p2p/external_ip.go

   1 package p2p
   2
   3 import (
   4         "net"
   5 )
   6
   7 // ExternalIPv4 returns the first IPv4 available.
   8 func ExternalIPv4() (string, error) {
   9         ifaces, err := net.Interfaces()
  10         if err != nil {
  11                 return "", err
  12         }
  13
  14         for _, iface := range ifaces {
  15                 // interface down
  16                 if iface.Flags&net.FlagUp == 0 {
  17                         continue
  18                 }
  19                 // loopback interface
  20                 if iface.Flags&net.FlagLoopback != 0 {
  21                         continue
  22                 }
  23                 addrs, err := iface.Addrs()
  24                 if err != nil {
  25                         return "", err
  26                 }
  27
  28                 for _, addr := range addrs {
  29                         var ip net.IP
  30                         switch v := addr.(type) {
  31                         case *net.IPNet:
  32                                 ip = v.IP
  33                         case *net.IPAddr:
  34                                 ip = v.IP
  35                         }
  36                         if ip == nil || ip.IsLoopback() {
  37                                 continue
  38                         }
  39                         ip = ip.To4()
  40                         if ip == nil {
  41                                 continue // not an ipv4 address
  42                         }
  43                         return ip.String(), nil
  44                 }
  45         }
  46         return "127.0.0.1", nil
  47 }