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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 fifo provides the implementation of data-link layer endpoints that
// wrap another endpoint and queues all outbound packets and asynchronously
// dispatches them to the lower endpoint.
package fifo
import (
"gvisor.dev/gvisor/pkg/sleep"
"gvisor.dev/gvisor/pkg/sync"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/pkg/tcpip/stack"
)
// endpoint represents a LinkEndpoint which implements a FIFO queue for all
// outgoing packets. endpoint can have 1 or more underlying queueDispatchers.
// All outgoing packets are consistenly hashed to a single underlying queue
// using the PacketBuffer.Hash if set, otherwise all packets are queued to the
// first queue to avoid reordering in case of missing hash.
type endpoint struct {
dispatcher stack.NetworkDispatcher
lower stack.LinkEndpoint
wg sync.WaitGroup
dispatchers []*queueDispatcher
}
// queueDispatcher is responsible for dispatching all outbound packets in its
// queue. It will also smartly batch packets when possible and write them
// through the lower LinkEndpoint.
type queueDispatcher struct {
lower stack.LinkEndpoint
q *packetBufferQueue
newPacketWaker sleep.Waker
closeWaker sleep.Waker
}
// New creates a new fifo link endpoint with the n queues with maximum
// capacity of queueLen.
func New(lower stack.LinkEndpoint, n int, queueLen int) stack.LinkEndpoint {
e := &endpoint{
lower: lower,
}
// Create the required dispatchers
for i := 0; i < n; i++ {
qd := &queueDispatcher{
q: &packetBufferQueue{limit: queueLen},
lower: lower,
}
e.dispatchers = append(e.dispatchers, qd)
e.wg.Add(1)
go func() {
defer e.wg.Done()
qd.dispatchLoop()
}()
}
return e
}
func (q *queueDispatcher) dispatchLoop() {
const newPacketWakerID = 1
const closeWakerID = 2
s := sleep.Sleeper{}
s.AddWaker(&q.newPacketWaker, newPacketWakerID)
s.AddWaker(&q.closeWaker, closeWakerID)
defer s.Done()
const batchSize = 32
var batch stack.PacketBufferList
for {
id, ok := s.Fetch(true)
if ok && id == closeWakerID {
return
}
for pkt := q.q.dequeue(); pkt != nil; pkt = q.q.dequeue() {
batch.PushBack(pkt)
if batch.Len() < batchSize && !q.q.empty() {
continue
}
// We pass a protocol of zero here because each packet carries its
// NetworkProtocol.
q.lower.WritePackets(stack.RouteInfo{}, nil /* gso */, batch, 0 /* protocol */)
for pkt := batch.Front(); pkt != nil; pkt = pkt.Next() {
batch.Remove(pkt)
}
batch.Reset()
}
}
}
// DeliverNetworkPacket implements stack.NetworkDispatcher.DeliverNetworkPacket.
func (e *endpoint) DeliverNetworkPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
e.dispatcher.DeliverNetworkPacket(remote, local, protocol, pkt)
}
// DeliverOutboundPacket implements stack.NetworkDispatcher.DeliverOutboundPacket.
func (e *endpoint) DeliverOutboundPacket(remote, local tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
e.dispatcher.DeliverOutboundPacket(remote, local, protocol, pkt)
}
// Attach implements stack.LinkEndpoint.Attach.
func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
e.dispatcher = dispatcher
e.lower.Attach(e)
}
// IsAttached implements stack.LinkEndpoint.IsAttached.
func (e *endpoint) IsAttached() bool {
return e.dispatcher != nil
}
// MTU implements stack.LinkEndpoint.MTU.
func (e *endpoint) MTU() uint32 {
return e.lower.MTU()
}
// Capabilities implements stack.LinkEndpoint.Capabilities.
func (e *endpoint) Capabilities() stack.LinkEndpointCapabilities {
return e.lower.Capabilities()
}
// MaxHeaderLength implements stack.LinkEndpoint.MaxHeaderLength.
func (e *endpoint) MaxHeaderLength() uint16 {
return e.lower.MaxHeaderLength()
}
// LinkAddress implements stack.LinkEndpoint.LinkAddress.
func (e *endpoint) LinkAddress() tcpip.LinkAddress {
return e.lower.LinkAddress()
}
// GSOMaxSize returns the maximum GSO packet size.
func (e *endpoint) GSOMaxSize() uint32 {
if gso, ok := e.lower.(stack.GSOEndpoint); ok {
return gso.GSOMaxSize()
}
return 0
}
// WritePacket implements stack.LinkEndpoint.WritePacket.
func (e *endpoint) WritePacket(r stack.RouteInfo, gso *stack.GSO, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) tcpip.Error {
// WritePacket caller's do not set the following fields in PacketBuffer
// so we populate them here.
pkt.EgressRoute = r
pkt.GSOOptions = gso
pkt.NetworkProtocolNumber = protocol
d := e.dispatchers[int(pkt.Hash)%len(e.dispatchers)]
if !d.q.enqueue(pkt) {
return &tcpip.ErrNoBufferSpace{}
}
d.newPacketWaker.Assert()
return nil
}
// WritePackets implements stack.LinkEndpoint.WritePackets.
//
// Being a batch API, each packet in pkts should have the following
// fields populated:
// - pkt.EgressRoute
// - pkt.GSOOptions
// - pkt.NetworkProtocolNumber
func (e *endpoint) WritePackets(r stack.RouteInfo, gso *stack.GSO, pkts stack.PacketBufferList, protocol tcpip.NetworkProtocolNumber) (int, tcpip.Error) {
enqueued := 0
for pkt := pkts.Front(); pkt != nil; {
d := e.dispatchers[int(pkt.Hash)%len(e.dispatchers)]
nxt := pkt.Next()
if !d.q.enqueue(pkt) {
if enqueued > 0 {
d.newPacketWaker.Assert()
}
return enqueued, &tcpip.ErrNoBufferSpace{}
}
pkt = nxt
enqueued++
d.newPacketWaker.Assert()
}
return enqueued, nil
}
// Wait implements stack.LinkEndpoint.Wait.
func (e *endpoint) Wait() {
e.lower.Wait()
// The linkEP is gone. Teardown the outbound dispatcher goroutines.
for i := range e.dispatchers {
e.dispatchers[i].closeWaker.Assert()
}
e.wg.Wait()
}
// ARPHardwareType implements stack.LinkEndpoint.ARPHardwareType
func (e *endpoint) ARPHardwareType() header.ARPHardwareType {
return e.lower.ARPHardwareType()
}
// AddHeader implements stack.LinkEndpoint.AddHeader.
func (e *endpoint) AddHeader(local, remote tcpip.LinkAddress, protocol tcpip.NetworkProtocolNumber, pkt *stack.PacketBuffer) {
e.lower.AddHeader(local, remote, protocol, pkt)
}
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