# My Evening Gone

## Trouble shooting a node on my network

### Specifically a laptop running alpine linux

Which was supposed to be connected via tailscale from a remote location but was in my house connected to my lan ( note that I had alrdy configured tailscale on ts and forgot about it )

This was "The Funny Part"

This incident was especially deceptive because every piece of evidence initially pointed somewhere else.

Evidence suggesting Wi-Fi

High latency to router

100-400ms ping times

Conclusion:

Internet completely dead

* * *

"Maybe the Qualcomm Wi-Fi card is dying."

Result:

Wrong.

* * *

Evidence suggesting firmware

ath10k driver

QCA9377 chipset

Various firmware messages in dmesg

Conclusion:

"Maybe ath10k firmware is broken."

Result:

Wrong.

* * *

Evidence suggesting MTU problems

HTTPS hangs

Docker pulls timeout

Tailscale interface present

Conclusion:

"Maybe PMTU discovery is broken."

Result:

Wrong.

* * *

Evidence suggesting DNS problems

Docker unable to pull images

External services unreachable

Conclusion:

"Maybe DNS is broken."

Result:

Wrong.

DNS worked.

* * *

Evidence suggesting firewall issues

nftables rules

iptables rules

Tailscale chains

Docker chains

Conclusion:

"Some firewall rule is dropping traffic."

Result:

Wrong.

Flushing nftables and iptables changed nothing.

* * *

Evidence suggesting Docker issues

docker pull timeouts

docker compose failures

Conclusion:

"Docker is broken."

Result:

Wrong.

Docker was innocent.

* * *

Evidence suggesting router issues

Internet unreachable

Traceroute fails

Conclusion:

"Router is broken."

Result:

Wrong.

Router responded perfectly.

* * *

Evidence suggesting Ethernet issues

After switching from Wi-Fi to Ethernet:

Problem still exists

Conclusion:

"Maybe the Ethernet port is broken."

Result:

Wrong.

* * *

The Clue Nobody Notices:

One observation never fit any theory:

ARP to router: ~0.5ms

Ping to router: 100-400ms

Layer 2 was perfect.

Layer 3 was nonsense.

That combination is extremely suspicious.

* * *

The Plot Twist

Every subsystem appeared guilty:

\- Wi-Fi

\- Ethernet

\- Docker

\- DNS

\- MTU

\- Router

\- Firmware

\- nftables

\- iptables

Yet every test slowly eliminated them.

The investigation kept narrowing until only one suspect remained:

Tailscale policy routing

And when route acceptance was disabled:

sudo tailscale set --accept-routes=false

Every symptom disappeared immediately.

Internet restored.

Docker restored.

Latency restored.

Sanity restored.

The entire outage was caused by a single route:

192.168.1.0/24 via tailscale0

advertised by MKS and accepted by Alpine-Node.

A one-line route entry managed to impersonate half a dozen unrelated networking failures.