decode gre protocol type

2 files changed, 12 insertions, 5 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))
diff --git a/pkg/tcpip/sample/tun_tcp_connect/main.go b/pkg/tcpip/sample/tun_tcp_connect/main.go
index 19276aca7..e0ab521ff 100644
--- a/pkg/tcpip/sample/tun_tcp_connect/main.go
+++ b/pkg/tcpip/sample/tun_tcp_connect/main.go
@@ -139,15 +139,17 @@ type GreHandlerInfo struct {
 func (info *GreHandlerInfo) greHandler(req *gre.ForwarderRequest) {
         pkt := req.Pkt
         log.Println("greHandler: ", req.Pkt.Size(), req.Pkt.Views())
+        greHdr := header.GRE(pkt.TransportHeader().View())
+        proto := greHdr.ProtocolType()
         views := pkt.Data.Views()
         size := pkt.Data.Size()
         data := buffer.NewVectorisedView(size, views)
 	newPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
 		Data: data,
 	})
-        log.Println("greHandler cloned: ", newPkt.Views())
+        log.Printf("greHandler proto: %d cloned: %v", proto, newPkt.Views())
 
-        info.ChEp.InjectInbound(header.IPv4ProtocolNumber, newPkt)
+        info.ChEp.InjectInbound(proto, newPkt)
 }
 
 func (info *GreHandlerInfo) greRead(ep *channel.Endpoint) {
@@ -155,7 +157,7 @@ func (info *GreHandlerInfo) greRead(ep *channel.Endpoint) {
                 pi, err := ep.ReadContext(context.Background());
                 linkHdr := pi.Pkt.LinkHeader()
                 greHdr := header.GRE(linkHdr.Push(4)) //header.IPv4MinimumSize + 4)
-                greHdr.SetProtocolType(header.IPv4ProtocolNumber)
+                greHdr.SetProtocolType(pi.Proto)
                 log.Printf("greRead %d %v %v %v", pi.Proto, pi, err, greHdr)
                 opts := tcpip.WriteOptions{
                         //To: &info.Raddr