github.com/go-board/x-go@v0.1.2-0.20220610024734-db1323f6cb15/xsys/sys.go (about)

     1  //+build linux
     2  
     3  /*
     4  Copyright 2015 The Kubernetes Authors.
     5  Licensed under the Apache License, Version 2.0 (the "License");
     6  you may not use this file except in compliance with the License.
     7  You may obtain a copy of the License at
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  Unless required by applicable law or agreed to in writing, software
    10  distributed under the License is distributed on an "AS IS" BASIS,
    11  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  See the License for the specific language governing permissions and
    13  limitations under the License.
    14  */
    15  package xsys
    16  
    17  import (
    18  	"io/ioutil"
    19  	"path"
    20  	"strconv"
    21  	"strings"
    22  )
    23  
    24  const (
    25  	sysctlBase = "/proc/sys"
    26  	// VMOvercommitMemory refers to the sysctl variable responsible for defining
    27  	// the memory over-commit policy used by kernel.
    28  	VMOvercommitMemory = "vm/overcommit_memory"
    29  	// VMPanicOnOOM refers to the sysctl variable responsible for defining
    30  	// the OOM behavior used by kernel.
    31  	VMPanicOnOOM = "vm/panic_on_oom"
    32  	// KernelPanic refers to the sysctl variable responsible for defining
    33  	// the timeout after a panic for the kernel to reboot.
    34  	KernelPanic = "kernel/panic"
    35  	// KernelPanicOnOops refers to the sysctl variable responsible for defining
    36  	// the kernel behavior when an oops or BUG is encountered.
    37  	KernelPanicOnOops = "kernel/panic_on_oops"
    38  	// RootMaxKeys refers to the sysctl variable responsible for defining
    39  	// the maximum number of keys that the root user (UID 0 in the root user namespace) may own.
    40  	RootMaxKeys = "kernel/keys/root_maxkeys"
    41  	// RootMaxBytes refers to the sysctl variable responsible for defining
    42  	// the maximum number of bytes of data that the root user (UID 0 in the root user namespace)
    43  	// can hold in the payloads of the keys owned by root.
    44  	RootMaxBytes = "kernel/keys/root_maxbytes"
    45  
    46  	// VMOvercommitMemoryAlways represents that kernel performs no memory over-commit handling.
    47  	VMOvercommitMemoryAlways = 1
    48  	// VMPanicOnOOMInvokeOOMKiller represents that kernel calls the oom_killer function when OOM occurs.
    49  	VMPanicOnOOMInvokeOOMKiller = 0
    50  
    51  	// KernelPanicOnOopsAlways represents that kernel panics on kernel oops.
    52  	KernelPanicOnOopsAlways = 1
    53  	// KernelPanicRebootTimeout is the timeout seconds after a panic for the kernel to reboot.
    54  	KernelPanicRebootTimeout = 10
    55  
    56  	// RootMaxKeysSetting is the maximum number of keys that the root user (UID 0 in the root user namespace) may own.
    57  	// Needed since docker creates a new key per container.
    58  	RootMaxKeysSetting = 1000000
    59  	// RootMaxBytesSetting is the maximum number of bytes of data that the root user (UID 0 in the root user namespace)
    60  	// can hold in the payloads of the keys owned by root.
    61  	// Allocate 25 bytes per key * number of MaxKeys.
    62  	RootMaxBytesSetting = RootMaxKeysSetting * 25
    63  )
    64  
    65  // Interface is an injectable interface for running sysctl commands.
    66  type Interface interface {
    67  	// GetSysctl returns the value for the specified sysctl setting
    68  	GetSysctl(sysctl string) (int, error)
    69  	// SetSysctl modifies the specified sysctl flag to the new value
    70  	SetSysctl(sysctl string, newVal int) error
    71  }
    72  
    73  // New returns a new Interface for accessing sysctl
    74  func New() Interface {
    75  	return &procSysctl{}
    76  }
    77  
    78  // procSysctl implements Interface by reading and writing files under /proc/sys
    79  type procSysctl struct{}
    80  
    81  // GetSysctl returns the value for the specified sysctl setting
    82  func (*procSysctl) GetSysctl(sysctl string) (int, error) {
    83  	data, err := ioutil.ReadFile(path.Join(sysctlBase, sysctl))
    84  	if err != nil {
    85  		return -1, err
    86  	}
    87  	val, err := strconv.Atoi(strings.Trim(string(data), " \n"))
    88  	if err != nil {
    89  		return -1, err
    90  	}
    91  	return val, nil
    92  }
    93  
    94  // SetSysctl modifies the specified sysctl flag to the new value
    95  func (*procSysctl) SetSysctl(sysctl string, newVal int) error {
    96  	return ioutil.WriteFile(path.Join(sysctlBase, sysctl), []byte(strconv.Itoa(newVal)), 0640)
    97  }