Ugly DDNS script for Huawei ONT's built-in OpenWrt

freednsv2.sh

#!/bin/sh
mkdir -p /tmp/freednsv2

exec_wget() {
    wget --no-hsts -O - $@ 2>&1 | head -c4096
}

wait_for_internet() {
    echo $(date) "Wait for Internet connection..."
    seq 0 300 | while read line; do
        nslookup sync.afraid.org && break
        sleep 1
    done
    echo -ne $(date) "Connected to the Internet\n\n"
}

update_dns() {
    echo $(date) "Update DNS..."
    wait_for_internet
    cat /root/ddns_urls.txt | while read url; do
        exec_wget "${url}"
    done
    echo -ne $(date) "Done\n\n"
}

update_dns_with_log() {
    tail -c131072 /tmp/freednsv2/log.txt > /tmp/freednsv2/log_.txt
    cat /tmp/freednsv2/log_.txt > /tmp/freednsv2/log.txt
    rm /tmp/freednsv2/log_.txt
    update_dns 2>&1 >> /tmp/freednsv2/log.txt
}

wait_and_update() {
    mkdir /tmp/freednsv2/lock || exit 1

    [ ! -e /tmp/freednsv2/fifo12380 ] && mkfifo /tmp/freednsv2/fifo12380
    if [ ! -p /tmp/freednsv2/fifo12380 ]; then echo "cannot mkfifo"; exit 2; fi

    # fake no-ip.com server
    cat /tmp/freednsv2/fifo12380 | nc -c -l -s 127.0.0.1 -p 12380 | while read line; do
        update_dns_with_log
        echo -ne "HTTP/1.1 200 OK\r\nContent-Length: 15\r\nConnection: close\r\n\r\ngood 127.0.0.1\n" > /tmp/freednsv2/fifo12380
        break
    done

    rmdir /tmp/freednsv2/lock
}

wait_loop() {
    update_dns_with_log
    while sleep 1; do wait_and_update || exit $?; done
}

fork_again() {
    wait_loop &
}


fork_again &