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// Copyright 2016 CNI authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package sysctl
import (
"fmt"
"io/ioutil"
"path/filepath"
"strings"
)
// Sysctl provides a method to set/get values from /proc/sys - in linux systems
// new interface to set/get values of variables formerly handled by sysctl syscall
// If optional `params` have only one string value - this function will
// set this value into corresponding sysctl variable
func Sysctl(name string, params ...string) (string, error) {
if len(params) > 1 {
return "", fmt.Errorf("unexcepted additional parameters")
} else if len(params) == 1 {
return setSysctl(name, params[0])
}
return getSysctl(name)
}
func getSysctl(name string) (string, error) {
fullName := filepath.Join("/proc/sys", toNormalName(name))
fullName = filepath.Clean(fullName)
data, err := ioutil.ReadFile(fullName)
if err != nil {
return "", err
}
return string(data[:len(data)-1]), nil
}
func setSysctl(name, value string) (string, error) {
fullName := filepath.Join("/proc/sys", toNormalName(name))
fullName = filepath.Clean(fullName)
if err := ioutil.WriteFile(fullName, []byte(value), 0644); err != nil {
return "", err
}
return getSysctl(name)
}
// Normalize names by using slash as separator
// Sysctl names can use dots or slashes as separator:
// - if dots are used, dots and slashes are interchanged.
// - if slashes are used, slashes and dots are left intact.
// Separator in use is determined by first occurrence.
func toNormalName(name string) string {
interchange := false
for _, c := range name {
if c == '.' {
interchange = true
break
}
if c == '/' {
break
}
}
if interchange {
r := strings.NewReplacer(".", "/", "/", ".")
return r.Replace(name)
}
return name
}
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