x/net/{internal/icmp,ipv4,ipv6}: better method for icmp.Type interface

LGTM=iant
R=iant, bradfitz
CC=golang-codereviews
https://golang.org/cl/173670044

1 files changed, 7 insertions, 0 deletions

diff --git a/ipv4/icmp.go b/ipv4/icmp.go
index d595967..4682e8c 100644
--- a/ipv4/icmp.go
+++ b/ipv4/icmp.go
@@ -4,6 +4,8 @@
 
 package ipv4
 
+import "golang.org/x/net/internal/iana"
+
 // An ICMPType represents a type of ICMP message.
 type ICMPType int
 
@@ -14,3 +16,8 @@ func (typ ICMPType) String() string {
 	}
 	return s
 }
+
+// Protocol returns the ICMPv4 protocol number.
+func (typ ICMPType) Protocol() int {
+	return iana.ProtocolICMP
+}