Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 567 insertions, 0 deletions

diff --git a/pkg/sentry/socket/rpcinet/socket.go b/pkg/sentry/socket/rpcinet/socket.go
new file mode 100644
index 000000000..574d99ba5
--- /dev/null
+++ b/pkg/sentry/socket/rpcinet/socket.go
@@ -0,0 +1,567 @@
+// Copyright 2018 Google Inc.
+//
+// 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 rpcinet
+
+import (
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/abi/linux"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/arch"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/kernel/kdefs"
+	ktime "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/time"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/socket"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/conn"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/notifier"
+	pb "gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/syscall_rpc_go_proto"
+	"gvisor.googlesource.com/gvisor/pkg/sentry/usermem"
+	"gvisor.googlesource.com/gvisor/pkg/syserr"
+	"gvisor.googlesource.com/gvisor/pkg/syserror"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
+	"gvisor.googlesource.com/gvisor/pkg/tcpip/transport/unix"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+// socketOperations implements fs.FileOperations and socket.Socket for a socket
+// implemented using a host socket.
+type socketOperations struct {
+	socket.ReceiveTimeout
+	fsutil.PipeSeek      `state:"nosave"`
+	fsutil.NotDirReaddir `state:"nosave"`
+	fsutil.NoFsync       `state:"nosave"`
+	fsutil.NoopFlush     `state:"nosave"`
+	fsutil.NoMMap        `state:"nosave"`
+
+	fd       uint32 // must be O_NONBLOCK
+	wq       *waiter.Queue
+	rpcConn  *conn.RPCConnection
+	notifier *notifier.Notifier
+}
+
+// Verify that we actually implement socket.Socket.
+var _ = socket.Socket(&socketOperations{})
+
+// New creates a new RPC socket.
+func newSocketFile(ctx context.Context, stack *Stack, family int, skType int, protocol int) (*fs.File, *syserr.Error) {
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Socket{&pb.SocketRequest{Family: int64(family), Type: int64(skType | syscall.SOCK_NONBLOCK), Protocol: int64(protocol)}}}, false /* ignoreResult */)
+	<-c
+
+	res := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_Socket).Socket.Result
+	if e, ok := res.(*pb.SocketResponse_ErrorNumber); ok {
+		return nil, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+	fd := res.(*pb.SocketResponse_Fd).Fd
+
+	var wq waiter.Queue
+	stack.notifier.AddFD(fd, &wq)
+
+	dirent := socket.NewDirent(ctx, socketDevice)
+	return fs.NewFile(ctx, dirent, fs.FileFlags{Read: true, Write: true}, &socketOperations{
+		wq:       &wq,
+		fd:       fd,
+		rpcConn:  stack.rpcConn,
+		notifier: stack.notifier,
+	}), nil
+}
+
+func isBlockingErrno(err error) bool {
+	return err == syscall.EAGAIN || err == syscall.EWOULDBLOCK
+}
+
+func translateIOSyscallError(err error) error {
+	if isBlockingErrno(err) {
+		return syserror.ErrWouldBlock
+	}
+	return err
+}
+
+// Release implements fs.FileOperations.Release.
+func (s *socketOperations) Release() {
+	s.notifier.RemoveFD(s.fd)
+
+	// We always need to close the FD.
+	_, _ = s.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Close{&pb.CloseRequest{Fd: s.fd}}}, true /* ignoreResult */)
+}
+
+// Readiness implements waiter.Waitable.Readiness.
+func (s *socketOperations) Readiness(mask waiter.EventMask) waiter.EventMask {
+	return s.notifier.NonBlockingPoll(s.fd, mask)
+}
+
+// EventRegister implements waiter.Waitable.EventRegister.
+func (s *socketOperations) EventRegister(e *waiter.Entry, mask waiter.EventMask) {
+	s.wq.EventRegister(e, mask)
+	s.notifier.UpdateFD(s.fd)
+}
+
+// EventUnregister implements waiter.Waitable.EventUnregister.
+func (s *socketOperations) EventUnregister(e *waiter.Entry) {
+	s.wq.EventUnregister(e)
+	s.notifier.UpdateFD(s.fd)
+}
+
+func rpcRead(t *kernel.Task, req *pb.SyscallRequest_Read) (*pb.ReadResponse_Data, *syserr.Error) {
+	s := t.NetworkContext().(*Stack)
+	id, c := s.rpcConn.NewRequest(pb.SyscallRequest{Args: req}, false /* ignoreResult */)
+	<-c
+
+	res := s.rpcConn.Request(id).Result.(*pb.SyscallResponse_Read).Read.Result
+	if e, ok := res.(*pb.ReadResponse_ErrorNumber); ok {
+		return nil, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+
+	return res.(*pb.ReadResponse_Data), nil
+}
+
+// Read implements fs.FileOperations.Read.
+func (s *socketOperations) Read(ctx context.Context, _ *fs.File, dst usermem.IOSequence, _ int64) (int64, error) {
+	req := &pb.SyscallRequest_Read{&pb.ReadRequest{
+		Fd:     s.fd,
+		Length: uint32(dst.NumBytes()),
+	}}
+
+	res, se := rpcRead(ctx.(*kernel.Task), req)
+	if se == nil {
+		n, e := dst.CopyOut(ctx, res.Data)
+		return int64(n), e
+	}
+	if se != syserr.ErrWouldBlock {
+		return 0, se.ToError()
+	}
+
+	// We'll have to block. Register for notifications and read again when ready.
+	e, ch := waiter.NewChannelEntry(nil)
+	s.EventRegister(&e, waiter.EventIn)
+	defer s.EventUnregister(&e)
+
+	for {
+		res, se := rpcRead(ctx.(*kernel.Task), req)
+		if se == nil {
+			n, e := dst.CopyOut(ctx, res.Data)
+			return int64(n), e
+		}
+		if se != syserr.ErrWouldBlock {
+			return 0, se.ToError()
+		}
+
+		if err := ctx.(*kernel.Task).Block(ch); err != nil {
+			return 0, err
+		}
+	}
+}
+
+func rpcWrite(t *kernel.Task, req *pb.SyscallRequest_Write) (uint32, *syserr.Error) {
+	s := t.NetworkContext().(*Stack)
+	id, c := s.rpcConn.NewRequest(pb.SyscallRequest{Args: req}, false /* ignoreResult */)
+	<-c
+
+	res := s.rpcConn.Request(id).Result.(*pb.SyscallResponse_Write).Write.Result
+	if e, ok := res.(*pb.WriteResponse_ErrorNumber); ok {
+		return 0, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+
+	return res.(*pb.WriteResponse_Length).Length, nil
+}
+
+// Write implements fs.FileOperations.Write.
+func (s *socketOperations) Write(ctx context.Context, _ *fs.File, src usermem.IOSequence, _ int64) (int64, error) {
+	t := ctx.(*kernel.Task)
+	v := buffer.NewView(int(src.NumBytes()))
+
+	// Copy all the data into the buffer.
+	if _, err := src.CopyIn(t, v); err != nil {
+		return 0, err
+	}
+
+	n, err := rpcWrite(t, &pb.SyscallRequest_Write{&pb.WriteRequest{Fd: s.fd, Data: v}})
+	return int64(n), err.ToError()
+}
+
+func rpcConnect(t *kernel.Task, fd uint32, sockaddr []byte) *syserr.Error {
+	s := t.NetworkContext().(*Stack)
+	id, c := s.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Connect{&pb.ConnectRequest{Fd: uint32(fd), Address: sockaddr}}}, false /* ignoreResult */)
+	<-c
+
+	if e := s.rpcConn.Request(id).Result.(*pb.SyscallResponse_Connect).Connect.ErrorNumber; e != 0 {
+		return syserr.FromHost(syscall.Errno(e))
+	}
+	return nil
+}
+
+// Connect implements socket.Socket.Connect.
+func (s *socketOperations) Connect(t *kernel.Task, sockaddr []byte, blocking bool) *syserr.Error {
+	if !blocking {
+		return rpcConnect(t, s.fd, sockaddr)
+	}
+
+	// Register for notification when the endpoint becomes writable, then
+	// initiate the connection.
+	e, ch := waiter.NewChannelEntry(nil)
+	s.EventRegister(&e, waiter.EventOut)
+	defer s.EventUnregister(&e)
+
+	if err := rpcConnect(t, s.fd, sockaddr); err != syserr.ErrConnectStarted && err != syserr.ErrAlreadyConnecting {
+		return err
+	}
+
+	// It's pending, so we have to wait for a notification, and fetch the
+	// result once the wait completes.
+	if err := t.Block(ch); err != nil {
+		return syserr.FromError(err)
+	}
+
+	// Call Connect() again after blocking to find connect's result.
+	return rpcConnect(t, s.fd, sockaddr)
+}
+
+func rpcAccept(t *kernel.Task, fd uint32, peer bool) (*pb.AcceptResponse_ResultPayload, *syserr.Error) {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Accept{&pb.AcceptRequest{Fd: fd, Peer: peer, Flags: syscall.SOCK_NONBLOCK}}}, false /* ignoreResult */)
+	<-c
+
+	res := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_Accept).Accept.Result
+	if e, ok := res.(*pb.AcceptResponse_ErrorNumber); ok {
+		return nil, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+	return res.(*pb.AcceptResponse_Payload).Payload, nil
+}
+
+// Accept implements socket.Socket.Accept.
+func (s *socketOperations) Accept(t *kernel.Task, peerRequested bool, flags int, blocking bool) (kdefs.FD, interface{}, uint32, *syserr.Error) {
+	payload, se := rpcAccept(t, s.fd, peerRequested)
+
+	// Check if we need to block.
+	if blocking && se == syserr.ErrWouldBlock {
+		// Register for notifications.
+		e, ch := waiter.NewChannelEntry(nil)
+		s.EventRegister(&e, waiter.EventIn)
+		defer s.EventUnregister(&e)
+
+		// Try to accept the connection again; if it fails, then wait until we
+		// get a notification.
+		for {
+			if payload, se = rpcAccept(t, s.fd, peerRequested); se != syserr.ErrWouldBlock {
+				break
+			}
+
+			if err := t.Block(ch); err != nil {
+				return 0, nil, 0, syserr.FromError(err)
+			}
+		}
+	}
+
+	// Handle any error from accept.
+	if se != nil {
+		return 0, nil, 0, se
+	}
+
+	var wq waiter.Queue
+	s.notifier.AddFD(payload.Fd, &wq)
+
+	dirent := socket.NewDirent(t, socketDevice)
+	file := fs.NewFile(t, dirent, fs.FileFlags{Read: true, Write: true, NonBlocking: flags&linux.SOCK_NONBLOCK != 0}, &socketOperations{
+		wq:       &wq,
+		fd:       payload.Fd,
+		notifier: s.notifier,
+	})
+
+	fdFlags := kernel.FDFlags{
+		CloseOnExec: flags&linux.SOCK_CLOEXEC != 0,
+	}
+	fd, err := t.FDMap().NewFDFrom(0, file, fdFlags, t.ThreadGroup().Limits())
+	if err != nil {
+		return 0, nil, 0, syserr.FromError(err)
+	}
+
+	return fd, payload.Address.Address, payload.Address.Length, nil
+}
+
+// Bind implements socket.Socket.Bind.
+func (s *socketOperations) Bind(t *kernel.Task, sockaddr []byte) *syserr.Error {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Bind{&pb.BindRequest{Fd: s.fd, Address: sockaddr}}}, false /* ignoreResult */)
+	<-c
+
+	if e := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_Bind).Bind.ErrorNumber; e != 0 {
+		syserr.FromHost(syscall.Errno(e))
+	}
+	return nil
+}
+
+// Listen implements socket.Socket.Listen.
+func (s *socketOperations) Listen(t *kernel.Task, backlog int) *syserr.Error {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Listen{&pb.ListenRequest{Fd: s.fd, Backlog: int64(backlog)}}}, false /* ignoreResult */)
+	<-c
+
+	if e := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_Listen).Listen.ErrorNumber; e != 0 {
+		syserr.FromHost(syscall.Errno(e))
+	}
+	return nil
+}
+
+// Shutdown implements socket.Socket.Shutdown.
+func (s *socketOperations) Shutdown(t *kernel.Task, how int) *syserr.Error {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Shutdown{&pb.ShutdownRequest{Fd: s.fd, How: int64(how)}}}, false /* ignoreResult */)
+	<-c
+
+	if e := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_Shutdown).Shutdown.ErrorNumber; e != 0 {
+		return syserr.FromHost(syscall.Errno(e))
+	}
+	return nil
+}
+
+// GetSockOpt implements socket.Socket.GetSockOpt.
+func (s *socketOperations) GetSockOpt(t *kernel.Task, level int, name int, outLen int) (interface{}, *syserr.Error) {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_GetSockOpt{&pb.GetSockOptRequest{Fd: s.fd, Level: int64(level), Name: int64(name), Length: uint32(outLen)}}}, false /* ignoreResult */)
+	<-c
+
+	res := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_GetSockOpt).GetSockOpt.Result
+	if e, ok := res.(*pb.GetSockOptResponse_ErrorNumber); ok {
+		return nil, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+
+	return res.(*pb.GetSockOptResponse_Opt).Opt, nil
+}
+
+// SetSockOpt implements socket.Socket.SetSockOpt.
+func (s *socketOperations) SetSockOpt(t *kernel.Task, level int, name int, opt []byte) *syserr.Error {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_SetSockOpt{&pb.SetSockOptRequest{Fd: s.fd, Level: int64(level), Name: int64(name), Opt: opt}}}, false /* ignoreResult */)
+	<-c
+
+	if e := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_SetSockOpt).SetSockOpt.ErrorNumber; e != 0 {
+		syserr.FromHost(syscall.Errno(e))
+	}
+	return nil
+}
+
+// GetPeerName implements socket.Socket.GetPeerName.
+func (s *socketOperations) GetPeerName(t *kernel.Task) (interface{}, uint32, *syserr.Error) {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_GetPeerName{&pb.GetPeerNameRequest{Fd: s.fd}}}, false /* ignoreResult */)
+	<-c
+
+	res := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_GetPeerName).GetPeerName.Result
+	if e, ok := res.(*pb.GetPeerNameResponse_ErrorNumber); ok {
+		return nil, 0, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+
+	addr := res.(*pb.GetPeerNameResponse_Address).Address
+	return addr.Address, addr.Length, nil
+}
+
+// GetSockName implements socket.Socket.GetSockName.
+func (s *socketOperations) GetSockName(t *kernel.Task) (interface{}, uint32, *syserr.Error) {
+	stack := t.NetworkContext().(*Stack)
+	id, c := stack.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_GetSockName{&pb.GetSockNameRequest{Fd: s.fd}}}, false /* ignoreResult */)
+	<-c
+
+	res := stack.rpcConn.Request(id).Result.(*pb.SyscallResponse_GetSockName).GetSockName.Result
+	if e, ok := res.(*pb.GetSockNameResponse_ErrorNumber); ok {
+		return nil, 0, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+
+	addr := res.(*pb.GetSockNameResponse_Address).Address
+	return addr.Address, addr.Length, nil
+}
+
+// Ioctl implements fs.FileOperations.Ioctl.
+func (s *socketOperations) Ioctl(ctx context.Context, io usermem.IO, args arch.SyscallArguments) (uintptr, error) {
+	return 0, syserror.ENOTTY
+}
+
+func rpcRecvMsg(t *kernel.Task, req *pb.SyscallRequest_Recvmsg) (*pb.RecvmsgResponse_ResultPayload, *syserr.Error) {
+	s := t.NetworkContext().(*Stack)
+	id, c := s.rpcConn.NewRequest(pb.SyscallRequest{Args: req}, false /* ignoreResult */)
+	<-c
+
+	res := s.rpcConn.Request(id).Result.(*pb.SyscallResponse_Recvmsg).Recvmsg.Result
+	if e, ok := res.(*pb.RecvmsgResponse_ErrorNumber); ok {
+		return nil, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+
+	return res.(*pb.RecvmsgResponse_Payload).Payload, nil
+}
+
+// RecvMsg implements socket.Socket.RecvMsg.
+func (s *socketOperations) RecvMsg(t *kernel.Task, dst usermem.IOSequence, flags int, haveDeadline bool, deadline ktime.Time, senderRequested bool, controlDataLen uint64) (int, interface{}, uint32, unix.ControlMessages, *syserr.Error) {
+	req := &pb.SyscallRequest_Recvmsg{&pb.RecvmsgRequest{
+		Fd:     s.fd,
+		Length: uint32(dst.NumBytes()),
+		Sender: senderRequested,
+		Trunc:  flags&linux.MSG_TRUNC != 0,
+		Peek:   flags&linux.MSG_PEEK != 0,
+	}}
+
+	res, err := rpcRecvMsg(t, req)
+	if err == nil {
+		n, e := dst.CopyOut(t, res.Data)
+		return int(n), res.Address.GetAddress(), res.Address.GetLength(), unix.ControlMessages{}, syserr.FromError(e)
+	}
+	if err != syserr.ErrWouldBlock || flags&linux.MSG_DONTWAIT != 0 {
+		return 0, nil, 0, unix.ControlMessages{}, err
+	}
+
+	// We'll have to block. Register for notifications and keep trying to
+	// send all the data.
+	e, ch := waiter.NewChannelEntry(nil)
+	s.EventRegister(&e, waiter.EventIn)
+	defer s.EventUnregister(&e)
+
+	for {
+		res, err := rpcRecvMsg(t, req)
+		if err == nil {
+			n, e := dst.CopyOut(t, res.Data)
+			return int(n), res.Address.GetAddress(), res.Address.GetLength(), unix.ControlMessages{}, syserr.FromError(e)
+		}
+		if err != syserr.ErrWouldBlock {
+			return 0, nil, 0, unix.ControlMessages{}, err
+		}
+
+		if err := t.BlockWithDeadline(ch, haveDeadline, deadline); err != nil {
+			if err == syserror.ETIMEDOUT {
+				return 0, nil, 0, unix.ControlMessages{}, syserr.ErrTryAgain
+			}
+			return 0, nil, 0, unix.ControlMessages{}, syserr.FromError(err)
+		}
+	}
+}
+
+func rpcSendMsg(t *kernel.Task, req *pb.SyscallRequest_Sendmsg) (uint32, *syserr.Error) {
+	s := t.NetworkContext().(*Stack)
+	id, c := s.rpcConn.NewRequest(pb.SyscallRequest{Args: req}, false /* ignoreResult */)
+	<-c
+
+	res := s.rpcConn.Request(id).Result.(*pb.SyscallResponse_Sendmsg).Sendmsg.Result
+	if e, ok := res.(*pb.SendmsgResponse_ErrorNumber); ok {
+		return 0, syserr.FromHost(syscall.Errno(e.ErrorNumber))
+	}
+
+	return res.(*pb.SendmsgResponse_Length).Length, nil
+}
+
+// SendMsg implements socket.Socket.SendMsg.
+func (s *socketOperations) SendMsg(t *kernel.Task, src usermem.IOSequence, to []byte, flags int, controlMessages unix.ControlMessages) (int, *syserr.Error) {
+	// Whitelist flags.
+	if flags&^(syscall.MSG_DONTWAIT|syscall.MSG_EOR|syscall.MSG_FASTOPEN|syscall.MSG_MORE|syscall.MSG_NOSIGNAL) != 0 {
+		return 0, syserr.ErrInvalidArgument
+	}
+
+	// Reject control messages.
+	if !controlMessages.Empty() {
+		return 0, syserr.ErrInvalidArgument
+	}
+
+	v := buffer.NewView(int(src.NumBytes()))
+
+	// Copy all the data into the buffer.
+	if _, err := src.CopyIn(t, v); err != nil {
+		return 0, syserr.FromError(err)
+	}
+
+	// TODO: this needs to change to map directly to a SendMsg syscall
+	// in the RPC.
+	req := &pb.SyscallRequest_Sendmsg{&pb.SendmsgRequest{
+		Fd:          uint32(s.fd),
+		Data:        v,
+		Address:     to,
+		More:        flags&linux.MSG_MORE != 0,
+		EndOfRecord: flags&linux.MSG_EOR != 0,
+	}}
+
+	n, err := rpcSendMsg(t, req)
+	if err != syserr.ErrWouldBlock || flags&linux.MSG_DONTWAIT != 0 {
+		return int(n), err
+	}
+
+	// We'll have to block. Register for notification and keep trying to
+	// send all the data.
+	e, ch := waiter.NewChannelEntry(nil)
+	s.EventRegister(&e, waiter.EventOut)
+	defer s.EventUnregister(&e)
+
+	for {
+		n, err := rpcSendMsg(t, req)
+		if err != syserr.ErrWouldBlock {
+			return int(n), err
+		}
+
+		if err := t.Block(ch); err != nil {
+			return 0, syserr.FromError(err)
+		}
+	}
+}
+
+type socketProvider struct {
+	family int
+}
+
+// Socket implements socket.Provider.Socket.
+func (p *socketProvider) Socket(t *kernel.Task, stypeflags unix.SockType, protocol int) (*fs.File, *syserr.Error) {
+	// Check that we are using the RPC network stack.
+	stack := t.NetworkContext()
+	if stack == nil {
+		return nil, nil
+	}
+
+	s, ok := stack.(*Stack)
+	if !ok {
+		return nil, nil
+	}
+
+	// Only accept TCP and UDP.
+	//
+	// Try to restrict the flags we will accept to minimize backwards
+	// incompatability with netstack.
+	stype := int(stypeflags) & linux.SOCK_TYPE_MASK
+	switch stype {
+	case syscall.SOCK_STREAM:
+		switch protocol {
+		case 0, syscall.IPPROTO_TCP:
+			// ok
+		default:
+			return nil, nil
+		}
+	case syscall.SOCK_DGRAM:
+		switch protocol {
+		case 0, syscall.IPPROTO_UDP:
+			// ok
+		default:
+			return nil, nil
+		}
+	default:
+		return nil, nil
+	}
+
+	return newSocketFile(t, s, p.family, stype, 0)
+}
+
+// Pair implements socket.Provider.Pair.
+func (p *socketProvider) Pair(t *kernel.Task, stype unix.SockType, protocol int) (*fs.File, *fs.File, *syserr.Error) {
+	// Not supported by AF_INET/AF_INET6.
+	return nil, nil, nil
+}
+
+func init() {
+	for _, family := range []int{syscall.AF_INET, syscall.AF_INET6} {
+		socket.RegisterProvider(family, &socketProvider{family})
+	}
+}