Do not resolve routes immediately

When a response needs to be sent to an incoming packet, the stack should
consult its neighbour table to determine the remote address's link
address.

When an entry does not exist in the stack's neighbor table, the stack
should queue the packet while link resolution completes. See comments.

PiperOrigin-RevId: 336185457

1 files changed, 124 insertions, 0 deletions

diff --git a/pkg/tcpip/link/pipe/pipe.go b/pkg/tcpip/link/pipe/pipe.go
new file mode 100644
index 000000000..76f563811
--- /dev/null
+++ b/pkg/tcpip/link/pipe/pipe.go
@@ -0,0 +1,124 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package pipe provides the implementation of pipe-like data-link layer
+// endpoints. Such endpoints allow packets to be sent between two interfaces.
+package pipe
+
+import (
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+)
+
+var _ stack.LinkEndpoint = (*Endpoint)(nil)
+
+// New returns both ends of a new pipe.
+func New(linkAddr1, linkAddr2 tcpip.LinkAddress, capabilities stack.LinkEndpointCapabilities) (*Endpoint, *Endpoint) {
+	ep1 := &Endpoint{
+		linkAddr:     linkAddr1,
+		capabilities: capabilities,
+	}
+	ep2 := &Endpoint{
+		linkAddr:     linkAddr2,
+		linked:       ep1,
+		capabilities: capabilities,
+	}
+	ep1.linked = ep2
+	return ep1, ep2
+}
+
+// Endpoint is one end of a pipe.
+type Endpoint struct {
+	capabilities  stack.LinkEndpointCapabilities
+	linkAddr      tcpip.LinkAddress
+	dispatcher    stack.NetworkDispatcher
+	linked        *Endpoint
+	onWritePacket func(*stack.PacketBuffer)
+}
+
+// WritePacket implements stack.LinkEndpoint.
+func (e *Endpoint) WritePacket(r *stack.Route, _ *stack.GSO, proto tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) *tcpip.Error {
+	if !e.linked.IsAttached() {
+		return nil
+	}
+
+	// The pipe endpoint will accept all multicast/broadcast link traffic and only
+	// unicast traffic destined to itself.
+	if len(e.linked.linkAddr) != 0 &&
+		r.RemoteLinkAddress != e.linked.linkAddr &&
+		r.RemoteLinkAddress != header.EthernetBroadcastAddress &&
+		!header.IsMulticastEthernetAddress(r.RemoteLinkAddress) {
+		return nil
+	}
+
+	e.linked.dispatcher.DeliverNetworkPacket(e.linkAddr, r.RemoteLinkAddress, proto, stack.NewPacketBuffer(stack.PacketBufferOptions{
+		Data: buffer.NewVectorisedView(pkt.Size(), pkt.Views()),
+	}))
+
+	return nil
+}
+
+// WritePackets implements stack.LinkEndpoint.
+func (*Endpoint) WritePackets(*stack.Route, *stack.GSO, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+	panic("not implemented")
+}
+
+// WriteRawPacket implements stack.LinkEndpoint.
+func (*Endpoint) WriteRawPacket(buffer.VectorisedView) *tcpip.Error {
+	panic("not implemented")
+}
+
+// Attach implements stack.LinkEndpoint.
+func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
+	e.dispatcher = dispatcher
+}
+
+// IsAttached implements stack.LinkEndpoint.
+func (e *Endpoint) IsAttached() bool {
+	return e.dispatcher != nil
+}
+
+// Wait implements stack.LinkEndpoint.
+func (*Endpoint) Wait() {}
+
+// MTU implements stack.LinkEndpoint.
+func (*Endpoint) MTU() uint32 {
+	return header.IPv6MinimumMTU
+}
+
+// Capabilities implements stack.LinkEndpoint.
+func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
+	return e.capabilities
+}
+
+// MaxHeaderLength implements stack.LinkEndpoint.
+func (*Endpoint) MaxHeaderLength() uint16 {
+	return 0
+}
+
+// LinkAddress implements stack.LinkEndpoint.
+func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
+	return e.linkAddr
+}
+
+// ARPHardwareType implements stack.LinkEndpoint.
+func (*Endpoint) ARPHardwareType() header.ARPHardwareType {
+	return header.ARPHardwareEther
+}
+
+// AddHeader implements stack.LinkEndpoint.
+func (*Endpoint) AddHeader(_, _ tcpip.LinkAddress, _ tcpip.NetworkProtocolNumber, _ *stack.PacketBuffer) {
+}