diff options
Diffstat (limited to 'pkg/p9/transport_flipcall.go')
| -rwxr-xr-x | pkg/p9/transport_flipcall.go | 254 |
1 files changed, 254 insertions, 0 deletions
diff --git a/pkg/p9/transport_flipcall.go b/pkg/p9/transport_flipcall.go new file mode 100755 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 +} |