safesocket: fix Plan 9 implementation

This wasn't right; it was spinning up new goroutines non-stop.
Revert to a boring localhost TCP implementation for now.

Updates #5794

Change-Id: If93caa20a12ee4e741c0c72b0d91cc0cc5870152
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

safesocket/safesocket_plan9.go

@@ -7,119 +7,13 @@ package safesocket
 
 import (
 	"context"
-	"fmt"
 	"net"
-	"os"
-	"syscall"
-	"time"
-
-	"golang.org/x/sys/plan9"
 )
 
-// Plan 9's devsrv srv(3) is a server registry  and
-// it is conventionally bound to "/srv" in the default
-// namespace. It is "a one level directory for holding
-// already open channels to services". Post one end of
-// a pipe to "/srv/tailscale.sock" and use the other
-// end for communication with a requestor. Plan 9 pipes
-// are bidirectional.
-
-type plan9SrvAddr string
-
-func (sl plan9SrvAddr) Network() string {
-	return "/srv"
-}
-
-func (sl plan9SrvAddr) String() string {
-	return string(sl)
-}
-
-// There is no net.FileListener for Plan 9 at this time
-type plan9SrvListener struct {
-	name string
-	srvf *os.File
-	file *os.File
-}
-
-func (sl *plan9SrvListener) Accept() (net.Conn, error) {
-	// sl.file is the server end of the pipe that's
-	// connected to /srv/tailscale.sock
-	return plan9FileConn{name: sl.name, file: sl.file}, nil
-}
-
-func (sl *plan9SrvListener) Close() error {
-	sl.file.Close()
-	return sl.srvf.Close()
-}
-
-func (sl *plan9SrvListener) Addr() net.Addr {
-	return plan9SrvAddr(sl.name)
-}
-
-type plan9FileConn struct {
-	name string
-	file *os.File
-}
-
-func (fc plan9FileConn) Read(b []byte) (n int, err error) {
-	return fc.file.Read(b)
-}
-func (fc plan9FileConn) Write(b []byte) (n int, err error) {
-	return fc.file.Write(b)
-}
-func (fc plan9FileConn) Close() error {
-	return fc.file.Close()
-}
-func (fc plan9FileConn) LocalAddr() net.Addr {
-	return plan9SrvAddr(fc.name)
-}
-func (fc plan9FileConn) RemoteAddr() net.Addr {
-	return plan9SrvAddr(fc.name)
-}
-func (fc plan9FileConn) SetDeadline(t time.Time) error {
-	return syscall.EPLAN9
-}
-func (fc plan9FileConn) SetReadDeadline(t time.Time) error {
-	return syscall.EPLAN9
-}
-func (fc plan9FileConn) SetWriteDeadline(t time.Time) error {
-	return syscall.EPLAN9
-}
-
 func connect(_ context.Context, path string) (net.Conn, error) {
-	f, err := os.OpenFile(path, os.O_RDWR, 0666)
-	if err != nil {
-		return nil, err
+	return net.Dial("tcp", "localhost:5252")
 }
 
-	return plan9FileConn{name: path, file: f}, nil
-}
-
-// Create an entry in /srv, open a pipe, write the
-// client end to the entry and return the server
-// end of the pipe to the caller. When the server
-// end of the pipe is closed, /srv name associated
-// with it will be removed (controlled by ORCLOSE flag)
 func listen(path string) (net.Listener, error) {
-	const O_RCLOSE = 64 // remove on close; should be in plan9 package
-	var pip [2]int
-
-	err := plan9.Pipe(pip[:])
-	if err != nil {
-		return nil, err
-	}
-	defer plan9.Close(pip[1])
-
-	srvfd, err := plan9.Create(path, plan9.O_WRONLY|plan9.O_CLOEXEC|O_RCLOSE, 0600)
-	if err != nil {
-		return nil, err
-	}
-	srv := os.NewFile(uintptr(srvfd), path)
-
-	_, err = fmt.Fprintf(srv, "%d", pip[1])
-	if err != nil {
-		return nil, err
-	}
-
-	return &plan9SrvListener{name: path, srvf: srv, file: os.NewFile(uintptr(pip[0]), path)}, nil
+	return net.Listen("tcp", "localhost:5252")
 }