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connectioned.go
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connectioned.go
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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 transport
import (
"golang.org/x/sys/unix"
"github.com/nicocha30/gvisor-ligolo/pkg/abi/linux"
"github.com/nicocha30/gvisor-ligolo/pkg/context"
"github.com/nicocha30/gvisor-ligolo/pkg/fdnotifier"
"github.com/nicocha30/gvisor-ligolo/pkg/sentry/uniqueid"
"github.com/nicocha30/gvisor-ligolo/pkg/syserr"
"github.com/nicocha30/gvisor-ligolo/pkg/tcpip"
"github.com/nicocha30/gvisor-ligolo/pkg/waiter"
)
type locker interface {
Lock()
Unlock()
NestedLock(endpointlockNameIndex)
NestedUnlock(endpointlockNameIndex)
}
// A ConnectingEndpoint is a connectioned unix endpoint that is attempting to
// establish a bidirectional connection with a BoundEndpoint.
type ConnectingEndpoint interface {
// ID returns the endpoint's globally unique identifier. This identifier
// must be used to determine locking order if more than one endpoint is
// to be locked in the same codepath. The endpoint with the smaller
// identifier must be locked before endpoints with larger identifiers.
ID() uint64
// Passcred implements socket.Credentialer.Passcred.
Passcred() bool
// Type returns the socket type, typically either SockStream or
// SockSeqpacket. The connection attempt must be aborted if this
// value doesn't match the BoundEndpoint's type.
Type() linux.SockType
// GetLocalAddress returns the bound path.
GetLocalAddress() (Address, tcpip.Error)
// Locker protects the following methods. While locked, only the holder of
// the lock can change the return value of the protected methods.
locker
// Connected returns true iff the ConnectingEndpoint is in the connected
// state. ConnectingEndpoints can only be connected to a single endpoint,
// so the connection attempt must be aborted if this returns true.
Connected() bool
// ListeningLocked returns true iff the ConnectingEndpoint is in the
// listening state. ConnectingEndpoints cannot make connections while
// listening, so the connection attempt must be aborted if this returns
// true.
ListeningLocked() bool
// WaiterQueue returns a pointer to the endpoint's waiter queue.
WaiterQueue() *waiter.Queue
}
// connectionedEndpoint is a Unix-domain connected or connectable endpoint and implements
// ConnectingEndpoint, BoundEndpoint and tcpip.Endpoint.
//
// connectionedEndpoints must be in connected state in order to transfer data.
//
// This implementation includes STREAM and SEQPACKET Unix sockets created with
// socket(2), accept(2) or socketpair(2) and dgram unix sockets created with
// socketpair(2). See unix_connectionless.go for the implementation of DGRAM
// Unix sockets created with socket(2).
//
// The state is much simpler than a TCP endpoint, so it is not encoded
// explicitly. Instead we enforce the following invariants:
//
// receiver != nil, connected != nil => connected.
// path != "" && acceptedChan == nil => bound, not listening.
// path != "" && acceptedChan != nil => bound and listening.
//
// Only one of these will be true at any moment.
//
// +stateify savable
type connectionedEndpoint struct {
baseEndpoint
// id is the unique endpoint identifier. This is used exclusively for
// lock ordering within connect.
id uint64
// idGenerator is used to generate new unique endpoint identifiers.
idGenerator uniqueid.Provider
// stype is used by connecting sockets to ensure that they are the
// same type. The value is typically either tcpip.SockSeqpacket or
// tcpip.SockStream.
stype linux.SockType
// acceptedChan is per the TCP endpoint implementation. Note that the
// sockets in this channel are _already in the connected state_, and
// have another associated connectionedEndpoint.
//
// If nil, then no listen call has been made.
acceptedChan chan *connectionedEndpoint `state:".([]*connectionedEndpoint)"`
// boundSocketFD corresponds to a bound socket on the host filesystem
// that may listen and accept incoming connections.
//
// boundSocketFD is protected by baseEndpoint.mu.
boundSocketFD BoundSocketFD
}
var (
_ = BoundEndpoint((*connectionedEndpoint)(nil))
_ = Endpoint((*connectionedEndpoint)(nil))
)
// NewConnectioned creates a new unbound connectionedEndpoint.
func NewConnectioned(ctx context.Context, stype linux.SockType, uid uniqueid.Provider) Endpoint {
return newConnectioned(ctx, stype, uid)
}
func newConnectioned(ctx context.Context, stype linux.SockType, uid uniqueid.Provider) *connectionedEndpoint {
ep := &connectionedEndpoint{
baseEndpoint: baseEndpoint{Queue: &waiter.Queue{}},
id: uid.UniqueID(),
idGenerator: uid,
stype: stype,
}
ep.ops.InitHandler(ep, &stackHandler{}, getSendBufferLimits, getReceiveBufferLimits)
ep.ops.SetSendBufferSize(defaultBufferSize, false /* notify */)
ep.ops.SetReceiveBufferSize(defaultBufferSize, false /* notify */)
return ep
}
// NewPair allocates a new pair of connected unix-domain connectionedEndpoints.
func NewPair(ctx context.Context, stype linux.SockType, uid uniqueid.Provider) (Endpoint, Endpoint) {
a := newConnectioned(ctx, stype, uid)
b := newConnectioned(ctx, stype, uid)
q1 := &queue{ReaderQueue: a.Queue, WriterQueue: b.Queue, limit: defaultBufferSize}
q1.InitRefs()
q2 := &queue{ReaderQueue: b.Queue, WriterQueue: a.Queue, limit: defaultBufferSize}
q2.InitRefs()
if stype == linux.SOCK_STREAM {
a.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{q1}}
b.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{q2}}
} else {
a.receiver = &queueReceiver{q1}
b.receiver = &queueReceiver{q2}
}
q2.IncRef()
a.connected = &connectedEndpoint{
endpoint: b,
writeQueue: q2,
}
q1.IncRef()
b.connected = &connectedEndpoint{
endpoint: a,
writeQueue: q1,
}
return a, b
}
// NewExternal creates a new externally backed Endpoint. It behaves like a
// socketpair.
func NewExternal(stype linux.SockType, uid uniqueid.Provider, queue *waiter.Queue, receiver Receiver, connected ConnectedEndpoint) Endpoint {
ep := &connectionedEndpoint{
baseEndpoint: baseEndpoint{Queue: queue, receiver: receiver, connected: connected},
id: uid.UniqueID(),
idGenerator: uid,
stype: stype,
}
ep.ops.InitHandler(ep, &stackHandler{}, getSendBufferLimits, getReceiveBufferLimits)
ep.ops.SetSendBufferSize(connected.SendMaxQueueSize(), false /* notify */)
ep.ops.SetReceiveBufferSize(defaultBufferSize, false /* notify */)
return ep
}
// ID implements ConnectingEndpoint.ID.
func (e *connectionedEndpoint) ID() uint64 {
return e.id
}
// Type implements ConnectingEndpoint.Type and Endpoint.Type.
func (e *connectionedEndpoint) Type() linux.SockType {
return e.stype
}
// WaiterQueue implements ConnectingEndpoint.WaiterQueue.
func (e *connectionedEndpoint) WaiterQueue() *waiter.Queue {
return e.Queue
}
// isBound returns true iff the connectionedEndpoint is bound (but not
// listening).
func (e *connectionedEndpoint) isBound() bool {
return e.path != "" && e.acceptedChan == nil
}
// Listening implements ConnectingEndpoint.Listening.
func (e *connectionedEndpoint) Listening() bool {
e.Lock()
defer e.Unlock()
return e.ListeningLocked()
}
func (e *connectionedEndpoint) ListeningLocked() bool {
return e.acceptedChan != nil
}
// Close puts the connectionedEndpoint in a closed state and frees all
// resources associated with it.
//
// The socket will be a fresh state after a call to close and may be reused.
// That is, close may be used to "unbind" or "disconnect" the socket in error
// paths.
func (e *connectionedEndpoint) Close(ctx context.Context) {
var acceptedChan chan *connectionedEndpoint
e.Lock()
var (
c ConnectedEndpoint
r Receiver
)
switch {
case e.Connected():
e.connected.CloseSend()
e.receiver.CloseRecv()
// Still have unread data? If yes, we set this into the write
// end so that the peer can get ECONNRESET) when it does read.
if e.receiver.RecvQueuedSize() > 0 {
e.connected.CloseUnread()
}
c = e.connected
r = e.receiver
e.connected = nil
e.receiver = nil
case e.isBound():
e.path = ""
case e.ListeningLocked():
close(e.acceptedChan)
acceptedChan = e.acceptedChan
e.acceptedChan = nil
e.path = ""
}
e.Unlock()
if acceptedChan != nil {
for n := range acceptedChan {
n.Close(ctx)
}
}
if c != nil {
c.CloseNotify()
c.Release(ctx)
}
e.ResetBoundSocketFD(ctx)
if r != nil {
r.CloseNotify()
r.Release(ctx)
}
}
// BidirectionalConnect implements BoundEndpoint.BidirectionalConnect.
func (e *connectionedEndpoint) BidirectionalConnect(ctx context.Context, ce ConnectingEndpoint, returnConnect func(Receiver, ConnectedEndpoint)) *syserr.Error {
if ce.Type() != e.stype {
return syserr.ErrWrongProtocolForSocket
}
// Check if ce is e to avoid a deadlock.
if ce, ok := ce.(*connectionedEndpoint); ok && ce == e {
return syserr.ErrInvalidEndpointState
}
// Do a dance to safely acquire locks on both endpoints.
if e.id < ce.ID() {
e.Lock()
ce.NestedLock(endpointLockHigherid)
} else {
ce.Lock()
e.NestedLock(endpointLockHigherid)
}
// Check connecting state.
if ce.Connected() {
e.NestedUnlock(endpointLockHigherid)
ce.Unlock()
return syserr.ErrAlreadyConnected
}
if ce.ListeningLocked() {
e.NestedUnlock(endpointLockHigherid)
ce.Unlock()
return syserr.ErrInvalidEndpointState
}
// Check bound state.
if !e.ListeningLocked() {
e.NestedUnlock(endpointLockHigherid)
ce.Unlock()
return syserr.ErrConnectionRefused
}
// Create a newly bound connectionedEndpoint.
ne := &connectionedEndpoint{
baseEndpoint: baseEndpoint{
path: e.path,
Queue: &waiter.Queue{},
},
id: e.idGenerator.UniqueID(),
idGenerator: e.idGenerator,
stype: e.stype,
}
ne.ops.InitHandler(ne, &stackHandler{}, getSendBufferLimits, getReceiveBufferLimits)
ne.ops.SetSendBufferSize(defaultBufferSize, false /* notify */)
ne.ops.SetReceiveBufferSize(defaultBufferSize, false /* notify */)
ne.SocketOptions().SetPassCred(e.SocketOptions().GetPassCred())
readQueue := &queue{ReaderQueue: ce.WaiterQueue(), WriterQueue: ne.Queue, limit: defaultBufferSize}
readQueue.InitRefs()
ne.connected = &connectedEndpoint{
endpoint: ce,
writeQueue: readQueue,
}
// Make sure the accepted endpoint inherits this listening socket's SO_SNDBUF.
writeQueue := &queue{ReaderQueue: ne.Queue, WriterQueue: ce.WaiterQueue(), limit: e.ops.GetSendBufferSize()}
writeQueue.InitRefs()
if e.stype == linux.SOCK_STREAM {
ne.receiver = &streamQueueReceiver{queueReceiver: queueReceiver{readQueue: writeQueue}}
} else {
ne.receiver = &queueReceiver{readQueue: writeQueue}
}
select {
case e.acceptedChan <- ne:
// Commit state.
writeQueue.IncRef()
connected := &connectedEndpoint{
endpoint: ne,
writeQueue: writeQueue,
}
readQueue.IncRef()
if e.stype == linux.SOCK_STREAM {
returnConnect(&streamQueueReceiver{queueReceiver: queueReceiver{readQueue: readQueue}}, connected)
} else {
returnConnect(&queueReceiver{readQueue: readQueue}, connected)
}
// Notify can deadlock if we are holding these locks.
e.NestedUnlock(endpointLockHigherid)
ce.Unlock()
// Notify on both ends.
e.Notify(waiter.ReadableEvents)
ce.WaiterQueue().Notify(waiter.WritableEvents)
return nil
default:
// Busy; return EAGAIN per spec.
e.NestedUnlock(endpointLockHigherid)
ce.Unlock()
ne.Close(ctx)
return syserr.ErrTryAgain
}
}
// UnidirectionalConnect implements BoundEndpoint.UnidirectionalConnect.
func (e *connectionedEndpoint) UnidirectionalConnect(ctx context.Context) (ConnectedEndpoint, *syserr.Error) {
return nil, syserr.ErrConnectionRefused
}
// Connect attempts to directly connect to another Endpoint.
// Implements Endpoint.Connect.
func (e *connectionedEndpoint) Connect(ctx context.Context, server BoundEndpoint) *syserr.Error {
returnConnect := func(r Receiver, ce ConnectedEndpoint) {
e.receiver = r
e.connected = ce
// Make sure the newly created connected endpoint's write queue is updated
// to reflect this endpoint's send buffer size.
if bufSz := e.connected.SetSendBufferSize(e.ops.GetSendBufferSize()); bufSz != e.ops.GetSendBufferSize() {
e.ops.SetSendBufferSize(bufSz, false /* notify */)
e.ops.SetReceiveBufferSize(bufSz, false /* notify */)
}
}
return server.BidirectionalConnect(ctx, e, returnConnect)
}
// Listen starts listening on the connection.
func (e *connectionedEndpoint) Listen(ctx context.Context, backlog int) *syserr.Error {
e.Lock()
defer e.Unlock()
if e.ListeningLocked() {
// Adjust the size of the channel iff we can fix existing
// pending connections into the new one.
if len(e.acceptedChan) > backlog {
return syserr.ErrInvalidEndpointState
}
origChan := e.acceptedChan
e.acceptedChan = make(chan *connectionedEndpoint, backlog)
close(origChan)
for ep := range origChan {
e.acceptedChan <- ep
}
if e.boundSocketFD != nil {
if err := e.boundSocketFD.Listen(ctx, int32(backlog)); err != nil {
return syserr.FromError(err)
}
}
return nil
}
if !e.isBound() {
return syserr.ErrInvalidEndpointState
}
// Normal case.
e.acceptedChan = make(chan *connectionedEndpoint, backlog)
if e.boundSocketFD != nil {
if err := e.boundSocketFD.Listen(ctx, int32(backlog)); err != nil {
return syserr.FromError(err)
}
}
return nil
}
// Accept accepts a new connection.
func (e *connectionedEndpoint) Accept(ctx context.Context, peerAddr *Address) (Endpoint, *syserr.Error) {
e.Lock()
if !e.ListeningLocked() {
e.Unlock()
return nil, syserr.ErrInvalidEndpointState
}
ne, err := e.getAcceptedEndpointLocked(ctx)
e.Unlock()
if err != nil {
return nil, err
}
if peerAddr != nil {
ne.Lock()
c := ne.connected
ne.Unlock()
if c != nil {
addr, err := c.GetLocalAddress()
if err != nil {
return nil, syserr.TranslateNetstackError(err)
}
*peerAddr = addr
}
}
return ne, nil
}
// Preconditions:
// - e.Listening()
// - e is locked.
func (e *connectionedEndpoint) getAcceptedEndpointLocked(ctx context.Context) (*connectionedEndpoint, *syserr.Error) {
// Accept connections from within the sentry first, since this avoids
// an RPC to the gofer on the common path.
select {
case ne := <-e.acceptedChan:
return ne, nil
default:
// No internal connections.
}
if e.boundSocketFD == nil {
return nil, syserr.ErrWouldBlock
}
// Check for external connections.
nfd, err := e.boundSocketFD.Accept(ctx)
if err == unix.EWOULDBLOCK {
return nil, syserr.ErrWouldBlock
}
if err != nil {
return nil, syserr.FromError(err)
}
q := &waiter.Queue{}
scme, serr := NewSCMEndpoint(nfd, q, e.path)
if serr != nil {
unix.Close(nfd)
return nil, serr
}
scme.Init()
return NewExternal(e.stype, e.idGenerator, q, scme, scme).(*connectionedEndpoint), nil
}
// Bind binds the connection.
//
// For Unix connectionedEndpoints, this _only sets the address associated with
// the socket_. Work associated with sockets in the filesystem or finding those
// sockets must be done by a higher level.
//
// Bind will fail only if the socket is connected, bound or the passed address
// is invalid (the empty string).
func (e *connectionedEndpoint) Bind(addr Address) *syserr.Error {
e.Lock()
defer e.Unlock()
if e.isBound() || e.ListeningLocked() {
return syserr.ErrAlreadyBound
}
if addr.Addr == "" {
// The empty string is not permitted.
return syserr.ErrBadLocalAddress
}
// Save the bound address.
e.path = addr.Addr
return nil
}
// SendMsg writes data and a control message to the endpoint's peer.
// This method does not block if the data cannot be written.
func (e *connectionedEndpoint) SendMsg(ctx context.Context, data [][]byte, c ControlMessages, to BoundEndpoint) (int64, func(), *syserr.Error) {
// Stream sockets do not support specifying the endpoint. Seqpacket
// sockets ignore the passed endpoint.
if e.stype == linux.SOCK_STREAM && to != nil {
return 0, nil, syserr.ErrNotSupported
}
return e.baseEndpoint.SendMsg(ctx, data, c, to)
}
func (e *connectionedEndpoint) isBoundSocketReadable() bool {
if e.boundSocketFD == nil {
return false
}
return fdnotifier.NonBlockingPoll(e.boundSocketFD.NotificationFD(), waiter.ReadableEvents)&waiter.ReadableEvents != 0
}
// Readiness returns the current readiness of the connectionedEndpoint. For
// example, if waiter.EventIn is set, the connectionedEndpoint is immediately
// readable.
func (e *connectionedEndpoint) Readiness(mask waiter.EventMask) waiter.EventMask {
e.Lock()
defer e.Unlock()
ready := waiter.EventMask(0)
switch {
case e.Connected():
if mask&waiter.ReadableEvents != 0 && e.receiver.Readable() {
ready |= waiter.ReadableEvents
}
if mask&waiter.WritableEvents != 0 && e.connected.Writable() {
ready |= waiter.WritableEvents
}
case e.ListeningLocked():
if mask&waiter.ReadableEvents != 0 && (len(e.acceptedChan) > 0 || e.isBoundSocketReadable()) {
ready |= waiter.ReadableEvents
}
}
return ready
}
// State implements socket.Socket.State.
func (e *connectionedEndpoint) State() uint32 {
e.Lock()
defer e.Unlock()
if e.Connected() {
return linux.SS_CONNECTED
}
return linux.SS_UNCONNECTED
}
// OnSetSendBufferSize implements tcpip.SocketOptionsHandler.OnSetSendBufferSize.
func (e *connectionedEndpoint) OnSetSendBufferSize(v int64) (newSz int64) {
e.Lock()
defer e.Unlock()
if e.Connected() {
return e.baseEndpoint.connected.SetSendBufferSize(v)
}
return v
}
// WakeupWriters implements tcpip.SocketOptionsHandler.WakeupWriters.
func (e *connectionedEndpoint) WakeupWriters() {}
// SetBoundSocketFD implement HostBountEndpoint.SetBoundSocketFD.
func (e *connectionedEndpoint) SetBoundSocketFD(ctx context.Context, bsFD BoundSocketFD) error {
e.Lock()
defer e.Unlock()
if e.path != "" || e.boundSocketFD != nil {
bsFD.Close(ctx)
return syserr.ErrAlreadyBound.ToError()
}
e.boundSocketFD = bsFD
fdnotifier.AddFD(bsFD.NotificationFD(), e.Queue)
return nil
}
// SetBoundSocketFD implement HostBountEndpoint.ResetBoundSocketFD.
func (e *connectionedEndpoint) ResetBoundSocketFD(ctx context.Context) {
e.Lock()
defer e.Unlock()
if e.boundSocketFD == nil {
return
}
fdnotifier.RemoveFD(e.boundSocketFD.NotificationFD())
e.boundSocketFD.Close(ctx)
e.boundSocketFD = nil
}
// EventRegister implements waiter.Waitable.EventRegister.
func (e *connectionedEndpoint) EventRegister(we *waiter.Entry) error {
if err := e.baseEndpoint.EventRegister(we); err != nil {
return err
}
e.Lock()
bsFD := e.boundSocketFD
e.Unlock()
if bsFD != nil {
fdnotifier.UpdateFD(bsFD.NotificationFD())
}
return nil
}
// EventUnregister implements waiter.Waitable.EventUnregister.
func (e *connectionedEndpoint) EventUnregister(we *waiter.Entry) {
e.baseEndpoint.EventUnregister(we)
e.Lock()
bsFD := e.boundSocketFD
e.Unlock()
if bsFD != nil {
fdnotifier.UpdateFD(bsFD.NotificationFD())
}
}