/
receive.go
88 lines (73 loc) · 1.97 KB
/
receive.go
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package shimsocket
import (
"encoding/json"
"errors"
"fmt"
"io"
"net"
"os"
"code.cloudfoundry.org/netplugin-shim/garden-plugin/message"
"golang.org/x/sys/unix"
)
func Receive(conn *net.UnixConn) (*os.File, message.Message, error) {
fd, err := receiveFD(conn)
if err != nil {
return nil, message.Message{}, err
}
nsFile := os.NewFile(fd, fmt.Sprintf("fd%d", fd))
msg, err := decodeMsg(conn)
if err != nil {
defer nsFile.Close()
return nil, message.Message{}, err
}
return nsFile, msg, nil
}
func decodeMsg(r io.Reader) (message.Message, error) {
var content message.Message
decoder := json.NewDecoder(r)
if err := decoder.Decode(&content); err != nil {
return message.Message{}, err
}
return content, nil
}
func receiveFD(conn *net.UnixConn) (uintptr, error) {
controlMessageBytesSpace := unix.CmsgSpace(4)
controlMessageBytes := make([]byte, controlMessageBytesSpace)
_, readSocketControlMessageBytes, _, _, err := conn.ReadMsgUnix(nil, controlMessageBytes)
if err != nil {
return 0, err
}
if readSocketControlMessageBytes > controlMessageBytesSpace {
return 0, errors.New("received too many bytes from socket control message")
}
controlMessageBytes = controlMessageBytes[:readSocketControlMessageBytes]
socketControlMessages, err := parseSocketControlMessage(controlMessageBytes)
if err != nil {
return 0, err
}
fds, err := parseUnixRights(&socketControlMessages[0])
if err != nil {
return 0, err
}
return uintptr(fds[0]), nil
}
func parseUnixRights(m *unix.SocketControlMessage) ([]int, error) {
messages, err := unix.ParseUnixRights(m)
if err != nil {
return nil, err
}
if len(messages) != 1 {
return nil, errors.New("no messages parsed")
}
return messages, nil
}
func parseSocketControlMessage(b []byte) ([]unix.SocketControlMessage, error) {
messages, err := unix.ParseSocketControlMessage(b)
if err != nil {
return nil, err
}
if len(messages) != 1 {
return nil, errors.New("no messages parsed")
}
return messages, nil
}