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// Copyright 2009 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.
package net
import "syscall"
func kernelVersion() (major int, minor int) {
var uname syscall.Utsname
if err := syscall.Uname(&uname); err != nil {
return
}
rl := uname.Release
var values [2]int
vi := 0
value := 0
for _, c := range rl {
if c >= '0' && c <= '9' {
value = (value * 10) + int(c-'0')
} else {
// Note that we're assuming N.N.N here. If we see anything else we are likely to
// mis-parse it.
values[vi] = value
vi++
if vi >= len(values) {
break
}
value = 0
}
}
switch vi {
case 0:
return 0, 0
case 1:
return values[0], 0
case 2:
return values[0], values[1]
}
return
}
// Linux stores the backlog as:
//
// - uint16 in kernel version < 4.1,
// - uint32 in kernel version >= 4.1
//
// Truncate number to avoid wrapping.
//
// See issue 5030 and 41470.
func maxAckBacklog(n int) int {
major, minor := kernelVersion()
size := 16
if major > 4 || (major == 4 && minor >= 1) {
size = 32
}
var max uint = 1<<size - 1
if uint(n) > max {
n = int(max)
}
return n
}
func maxListenerBacklog() int {
fd, err := open("/proc/sys/net/core/somaxconn")
if err != nil {
return syscall.SOMAXCONN
}
defer fd.close()
l, ok := fd.readLine()
if !ok {
return syscall.SOMAXCONN
}
f := getFields(l)
n, _, ok := dtoi(f[0])
if n == 0 || !ok {
return syscall.SOMAXCONN
}
if n > 1<<16-1 {
return maxAckBacklog(n)
}
return n
}
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