getpsrc/main.go

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2021-06-14 07:53:26 +00:00
package main
import (
"fmt"
"log"
"net"
"os"
"strings"
"github.com/google/gopacket/routing"
)
func main() {
ips := os.Args[1:]
switch {
case len(ips) == 0:
log.Fatal("Expect exactly one argument")
case len(ips) >= 2:
log.Fatal("Expect only one argument")
}
rawIP := strings.Split(ips[0], "/")[0]
ip := net.ParseIP(rawIP)
if ip == nil {
log.Fatal("failed to parse raw ip")
}
router, err := routing.New()
if err != nil {
log.Fatalf("failed to get new routing instance: %v", err.Error())
}
_, _, prefferedSrc, err := router.Route(ip)
if err != nil {
log.Fatalf("failed to find gateway for ip: %v", err.Error())
}
fmt.Fprintln(os.Stdout, prefferedSrc.String())
}