Initial Commit

main.go

@@ -0,0 +1,40 @@
+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())
+}