pkg/utils: add functions to work with sysctl

diff --git a/utils/sysctl/sysctl_linux.go b/utils/sysctl/sysctl_linux.go
new file mode 100644 (file)
index 0000000..c0fba38
--- /dev/null
+++ b/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)
+}