Question

Clear guide on Outbound network through Floating IP

Posted November 10, 2021 70 views
NetworkingDigitalOcean Droplets

Hi, I spent half a day trying to figure out how to use a floating IP for outbound traffic, I began having nightmares with such a bad time I am having, there is no single guide with clear documentation on how to use this.
All these trickeries with “route” or “ip route”, first don’t seem correct to me, If I have 2 IPs I have to have the ability to send traffic from either IP, why should I set the default for all traffic to the floating IP.
Second, the official guide does not explain how to revert the changes if we use a floating IP.
Third, the official guide does not work for me ....

This is more or less the experiment I am running, I can’t make it run not even a single cycle … It crashes because the IPs are the same, just after the application crashes I do curl checkip.amazonaws.com and it reflects the new IP … It is very obscure and the documentation is extremely poor, it does not explain a single thing that can help.

func GetHttp(urlStr string) ([]byte, error) {
    res, err := http.Get(urlStr)
    if err != nil {
        return nil, err
    }

    content, err := ioutil.ReadAll(res.Body)
    if err != nil {
        return nil, err
    }

    return content, err
}


func ExecuteSystemCommand(command string, pipeErr bool) error {

    var cmd *exec.Cmd
    if runtime.GOOS == "windows" {
        cmd = exec.Command("cmd", "/k", command)
    } else if runtime.GOOS == "linux" {
        cmd = exec.Command("bash", "-c", command)
    } else {
        panic("not supported platform")
    }

    cmd.Stdout = os.Stdout

    if pipeErr {
        cmd.Stderr = os.Stderr
    }

    err := cmd.Run()

    return err
}

func GetMyIp() (string, error) {

    res, err := GetHttp("https://checkip.amazonaws.com")
    if err == nil && len(res) > 0 {
        return strings.TrimSpace(string(res)), nil
    }

    return "", err
}

func experiment() {
    currentIp, err := GetMyIp()
    if err != nil {
        panic(err)
    }

    godoClient := godo.NewFromToken("<MY_TOKEN>")
    response, err := http.Get("http://169.254.169.254/metadata/v1/id")
    if err != nil {
        panic(err)
    }

    respBody, err := ioutil.ReadAll(response.Body)
    if err != nil {
        panic(err)
    }
    response.Body.Close()

    dropletId, err := strconv.Atoi(string(respBody))
    if err != nil {
        panic(err)
    }

    response, err = http.Get("http://169.254.169.254/metadata/v1/region")
    if err != nil {
        panic(err)
    }

    respBody, err = ioutil.ReadAll(response.Body)
    if err != nil {
        panic(err)
    }
    response.Body.Close()

    region := string(respBody)
    message := fmt.Sprintf("Initial IP: %s, Droplet ID: %d, Region: %s\n", currentIp, dropletId, region)
    log.Print(message)

    for {
        fp, res, err := godoClient.FloatingIPs.Create(context.Background(), &godo.FloatingIPCreateRequest{
            Region: region,
            // DropletID: dropletId,
        })

        if err != nil {
            panic(err)
        }

        if res.StatusCode != 202 {
            resBody, err := ioutil.ReadAll(res.Body)
            if err != nil {

            }

            message = fmt.Sprintf("Status code not 202 - %s %v\n", resBody, err)
            NotifySlack(message)
            defaultLog.Error(message)
            panic(message)
        }

        _ = res.Body.Close()

        fmt.Printf("We have IP: %s\n", fp.IP)
        action, res, err := godoClient.FloatingIPActions.Assign(context.Background(), fp.IP, dropletId)
        if err != nil {
            panic(err)
        }

        fmt.Printf("Action %#v\n", action)

        response, err = http.Get("http://169.254.169.254/metadata/v1/interfaces/public/0/anchor_ipv4/gateway")
        if err != nil {
            panic(err)
        }

        respBody, err = ioutil.ReadAll(response.Body)
        if err != nil {
            panic(err)
        }

        _ = response.Body.Close()
        anchor := string(respBody)
        // command := "ip route del 0/0"
        command := fmt.Sprintf("route del default gw %s", anchor)
        log.Print(command + "\n")
        err = ExecuteSystemCommand(command, true)
        if err != nil {
            fmt.Printf("Error on deleting route %v\n", err)
        }

        log.Print(fmt.Sprintf("Anchor: %s\n", anchor))

        command = fmt.Sprintf("route add default gw %s", anchor)
        // command := fmt.Sprintf("ip route add default via %s dev eth0", anchor)
        err = ExecuteSystemCommand(command, true)

        if err != nil {
            panic(err)
        }

        message = fmt.Sprintf("Got Floating IP %s\n", fp.IP)
        log.Print(message)

        time.Sleep(time.Second * 20)
        currentIp2, _ := libNet.GetMyIp()

        if currentIp2 == currentIp {
            message = fmt.Sprintf("Same IP %s\n", currentIp)
            log.Print(message)
            panic(message)
        } else {
            message = fmt.Sprintf("Switched from %s to %s (%s)\n", currentIp, currentIp2, anchor)
            log.Print(message)
            currentIp = currentIp2
        }

        time.Sleep(time.Second * 30)

        res, err = godoClient.FloatingIPs.Delete(context.Background(), fp.IP)
        if err != nil {
            panic(err)
        }
        fmt.Printf("Done cycle\n")
    }
}

Please help, I need a way to set the floating IP to a network interface, so I can bind to ip from any programming language, I don’t want to depend on route or “ip route”, I want an easy way to have the floating IP on my droplet and available from a network interface.

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2 answers

Hey there!

I’m sorry to hear this has been such a bad experience. The reason that it appears this documentation is lacking is that outbound traffic through a floating IP isn’t technically supported on our services. There are work-around guides and suggestions on how to do so, but it isn’t something that was intended for floating IPs. Floating IP’s point to the anchor IP address of your droplet and such do not have their own interface. The floating IP won’t ever appear as another interface as one does not exist for it. Floating IP’s are for inbound traffic to allow DNS records to be retained while having the ability to move that IP between droplets.

There really isn’t a way to setup a floating IP on its own interface or as its own IP address as it is tied to the anchor IP. Your application looks like it requires 2 separate IP’s using different interfaces to work, which unfortunately we don’t support at this time.

I’d suggest adding the idea of additional IP addresses to our ideas page. DigitalOcean Ideas

Hope it helps!
Nate

Thanks for clarifying that, I was still searching how to do it, will stop and look for alternative solutions somewhere else. Thanks!