Sam & Claude
c3056ac489
Replace live 100.x IPs with , per SOUL.md convention. Removed stale device IP from network-ssh-wifi-diagnostics reference.
90 lines
3.1 KiB
Markdown
90 lines
3.1 KiB
Markdown
# Network / SSH / Wi-Fi diagnostic notes
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Use this reference when investigating SSH/tmux lag, Wi-Fi jitter, hotspot switching, Tailscale reachability, or projector/network interference.
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## Logging convention for this user
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The user dislikes Desktop clutter. For repeated diagnostics, prefer one timestamped logfile under:
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```bash
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mkdir -p "$HOME/.local/state/hermes/net-tests"
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LOG="$HOME/.local/state/hermes/net-tests/net-test-$(date +%Y%m%d-%H%M%S).log"
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{ ...diagnostics...; } | tee "$LOG"
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```
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Use `/tmp` only for throwaway scratch output. Do not create multiple Desktop files unless explicitly requested.
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## Network-switch pitfall: stale SSH sessions
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When a host switches Wi-Fi networks, existing public SSH sessions may break even if the server is still reachable. Inspect live sockets before concluding the remote is down:
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```bash
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ss -nti '( sport = :22 or dport = :22 )'
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ip -brief addr
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ip route
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```
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Signs of a stale/broken old path include:
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- socket local address from previous network, or FIN-WAIT state
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- nonzero Send-Q / notsent data
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- retrans/backoff
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- weird PMTU collapse
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A Tailscale SSH session to another host may survive the same switch if it is bound to the Tailscale path, while a public SSH session to the same or another host may die.
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## Always compare public vs tailnet identities
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For hosts with both public DNS and MagicDNS/tailnet DNS, resolve and test both forms:
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```bash
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getent ahosts osa.smilepowered.org
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getent ahosts osa.taile682b7.ts.net
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ip route get <public-ip>
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ip route get <tailscale-ip>
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tailscale ping --timeout=5s --c 5 <name>
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timeout 6 bash -c '</dev/tcp/<host>/22' && echo TCP/22-open || echo TCP/22-failed
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```
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ICMP ping may fail while TCP/22 and `tailscale ping` work, so do not use ICMP alone as the availability test.
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## Hotspot/router gateway test
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Do not hardcode the gateway when comparing Wi-Fi vs phone hotspot. Derive it from the current route:
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```bash
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GW=$(ip route show default | awk '{print $3; exit}')
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ping -c 80 -i 0.1 "$GW"
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ping -c 80 -i 0.1 1.1.1.1
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```
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For the user's tested setup, home Wi-Fi used `192.168.1.1`, while phone hotspot `osa` used `10.91.179.29`. A script hardcoded to `192.168.1.1` falsely reports gateway loss after switching to the hotspot.
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## Useful single-log command skeleton
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```bash
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mkdir -p "$HOME/.local/state/hermes/net-tests"
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LOG="$HOME/.local/state/hermes/net-tests/ssh-wifi-$(date +%Y%m%d-%H%M%S).log"
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{
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date
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echo '## wifi/default route'
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ip -brief addr show wlp1s0 || true
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ip route || true
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nmcli -f GENERAL.CONNECTION,GENERAL.DEVICE,GENERAL.STATE,GENERAL.METERED,IP4.ADDRESS,IP4.GATEWAY,IP4.DNS device show wlp1s0 2>/dev/null || true
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nmcli -f IN-USE,SSID,BSSID,CHAN,FREQ,RATE,SIGNAL,BARS,SECURITY dev wifi list --rescan no 2>/dev/null || true
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echo '## tailscale'
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tailscale status 2>&1 || true
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tailscale netcheck 2>&1 || true
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echo '## routes and sockets'
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ss -nti '( sport = :22 or dport = :22 )' 2>/dev/null || true
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GW=$(ip route show default | awk '{print $3; exit}')
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for target in "$GW" 1.1.1.1 ${DOMEDOG_TS_IP}; do
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echo "--- ping $target"
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ping -c 30 -i 0.2 "$target" 2>&1 | tail -8 || true
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done
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} | tee "$LOG"
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echo "$LOG"
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```
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