decode gre protocol type

1 files changed, 7 insertions, 2 deletions

diff --git a/pkg/tcpip/header/gre.go b/pkg/tcpip/header/gre.go
index 65f5c1894..326d03ba8 100644
--- a/pkg/tcpip/header/gre.go
+++ b/pkg/tcpip/header/gre.go
@@ -1,8 +1,8 @@
 package header
 
 import (
-        "encoding/binary"
-        
+	"encoding/binary"
+
 	"gvisor.dev/gvisor/pkg/tcpip"
 )
 
@@ -18,6 +18,11 @@ const (
 	GREProtocolNumber tcpip.TransportProtocolNumber = 47
 )
 
+func (b GRE) ProtocolType() tcpip.NetworkProtocolNumber {
+	proto := binary.BigEndian.Uint16(b[greProtocolType:])
+	return tcpip.NetworkProtocolNumber(proto)
+}
+
 // SetLength sets the "length" field of the udp header.
 func (b GRE) SetProtocolType(protocol tcpip.NetworkProtocolNumber) {
 	binary.BigEndian.PutUint16(b[greProtocolType:], uint16(protocol))