Cast and Loopback

multiaddr.go

@@ -124,3 +124,21 @@ func (m *multiaddr) Split() []Multiaddr {
 	}
 	return addrs
 }
+
+// Cast re-casts a byte slice as a multiaddr. will panic if it fails to parse.
+func Cast(b []byte) Multiaddr {
+	_, err := bytesToString(b)
+	if err != nil {
+		panic(fmt.Errorf("multiaddr failed to parse: %s", err))
+	}
+	return &multiaddr{bytes: b}
+}
+
+// StringCast like Cast, but parses a string. Will also panic if it fails to parse.
+func StringCast(s string) Multiaddr {
+	m, err := NewMultiaddr(s)
+	if err != nil {
+		panic(fmt.Errorf("multiaddr failed to parse: %s", err))
+	}
+	return m
+}

net/convert.go

@@ -8,6 +8,14 @@ import (
 	ma "github.com/jbenet/go-multiaddr"
 )
 
+var (
+	// IP4Loopback is the ip4 loopback multiaddr
+	IP4Loopback = ma.StringCast("/ip4/127.0.0.1")
+
+	// IP6Loopback is the ip6 loopback multiaddr
+	IP6Loopback = ma.StringCast("/ip6/::1")
+)
+
 var errIncorrectNetAddr = fmt.Errorf("incorrect network addr conversion")
 
 // FromNetAddr converts a net.Addr type to a Multiaddr.
@@ -150,3 +158,9 @@ func IsThinWaist(m ma.Multiaddr) bool {
 		return false
 	}
 }
+
+// IsIPLoopback returns whether a Multiaddr is a "Loopback" IP address
+// This means either /ip4/127.0.0.1 or /ip6/::1
+func IsIPLoopback(m ma.Multiaddr) bool {
+	return m.Equal(IP4Loopback) || m.Equal(IP6Loopback)
+}

net/net_test.go

@@ -198,3 +198,21 @@ func TestListenAndDial(t *testing.T) {
 	cA.Close()
 	wg.Wait()
 }
+
+func TestLoopback(t *testing.T) {
+	if IP4Loopback.String() != "/ip4/127.0.0.1" {
+		t.Error("IP4Loopback incorrect:", IP4Loopback)
+	}
+
+	if IP6Loopback.String() != "/ip6/::1" {
+		t.Error("IP6Loopback incorrect:", IP6Loopback)
+	}
+
+	if !IsIPLoopback(IP4Loopback) {
+		t.Error("IsIPLoopback failed (IP4)")
+	}
+
+	if !IsIPLoopback(IP6Loopback) {
+		t.Error("IsIPLoopback failed (IP6)")
+	}
+}