fixed consts + test

ip.go

@@ -57,7 +57,7 @@ func IsIPLoopback(m ma.Multiaddr) bool {
 	b := m.Bytes()
 
 	// /ip4/127 prefix (_entire_ /8 is loopback...)
-	if bytes.HasPrefix(b, []byte{4, 127}) {
+	if bytes.HasPrefix(b, []byte{ma.P_IP4, 127}) {
 		return true
 	}
 
@@ -69,10 +69,12 @@ func IsIPLoopback(m ma.Multiaddr) bool {
 	return false
 }
 
-// IPV6 Link Local addresses are non routable.
-func IsIPV6LinkLocal(m ma.Multiaddr) bool {
-	b := m.Bytes()
-	return bytes.HasPrefix(b, []byte{41, 254, 128})
+// IP6 Link Local addresses are non routable. The prefix is technically
+// fe80::/10, but we test fe80::/12 for simplicity (no need to mask).
+// So far, no hardware interfaces exist long enough to use those 2 bits.
+// Send a PR if there is.
+func IsIP6LinkLocal(m ma.Multiaddr) bool {
+	return bytes.HasPrefix(m.Bytes(), []byte{ma.P_IP6, 0xfe, 0x80, 0})
 }
 
 // IsIPUnspecified returns whether a Multiaddr is am Unspecified IP address

net_test.go

@@ -2,6 +2,7 @@ package manet
 
 import (
 	"bytes"
+	"fmt"
 	"net"
 	"sync"
 	"testing"
@@ -334,3 +335,17 @@ func TestIPUnspecified(t *testing.T) {
 		t.Error("IsIPUnspecified failed (IP6Unspecified)")
 	}
 }
+
+func TestIP6LinkLocal(t *testing.T) {
+	if !IsIP6LinkLocal(IP6LinkLocalLoopback) {
+		t.Error("IsIP6LinkLocal failed (IP6LinkLocalLoopback)")
+	}
+
+	for a := 0; a < 65536; a++ {
+		isLinkLocal := (a == 0xfe80)
+		m := newMultiaddr(t, fmt.Sprintf("/ip6/%x::1", a))
+		if IsIP6LinkLocal(m) != isLinkLocal {
+			t.Error("IsIP6LinkLocal failed (%s != %v)", m, isLinkLocal)
+		}
+	}
+}