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tun_unix.go
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tun_unix.go
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//go:build darwin || linux
// +build darwin linux
/*
* Copyright (c) 2021, Psiphon Inc.
* All rights reserved.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
package tun
import (
"os"
"syscall"
"github.com/Psiphon-Labs/psiphon-tunnel-core/psiphon/common/errors"
"golang.org/x/sys/unix"
)
// fileFromFD duplicates the file descriptor; sets O_CLOEXEC to avoid leaking
// to child processes; sets the mode to nonblocking; and creates a os.File
// using os.NewFile.
func fileFromFD(fd int, name string) (*os.File, error) {
// Prevent fork between duplicating fd and setting CLOEXEC
syscall.ForkLock.RLock()
defer syscall.ForkLock.RUnlock()
dupfd, err := unix.Dup(fd)
if err != nil {
return nil, errors.Trace(err)
}
// Set CLOEXEC so file descriptor not leaked to network config command
// subprocesses.
unix.CloseOnExec(dupfd)
err = unix.SetNonblock(dupfd, true)
if err != nil {
unix.Close(dupfd)
return nil, errors.Trace(err)
}
return os.NewFile(uintptr(dupfd), name), nil
}