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// Copyright 2018 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 eventchannel contains functionality for sending any protobuf message
// on a socketpair.
//
// The wire format is a uvarint length followed by a binary protobuf.Any
// message.
package eventchannel
import (
"encoding/binary"
"fmt"
"sync"
"syscall"
"github.com/golang/protobuf/proto"
"github.com/golang/protobuf/ptypes"
pb "gvisor.dev/gvisor/pkg/eventchannel/eventchannel_go_proto"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/unet"
)
// Emitter emits a proto message.
type Emitter interface {
// Emit writes a single eventchannel message to an emitter. Emit should
// return hangup = true to indicate an emitter has "hung up" and no further
// messages should be directed to it.
Emit(msg proto.Message) (hangup bool, err error)
// Close closes this emitter. Emit cannot be used after Close is called.
Close() error
}
var (
mu sync.Mutex
emitters = make(map[Emitter]struct{})
)
// Emit emits a message using all added emitters.
func Emit(msg proto.Message) error {
mu.Lock()
defer mu.Unlock()
var err error
for e := range emitters {
hangup, eerr := e.Emit(msg)
if eerr != nil {
if err == nil {
err = fmt.Errorf("error emitting %v: on %v: %v", msg, e, eerr)
} else {
err = fmt.Errorf("%v; on %v: %v", err, e, eerr)
}
// Log as well, since most callers ignore the error.
log.Warningf("Error emitting %v on %v: %v", msg, e, eerr)
}
if hangup {
log.Infof("Hangup on eventchannel emitter %v.", e)
delete(emitters, e)
}
}
return err
}
// AddEmitter adds a new emitter.
func AddEmitter(e Emitter) {
mu.Lock()
defer mu.Unlock()
emitters[e] = struct{}{}
}
func marshal(msg proto.Message) ([]byte, error) {
anypb, err := ptypes.MarshalAny(msg)
if err != nil {
return nil, err
}
// Wire format is uvarint message length followed by binary proto.
bufMsg, err := proto.Marshal(anypb)
if err != nil {
return nil, err
}
p := make([]byte, binary.MaxVarintLen64)
n := binary.PutUvarint(p, uint64(len(bufMsg)))
return append(p[:n], bufMsg...), nil
}
// socketEmitter emits proto messages on a socket.
type socketEmitter struct {
socket *unet.Socket
}
// SocketEmitter creates a new event channel based on the given fd.
//
// SocketEmitter takes ownership of fd.
func SocketEmitter(fd int) (Emitter, error) {
s, err := unet.NewSocket(fd)
if err != nil {
return nil, err
}
return &socketEmitter{
socket: s,
}, nil
}
// Emit implements Emitter.Emit.
func (s *socketEmitter) Emit(msg proto.Message) (bool, error) {
p, err := marshal(msg)
if err != nil {
return false, err
}
for done := 0; done < len(p); {
n, err := s.socket.Write(p[done:])
if err != nil {
return (err == syscall.EPIPE), err
}
done += n
}
return false, nil
}
// Close implements Emitter.Emit.
func (s *socketEmitter) Close() error {
return s.socket.Close()
}
// debugEmitter wraps an emitter to emit stringified event messages. This is
// useful for debugging -- when the messages are intended for humans.
type debugEmitter struct {
inner Emitter
}
// DebugEmitterFrom creates a new event channel emitter by wraping an existing
// raw emitter.
func DebugEmitterFrom(inner Emitter) Emitter {
return &debugEmitter{
inner: inner,
}
}
func (d *debugEmitter) Emit(msg proto.Message) (bool, error) {
ev := &pb.DebugEvent{
Name: proto.MessageName(msg),
Text: proto.MarshalTextString(msg),
}
return d.inner.Emit(ev)
}
func (d *debugEmitter) Close() error {
return d.inner.Close()
}
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