2 files changed, 234 insertions, 0 deletions
diff --git a/pkg/sentry/socket/rpcinet/notifier/notifier.go b/pkg/sentry/socket/rpcinet/notifier/notifier.go
new file mode 100644
index 000000000..601e05994
--- /dev/null
+++ b/pkg/sentry/socket/rpcinet/notifier/notifier.go
@@ -0,0 +1,230 @@
+// 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 notifier implements an FD notifier implementation over RPC.
+package notifier
+
+import (
+	"fmt"
+	"sync"
+	"syscall"
+
+	"gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/conn"
+	pb "gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/syscall_rpc_go_proto"
+	"gvisor.googlesource.com/gvisor/pkg/waiter"
+)
+
+type fdInfo struct {
+	queue   *waiter.Queue
+	waiting bool
+}
+
+// Notifier holds all the state necessary to issue notifications when IO events
+// occur in the observed FDs.
+type Notifier struct {
+	// rpcConn is the connection that is used for sending RPCs.
+	rpcConn *conn.RPCConnection
+
+	// epFD is the epoll file descriptor used to register for io
+	// notifications.
+	epFD uint32
+
+	// mu protects fdMap.
+	mu sync.Mutex
+
+	// fdMap maps file descriptors to their notification queues and waiting
+	// status.
+	fdMap map[uint32]*fdInfo
+}
+
+// NewRPCNotifier creates a new notifier object.
+func NewRPCNotifier(cn *conn.RPCConnection) (*Notifier, error) {
+	id, c := cn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_EpollCreate1{&pb.EpollCreate1Request{}}}, false /* ignoreResult */)
+	<-c
+
+	res := cn.Request(id).Result.(*pb.SyscallResponse_EpollCreate1).EpollCreate1.Result
+	if e, ok := res.(*pb.EpollCreate1Response_ErrorNumber); ok {
+		return nil, syscall.Errno(e.ErrorNumber)
+	}
+
+	w := &Notifier{
+		rpcConn: cn,
+		epFD:    res.(*pb.EpollCreate1Response_Fd).Fd,
+		fdMap:   make(map[uint32]*fdInfo),
+	}
+
+	go w.waitAndNotify() // S/R-FIXME(b/77962828)
+
+	return w, nil
+}
+
+// waitFD waits on mask for fd. The fdMap mutex must be hold.
+func (n *Notifier) waitFD(fd uint32, fi *fdInfo, mask waiter.EventMask) error {
+	if !fi.waiting && mask == 0 {
+		return nil
+	}
+
+	e := pb.EpollEvent{
+		Events: mask.ToLinux() | -syscall.EPOLLET,
+		Fd:     fd,
+	}
+
+	switch {
+	case !fi.waiting && mask != 0:
+		id, c := n.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_EpollCtl{&pb.EpollCtlRequest{Epfd: n.epFD, Op: syscall.EPOLL_CTL_ADD, Fd: fd, Event: &e}}}, false /* ignoreResult */)
+		<-c
+
+		e := n.rpcConn.Request(id).Result.(*pb.SyscallResponse_EpollCtl).EpollCtl.ErrorNumber
+		if e != 0 {
+			return syscall.Errno(e)
+		}
+
+		fi.waiting = true
+	case fi.waiting && mask == 0:
+		id, c := n.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_EpollCtl{&pb.EpollCtlRequest{Epfd: n.epFD, Op: syscall.EPOLL_CTL_DEL, Fd: fd}}}, false /* ignoreResult */)
+		<-c
+		n.rpcConn.Request(id)
+
+		fi.waiting = false
+	case fi.waiting && mask != 0:
+		id, c := n.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_EpollCtl{&pb.EpollCtlRequest{Epfd: n.epFD, Op: syscall.EPOLL_CTL_MOD, Fd: fd, Event: &e}}}, false /* ignoreResult */)
+		<-c
+
+		e := n.rpcConn.Request(id).Result.(*pb.SyscallResponse_EpollCtl).EpollCtl.ErrorNumber
+		if e != 0 {
+			return syscall.Errno(e)
+		}
+	}
+
+	return nil
+}
+
+// addFD adds an FD to the list of FDs observed by n.
+func (n *Notifier) addFD(fd uint32, queue *waiter.Queue) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	// Panic if we're already notifying on this FD.
+	if _, ok := n.fdMap[fd]; ok {
+		panic(fmt.Sprintf("File descriptor %d added twice", fd))
+	}
+
+	// We have nothing to wait for at the moment. Just add it to the map.
+	n.fdMap[fd] = &fdInfo{queue: queue}
+}
+
+// updateFD updates the set of events the FD needs to be notified on.
+func (n *Notifier) updateFD(fd uint32) error {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	if fi, ok := n.fdMap[fd]; ok {
+		return n.waitFD(fd, fi, fi.queue.Events())
+	}
+
+	return nil
+}
+
+// RemoveFD removes an FD from the list of FDs observed by n.
+func (n *Notifier) removeFD(fd uint32) {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	// Remove from map, then from epoll object.
+	n.waitFD(fd, n.fdMap[fd], 0)
+	delete(n.fdMap, fd)
+}
+
+// hasFD returns true if the FD is in the list of observed FDs.
+func (n *Notifier) hasFD(fd uint32) bool {
+	n.mu.Lock()
+	defer n.mu.Unlock()
+
+	_, ok := n.fdMap[fd]
+	return ok
+}
+
+// waitAndNotify loops waiting for io event notifications from the epoll
+// object. Once notifications arrive, they are dispatched to the
+// registered queue.
+func (n *Notifier) waitAndNotify() error {
+	for {
+		id, c := n.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_EpollWait{&pb.EpollWaitRequest{Fd: n.epFD, NumEvents: 100, Msec: -1}}}, false /* ignoreResult */)
+		<-c
+
+		res := n.rpcConn.Request(id).Result.(*pb.SyscallResponse_EpollWait).EpollWait.Result
+		if e, ok := res.(*pb.EpollWaitResponse_ErrorNumber); ok {
+			err := syscall.Errno(e.ErrorNumber)
+			// NOTE(magi): I don't think epoll_wait can return EAGAIN but I'm being
+			// conseratively careful here since exiting the notification thread
+			// would be really bad.
+			if err == syscall.EINTR || err == syscall.EAGAIN {
+				continue
+			}
+			return err
+		}
+
+		n.mu.Lock()
+		for _, e := range res.(*pb.EpollWaitResponse_Events).Events.Events {
+			if fi, ok := n.fdMap[e.Fd]; ok {
+				fi.queue.Notify(waiter.EventMaskFromLinux(e.Events))
+			}
+		}
+		n.mu.Unlock()
+	}
+}
+
+// AddFD adds an FD to the list of observed FDs.
+func (n *Notifier) AddFD(fd uint32, queue *waiter.Queue) error {
+	n.addFD(fd, queue)
+	return nil
+}
+
+// UpdateFD updates the set of events the FD needs to be notified on.
+func (n *Notifier) UpdateFD(fd uint32) error {
+	return n.updateFD(fd)
+}
+
+// RemoveFD removes an FD from the list of observed FDs.
+func (n *Notifier) RemoveFD(fd uint32) {
+	n.removeFD(fd)
+}
+
+// HasFD returns true if the FD is in the list of observed FDs.
+//
+// This should only be used by tests to assert that FDs are correctly
+// registered.
+func (n *Notifier) HasFD(fd uint32) bool {
+	return n.hasFD(fd)
+}
+
+// NonBlockingPoll polls the given fd in non-blocking fashion. It is used just
+// to query the FD's current state; this method will block on the RPC response
+// although the syscall is non-blocking.
+func (n *Notifier) NonBlockingPoll(fd uint32, mask waiter.EventMask) waiter.EventMask {
+	for {
+		id, c := n.rpcConn.NewRequest(pb.SyscallRequest{Args: &pb.SyscallRequest_Poll{&pb.PollRequest{Fd: fd, Events: mask.ToLinux()}}}, false /* ignoreResult */)
+		<-c
+
+		res := n.rpcConn.Request(id).Result.(*pb.SyscallResponse_Poll).Poll.Result
+		if e, ok := res.(*pb.PollResponse_ErrorNumber); ok {
+			if syscall.Errno(e.ErrorNumber) == syscall.EINTR {
+				continue
+			}
+			return mask
+		}
+
+		return waiter.EventMaskFromLinux(res.(*pb.PollResponse_Events).Events)
+	}
+}
diff --git a/pkg/sentry/socket/rpcinet/notifier/notifier_state_autogen.go b/pkg/sentry/socket/rpcinet/notifier/notifier_state_autogen.go
new file mode 100755
index 000000000..f108d91c1
--- /dev/null
+++ b/pkg/sentry/socket/rpcinet/notifier/notifier_state_autogen.go
@@ -0,0 +1,4 @@
+// automatically generated by stateify.
+
+package notifier
+