P2P compatibility with Winlink Express (`X-P2P` header)

[bleriotx]

To recreate the issue:

1. From PAT Winlink create a new message destined for a Windows Winlink Express user and click the "P2P Only" checkbox.
2. Post the message to the Outbox.
3. Send the message via AX.25 packet P2P to the recipient.
4. Winlink Express recipient receives the P2P message successfully.
   Problem:

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5. Winlink Express does not identify the inbound message as a P2P message, as it does if sent from another Winlink Express user.
6. This inhibits the Winlink Express recipient from "replying" to the inbound message via a P2P message back to the sender.
7. The Winlink Express user has to create a NEW P2P message and post it to the Outbox to reply.
   (WL2K to WL2K users do not have to create a new P2P message.)

I apologize if this is not clear, or is an issue that is already known. I could not find any posts that describe this problem.

Bleriotx

[jboverfelt]

Seems like it might be related to PR #480

[bleriotx]

I agree. Sorry I missed this.
It looks like this issue has been discussed thoroughly and it is best not to make any changes to the code.

Thanks for you quick response. Please close this issue.

Thanks,
Bleriotx

[jboverfelt]

Well it's Martin's decision I just happened to be in here :-)

I do think that it's worth discussing what we might do to improve compatibility and if Phil (Winlink Express developer) would be willing to work with us to improve this situation.

[martinhpedersen]

Thanks for opening this issue @bleriotx 😊

I agree with @jboverfelt that we need to discuss this further. At the very least we should consider aligning our P2P header with the one Winlink Express has introduced so we get the expected result setting the "P2P Only" flag in the composer modal.

But I agree that we should try discussing this with Phil as Justin suggests. I believe it's possible to detect a P2P connection at the receiving end, so both clients can set this flag properly without relying on a header injected into the actual message. I believe this would be more flexible in terms of compatibility with the various clients, not only Winlink-specific FBB clients with a clear distinction between a "P2P" message and regular messages.

[bleriotx]

Please let me know if there is anything you need me to do here. Be glad to help any way that I can.

Bleriotx

[martinhpedersen]

Thanks @bleriotx 😊 I think as a start, we should try aligning the headers. Is that something you'd be willing to have a go at?

I think we should make the change backwards compatible, if it's not too much hassle: We should check for both X-P2POnly and X-P2P where we now only check for X-P2POnly. But only produce new messages with the X-P2P header.

I believe we might need to make changes in the wl2k-go repo. I usually do that by cloning both repos in the same parent dir and add this at the bottom of go.mod in pat repo: replace github.com/la5nta/wl2k-go => ../wl2k-go.