Palo Alto firewalls have a typically hard NAT, but also have a mode
called Persistent DIPP that is supposed to provide consistent port
mapping suitable for STUN resolution of public ports. Persistent DIPP
works initially on most Palo Alto firewalls, but some models/software
versions have a bug which this works around.
The bug symptom presents as follows:
- STUN sessions resolve a consistent public IP:port to start with
- Much later netchecks report the same IP:Port for a subset of
sessions, most often the users active DERP, and/or the port related
to sustained traffic.
- The broader set of DERPs in a full netcheck will now consistently
observe a new IP:Port.
- After this point of observation, new inbound connections will only
succeed to the new IP:Port observed, and existing/old sessions will
only work to the old binding.
In this patch we now advertise the lowest latency global endpoint
discovered as we always have, but in addition any global endpoints that
are observed more than once in a single netcheck report. This should
provide viable endpoints for potential connection establishment across
a NAT with this behavior.
Updates tailscale/corp#19106
Signed-off-by: James Tucker <james@tailscale.com>
James Tucker
8d1249550a