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package msg
import (
"net"
"time"
"github.com/pkg/errors"
"golang.org/x/sys/unix"
"github.com/rootless-containers/rootlesskit/pkg/msgutil"
"github.com/rootless-containers/rootlesskit/pkg/port"
)
const (
RequestTypeInit = "init"
RequestTypeConnect = "connect"
)
// Request and Response are encoded as JSON with uint32le length header.
type Request struct {
Type string // "init" or "connect"
Proto string // "tcp" or "udp"
IP string
Port int
}
// Reply may contain FD as OOB
type Reply struct {
Error string
}
// Initiate sends "init" request to the child UNIX socket.
func Initiate(c *net.UnixConn) error {
req := Request{
Type: RequestTypeInit,
}
if _, err := msgutil.MarshalToWriter(c, &req); err != nil {
return err
}
if err := c.CloseWrite(); err != nil {
return err
}
var rep Reply
if _, err := msgutil.UnmarshalFromReader(c, &rep); err != nil {
return err
}
return c.CloseRead()
}
// ConnectToChild connects to the child UNIX socket, and obtains TCP or UDP socket FD
// that corresponds to the port spec.
func ConnectToChild(c *net.UnixConn, spec port.Spec) (int, error) {
req := Request{
Type: RequestTypeConnect,
Proto: spec.Proto,
Port: spec.ChildPort,
IP: spec.ChildIP,
}
if _, err := msgutil.MarshalToWriter(c, &req); err != nil {
return 0, err
}
if err := c.CloseWrite(); err != nil {
return 0, err
}
oobSpace := unix.CmsgSpace(4)
oob := make([]byte, oobSpace)
var (
oobN int
err error
)
for {
_, oobN, _, _, err = c.ReadMsgUnix(nil, oob)
if err != unix.EINTR {
break
}
}
if err != nil {
return 0, err
}
if oobN != oobSpace {
return 0, errors.Errorf("expected OOB space %d, got %d", oobSpace, oobN)
}
oob = oob[:oobN]
fd, err := parseFDFromOOB(oob)
if err != nil {
return 0, err
}
if err := c.CloseRead(); err != nil {
return 0, err
}
return fd, nil
}
// ConnectToChildWithSocketPath wraps ConnectToChild
func ConnectToChildWithSocketPath(socketPath string, spec port.Spec) (int, error) {
var dialer net.Dialer
conn, err := dialer.Dial("unix", socketPath)
if err != nil {
return 0, err
}
defer conn.Close()
c := conn.(*net.UnixConn)
return ConnectToChild(c, spec)
}
// ConnectToChildWithRetry retries ConnectToChild every (i*5) milliseconds.
func ConnectToChildWithRetry(socketPath string, spec port.Spec, retries int) (int, error) {
for i := 0; i < retries; i++ {
fd, err := ConnectToChildWithSocketPath(socketPath, spec)
if i == retries-1 && err != nil {
return 0, err
}
if err == nil {
return fd, err
}
// TODO: backoff
time.Sleep(time.Duration(i*5) * time.Millisecond)
}
// NOT REACHED
return 0, errors.New("reached max retry")
}
func parseFDFromOOB(oob []byte) (int, error) {
scms, err := unix.ParseSocketControlMessage(oob)
if err != nil {
return 0, err
}
if len(scms) != 1 {
return 0, errors.Errorf("unexpected scms: %v", scms)
}
scm := scms[0]
fds, err := unix.ParseUnixRights(&scm)
if err != nil {
return 0, err
}
if len(fds) != 1 {
return 0, errors.Errorf("unexpected fds: %v", fds)
}
return fds[0], nil
}
|
