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// 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 conn is an RPC connection to a syscall RPC server.
package conn
import (
"fmt"
"sync"
"sync/atomic"
"syscall"
"github.com/golang/protobuf/proto"
"gvisor.googlesource.com/gvisor/pkg/binary"
"gvisor.googlesource.com/gvisor/pkg/syserr"
"gvisor.googlesource.com/gvisor/pkg/unet"
pb "gvisor.googlesource.com/gvisor/pkg/sentry/socket/rpcinet/syscall_rpc_go_proto"
)
type request struct {
response []byte
ready chan struct{}
ignoreResult bool
}
// RPCConnection represents a single RPC connection to a syscall gofer.
type RPCConnection struct {
// reqID is the ID of the last request and must be accessed atomically.
reqID uint64
sendMu sync.Mutex
socket *unet.Socket
reqMu sync.Mutex
requests map[uint64]request
}
// NewRPCConnection initializes a RPC connection to a socket gofer.
func NewRPCConnection(s *unet.Socket) *RPCConnection {
conn := &RPCConnection{socket: s, requests: map[uint64]request{}}
go func() { // S/R-FIXME(b/77962828)
var nums [16]byte
for {
for n := 0; n < len(nums); {
nn, err := conn.socket.Read(nums[n:])
if err != nil {
panic(fmt.Sprint("error reading length from socket rpc gofer: ", err))
}
n += nn
}
b := make([]byte, binary.LittleEndian.Uint64(nums[:8]))
id := binary.LittleEndian.Uint64(nums[8:])
for n := 0; n < len(b); {
nn, err := conn.socket.Read(b[n:])
if err != nil {
panic(fmt.Sprint("error reading request from socket rpc gofer: ", err))
}
n += nn
}
conn.reqMu.Lock()
r := conn.requests[id]
if r.ignoreResult {
delete(conn.requests, id)
} else {
r.response = b
conn.requests[id] = r
}
conn.reqMu.Unlock()
close(r.ready)
}
}()
return conn
}
// NewRequest makes a request to the RPC gofer and returns the request ID and a
// channel which will be closed once the request completes.
func (c *RPCConnection) NewRequest(req pb.SyscallRequest, ignoreResult bool) (uint64, chan struct{}) {
b, err := proto.Marshal(&req)
if err != nil {
panic(fmt.Sprint("invalid proto: ", err))
}
id := atomic.AddUint64(&c.reqID, 1)
ch := make(chan struct{})
c.reqMu.Lock()
c.requests[id] = request{ready: ch, ignoreResult: ignoreResult}
c.reqMu.Unlock()
c.sendMu.Lock()
defer c.sendMu.Unlock()
var nums [16]byte
binary.LittleEndian.PutUint64(nums[:8], uint64(len(b)))
binary.LittleEndian.PutUint64(nums[8:], id)
for n := 0; n < len(nums); {
nn, err := c.socket.Write(nums[n:])
if err != nil {
panic(fmt.Sprint("error writing length and ID to socket gofer: ", err))
}
n += nn
}
for n := 0; n < len(b); {
nn, err := c.socket.Write(b[n:])
if err != nil {
panic(fmt.Sprint("error writing request to socket gofer: ", err))
}
n += nn
}
return id, ch
}
// RPCReadFile will execute the ReadFile helper RPC method which avoids the
// common pattern of open(2), read(2), close(2) by doing all three operations
// as a single RPC. It will read the entire file or return EFBIG if the file
// was too large.
func (c *RPCConnection) RPCReadFile(path string) ([]byte, *syserr.Error) {
req := &pb.SyscallRequest_ReadFile{&pb.ReadFileRequest{
Path: path,
}}
id, ch := c.NewRequest(pb.SyscallRequest{Args: req}, false /* ignoreResult */)
<-ch
res := c.Request(id).Result.(*pb.SyscallResponse_ReadFile).ReadFile.Result
if e, ok := res.(*pb.ReadFileResponse_ErrorNumber); ok {
return nil, syserr.FromHost(syscall.Errno(e.ErrorNumber))
}
return res.(*pb.ReadFileResponse_Data).Data, nil
}
// RPCWriteFile will execute the WriteFile helper RPC method which avoids the
// common pattern of open(2), write(2), write(2), close(2) by doing all
// operations as a single RPC.
func (c *RPCConnection) RPCWriteFile(path string, data []byte) (int64, *syserr.Error) {
req := &pb.SyscallRequest_WriteFile{&pb.WriteFileRequest{
Path: path,
Content: data,
}}
id, ch := c.NewRequest(pb.SyscallRequest{Args: req}, false /* ignoreResult */)
<-ch
res := c.Request(id).Result.(*pb.SyscallResponse_WriteFile).WriteFile
if e := res.ErrorNumber; e != 0 {
return int64(res.Written), syserr.FromHost(syscall.Errno(e))
}
return int64(res.Written), nil
}
// Request retrieves the request corresponding to the given request ID.
//
// The channel returned by NewRequest must have been closed before Request can
// be called. This will happen automatically, do not manually close the
// channel.
func (c *RPCConnection) Request(id uint64) pb.SyscallResponse {
c.reqMu.Lock()
r := c.requests[id]
delete(c.requests, id)
c.reqMu.Unlock()
var resp pb.SyscallResponse
if err := proto.Unmarshal(r.response, &resp); err != nil {
panic(fmt.Sprint("invalid proto: ", err))
}
return resp
}
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