ipv6: ICMP support

This CL does NDP link-address discovery for IPv6.

It includes several small changes necessary to get linux to talk to
this implementation. In particular, a hop limit of 255 is necessary
for ICMPv6.

PiperOrigin-RevId: 211103930
Change-Id: If25370ab84c6b1decfb15de917f3b0020f2c4e0e

2 files changed, 44 insertions, 10 deletions

diff --git a/pkg/tcpip/transport/ping/endpoint.go b/pkg/tcpip/transport/ping/endpoint.go
index f097ac057..7e10c0aae 100644
--- a/pkg/tcpip/transport/ping/endpoint.go
+++ b/pkg/tcpip/transport/ping/endpoint.go
@@ -56,6 +56,7 @@ type endpoint struct {
 	// change throughout the lifetime of the endpoint.
 	stack       *stack.Stack `state:"manual"`
 	netProto    tcpip.NetworkProtocolNumber
+	transProto  tcpip.TransportProtocolNumber
 	waiterQueue *waiter.Queue
 
 	// The following fields are used to manage the receive queue, and are
@@ -81,10 +82,11 @@ type endpoint struct {
 	route         stack.Route `state:"manual"`
 }
 
-func newEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, waiterQueue *waiter.Queue) *endpoint {
+func newEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtocolNumber, transProto tcpip.TransportProtocolNumber, waiterQueue *waiter.Queue) *endpoint {
 	return &endpoint{
 		stack:         stack,
 		netProto:      netProto,
+		transProto:    transProto,
 		waiterQueue:   waiterQueue,
 		rcvBufSizeMax: 32 * 1024,
 		sndBufSize:    32 * 1024,
@@ -98,7 +100,7 @@ func (e *endpoint) Close() {
 	e.shutdownFlags = tcpip.ShutdownRead | tcpip.ShutdownWrite
 	switch e.state {
 	case stateBound, stateConnected:
-		e.stack.UnregisterTransportEndpoint(e.regNICID, []tcpip.NetworkProtocolNumber{e.netProto}, ProtocolNumber4, e.id)
+		e.stack.UnregisterTransportEndpoint(e.regNICID, []tcpip.NetworkProtocolNumber{e.netProto}, e.transProto, e.id)
 	}
 
 	// Close the receive list and drain it.
@@ -297,7 +299,7 @@ func (e *endpoint) Write(p tcpip.Payload, opts tcpip.WriteOptions) (uintptr, *tc
 		err = sendPing4(route, e.id.LocalPort, v)
 
 	case header.IPv6ProtocolNumber:
-		// TODO: Support IPv6.
+		err = sendPing6(route, e.id.LocalPort, v)
 	}
 
 	return uintptr(len(v)), err
@@ -385,6 +387,30 @@ func sendPing4(r *stack.Route, ident uint16, data buffer.View) *tcpip.Error {
 	return r.WritePacket(&hdr, data, header.ICMPv4ProtocolNumber)
 }
 
+func sendPing6(r *stack.Route, ident uint16, data buffer.View) *tcpip.Error {
+	if len(data) < header.ICMPv6EchoMinimumSize {
+		return tcpip.ErrInvalidEndpointState
+	}
+
+	// Set the ident. Sequence number is provided by the user.
+	binary.BigEndian.PutUint16(data[header.ICMPv6MinimumSize:], ident)
+
+	hdr := buffer.NewPrependable(header.ICMPv6EchoMinimumSize + int(r.MaxHeaderLength()))
+
+	icmpv6 := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
+	copy(icmpv6, data)
+	data = data[header.ICMPv6EchoMinimumSize:]
+
+	if icmpv6.Type() != header.ICMPv6EchoRequest || icmpv6.Code() != 0 {
+		return tcpip.ErrInvalidEndpointState
+	}
+
+	icmpv6.SetChecksum(0)
+	icmpv6.SetChecksum(^header.Checksum(icmpv6, header.Checksum(data, 0)))
+
+	return r.WritePacket(&hdr, data, header.ICMPv6ProtocolNumber)
+}
+
 func (e *endpoint) checkV4Mapped(addr *tcpip.FullAddress, allowMismatch bool) (tcpip.NetworkProtocolNumber, *tcpip.Error) {
 	netProto := e.netProto
 	if header.IsV4MappedAddress(addr.Addr) {
@@ -508,14 +534,14 @@ func (e *endpoint) registerWithStack(nicid tcpip.NICID, netProtos []tcpip.Networ
 	if id.LocalPort != 0 {
 		// The endpoint already has a local port, just attempt to
 		// register it.
-		err := e.stack.RegisterTransportEndpoint(nicid, netProtos, ProtocolNumber4, id, e)
+		err := e.stack.RegisterTransportEndpoint(nicid, netProtos, e.transProto, id, e)
 		return id, err
 	}
 
 	// We need to find a port for the endpoint.
 	_, err := e.stack.PickEphemeralPort(func(p uint16) (bool, *tcpip.Error) {
 		id.LocalPort = p
-		err := e.stack.RegisterTransportEndpoint(nicid, netProtos, ProtocolNumber4, id, e)
+		err := e.stack.RegisterTransportEndpoint(nicid, netProtos, e.transProto, id, e)
 		switch err {
 		case nil:
 			return true, nil
@@ -564,7 +590,7 @@ func (e *endpoint) bindLocked(addr tcpip.FullAddress, commit func() *tcpip.Error
 	if commit != nil {
 		if err := commit(); err != nil {
 			// Unregister, the commit failed.
-			e.stack.UnregisterTransportEndpoint(addr.NIC, netProtos, ProtocolNumber4, id)
+			e.stack.UnregisterTransportEndpoint(addr.NIC, netProtos, e.transProto, id)
 			return err
 		}
 	}
diff --git a/pkg/tcpip/transport/ping/protocol.go b/pkg/tcpip/transport/ping/protocol.go
index 8a8192064..b885f3627 100644
--- a/pkg/tcpip/transport/ping/protocol.go
+++ b/pkg/tcpip/transport/ping/protocol.go
@@ -71,7 +71,7 @@ func (p *protocol) NewEndpoint(stack *stack.Stack, netProto tcpip.NetworkProtoco
 	if netProto != p.netProto() {
 		return nil, tcpip.ErrUnknownProtocol
 	}
-	return newEndpoint(stack, netProto, waiterQueue), nil
+	return newEndpoint(stack, netProto, p.number, waiterQueue), nil
 }
 
 // MinimumPacketSize returns the minimum valid ping packet size.
@@ -87,8 +87,14 @@ func (p *protocol) MinimumPacketSize() int {
 
 // ParsePorts returns the source and destination ports stored in the given ping
 // packet.
-func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
-	return 0, binary.BigEndian.Uint16(v[header.ICMPv4MinimumSize:]), nil
+func (p *protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) {
+	switch p.number {
+	case ProtocolNumber4:
+		return 0, binary.BigEndian.Uint16(v[header.ICMPv4MinimumSize:]), nil
+	case ProtocolNumber6:
+		return 0, binary.BigEndian.Uint16(v[header.ICMPv6MinimumSize:]), nil
+	}
+	panic(fmt.Sprint("unknown protocol number: ", p.number))
 }
 
 // HandleUnknownDestinationPacket handles packets targeted at this protocol but
@@ -112,5 +118,7 @@ func init() {
 		return &protocol{ProtocolNumber4}
 	})
 
-	// TODO: Support IPv6.
+	stack.RegisterTransportProtocolFactory(ProtocolName6, func() stack.TransportProtocol {
+		return &protocol{ProtocolNumber6}
+	})
 }