124 lines
4.4 KiB
Go
124 lines
4.4 KiB
Go
// Copyright 2018 Google LLC
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package waitable provides the implementation of data-link layer endpoints
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// that wrap other endpoints, and can wait for inflight calls to WritePacket or
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// DeliverNetworkPacket to finish (and new ones to be prevented).
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//
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// Waitable endpoints can be used in the networking stack by calling New(eID) to
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// create a new endpoint, where eID is the ID of the endpoint being wrapped,
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// and then passing it as an argument to Stack.CreateNIC().
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package waitable
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import (
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"gvisor.googlesource.com/gvisor/pkg/gate"
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"gvisor.googlesource.com/gvisor/pkg/tcpip"
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"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
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"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
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)
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// Endpoint is a waitable link-layer endpoint.
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type Endpoint struct {
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dispatchGate gate.Gate
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dispatcher stack.NetworkDispatcher
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writeGate gate.Gate
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lower stack.LinkEndpoint
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}
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// New creates a new waitable link-layer endpoint. It wraps around another
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// endpoint and allows the caller to block new write/dispatch calls and wait for
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// the inflight ones to finish before returning.
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func New(lower tcpip.LinkEndpointID) (tcpip.LinkEndpointID, *Endpoint) {
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e := &Endpoint{
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lower: stack.FindLinkEndpoint(lower),
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}
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return stack.RegisterLinkEndpoint(e), e
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}
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// DeliverNetworkPacket implements stack.NetworkDispatcher.DeliverNetworkPacket.
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// It is called by the link-layer endpoint being wrapped when a packet arrives,
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// and only forwards to the actual dispatcher if Wait or WaitDispatch haven't
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// been called.
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func (e *Endpoint) DeliverNetworkPacket(linkEP stack.LinkEndpoint, remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, vv buffer.VectorisedView) {
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if !e.dispatchGate.Enter() {
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return
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}
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e.dispatcher.DeliverNetworkPacket(e, remote, local, protocol, vv)
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e.dispatchGate.Leave()
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}
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// Attach implements stack.LinkEndpoint.Attach. It saves the dispatcher and
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// registers with the lower endpoint as its dispatcher so that "e" is called
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// for inbound packets.
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func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
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e.dispatcher = dispatcher
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e.lower.Attach(e)
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}
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// IsAttached implements stack.LinkEndpoint.IsAttached.
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func (e *Endpoint) IsAttached() bool {
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return e.dispatcher != nil
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}
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// MTU implements stack.LinkEndpoint.MTU. It just forwards the request to the
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// lower endpoint.
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func (e *Endpoint) MTU() uint32 {
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return e.lower.MTU()
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}
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// Capabilities implements stack.LinkEndpoint.Capabilities. It just forwards the
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// request to the lower endpoint.
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func (e *Endpoint) Capabilities() stack.LinkEndpointCapabilities {
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return e.lower.Capabilities()
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}
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// MaxHeaderLength implements stack.LinkEndpoint.MaxHeaderLength. It just
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// forwards the request to the lower endpoint.
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func (e *Endpoint) MaxHeaderLength() uint16 {
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return e.lower.MaxHeaderLength()
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}
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// LinkAddress implements stack.LinkEndpoint.LinkAddress. It just forwards the
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// request to the lower endpoint.
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func (e *Endpoint) LinkAddress() tcpip.LinkAddress {
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return e.lower.LinkAddress()
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}
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// WritePacket implements stack.LinkEndpoint.WritePacket. It is called by
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// higher-level protocols to write packets. It only forwards packets to the
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// lower endpoint if Wait or WaitWrite haven't been called.
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func (e *Endpoint) WritePacket(r *stack.Route, gso *stack.GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.NetworkProtocolNumber) *tcpip.Error {
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if !e.writeGate.Enter() {
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return nil
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}
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err := e.lower.WritePacket(r, gso, hdr, payload, protocol)
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e.writeGate.Leave()
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return err
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}
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// WaitWrite prevents new calls to WritePacket from reaching the lower endpoint,
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// and waits for inflight ones to finish before returning.
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func (e *Endpoint) WaitWrite() {
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e.writeGate.Close()
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}
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// WaitDispatch prevents new calls to DeliverNetworkPacket from reaching the
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// actual dispatcher, and waits for inflight ones to finish before returning.
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func (e *Endpoint) WaitDispatch() {
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e.dispatchGate.Close()
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}
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