From 2ce080f581556f9512a481e7fcddecaed0ae7be7 Mon Sep 17 00:00:00 2001
From: Mikael Magnusson <mikma@users.sourceforge.net>
Date: Sat, 23 Jan 2021 01:14:51 +0100
Subject: WIP GRE tunnel

---
 pkg/tcpip/header/gre.go         | 19 +++++++++++++++++++
 pkg/tcpip/header/parse/parse.go | 10 ++++++++++
 2 files changed, 29 insertions(+)
 create mode 100644 pkg/tcpip/header/gre.go

(limited to 'pkg/tcpip/header')

diff --git a/pkg/tcpip/header/gre.go b/pkg/tcpip/header/gre.go
new file mode 100644
index 000000000..3d1cc97d9
--- /dev/null
+++ b/pkg/tcpip/header/gre.go
@@ -0,0 +1,19 @@
+package header
+
+import (
+        "encoding/binary"
+        
+	"gvisor.dev/gvisor/pkg/tcpip"
+)
+
+const (
+	greProtocolType  = 2
+)
+
+// GRE represents a GRE header stored in a byte array.
+type GRE []byte
+
+// 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/header/parse/parse.go b/pkg/tcpip/header/parse/parse.go
index 2042f214a..3e5336c04 100644
--- a/pkg/tcpip/header/parse/parse.go
+++ b/pkg/tcpip/header/parse/parse.go
@@ -169,3 +169,13 @@ func TCP(pkt *stack.PacketBuffer) bool {
 	pkt.TransportProtocolNumber = header.TCPProtocolNumber
 	return ok
 }
+
+// GRE parses a GRE packet found in pkt.Data and populates pkt's transport
+// header with the GRE header.
+//
+// Returns true if the header was successfully parsed.
+func GRE(pkt *stack.PacketBuffer) bool {
+	_, ok := pkt.TransportHeader().Consume(4)
+	pkt.TransportProtocolNumber = 47
+	return ok
+}
-- 
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