The control plane sends an X-Tailscale-Request-Id response header for
debugging. It's not part of the Tailscale protocol, but if it's present,
log it when something goes wrong so client logs can be correlated with
server-side logs: when the server returns an error reply (non-200 status
or a RegisterResponse error), when response headers are slow to arrive
(over five seconds), when the server hangs before sending a
RegisterResponse or its first MapResponse, or when the map long-poll
watchdog fires.
Move the header name constant to tsconst so the client doesn't need to
depend on tsweb.
Updates tailscale/corp#46147
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: I35e179aa335ce4cbe1ab5c7c54d0682ff7975425
Brad Fitzpatrick
bc5a7da03d