generate and manage offers securely without exposing their channels publicly."

Not sure why you don't have an option to create blinded paths if you do have public channels?

Either way, there is no logging (either in the log file (I have log-level=debug:plugin-offers set by the way) or in response to lightning-cli offer or lightning-cli listoffers) indicating that a blinded path is used or not used, and I think that should definitely be done. Currently I have to use lightning-cli decode lno1xxxxxx in order to check. Lots of people think BOLT12 offers are private and use blinded paths, but it seems very easy to not do so in CLN with the current behavior.

[21M4TW]

Running v25.02 here with only private channels that existed prior to upgrading. Creating an offer results in a bolt12 that does not contain blinded paths either, it just gives my node ID away under offer_id. I think the offer command should have a blinded_paths argument that enforces the use of blinded paths if desired. And in addition it seems there is still a bug that causes offers to be not blinded in some situations even in the absence of public channels...

I do see "UNUSUAL plugin-offers: No incoming channel to public peer, so no blinded path", and supposedly maybe it will get resolved by itself after about 15 hours. I will wait and see, but I think the offer command should have thrown an error in that situation instead?

[21M4TW]

Just tried it again, about 24h after upgrading to v25. Still the same result, before and after restarting the node. I am not sure if there is anything else I can try, such as deleting gossip_store to poke and force the node to reprocess the gossips?

Edit: Same issue after almost to days. Just tried deleting the gossip_store to see if it wakes things up or not.

[21M4TW]

Ok so I just looked in plugins/offers_offer.c, and it seems the lack of option_onion_messages bits (bits 38/39) in my peers' feature bits is what triggers the error message about my peers not being public. All my peers have the following feature bits:
800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002000888252a1

After looking into this I think the message was misleading and it has nothing to do with the node being public, but rather because vanilla LND nodes do not support option_onion_messages yet?