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

     1  // Copyright 2009 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  //go:build darwin || dragonfly || freebsd || netbsd || openbsd
     6  // +build darwin dragonfly freebsd netbsd openbsd
     7  
     8  package net
     9  
    10  import (
    11  	"runtime"
    12  	"syscall"
    13  )
    14  
    15  func maxListenerBacklog() int {
    16  	var (
    17  		n   uint32
    18  		err error
    19  	)
    20  	switch runtime.GOOS {
    21  	case "darwin", "ios":
    22  		n, err = syscall.SysctlUint32("kern.ipc.somaxconn")
    23  	case "freebsd":
    24  		n, err = syscall.SysctlUint32("kern.ipc.soacceptqueue")
    25  	case "netbsd":
    26  		// NOTE: NetBSD has no somaxconn-like kernel state so far
    27  	case "openbsd":
    28  		n, err = syscall.SysctlUint32("kern.somaxconn")
    29  	}
    30  	if n == 0 || err != nil {
    31  		return syscall.SOMAXCONN
    32  	}
    33  	// FreeBSD stores the backlog in a uint16, as does Linux.
    34  	// Assume the other BSDs do too. Truncate number to avoid wrapping.
    35  	// See issue 5030.
    36  	if n > 1<<16-1 {
    37  		n = 1<<16 - 1
    38  	}
    39  	return int(n)
    40  }