Update p9 to support flipcall.

PiperOrigin-RevId: 268845090

1 files changed, 254 insertions, 0 deletions

diff --git a/pkg/p9/transport_flipcall.go b/pkg/p9/transport_flipcall.go
new file mode 100644
index 000000000..aebb54959
--- /dev/null
+++ b/pkg/p9/transport_flipcall.go
@@ -0,0 +1,254 @@
+// 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 p9
+
+import (
+	"runtime"
+	"syscall"
+
+	"gvisor.dev/gvisor/pkg/fd"
+	"gvisor.dev/gvisor/pkg/fdchannel"
+	"gvisor.dev/gvisor/pkg/flipcall"
+	"gvisor.dev/gvisor/pkg/log"
+)
+
+// channelsPerClient is the number of channels to create per client.
+//
+// While the client and server will generally agree on this number, in reality
+// it's completely up to the server. We simply define a minimum of 2, and a
+// maximum of 4, and select the number of available processes as a tie-breaker.
+// Note that we don't want the number of channels to be too large, because each
+// will account for channelSize memory used, which can be large.
+var channelsPerClient = func() int {
+	n := runtime.NumCPU()
+	if n < 2 {
+		return 2
+	}
+	if n > 4 {
+		return 4
+	}
+	return n
+}()
+
+// channelSize is the channel size to create.
+//
+// We simply ensure that this is larger than the largest possible message size,
+// plus the flipcall packet header, plus the two bytes we write below.
+const channelSize = int(2 + flipcall.PacketHeaderBytes + 2 + maximumLength)
+
+// channel is a fast IPC channel.
+//
+// The same object is used by both the server and client implementations. In
+// general, the client will use only the send and recv methods.
+type channel struct {
+	desc flipcall.PacketWindowDescriptor
+	data flipcall.Endpoint
+	fds  fdchannel.Endpoint
+	buf  buffer
+
+	// -- client only --
+	connected bool
+
+	// -- server only --
+	client *fd.FD
+	done   chan struct{}
+}
+
+// reset resets the channel buffer.
+func (ch *channel) reset(sz uint32) {
+	ch.buf.data = ch.data.Data()[:sz]
+}
+
+// service services the channel.
+func (ch *channel) service(cs *connState) error {
+	rsz, err := ch.data.RecvFirst()
+	if err != nil {
+		return err
+	}
+	for rsz > 0 {
+		m, err := ch.recv(nil, rsz)
+		if err != nil {
+			return err
+		}
+		r := cs.handle(m)
+		msgRegistry.put(m)
+		rsz, err = ch.send(r)
+		if err != nil {
+			return err
+		}
+	}
+	return nil // Done.
+}
+
+// Shutdown shuts down the channel.
+//
+// This must be called before Close.
+func (ch *channel) Shutdown() {
+	ch.data.Shutdown()
+}
+
+// Close closes the channel.
+//
+// This must only be called once, and cannot return an error. Note that
+// synchronization for this method is provided at a high-level, depending on
+// whether it is the client or server. This cannot be called while there are
+// active callers in either service or sendRecv.
+//
+// Precondition: the channel should be shutdown.
+func (ch *channel) Close() error {
+	// Close all backing transports.
+	ch.fds.Destroy()
+	ch.data.Destroy()
+	if ch.client != nil {
+		ch.client.Close()
+	}
+	return nil
+}
+
+// send sends the given message.
+//
+// The return value is the size of the received response. Not that in the
+// server case, this is the size of the next request.
+func (ch *channel) send(m message) (uint32, error) {
+	if log.IsLogging(log.Debug) {
+		log.Debugf("send [channel @%p] %s", ch, m.String())
+	}
+
+	// Send any file payload.
+	sentFD := false
+	if filer, ok := m.(filer); ok {
+		if f := filer.FilePayload(); f != nil {
+			if err := ch.fds.SendFD(f.FD()); err != nil {
+				return 0, syscall.EIO // Map everything to EIO.
+			}
+			f.Close()     // Per sendRecvLegacy.
+			sentFD = true // To mark below.
+		}
+	}
+
+	// Encode the message.
+	//
+	// Note that IPC itself encodes the length of messages, so we don't
+	// need to encode a standard 9P header. We write only the message type.
+	ch.reset(0)
+
+	ch.buf.WriteMsgType(m.Type())
+	if sentFD {
+		ch.buf.Write8(1) // Incoming FD.
+	} else {
+		ch.buf.Write8(0) // No incoming FD.
+	}
+	m.Encode(&ch.buf)
+	ssz := uint32(len(ch.buf.data)) // Updated below.
+
+	// Is there a payload?
+	if payloader, ok := m.(payloader); ok {
+		p := payloader.Payload()
+		copy(ch.data.Data()[ssz:], p)
+		ssz += uint32(len(p))
+	}
+
+	// Perform the one-shot communication.
+	n, err := ch.data.SendRecv(ssz)
+	if err != nil {
+		if n > 0 {
+			return n, nil
+		}
+		return 0, syscall.EIO // See above.
+	}
+
+	return n, nil
+}
+
+// recv decodes a message that exists on the channel.
+//
+// If the passed r is non-nil, then the type must match or an error will be
+// generated. If the passed r is nil, then a new message will be created and
+// returned.
+func (ch *channel) recv(r message, rsz uint32) (message, error) {
+	// Decode the response from the inline buffer.
+	ch.reset(rsz)
+	t := ch.buf.ReadMsgType()
+	hasFD := ch.buf.Read8() != 0
+	if t == MsgRlerror {
+		// Change the message type. We check for this special case
+		// after decoding below, and transform into an error.
+		r = &Rlerror{}
+	} else if r == nil {
+		nr, err := msgRegistry.get(0, t)
+		if err != nil {
+			return nil, err
+		}
+		r = nr // New message.
+	} else if t != r.Type() {
+		// Not an error and not the expected response; propagate.
+		return nil, &ErrBadResponse{Got: t, Want: r.Type()}
+	}
+
+	// Is there a payload? Set to the latter portion.
+	if payloader, ok := r.(payloader); ok {
+		fs := payloader.FixedSize()
+		payloader.SetPayload(ch.buf.data[fs:])
+		ch.buf.data = ch.buf.data[:fs]
+	}
+
+	r.Decode(&ch.buf)
+	if ch.buf.isOverrun() {
+		// Nothing valid was available.
+		log.Debugf("recv [got %d bytes, needed more]", rsz)
+		return nil, ErrNoValidMessage
+	}
+
+	// Read any FD result.
+	if hasFD {
+		if rfd, err := ch.fds.RecvFDNonblock(); err == nil {
+			f := fd.New(rfd)
+			if filer, ok := r.(filer); ok {
+				// Set the payload.
+				filer.SetFilePayload(f)
+			} else {
+				// Don't want the FD.
+				f.Close()
+			}
+		} else {
+			// The header bit was set but nothing came in.
+			log.Warningf("expected FD, got err: %v", err)
+		}
+	}
+
+	// Log a message.
+	if log.IsLogging(log.Debug) {
+		log.Debugf("recv [channel @%p] %s", ch, r.String())
+	}
+
+	// Convert errors appropriately; see above.
+	if rlerr, ok := r.(*Rlerror); ok {
+		return nil, syscall.Errno(rlerr.Error)
+	}
+
+	return r, nil
+}
+
+// sendRecv sends the given message over the channel.
+//
+// This is used by the client.
+func (ch *channel) sendRecv(c *Client, m, r message) error {
+	rsz, err := ch.send(m)
+	if err != nil {
+		return err
+	}
+	_, err = ch.recv(r, rsz)
+	return err
+}