Webhooks: Does Microsoft only support IPv4 targets?

[Hoempi]

Hey everyone,

I have been setting up the Docker container this afternoon and at first could not get the webhooks running. I forwarded the port in my docker compose, set up the webhook_enabled and webhook_public_url entries and verified with my mobile from outside my LAN that https://onedrive.mydomain.com/webhooks/onedrive was returning a 200/OK when queried with a browser.

Still, I got the error message "subscription validation request timed out". So I started looking into my Caddy config for the endpoint, but could not find anything.

Finally, I was able to resolve the issue by activating the Cloudlfare proxy option. Aside from the additional proxying it also gave my URL a public IPv4. Without this, Cloudflare would only resolve return an IPv6. I set Cloudflare up this way because I only got a public IPv6 and my IPv4 is behind carrier grade NAT.

So I was thinking that Microsoft's service either a) does not query the AAAA record or b) does not do a DNS query at all and just takes the IP from the received TCP/IP package.

On further thought b) would not explain why the problem was resolved by activating Cloudflare's proxy, as the IPv4 Cloudflare is serving is not in the TCP/IP package send by the OneDrive client in the Docker container.

So, for me it is fixed and I'm writing this down for two reasons. Firstly, to possibly help someone else out when experiencing the same problem. And secondly to see if perhaps someone knows for sure that my description and assumptions fit the reality.