1 files changed, 153 insertions, 0 deletions
diff --git a/pkg/tcpip/link/tunnel/gre.go b/pkg/tcpip/link/tunnel/gre.go
new file mode 100644
index 000000000..8f6f1649a
--- /dev/null
+++ b/pkg/tcpip/link/tunnel/gre.go
@@ -0,0 +1,153 @@
+package tunnel
+
+import (
+	"context"
+	"log"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+	"gvisor.dev/gvisor/pkg/tcpip/transport/gre"
+	"gvisor.dev/gvisor/pkg/tcpip/transport/raw"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+var SIZE = 16
+
+type Endpoint struct {
+	channel.Endpoint
+}
+
+type writer Endpoint
+
+func New(mtu uint32) *Endpoint {
+	var linkAddress tcpip.LinkAddress
+
+	ch := channel.New(SIZE, mtu, linkAddress)
+	return &Endpoint{
+		Endpoint: *ch,
+	}
+}
+
+func (e *Endpoint) GetChannel() *channel.Endpoint {
+	return &e.Endpoint
+}
+
+// Attach saves the stack network-layer dispatcher for use later when packets
+// are injected.
+func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
+	log.Println("GRE: Attach")
+
+	e.Endpoint.Attach(dispatcher)
+}
+
+type GrePacketInfo struct {
+	pi *channel.PacketInfo
+}
+
+func (g GrePacketInfo) FullPayload() ([]byte, *tcpip.Error){
+	log.Println("FullPayload")
+	pkt := g.pi.Pkt
+	size := pkt.Size()
+	vv := buffer.NewVectorisedView(size, pkt.Views())
+	var buf = make([]byte, size, size)
+	pos := 0
+	for {
+		copied, err := vv.Read(buf[pos:])
+		log.Printf("VectorisedView Read: %d %d %d %v", size, pos, copied, err)
+		if err != nil {
+			return nil, tcpip.ErrBadBuffer
+		}
+		pos = pos + copied
+		if pos == size {
+			break
+		}
+	}
+
+	log.Printf("FullPayload return: %d %v", len(buf), buf)
+	return buf, nil
+}
+
+func (g GrePacketInfo) Payload(size int) ([]byte, *tcpip.Error){
+	log.Println("Payload")
+	return nil, tcpip.ErrNotSupported
+}
+
+type GreHandlerInfo struct {
+	ChEp *channel.Endpoint
+	Raw tcpip.Endpoint
+	Raddr tcpip.FullAddress
+}
+
+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.Printf("greHandler proto: %d cloned: %v", proto, newPkt.Views())
+
+	info.ChEp.InjectInbound(proto, newPkt)
+}
+
+func (info *GreHandlerInfo) greRead(ep *channel.Endpoint) {
+	for {
+		pi, err := ep.ReadContext(context.Background());
+		linkHdr := pi.Pkt.LinkHeader()
+		greHdr := header.GRE(linkHdr.Push(header.GREHeaderSize))
+		greHdr.SetProtocolType(pi.Proto)
+		log.Printf("greRead %d %v %v %v", pi.Proto, pi, err, greHdr)
+		opts := tcpip.WriteOptions{
+			//To: &info.Raddr
+		}
+		info.Raw.Write(GrePacketInfo{&pi}, opts)
+	}
+}
+
+func (e *Endpoint) Start(s *stack.Stack, laddr, raddr *tcpip.Address) {
+	// Create TCP endpoint.
+	var rawWq waiter.Queue
+	rawEp, tcperr := raw.NewEndpoint(s, ipv4.ProtocolNumber, header.GREProtocolNumber, &rawWq)
+	if tcperr != nil {
+		log.Fatal(tcperr)
+	}
+	log.Println("EP: %s", rawEp)
+
+	fraddr := tcpip.FullAddress{NIC: 1, Addr: *raddr}
+	flAddr := tcpip.FullAddress{NIC: 1, Addr: *laddr}
+	tcperr = rawEp.Bind(flAddr)
+	if tcperr != nil {
+		log.Fatal(tcperr)
+	}
+	log.Printf("Remote: %v %v", raddr, fraddr)
+
+	// Create GRE
+	// greEP := grelink.New(mtu - 24)
+	chEP := e.GetChannel()
+	// TODO detect IPv4/IPv6
+	e.NMaxHeaderLength = header.IPv6FixedHeaderSize + header.GREHeaderSize
+
+	greInfo := GreHandlerInfo{
+//		Ep: loEP,
+		ChEp: chEP,
+		Raw: rawEp,
+		Raddr: fraddr,
+	}
+	greFwd := gre.NewForwarder(s, greInfo.greHandler)
+	s.SetTransportProtocolHandler(header.GREProtocolNumber, greFwd.HandlePacket)
+
+	go greInfo.greRead(chEP)
+
+	tcperr = rawEp.Connect(fraddr)
+	if tcperr != nil {
+		log.Fatal(tcperr)
+	}
+}