Merge pull request #117 from kinvolk/alban/net-tuning

new plugin: tuning

Documentation/tuning.md

@@ -0,0 +1,36 @@
+# tuning plugin
+
+## Overview
+
+This plugin can change some system controls (sysctls) in the network namespace.
+It does not create any network interfaces and therefore does not bring connectivity by itself.
+It is only useful when used in addition to other plugins.
+
+## Operation
+The following network configuration file
+```
+{
+  "name": "mytuning",
+  "type": "tuning",
+  "sysctl": {
+          "net.core.somaxconn": "500"
+  }
+}
+```
+will set /proc/sys/net/core/somaxconn to 500.
+Other sysctls can be modified as long as they belong to the network namespace (`/proc/sys/net/*`).
+
+A successful result would simply be:
+```
+{
+  "cniVersion": "0.1.0"
+}
+```
+
+## Network sysctls documentation
+
+Some network sysctls are documented in the Linux sources:
+
+- [Documentation/sysctl/net.txt](https://www.kernel.org/doc/Documentation/sysctl/net.txt)
+- [Documentation/networking/ip-sysctl.txt](https://www.kernel.org/doc/Documentation/networking/ip-sysctl.txt)
+- [Documentation/networking/](https://www.kernel.org/doc/Documentation/networking/)

plugins/meta/tuning/tuning.go

@@ -0,0 +1,83 @@
+// 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.
+
+// This is a "meta-plugin". It reads in its own netconf, it does not create
+// any network interface but just changes the network sysctl.
+
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strings"
+
+	"github.com/appc/cni/pkg/ns"
+	"github.com/appc/cni/pkg/skel"
+	"github.com/appc/cni/pkg/types"
+)
+
+// TuningConf represents the network tuning configuration.
+type TuningConf struct {
+	types.NetConf
+	SysCtl map[string]string `json:"sysctl"`
+}
+
+func cmdAdd(args *skel.CmdArgs) error {
+	tuningConf := TuningConf{}
+	if err := json.Unmarshal(args.StdinData, &tuningConf); err != nil {
+		return fmt.Errorf("failed to load netconf: %v", err)
+	}
+
+	// The directory /proc/sys/net is per network namespace. Enter in the
+	// network namespace before writing on it.
+
+	err := ns.WithNetNSPath(args.Netns, false, func(hostNS *os.File) error {
+		for key, value := range tuningConf.SysCtl {
+			fileName := filepath.Join("/proc/sys", strings.Replace(key, ".", "/", -1))
+			fileName = filepath.Clean(fileName)
+
+			// Refuse to modify sysctl parameters that don't belong
+			// to the network subsystem.
+			if !strings.HasPrefix(fileName, "/proc/sys/net/") {
+				return fmt.Errorf("invalid net sysctl key: %q", key)
+			}
+			content := []byte(value)
+			err := ioutil.WriteFile(fileName, content, 0644)
+			if err != nil {
+				return err
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		return err
+	}
+
+	result := types.Result{}
+	return result.Print()
+}
+
+func cmdDel(args *skel.CmdArgs) error {
+	// TODO: the settings are not reverted to the previous values. Reverting the
+	// settings is not useful when the whole container goes away but it could be
+	// useful in scenarios where plugins are added and removed at runtime.
+	return nil
+}
+
+func main() {
+	skel.PluginMain(cmdAdd, cmdDel)
+}

test

@@ -12,7 +12,7 @@ set -e
 source ./build
 
 TESTABLE="plugins/ipam/dhcp"
-FORMATTABLE="$TESTABLE libcni pkg/ip pkg/ns pkg/invoke pkg/types pkg/ipam pkg/skel plugins/ipam/host-local plugins/main/bridge plugins/meta/flannel"
+FORMATTABLE="$TESTABLE libcni pkg/ip pkg/ns pkg/invoke pkg/types pkg/ipam pkg/skel plugins/ipam/host-local plugins/main/bridge plugins/meta/flannel plugins/meta/tuning"
 
 # user has not provided PKG override
 if [ -z "$PKG" ]; then