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// Copyright 2021 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 lisafs
import (
"path"
"path/filepath"
"golang.org/x/sys/unix"
"gvisor.dev/gvisor/pkg/flipcall"
"gvisor.dev/gvisor/pkg/log"
"gvisor.dev/gvisor/pkg/marshal/primitive"
)
// RPCHandler defines a handler that is invoked when the associated message is
// received. The handler is responsible for:
//
// * Unmarshalling the request from the passed payload and interpreting it.
// * Marshalling the response into the communicator's payload buffer.
// * Return the number of payload bytes written.
// * Donate any FDs (if needed) to comm which will in turn donate it to client.
type RPCHandler func(c *Connection, comm Communicator, payloadLen uint32) (uint32, error)
var handlers = [...]RPCHandler{
Error: ErrorHandler,
Mount: MountHandler,
Channel: ChannelHandler,
}
// ErrorHandler handles Error message.
func ErrorHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
// Client should never send Error.
return 0, unix.EINVAL
}
// MountHandler handles the Mount RPC. Note that there can not be concurrent
// executions of MountHandler on a connection because the connection enforces
// that Mount is the first message on the connection. Only after the connection
// has been successfully mounted can other channels be created.
func MountHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
var req MountReq
req.UnmarshalBytes(comm.PayloadBuf(payloadLen))
mountPath := path.Clean(string(req.MountPath))
if !filepath.IsAbs(mountPath) {
log.Warningf("mountPath %q is not absolute", mountPath)
return 0, unix.EINVAL
}
if c.mounted {
log.Warningf("connection has already been mounted at %q", mountPath)
return 0, unix.EBUSY
}
rootFD, rootIno, err := c.ServerImpl().Mount(c, mountPath)
if err != nil {
return 0, err
}
c.server.addMountPoint(rootFD.FD())
c.mounted = true
resp := MountResp{
Root: rootIno,
SupportedMs: c.ServerImpl().SupportedMessages(),
MaxMessageSize: primitive.Uint32(c.ServerImpl().MaxMessageSize()),
}
respPayloadLen := uint32(resp.SizeBytes())
resp.MarshalBytes(comm.PayloadBuf(respPayloadLen))
return respPayloadLen, nil
}
// ChannelHandler handles the Channel RPC.
func ChannelHandler(c *Connection, comm Communicator, payloadLen uint32) (uint32, error) {
ch, desc, fdSock, err := c.createChannel(c.ServerImpl().MaxMessageSize())
if err != nil {
return 0, err
}
// Start servicing the channel in a separate goroutine.
c.activeWg.Add(1)
go func() {
if err := c.service(ch); err != nil {
// Don't log shutdown error which is expected during server shutdown.
if _, ok := err.(flipcall.ShutdownError); !ok {
log.Warningf("lisafs.Connection.service(channel = @%p): %v", ch, err)
}
}
c.activeWg.Done()
}()
clientDataFD, err := unix.Dup(desc.FD)
if err != nil {
unix.Close(fdSock)
ch.shutdown()
return 0, err
}
// Respond to client with successful channel creation message.
if err := comm.DonateFD(clientDataFD); err != nil {
return 0, err
}
if err := comm.DonateFD(fdSock); err != nil {
return 0, err
}
resp := ChannelResp{
dataOffset: desc.Offset,
dataLength: uint64(desc.Length),
}
respLen := uint32(resp.SizeBytes())
resp.MarshalUnsafe(comm.PayloadBuf(respLen))
return respLen, nil
}
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