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// 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 nested provides helpers to implement the pattern of nested
// stack.LinkEndpoints.
package nested
import (
"inet.af/netstack/sync"
"inet.af/netstack/tcpip"
"inet.af/netstack/tcpip/header"
"inet.af/netstack/tcpip/stack"
)
// Endpoint is a wrapper around stack.LinkEndpoint and stack.NetworkDispatcher
// that can be used to implement nesting safely by providing lifecycle
// concurrency guards.
//
// See the tests in this package for example usage.
type Endpoint struct {
child stack.LinkEndpoint
embedder stack.NetworkDispatcher
// mu protects dispatcher.
mu sync.RWMutex
dispatcher stack.NetworkDispatcher
}
var _ stack.GSOEndpoint = (*Endpoint)(nil)
var _ stack.LinkEndpoint = (*Endpoint)(nil)
var _ stack.NetworkDispatcher = (*Endpoint)(nil)
// Init initializes a nested.Endpoint that uses embedder as the dispatcher for
// child on Attach.
//
// See the tests in this package for example usage.
func (e *Endpoint) Init(child stack.LinkEndpoint, embedder stack.NetworkDispatcher) {
e.child = child
e.embedder = embedder
}
// DeliverNetworkPacket implements stack.NetworkDispatcher.
func (e *Endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
e.mu.RLock()
d := e.dispatcher
e.mu.RUnlock()
if d != nil {
d.DeliverNetworkPacket(remote, local, protocol, pkt)
}
}
// Attach implements stack.LinkEndpoint.
func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
e.mu.Lock()
e.dispatcher = dispatcher
e.mu.Unlock()
// If we're attaching to a valid dispatcher, pass embedder as the dispatcher
// to our child, otherwise detach the child by giving it a nil dispatcher.
var pass stack.NetworkDispatcher
if dispatcher != nil {
pass = e.embedder
}
e.child.Attach(pass)
}
// IsAttached implements stack.LinkEndpoint.
func (e *Endpoint) IsAttached() bool {
e.mu.RLock()
isAttached := e.dispatcher != nil
e.mu.RUnlock()
return isAttached
}
// MTU implements stack.LinkEndpoint.
func (e *Endpoint) MTU() uint32 {
return e.child.MTU()
}
// Capabilities implements stack.LinkEndpoint.
func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
return e.child.Capabilities()
}
// MaxHeaderLength implements stack.LinkEndpoint.
func (e *Endpoint) MaxHeaderLength() uint16 {
return e.child.MaxHeaderLength()
}
// LinkAddress implements stack.LinkEndpoint.
func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
return e.child.LinkAddress()
}
// WritePacket implements stack.LinkEndpoint.
func (e *Endpoint) WritePacket(r stack.RouteInfo, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
return e.child.WritePacket(r, protocol, pkt)
}
// WritePackets implements stack.LinkEndpoint.
func (e *Endpoint) WritePackets(r stack.RouteInfo, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
return e.child.WritePackets(r, pkts, protocol)
}
// Wait implements stack.LinkEndpoint.
func (e *Endpoint) Wait() {
e.child.Wait()
}
// GSOMaxSize implements stack.GSOEndpoint.
func (e *Endpoint) GSOMaxSize() uint32 {
if e, ok := e.child.(stack.GSOEndpoint); ok {
return e.GSOMaxSize()
}
return 0
}
// SupportedGSO implements stack.GSOEndpoint.
func (e *Endpoint) SupportedGSO() stack.SupportedGSO {
if e, ok := e.child.(stack.GSOEndpoint); ok {
return e.SupportedGSO()
}
return stack.GSONotSupported
}
// ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType
func (e *Endpoint) ARPHardwareType() header.ARPHardwareType {
return e.child.ARPHardwareType()
}
// AddHeader implements stack.LinkEndpoint.AddHeader.
func (e *Endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
e.child.AddHeader(local, remote, protocol, pkt)
}
// WriteRawPacket implements stack.LinkEndpoint.
func (e *Endpoint) WriteRawPacket(pkt *stack.PacketBuffer) tcpip.Error {
return e.child.WriteRawPacket(pkt)
}
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