wg_keep_alive, A bash script to workaround NAT bugs

wg_keep_alive.sh

# When there's a upstream NAT bug, WireGuard will never succeed senting packets
# and will never receive any packets then. Detect sent increase while receive not change
# Change a random port for it.
function wg_keep_alive() {
    # Wait init
    sleep 10

    # Configuration
    CHECK_INTERVAL=3
    MAX_FAILED_CHECKS=3
    PORT_MIN=24000
    PORT_MAX=30000
    RESET_WAIT=10

    function wg_reset_port() {
        while true; do
            ((NEW_PORT=RANDOM%(PORT_MAX-PORT_MIN)+PORT_MIN))
            if ! ss -ulpn | grep "$NEW_PORT" >/dev/null 2>/dev/null; then
                break
            fi
        done
        wg set "$1" listen-port "$NEW_PORT"
    }

    declare -A PEER_RECEIVED_BYTES
    declare -A PEER_SENT_BYTES
    declare -A PEER_FAILED_CHECKES
    while true; do
        while read PEER RECEIVED_BYTES SENT_BYTES; do
            if [[ "$PEER" == "" ]]; then
                break
            fi
            if [[ "${PEER_RECEIVED_BYTES["$PEER"]}" != "$RECEIVED_BYTES" ]]; then
                PEER_RECEIVED_BYTES["$PEER"]="$RECEIVED_BYTES"
                PEER_SENT_BYTES["$PEER"]="$SENT_BYTES"
                PEER_FAILED_CHECKES["$PEER"]="0"
            elif [[ "${PEER_SENT_BYTES["$PEER"]}" != "$SENT_BYTES" ]]; then
                FAILED_CHECKES="${PEER_FAILED_CHECKES["$PEER"]}"
                ((FAILED_CHECKES=FAILED_CHECKES+1))
                echo wg_keep_alive: check failed! current fails = $FAILED_CHECKES
                if [[ "$FAILED_CHECKES" == "$MAX_FAILED_CHECKS" ]]; then
                    wg_reset_port "$1"
                    sleep "$RESET_WAIT"
                    PEER_FAILED_CHECKES["$PEER"]=0
                    break
                fi
                PEER_FAILED_CHECKES["$PEER"]="$FAILED_CHECKES"
            fi
        done <<< "$(wg show "$1" transfer)"
        sleep "$CHECK_INTERVAL"
    done
}
# wg_keep_alive <wg-interface-name>