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Source file src/net/sock_cloexec.go

  // Copyright 2013 The Go Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style
  // license that can be found in the LICENSE file.
  
  // This file implements sysSocket and accept for platforms that
  // provide a fast path for setting SetNonblock and CloseOnExec.
  
  // +build freebsd linux
  
  package net
  
  import (
  	"os"
  	"syscall"
  )
  
  // Wrapper around the socket system call that marks the returned file
  // descriptor as nonblocking and close-on-exec.
  func sysSocket(family, sotype, proto int) (int, error) {
  	s, err := socketFunc(family, sotype|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, proto)
  	// On Linux the SOCK_NONBLOCK and SOCK_CLOEXEC flags were
  	// introduced in 2.6.27 kernel and on FreeBSD both flags were
  	// introduced in 10 kernel. If we get an EINVAL error on Linux
  	// or EPROTONOSUPPORT error on FreeBSD, fall back to using
  	// socket without them.
  	switch err {
  	case nil:
  		return s, nil
  	default:
  		return -1, os.NewSyscallError("socket", err)
  	case syscall.EPROTONOSUPPORT, syscall.EINVAL:
  	}
  
  	// See ../syscall/exec_unix.go for description of ForkLock.
  	syscall.ForkLock.RLock()
  	s, err = socketFunc(family, sotype, proto)
  	if err == nil {
  		syscall.CloseOnExec(s)
  	}
  	syscall.ForkLock.RUnlock()
  	if err != nil {
  		return -1, os.NewSyscallError("socket", err)
  	}
  	if err = syscall.SetNonblock(s, true); err != nil {
  		closeFunc(s)
  		return -1, os.NewSyscallError("setnonblock", err)
  	}
  	return s, nil
  }
  
  // Wrapper around the accept system call that marks the returned file
  // descriptor as nonblocking and close-on-exec.
  func accept(s int) (int, syscall.Sockaddr, error) {
  	ns, sa, err := accept4Func(s, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
  	// On Linux the accept4 system call was introduced in 2.6.28
  	// kernel and on FreeBSD it was introduced in 10 kernel. If we
  	// get an ENOSYS error on both Linux and FreeBSD, or EINVAL
  	// error on Linux, fall back to using accept.
  	switch err {
  	case nil:
  		return ns, sa, nil
  	default: // errors other than the ones listed
  		return -1, sa, os.NewSyscallError("accept4", err)
  	case syscall.ENOSYS: // syscall missing
  	case syscall.EINVAL: // some Linux use this instead of ENOSYS
  	case syscall.EACCES: // some Linux use this instead of ENOSYS
  	case syscall.EFAULT: // some Linux use this instead of ENOSYS
  	}
  
  	// See ../syscall/exec_unix.go for description of ForkLock.
  	// It is probably okay to hold the lock across syscall.Accept
  	// because we have put fd.sysfd into non-blocking mode.
  	// However, a call to the File method will put it back into
  	// blocking mode. We can't take that risk, so no use of ForkLock here.
  	ns, sa, err = acceptFunc(s)
  	if err == nil {
  		syscall.CloseOnExec(ns)
  	}
  	if err != nil {
  		return -1, nil, os.NewSyscallError("accept", err)
  	}
  	if err = syscall.SetNonblock(ns, true); err != nil {
  		closeFunc(ns)
  		return -1, nil, os.NewSyscallError("setnonblock", err)
  	}
  	return ns, sa, nil
  }
  

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