4 files changed, 113 insertions, 0 deletions
diff --git a/pkg/sentry/inet/BUILD b/pkg/sentry/inet/BUILD
index 334432abf..07bf39fed 100644
--- a/pkg/sentry/inet/BUILD
+++ b/pkg/sentry/inet/BUILD
@@ -10,6 +10,7 @@ go_library(
     srcs = [
         "context.go",
         "inet.go",
+        "namespace.go",
         "test_stack.go",
     ],
     deps = [
diff --git a/pkg/sentry/inet/inet.go b/pkg/sentry/inet/inet.go
index a7dfb78a7..2916a0644 100644
--- a/pkg/sentry/inet/inet.go
+++ b/pkg/sentry/inet/inet.go
@@ -28,6 +28,10 @@ type Stack interface {
 	// interface indexes to a slice of associated interface address properties.
 	InterfaceAddrs() map[int32][]InterfaceAddr
 
+	// AddInterfaceAddr adds an address to the network interface identified by
+	// index.
+	AddInterfaceAddr(idx int32, addr InterfaceAddr) error
+
 	// SupportsIPv6 returns true if the stack supports IPv6 connectivity.
 	SupportsIPv6() bool
 
diff --git a/pkg/sentry/inet/namespace.go b/pkg/sentry/inet/namespace.go
new file mode 100644
index 000000000..029af3025
--- /dev/null
+++ b/pkg/sentry/inet/namespace.go
@@ -0,0 +1,102 @@
+// 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 inet
+
+// Namespace represents a network namespace. See network_namespaces(7).
+//
+// +stateify savable
+type Namespace struct {
+	// stack is the network stack implementation of this network namespace.
+	stack Stack `state:"nosave"`
+
+	// creator allows kernel to create new network stack for network namespaces.
+	// If nil, no networking will function if network is namespaced.
+	//
+	// At afterLoad(), creator will be used to create network stack. Stateify
+	// needs to wait for this field to be loaded before calling afterLoad().
+	creator NetworkStackCreator `state:"wait"`
+
+	// isRoot indicates whether this is the root network namespace.
+	isRoot bool
+}
+
+// NewRootNamespace creates the root network namespace, with creator
+// allowing new network namespaces to be created. If creator is nil, no
+// networking will function if the network is namespaced.
+func NewRootNamespace(stack Stack, creator NetworkStackCreator) *Namespace {
+	return &Namespace{
+		stack:   stack,
+		creator: creator,
+		isRoot:  true,
+	}
+}
+
+// NewNamespace creates a new network namespace from the root.
+func NewNamespace(root *Namespace) *Namespace {
+	n := &Namespace{
+		creator: root.creator,
+	}
+	n.init()
+	return n
+}
+
+// Stack returns the network stack of n. Stack may return nil if no network
+// stack is configured.
+func (n *Namespace) Stack() Stack {
+	return n.stack
+}
+
+// IsRoot returns whether n is the root network namespace.
+func (n *Namespace) IsRoot() bool {
+	return n.isRoot
+}
+
+// RestoreRootStack restores the root network namespace with stack. This should
+// only be called when restoring kernel.
+func (n *Namespace) RestoreRootStack(stack Stack) {
+	if !n.isRoot {
+		panic("RestoreRootStack can only be called on root network namespace")
+	}
+	if n.stack != nil {
+		panic("RestoreRootStack called after a stack has already been set")
+	}
+	n.stack = stack
+}
+
+func (n *Namespace) init() {
+	// Root network namespace will have stack assigned later.
+	if n.isRoot {
+		return
+	}
+	if n.creator != nil {
+		var err error
+		n.stack, err = n.creator.CreateStack()
+		if err != nil {
+			panic(err)
+		}
+	}
+}
+
+// afterLoad is invoked by stateify.
+func (n *Namespace) afterLoad() {
+	n.init()
+}
+
+// NetworkStackCreator allows new instances of a network stack to be created. It
+// is used by the kernel to create new network namespaces when requested.
+type NetworkStackCreator interface {
+	// CreateStack creates a new network stack for a network namespace.
+	CreateStack() (Stack, error)
+}
diff --git a/pkg/sentry/inet/test_stack.go b/pkg/sentry/inet/test_stack.go
index dcfcbd97e..d8961fc94 100644
--- a/pkg/sentry/inet/test_stack.go
+++ b/pkg/sentry/inet/test_stack.go
@@ -47,6 +47,12 @@ func (s *TestStack) InterfaceAddrs() map[int32][]InterfaceAddr {
 	return s.InterfaceAddrsMap
 }
 
+// AddInterfaceAddr implements Stack.AddInterfaceAddr.
+func (s *TestStack) AddInterfaceAddr(idx int32, addr InterfaceAddr) error {
+	s.InterfaceAddrsMap[idx] = append(s.InterfaceAddrsMap[idx], addr)
+	return nil
+}
+
 // SupportsIPv6 implements Stack.SupportsIPv6.
 func (s *TestStack) SupportsIPv6() bool {
 	return s.SupportsIPv6Flag