76 lines
1.7 KiB
Go
76 lines
1.7 KiB
Go
package common
|
|
|
|
import (
|
|
"net"
|
|
"sort"
|
|
"strings"
|
|
)
|
|
|
|
// GetOutboundIP returns an outbound IP address of this machine.
|
|
// It tries to access the internet and returns the local IP address of the connection.
|
|
// If the machine cannot access the internet, it returns a preferred IP address from network interfaces.
|
|
// It returns nil if no IP address is found.
|
|
func GetOutboundIP() net.IP {
|
|
// See https://stackoverflow.com/a/37382208
|
|
conn, err := net.Dial("udp", "8.8.8.8:80")
|
|
if err == nil {
|
|
defer conn.Close()
|
|
return conn.LocalAddr().(*net.UDPAddr).IP
|
|
}
|
|
|
|
// So the machine cannot access the internet. Pick an IP address from network interfaces.
|
|
if ifs, err := net.Interfaces(); err == nil {
|
|
type IP struct {
|
|
net.IP
|
|
net.Interface
|
|
}
|
|
var ips []IP
|
|
for _, i := range ifs {
|
|
if addrs, err := i.Addrs(); err == nil {
|
|
for _, addr := range addrs {
|
|
var ip net.IP
|
|
switch v := addr.(type) {
|
|
case *net.IPNet:
|
|
ip = v.IP
|
|
case *net.IPAddr:
|
|
ip = v.IP
|
|
}
|
|
if ip.IsGlobalUnicast() {
|
|
ips = append(ips, IP{ip, i})
|
|
}
|
|
}
|
|
}
|
|
}
|
|
if len(ips) > 1 {
|
|
sort.Slice(ips, func(i, j int) bool {
|
|
ifi := ips[i].Interface
|
|
ifj := ips[j].Interface
|
|
|
|
// ethernet is preferred
|
|
if vi, vj := strings.HasPrefix(ifi.Name, "e"), strings.HasPrefix(ifj.Name, "e"); vi != vj {
|
|
return vi
|
|
}
|
|
|
|
ipi := ips[i].IP
|
|
ipj := ips[j].IP
|
|
|
|
// IPv4 is preferred
|
|
if vi, vj := ipi.To4() != nil, ipj.To4() != nil; vi != vj {
|
|
return vi
|
|
}
|
|
|
|
// en0 is preferred to en1
|
|
if ifi.Name != ifj.Name {
|
|
return ifi.Name < ifj.Name
|
|
}
|
|
|
|
// fallback
|
|
return ipi.String() < ipj.String()
|
|
})
|
|
return ips[0].IP
|
|
}
|
|
}
|
|
|
|
return nil
|
|
}
|