Script to switch server wifi safely

switch-wifi.sh

#!/usr/bin/env bash
set -Eeuo pipefail

INTERFACE="${INTERFACE:-wlp1s0}"
TARGET_SSID="${TARGET_SSID:-CHANGE_ME_SSID}"
TARGET_PASSWORD="${TARGET_PASSWORD:-CHANGE_ME_PASSWORD}"
TARGET_BSSID="${TARGET_BSSID:-}"
ROLLBACK_DELAY="${ROLLBACK_DELAY:-45}"
VERIFY_SECONDS="${VERIFY_SECONDS:-25}"
PING_HOST="${PING_HOST:-1.1.1.1}"

ROLLBACK_PID=""
ROLLBACK_FILE=""

log() {
	printf '[%s] %s\n' "$(date '+%F %T')" "$*"
}

fail() {
	log "ERROR: $*"
	exit 1
}

require_root() {
	[[ "${EUID}" -eq 0 ]] || fail "run as root"
}

require_cmd() {
	command -v "$1" >/dev/null 2>&1 || fail "missing command: $1"
}

current_connection() {
	nmcli -t -f GENERAL.CONNECTION device show "$INTERFACE" 2>/dev/null | head -n1 | cut -d: -f2-
}

connection_exists() {
	local name="$1"
	[[ -n "$name" && "$name" != "--" ]] || return 1
	nmcli -t -f NAME connection show | grep -Fxq "$name"
}

is_healthy() {
	local state=""
	state=$(nmcli -t -f GENERAL.STATE device show "$INTERFACE" 2>/dev/null | head -n1 | cut -d: -f2-)

	[[ "$state" == "100 (connected)" ]] || return 1
	ping -I "$INTERFACE" -c 1 -W 3 "$PING_HOST" >/dev/null 2>&1
}

wait_for_health() {
	local seconds="$1"
	local deadline=$((SECONDS + seconds))

	while ((SECONDS < deadline)); do
		if is_healthy; then
			return 0
		fi
		sleep 2
	done

	return 1
}

start_rollback_timer() {
	local previous="$1"

	connection_exists "$previous" || fail "previous connection not found: $previous"

	ROLLBACK_FILE="/tmp/wifi-rollback-${INTERFACE}.flag"
	printf 'armed\n' >"$ROLLBACK_FILE"

	(
		sleep "$ROLLBACK_DELAY"

		if [[ -f "$ROLLBACK_FILE" ]]; then
			logger -t switch-wifi "rollback timer fired; restoring [$previous] on [$INTERFACE]"
			nmcli connection up "$previous" ifname "$INTERFACE" >/tmp/switch-wifi-rollback.log 2>&1 || true
		fi
	) &
	ROLLBACK_PID=$!

	log "Rollback armed: ${ROLLBACK_DELAY}s, pid=$ROLLBACK_PID"
}

disarm_rollback_timer() {
	[[ -n "${ROLLBACK_FILE:-}" && -f "${ROLLBACK_FILE:-}" ]] && rm -f "$ROLLBACK_FILE" || true

	if [[ -n "${ROLLBACK_PID:-}" ]]; then
		kill "$ROLLBACK_PID" >/dev/null 2>&1 || true
		wait "$ROLLBACK_PID" 2>/dev/null || true
	fi

	log "Rollback disarmed"
}

restore_previous_now() {
	local previous="$1"

	connection_exists "$previous" || fail "cannot restore previous connection: $previous"
	log "Restoring previous connection now: $previous"
	nmcli connection up "$previous" ifname "$INTERFACE"
}

cleanup_on_exit() {
	local ec=$?

	if ((ec != 0)); then
		log "Script exit non-zero ($ec). Rollback remains armed if timer exists"
	fi
}

trap cleanup_on_exit EXIT

main() {
	require_root
	require_cmd nmcli
	require_cmd ping
	require_cmd logger

	[[ "$TARGET_SSID" != "CHANGE_ME_SSID" ]] || fail "set TARGET_SSID first"
	[[ "$TARGET_PASSWORD" != "CHANGE_ME_PASSWORD" ]] || fail "set TARGET_PASSWORD first"

	local previous
	previous=$(current_connection)

	connection_exists "$previous" || fail "no valid current connection to fallback to"

	log "Current connection: $previous"
	log "Target SSID: $TARGET_SSID"
	[[ -n "$TARGET_BSSID" ]] && log "Target BSSID: $TARGET_BSSID"

	nmcli device wifi rescan ifname "$INTERFACE" >/dev/null 2>&1 || true

	start_rollback_timer "$previous"

	local -a cmd=(nmcli device wifi connect "$TARGET_SSID" password "$TARGET_PASSWORD" ifname "$INTERFACE")
	[[ -n "$TARGET_BSSID" ]] && cmd+=(bssid "$TARGET_BSSID")

	log "Connecting to target Wi-Fi"
	if ! "${cmd[@]}"; then
		log "Target connect command failed"
		restore_previous_now "$previous"
		wait_for_health "$VERIFY_SECONDS" || fail "fallback attempted but health check failed"
		disarm_rollback_timer
		fail "restored previous connection after immediate connect failure"
	fi

	log "Connect command accepted. Verifying health"
	if wait_for_health "$VERIFY_SECONDS"; then
		log "Target Wi-Fi healthy"
		disarm_rollback_timer
		exit 0
	fi

	log "Target Wi-Fi not healthy in time. Immediate fallback"
	restore_previous_now "$previous"
	wait_for_health "$VERIFY_SECONDS" || fail "fallback attempted but health check failed"
	disarm_rollback_timer
	fail "restored previous connection after failed verification"
}

main "$@"

Cara pakai:

chmod +x switch-wifi.sh
sudo TARGET_SSID="NamaWifiBaru" TARGET_PASSWORD="PasswordWifi" ./switch-wifi.sh 

Kalau mau pakai BSSID spesifik:

sudo TARGET_SSID="NamaWifiBaru" TARGET_PASSWORD="PasswordWifi" TARGET_BSSID="AA:BB:CC:DD:EE:FF" ./switch-wifi.sh