sock_cloexec_accept.go

     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 accept for platforms that provide a fast path for
     6  // setting SetNonblock and CloseOnExec, but don't necessarily have accept4.
     7  // This is the code we used for accept in Go 1.17 and earlier.
     8  // On Linux the accept4 system call was introduced in 2.6.28 kernel,
     9  // and our minimum requirement is 2.6.32, so we simplified the function.
    10  // Unfortunately, on ARM accept4 wasn't added until 2.6.36, so for ARM
    11  // only we continue using the older code.
    12  
    13  //go:build linux && arm
    14  
    15  package poll
    16  
    17  import "syscall"
    18  
    19  // Wrapper around the accept system call that marks the returned file
    20  // descriptor as nonblocking and close-on-exec.
    21  func accept(s int) (int, syscall.Sockaddr, string, error) {
    22  	ns, sa, err := Accept4Func(s, syscall.SOCK_NONBLOCK|syscall.SOCK_CLOEXEC)
    23  	switch err {
    24  	case nil:
    25  		return ns, sa, "", nil
    26  	default: // errors other than the ones listed
    27  		return -1, sa, "accept4", err
    28  	case syscall.ENOSYS: // syscall missing
    29  	case syscall.EINVAL: // some Linux use this instead of ENOSYS
    30  	case syscall.EACCES: // some Linux use this instead of ENOSYS
    31  	case syscall.EFAULT: // some Linux use this instead of ENOSYS
    32  	}
    33  
    34  	// See ../syscall/exec_unix.go for description of ForkLock.
    35  	// It is probably okay to hold the lock across syscall.Accept
    36  	// because we have put fd.sysfd into non-blocking mode.
    37  	// However, a call to the File method will put it back into
    38  	// blocking mode. We can't take that risk, so no use of ForkLock here.
    39  	ns, sa, err = AcceptFunc(s)
    40  	if err == nil {
    41  		syscall.CloseOnExec(ns)
    42  	}
    43  	if err != nil {
    44  		return -1, nil, "accept", err
    45  	}
    46  	if err = syscall.SetNonblock(ns, true); err != nil {
    47  		CloseFunc(ns)
    48  		return -1, nil, "setnonblock", err
    49  	}
    50  	return ns, sa, "", nil
    51  }
    52
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