81 lines
1.8 KiB
Go
81 lines
1.8 KiB
Go
package utils
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import (
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"errors"
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"fmt"
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"net"
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"net/url"
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"strconv"
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"strings"
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"syscall"
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"time"
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)
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// URLtoListenIPandPort for a given internal URL,
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// find the correct IP/Interface to listen to.
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func URLtoListenIPandPort(u string) (string, error) {
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parsedURL, err := url.Parse(u)
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if err != nil {
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return "", fmt.Errorf("URLtoListenIPandPort parse error: %w", err)
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}
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callURL := parsedURL.Host
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if parsedURL.Port() == "" {
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switch parsedURL.Scheme {
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case "http":
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callURL = callURL + ":80"
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case "https":
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callURL = callURL + ":443"
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}
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}
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conn, err := net.Dial("udp", callURL)
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if err != nil {
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return "", fmt.Errorf("URLtoListenIPandPort UDP call error: %w", err)
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}
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ipToListen := strings.Split(conn.LocalAddr().String(), ":")[0]
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portToListen, err := checkAndPickPort(ipToListen, 3500)
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if err != nil {
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return "", fmt.Errorf("URLtoListenIPandPort port error: %w", err)
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}
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res := net.JoinHostPort(ipToListen, portToListen)
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return res, nil
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}
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func checkAndPickPort(ip string, port int) (string, error) {
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const maxAttempts = 1000
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for attempt := 1; attempt <= maxAttempts; attempt++ {
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conn, err := net.Listen("tcp", net.JoinHostPort(ip, strconv.Itoa(port)))
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if err != nil {
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if errors.Is(err, syscall.EADDRINUSE) {
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if attempt == maxAttempts {
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break
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}
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port++
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continue
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}
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return "", fmt.Errorf("port pick error: %w", err)
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}
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conn.Close()
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return strconv.Itoa(port), nil
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}
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return "", fmt.Errorf("port pick error. Exceeded maximum attempts")
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}
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// HostPortIsAlive - We use this function to periodically
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// health check the selected device and decide if we want
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// to keep the entry in the list or to remove it.
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func HostPortIsAlive(h string) bool {
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conn, err := net.DialTimeout("tcp", h, time.Duration(2*time.Second))
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if err != nil {
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return false
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}
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conn.Close()
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return true
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}
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