pkg/utils: add functions to work with sysctl

pkg/utils/sysctl/sysctl_linux.go

@@ -0,0 +1,58 @@
+// 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.
+
+// build +linux
+
+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 coresponding 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", strings.Replace(name, ".", "/", -1))
+	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", strings.Replace(name, ".", "/", -1))
+	fullName = filepath.Clean(fullName)
+	if err := ioutil.WriteFile(fullName, []byte(value), 0644); err != nil {
+		return "", err
+	}
+
+	return getSysctl(name)
+}