easytether doctor script

easytether_doctor.zsh

#!/usr/bin/env zsh
# Quick diagnostics for the EasyTether USB path.

set -u

header() {
  printf '\n== %s ==\n' "$1"
}

status() {
  # $1 = label, $2 = message
  printf '[%s] %s\n' "$1" "$2"
}

need_cmd() {
  for c in "$@"; do
    command -v "$c" >/dev/null 2>&1 || {
      status "MISSING" "install '$c' to run full checks"
      return 1
    }
  done
  return 0
}

# Prefer sudo if not root.
run() {
  if [[ $EUID -ne 0 ]]; then
    sudo "$@"
  else
    "$@"
  fi
}

# 1) Interface presence and state.
header "Interface"
if ip link show tun-easytether >/dev/null 2>&1; then
  ip -d link show tun-easytether | sed 's/^/  /'
else
  status "FAIL" "tun-easytether not present (is easytether-usb running and the phone connected?)"
fi

# 2) Routes.
header "Routes"
if need_cmd ip; then
  run ip route show | sed 's/^/  /'
  if ! run ip route show default | grep -q '192.168.117.1'; then
    status "WARN" "default via 192.168.117.1 missing; add: sudo ip route replace default via 192.168.117.1 dev tun-easytether metric 50"
  fi
fi

# 3) Ping the phone-side gateway.
header "Gateway ping"
if need_cmd ping; then
  if run ping -c 3 -w 5 192.168.117.1 >/tmp/easytether_ping.$$ 2>&1; then
    status "OK" "gateway 192.168.117.1 reachable"
  else
    status "FAIL" "cannot reach 192.168.117.1 (check cable/app/adb prompt)"
  fi
  cat /tmp/easytether_ping.$$ | sed 's/^/  /'
  rm -f /tmp/easytether_ping.$$
fi

# 4) DNS config and lookup.
header "DNS"
if [[ -f /etc/resolv.conf ]]; then
  status "INFO" "current /etc/resolv.conf:"
  sed 's/^/  /' /etc/resolv.conf
  if ! grep -q '192\.168\.117\.1' /etc/resolv.conf; then
    status "WARN" "phone DNS not configured; echo 'nameserver 192.168.117.1' | sudo tee /etc/resolv.conf"
  fi
else
  status "FAIL" "/etc/resolv.conf missing"
fi

if need_cmd getent; then
  if run getent ahostsv4 example.com >/tmp/easytether_dns.$$ 2>&1; then
    status "OK" "example.com resolves (IPv4)"
  else
    status "FAIL" "example.com does not resolve; try forcing resolv.conf to 192.168.117.1"
  fi
  cat /tmp/easytether_dns.$$ | sed 's/^/  /'
  rm -f /tmp/easytether_dns.$$
fi

# 5) HTTP reachability (real-world traffic; ping may be blocked by carrier).
header "HTTP check"
if need_cmd curl; then
  if run curl -4 -I --silent --max-time 6 https://example.com >/tmp/easytether_http.$$ 2>&1; then
    status "OK" "HTTPS reachable over IPv4"
  else
    status "FAIL" "HTTPS failed; inspect output and routes"
  fi
  cat /tmp/easytether_http.$$ | sed 's/^/  /'
  rm -f /tmp/easytether_http.$$
fi

# 6) Journal tail for easytether.
header "Recent easytether logs"
if need_cmd journalctl; then
  run journalctl -u 'easytether-usb@*' -n 50 --no-pager 2>/tmp/easytether_journal.$$ && \
    cat /tmp/easytether_journal.$$ | sed 's/^/  /'
  rm -f /tmp/easytether_journal.$$
else
  status "INFO" "journalctl not found; skip logs"
fi

cat <<'HINT'

notes.md

Notes:

• If ping to the internet fails but HTTPS works, your carrier is likely blocking ICMP; use curl or a browser to verify real connectivity.
• If DNS keeps changing, NetworkManager may be overwriting /etc/resolv.conf; you can temporarily freeze it with: sudo chattr +i /etc/resolv.conf (undo with chattr -i).
• To reassert the default route if it is missing: sudo ip route replace default via 192.168.117.1 dev tun-easytether metric 50
• To drop conflicting VPN routes, disconnect the VPN or remove its default: sudo ip route del default dev tun0 HINT