DERP 部署后并设置了 "OmitDefaultRegions": true，tailscale netcheck 如下：
➜ ~ sudo tailscale netcheck --verbose
2024/03/29 14:23:15 netcheck: sent to 8.217.251.250:1222
2024/03/29 14:23:15 netcheck: received STUN packet from 8.217.251.250:1222
2024/03/29 14:23:15 netcheck: sent haircheck to 219.142.184.59:8975
2024/03/29 14:23:15 netcheck: hairCheck timeout
2024/03/29 14:23:15 netcheck: hairCheck done
2024/03/29 14:23:15 netcheck: portMap done
2024/03/29 14:23:15 netcheck: [v2] checkCaptivePortal url="http://6606576df2a0e.derps.link/generate_204" status_code=404 valid_response=false
2024/03/29 14:23:15 netcheck: [v1] report: udp=true v6=false v6os=true mapvarydest= hair=false portmap= v4a=219.142.184.59:8975 captiveportal=true derp=900 derpdist=900v4:43ms
2024/03/29 14:23:15 netcheck: GetReport took 291ms; err=<nil>
Report:
* UDP: true
* IPv4: yes, 219.142.184.59:8975
* IPv6: no, but OS has support
* MappingVariesByDestIP:
* HairPinning: false
* PortMapping:
* CaptivePortal: true
* Nearest DERP: Astera
* DERP latency:
- hk2-1113: 43.5ms (derp900, Astera)
只能 ping 通 LAN 设备，WAN 设备 timeout
