netaddr: add initial well-known IP addresses

Signed-off-by: Matt Layher <[email protected]>

netaddr.go

@@ -17,6 +17,12 @@ import (
 	"strings"
 )
 
+// Well known IP addresses.
+var (
+	IPv6LinkLocalAllNodes = mustIP("ff02::1")
+	IPv6Unspecified       = mustIP("::")
+)
+
 // Sizes: (64-bit)
 //   net.IP:     24 byte slice header + {4, 16} = 28 to 40 bytes
 //   net.IPAddr: 40 byte slice header + {4, 16} = 44 to 56 bytes + zone length
@@ -584,3 +590,13 @@ func (p IPPrefix) Contains(addr IP) bool {
 func (p IPPrefix) String() string {
 	return fmt.Sprintf("%s/%d", p.IP, p.Bits)
 }
+
+// mustIP parses s as an IP or panics.
+func mustIP(s string) IP {
+	ip, err := ParseIP(s)
+	if err != nil {
+		panic(err)
+	}
+
+	return ip
+}

netaddr_test.go

@@ -685,15 +685,6 @@ func TestParseIPPrefixError(t *testing.T) {
 	}
 }
 
-func mustIP(s string) IP {
-	ip, err := ParseIP(s)
-	if err != nil {
-		panic(err)
-	}
-
-	return ip
-}
-
 func mustIPs(strs ...string) []IP {
 	var res []IP
 	for _, s := range strs {