vendor: add j-keck/arping

vendor/github.com/j-keck/arping/netutils.go

@@ -0,0 +1,64 @@
+package arping
+
+import (
+	"errors"
+	"fmt"
+	"net"
+)
+
+func findIPInNetworkFromIface(dstIP net.IP, iface net.Interface) (net.IP, error) {
+	addrs, err := iface.Addrs()
+
+	if err != nil {
+		return nil, err
+	}
+
+	for _, a := range addrs {
+		if ipnet, ok := a.(*net.IPNet); ok {
+			if ipnet.Contains(dstIP) {
+				return ipnet.IP, nil
+			}
+		}
+	}
+	return nil, fmt.Errorf("iface: '%s' can't reach ip: '%s'", iface.Name, dstIP)
+}
+
+func findUsableInterfaceForNetwork(dstIP net.IP) (*net.Interface, error) {
+	ifaces, err := net.Interfaces()
+
+	if err != nil {
+		return nil, err
+	}
+
+	isDown := func(iface net.Interface) bool {
+		return iface.Flags&1 == 0
+	}
+
+	hasAddressInNetwork := func(iface net.Interface) bool {
+		if _, err := findIPInNetworkFromIface(dstIP, iface); err != nil {
+			return false
+		}
+		return true
+	}
+
+	verboseLog.Println("search usable interface")
+	logIfaceResult := func(msg string, iface net.Interface) {
+		verboseLog.Printf("%10s: %6s %18s  %s", msg, iface.Name, iface.HardwareAddr, iface.Flags)
+	}
+
+	for _, iface := range ifaces {
+		if isDown(iface) {
+			logIfaceResult("DOWN", iface)
+			continue
+		}
+
+		if !hasAddressInNetwork(iface) {
+			logIfaceResult("OTHER NET", iface)
+			continue
+		}
+
+		logIfaceResult("USABLE", iface)
+		return &iface, nil
+	}
+	return nil, errors.New("no usable interface found")
+}