github.com/sbinet/go@v0.0.0-20160827155028-54d7de7dd62b/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 and accept for platforms that
     6  // provide a fast path for setting SetNonblock and CloseOnExec.
     7  
     8  // +build freebsd linux
     9  
    10  package net
    11  
    12  import (
    13  	"os"
    14  	"syscall"
    15  )
    16  
    17  // Wrapper around the socket system call that marks the returned file
    18  // descriptor as nonblocking and close-on-exec.
    19  func sysSocket(family, sotype, proto int) (int, error) {
    20  	s, err := socketFunc(family, sotype|syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC, proto)
    21  	// On Linux the SOCK_NONBLOCK and SOCK_CLOEXEC flags were
    22  	// introduced in 2.6.27 kernel and on FreeBSD both flags were
    23  	// introduced in 10 kernel. If we get an EINVAL error on Linux
    24  	// or EPROTONOSUPPORT error on FreeBSD, fall back to using
    25  	// socket without them.
    26  	switch err {
    27  	case nil:
    28  		return s, nil
    29  	default:
    30  		return -1, os.NewSyscallError("socket", err)
    31  	case syscall.EPROTONOSUPPORT, syscall.EINVAL:
    32  	}
    33  
    34  	// See ../syscall/exec_unix.go for description of ForkLock.
    35  	syscall.ForkLock.RLock()
    36  	s, err = socketFunc(family, sotype, proto)
    37  	if err == nil {
    38  		syscall.CloseOnExec(s)
    39  	}
    40  	syscall.ForkLock.RUnlock()
    41  	if err != nil {
    42  		return -1, os.NewSyscallError("socket", err)
    43  	}
    44  	if err = syscall.SetNonblock(s, true); err != nil {
    45  		closeFunc(s)
    46  		return -1, os.NewSyscallError("setnonblock", err)
    47  	}
    48  	return s, nil
    49  }
    50  
    51  // Wrapper around the accept system call that marks the returned file
    52  // descriptor as nonblocking and close-on-exec.
    53  func accept(s int) (int, syscall.Sockaddr, error) {
    54  	ns, sa, err := accept4Func(s, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
    55  	// On Linux the accept4 system call was introduced in 2.6.28
    56  	// kernel and on FreeBSD it was introduced in 10 kernel. If we
    57  	// get an ENOSYS error on both Linux and FreeBSD, or EINVAL
    58  	// error on Linux, fall back to using accept.
    59  	switch err {
    60  	case nil:
    61  		return ns, sa, nil
    62  	default: // errors other than the ones listed
    63  		return -1, sa, os.NewSyscallError("accept4", err)
    64  	case syscall.ENOSYS: // syscall missing
    65  	case syscall.EINVAL: // some Linux use this instead of ENOSYS
    66  	case syscall.EACCES: // some Linux use this instead of ENOSYS
    67  	case syscall.EFAULT: // some Linux use this instead of ENOSYS
    68  	}
    69  
    70  	// See ../syscall/exec_unix.go for description of ForkLock.
    71  	// It is probably okay to hold the lock across syscall.Accept
    72  	// because we have put fd.sysfd into non-blocking mode.
    73  	// However, a call to the File method will put it back into
    74  	// blocking mode. We can't take that risk, so no use of ForkLock here.
    75  	ns, sa, err = acceptFunc(s)
    76  	if err == nil {
    77  		syscall.CloseOnExec(ns)
    78  	}
    79  	if err != nil {
    80  		return -1, nil, os.NewSyscallError("accept", err)
    81  	}
    82  	if err = syscall.SetNonblock(ns, true); err != nil {
    83  		closeFunc(ns)
    84  		return -1, nil, os.NewSyscallError("setnonblock", err)
    85  	}
    86  	return ns, sa, nil
    87  }