Implement dummy network interfacesfeature/dummy-iface

2 files changed, 114 insertions, 0 deletions

diff --git a/pkg/tcpip/link/dummy/BUILD b/pkg/tcpip/link/dummy/BUILD
new file mode 100644
index 000000000..050eb9397
--- /dev/null
+++ b/pkg/tcpip/link/dummy/BUILD
@@ -0,0 +1,14 @@
+load("//tools:defs.bzl", "go_library")
+
+package(licenses = ["notice"])
+
+go_library(
+    name = "dummy",
+    srcs = ["dummy.go"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/tcpip",
+        "//pkg/tcpip/header",
+        "//pkg/tcpip/stack",
+    ],
+)
diff --git a/pkg/tcpip/link/dummy/dummy.go b/pkg/tcpip/link/dummy/dummy.go
new file mode 100644
index 000000000..7e8c39ef1
--- /dev/null
+++ b/pkg/tcpip/link/dummy/dummy.go
@@ -0,0 +1,100 @@
+// Copyright 2021 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 dummy provides the implemention of dummy data-link layer
+// endpoints. Such endpoints just discards outgoing packets.
+//
+// Dummy endpoints can be used in the networking stack by calling New() to
+// create a new endpoint, and then passing it as an argument to
+// Stack.CreateNIC().
+package dummy
+
+import (
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+)
+
+type endpoint struct {
+	dispatcher stack.NetworkDispatcher
+}
+
+// New creates a new dummy endpoint. This link-layer endpoint just
+// discards outbound packets.
+func New() stack.LinkEndpoint {
+	return &endpoint{}
+}
+
+// Attach implements stack.LinkEndpoint.Attach. It just saves the stack network-
+// layer dispatcher for later use when packets need to be dispatched.
+func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
+	e.dispatcher = dispatcher
+}
+
+// IsAttached implements stack.LinkEndpoint.IsAttached.
+func (e *endpoint) IsAttached() bool {
+	return e.dispatcher != nil
+}
+
+// MTU implements stack.LinkEndpoint.MTU. It returns a constant that matches the
+// default value for the linux dummy interface.
+func (*endpoint) MTU() uint32 {
+	return 65536
+}
+
+// Capabilities implements stack.LinkEndpoint.Capabilities. Dummy advertises
+// itself as supporting checksum offload.
+func (*endpoint) Capabilities() stack.LinkEndpointCapabilities {
+	return stack.CapabilityRXChecksumOffload | stack.CapabilityTXChecksumOffload | stack.CapabilitySaveRestore
+}
+
+// MaxHeaderLength implements stack.LinkEndpoint.MaxHeaderLength. Given that the
+// dummy interface doesn't have a header, it just returns 0.
+func (*endpoint) MaxHeaderLength() uint16 {
+	return 0
+}
+
+// LinkAddress returns the link address of this endpoint.
+func (*endpoint) LinkAddress() tcpip.LinkAddress {
+	// TODO add link address
+	return ""
+}
+
+// Wait implements stack.LinkEndpoint.Wait.
+func (*endpoint) Wait() {}
+
+// WritePacket implements stack.LinkEndpoint.WritePacket. It delivers outbound
+// packets to the network-layer dispatcher.
+func (e *endpoint) WritePacket(_ stack.RouteInfo, _ tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
+	return e.WriteRawPacket(pkt)
+}
+
+// WritePackets implements stack.LinkEndpoint.WritePackets.
+func (e *endpoint) WritePackets(stack.RouteInfo, stack.PacketBufferList, tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
+	panic("not implemented")
+}
+
+// ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType.
+func (*endpoint) ARPHardwareType() header.ARPHardwareType {
+	return header.ARPHardwareEther
+}
+
+func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
+}
+
+// WriteRawPacket implements stack.LinkEndpoint.
+func (e *endpoint) WriteRawPacket(pkt *stack.PacketBuffer) tcpip.Error {
+	// Discard
+	return nil
+}