177 lines
4.8 KiB
Go
177 lines
4.8 KiB
Go
// Copyright 2019 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 flipcall
|
|
|
|
import (
|
|
"encoding/json"
|
|
"fmt"
|
|
"math"
|
|
"sync/atomic"
|
|
|
|
"gvisor.dev/gvisor/pkg/log"
|
|
)
|
|
|
|
type endpointControlImpl struct {
|
|
state int32
|
|
}
|
|
|
|
// Bits in endpointControlImpl.state.
|
|
const (
|
|
epsBlocked = 1 << iota
|
|
epsShutdown
|
|
)
|
|
|
|
func (ep *Endpoint) ctrlInit(opts ...EndpointOption) error {
|
|
if len(opts) != 0 {
|
|
return fmt.Errorf("unknown EndpointOption: %T", opts[0])
|
|
}
|
|
return nil
|
|
}
|
|
|
|
type ctrlHandshakeRequest struct{}
|
|
|
|
type ctrlHandshakeResponse struct{}
|
|
|
|
func (ep *Endpoint) ctrlConnect() error {
|
|
if err := ep.enterFutexWait(); err != nil {
|
|
return err
|
|
}
|
|
_, err := ep.futexConnect(&ctrlHandshakeRequest{})
|
|
ep.exitFutexWait()
|
|
return err
|
|
}
|
|
|
|
func (ep *Endpoint) ctrlWaitFirst() error {
|
|
if err := ep.enterFutexWait(); err != nil {
|
|
return err
|
|
}
|
|
defer ep.exitFutexWait()
|
|
|
|
// Wait for the handshake request.
|
|
if err := ep.futexSwitchFromPeer(); err != nil {
|
|
return err
|
|
}
|
|
|
|
// Read the handshake request.
|
|
reqLen := atomic.LoadUint32(ep.dataLen())
|
|
if reqLen > ep.dataCap {
|
|
return fmt.Errorf("invalid handshake request length %d (maximum %d)", reqLen, ep.dataCap)
|
|
}
|
|
var req ctrlHandshakeRequest
|
|
if err := json.NewDecoder(ep.NewReader(reqLen)).Decode(&req); err != nil {
|
|
return fmt.Errorf("error reading handshake request: %v", err)
|
|
}
|
|
|
|
// Write the handshake response.
|
|
w := ep.NewWriter()
|
|
if err := json.NewEncoder(w).Encode(ctrlHandshakeResponse{}); err != nil {
|
|
return fmt.Errorf("error writing handshake response: %v", err)
|
|
}
|
|
*ep.dataLen() = w.Len()
|
|
|
|
// Return control to the client.
|
|
raceBecomeInactive()
|
|
if err := ep.futexSwitchToPeer(); err != nil {
|
|
return err
|
|
}
|
|
|
|
// Wait for the first non-handshake message.
|
|
return ep.futexSwitchFromPeer()
|
|
}
|
|
|
|
func (ep *Endpoint) ctrlRoundTrip() error {
|
|
if err := ep.futexSwitchToPeer(); err != nil {
|
|
return err
|
|
}
|
|
if err := ep.enterFutexWait(); err != nil {
|
|
return err
|
|
}
|
|
err := ep.futexSwitchFromPeer()
|
|
ep.exitFutexWait()
|
|
return err
|
|
}
|
|
|
|
func (ep *Endpoint) ctrlWakeLast() error {
|
|
return ep.futexSwitchToPeer()
|
|
}
|
|
|
|
func (ep *Endpoint) enterFutexWait() error {
|
|
switch eps := atomic.AddInt32(&ep.ctrl.state, epsBlocked); eps {
|
|
case epsBlocked:
|
|
return nil
|
|
case epsBlocked | epsShutdown:
|
|
atomic.AddInt32(&ep.ctrl.state, -epsBlocked)
|
|
return ShutdownError{}
|
|
default:
|
|
// Most likely due to ep.enterFutexWait() being called concurrently
|
|
// from multiple goroutines.
|
|
panic(fmt.Sprintf("invalid flipcall.Endpoint.ctrl.state before flipcall.Endpoint.enterFutexWait(): %v", eps-epsBlocked))
|
|
}
|
|
}
|
|
|
|
func (ep *Endpoint) exitFutexWait() {
|
|
switch eps := atomic.AddInt32(&ep.ctrl.state, -epsBlocked); eps {
|
|
case 0:
|
|
return
|
|
case epsShutdown:
|
|
// ep.ctrlShutdown() was called while we were blocked, so we are
|
|
// repsonsible for indicating connection shutdown.
|
|
ep.shutdownConn()
|
|
default:
|
|
panic(fmt.Sprintf("invalid flipcall.Endpoint.ctrl.state after flipcall.Endpoint.exitFutexWait(): %v", eps+epsBlocked))
|
|
}
|
|
}
|
|
|
|
func (ep *Endpoint) ctrlShutdown() {
|
|
// Set epsShutdown to ensure that future calls to ep.enterFutexWait() fail.
|
|
if atomic.AddInt32(&ep.ctrl.state, epsShutdown)&epsBlocked != 0 {
|
|
// Wake the blocked thread. This must loop because it's possible that
|
|
// FUTEX_WAKE occurs after the waiter sets epsBlocked, but before it
|
|
// blocks in FUTEX_WAIT.
|
|
for {
|
|
// Wake MaxInt32 threads to prevent a broken or malicious peer from
|
|
// swallowing our wakeup by FUTEX_WAITing from multiple threads.
|
|
if err := ep.futexWakeConnState(math.MaxInt32); err != nil {
|
|
log.Warningf("failed to FUTEX_WAKE Endpoints: %v", err)
|
|
break
|
|
}
|
|
yieldThread()
|
|
if atomic.LoadInt32(&ep.ctrl.state)&epsBlocked == 0 {
|
|
break
|
|
}
|
|
}
|
|
} else {
|
|
// There is no blocked thread, so we are responsible for indicating
|
|
// connection shutdown.
|
|
ep.shutdownConn()
|
|
}
|
|
}
|
|
|
|
func (ep *Endpoint) shutdownConn() {
|
|
switch cs := atomic.SwapUint32(ep.connState(), csShutdown); cs {
|
|
case ep.activeState:
|
|
if err := ep.futexWakeConnState(1); err != nil {
|
|
log.Warningf("failed to FUTEX_WAKE peer Endpoint for shutdown: %v", err)
|
|
}
|
|
case ep.inactiveState:
|
|
// The peer is currently active and will detect shutdown when it tries
|
|
// to update the connection state.
|
|
case csShutdown:
|
|
// The peer also called Endpoint.Shutdown().
|
|
default:
|
|
log.Warningf("unexpected connection state before Endpoint.shutdownConn(): %v", cs)
|
|
}
|
|
}
|