Add IPFromAddr to netutils

network/netutils/address.go

@@ -0,0 +1,30 @@
+package netutils
+
+import (
+	"fmt"
+	"net"
+)
+
+// IPFromAddr extracts or parses the IP address contained in the given address.
+func IPFromAddr(addr net.Addr) (net.IP, error) {
+	// Convert addr to IP if needed.
+	switch v := addr.(type) {
+	case *net.TCPAddr:
+		return v.IP, nil
+	case *net.UDPAddr:
+		return v.IP, nil
+	case *net.IPAddr:
+		return v.IP, nil
+	default:
+		// Parse via string.
+		host, _, err := net.SplitHostPort(addr.String())
+		if err != nil {
+			return nil, fmt.Errorf("failed to split host and port of %q: %s", addr, err)
+		}
+		ip := net.ParseIP(host)
+		if ip == nil {
+			return nil, fmt.Errorf("address %q does not contain a valid IP address", addr)
+		}
+		return ip, nil
+	}
+}