github.com/code-reading/golang@v0.0.0-20220303082512-ba5bc0e589a3/go/src/net/sock_cloexec.go (about)

     1  // Copyright 2013 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  // This file implements sysSocket for platforms that provide a fast path for
     6  // setting SetNonblock and CloseOnExec.
     7  
     8  //go:build dragonfly || freebsd || illumos || linux || netbsd || openbsd
     9  // +build dragonfly freebsd illumos linux netbsd openbsd
    10  
    11  package net
    12  
    13  import (
    14  	"internal/poll"
    15  	"os"
    16  	"syscall"
    17  )
    18  
    19  // Wrapper around the socket system call that marks the returned file
    20  // descriptor as nonblocking and close-on-exec.
    21  func sysSocket(family, sotype, proto int) (int, error) {
    22  	s, err := socketFunc(family, sotype|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, proto)
    23  	// On Linux the SOCK_NONBLOCK and SOCK_CLOEXEC flags were
    24  	// introduced in 2.6.27 kernel and on FreeBSD both flags were
    25  	// introduced in 10 kernel. If we get an EINVAL error on Linux
    26  	// or EPROTONOSUPPORT error on FreeBSD, fall back to using
    27  	// socket without them.
    28  	switch err {
    29  	case nil:
    30  		return s, nil
    31  	default:
    32  		return -1, os.NewSyscallError("socket", err)
    33  	case syscall.EPROTONOSUPPORT, syscall.EINVAL:
    34  	}
    35  
    36  	// See ../syscall/exec_unix.go for description of ForkLock.
    37  	syscall.ForkLock.RLock()
    38  	s, err = socketFunc(family, sotype, proto)
    39  	if err == nil {
    40  		syscall.CloseOnExec(s)
    41  	}
    42  	syscall.ForkLock.RUnlock()
    43  	if err != nil {
    44  		return -1, os.NewSyscallError("socket", err)
    45  	}
    46  	if err = syscall.SetNonblock(s, true); err != nil {
    47  		poll.CloseFunc(s)
    48  		return -1, os.NewSyscallError("setnonblock", err)
    49  	}
    50  	return s, nil
    51  }