p2p/netutil: add AddrIP

p2p/netutil/addrutil.go

@@ -0,0 +1,33 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package netutil
+
+import "net"
+
+// AddrIP gets the IP address contained in addr. It returns nil if no address is present.
+func AddrIP(addr net.Addr) net.IP {
+	switch a := addr.(type) {
+	case *net.IPAddr:
+		return a.IP
+	case *net.TCPAddr:
+		return a.IP
+	case *net.UDPAddr:
+		return a.IP
+	default:
+		return nil
+	}
+}