From 53801a78819f19c4ddfe4b7582ab0458b34ee9c8 Mon Sep 17 00:00:00 2001
From: Gyu-Ho Lee <gyuhox@gmail.com>
Date: Wed, 16 Nov 2016 10:05:17 -0800
Subject: [PATCH] pkg/netutil: get list of Ethernet for tc command

Fix https://github.com/coreos/etcd/issues/6841.
---
 pkg/netutil/isolate_linux.go      | 83 +++++++++++++++++++++++++++++--
 pkg/netutil/isolate_linux_test.go | 25 ++++++++++
 2 files changed, 104 insertions(+), 4 deletions(-)
 create mode 100644 pkg/netutil/isolate_linux_test.go

diff --git a/pkg/netutil/isolate_linux.go b/pkg/netutil/isolate_linux.go
index c866cea8ee19..26b8585b3e84 100644
--- a/pkg/netutil/isolate_linux.go
+++ b/pkg/netutil/isolate_linux.go
@@ -15,8 +15,13 @@
 package netutil
 
 import (
+	"bytes"
 	"fmt"
+	"io/ioutil"
+	"os"
 	"os/exec"
+	"path/filepath"
+	"sort"
 )
 
 // DropPort drops all tcp packets that are received from the given port and sent to the given port.
@@ -43,14 +48,20 @@ func RecoverPort(port int) error {
 
 // SetLatency adds latency in millisecond scale with random variations.
 func SetLatency(ms, rv int) error {
+	eths, err := getEthernet()
+	if err != nil {
+		return err
+	}
+	eth := eths[0]
+
 	if rv > ms {
 		rv = 1
 	}
-	cmdStr := fmt.Sprintf("sudo tc qdisc add dev eth0 root netem delay %dms %dms distribution normal", ms, rv)
-	_, err := exec.Command("/bin/sh", "-c", cmdStr).Output()
+	cmdStr := fmt.Sprintf("sudo tc qdisc add dev %s root netem delay %dms %dms distribution normal", eth, ms, rv)
+	_, err = exec.Command("/bin/sh", "-c", cmdStr).Output()
 	if err != nil {
 		// the rule has already been added. Overwrite it.
-		cmdStr = fmt.Sprintf("sudo tc qdisc change dev eth0 root netem delay %dms %dms distribution normal", ms, rv)
+		cmdStr = fmt.Sprintf("sudo tc qdisc change dev %s root netem delay %dms %dms distribution normal", eth, ms, rv)
 		_, err = exec.Command("/bin/sh", "-c", cmdStr).Output()
 		if err != nil {
 			return err
@@ -61,6 +72,70 @@ func SetLatency(ms, rv int) error {
 
 // RemoveLatency resets latency configurations.
 func RemoveLatency() error {
-	_, err := exec.Command("/bin/sh", "-c", "sudo tc qdisc del dev eth0 root netem").Output()
+	eths, err := getEthernet()
+	if err != nil {
+		return err
+	}
+	eth := eths[0]
+
+	_, err = exec.Command("/bin/sh", "-c", fmt.Sprintf("sudo tc qdisc del dev %s root netem", eth)).Output()
 	return err
 }
+
+func getEthernet() (eths []string, err error) {
+	var ifs []string
+	ifs, err = readNetworkInterface()
+	if err != nil {
+		return
+	}
+
+	for _, name := range ifs {
+		if isEthernet(name) {
+			eths = append(eths, name)
+		}
+	}
+	if len(eths) == 0 {
+		return nil, fmt.Errorf("no ethernet network interface found (%v)", ifs)
+	}
+
+	sort.Strings(eths)
+	return
+}
+
+const sysClassNet = "/sys/class/net/"
+
+func readNetworkInterface() ([]string, error) {
+	d, err := os.Open(sysClassNet)
+	if err != nil {
+		return nil, err
+	}
+	defer d.Close()
+
+	ns, err := d.Readdirnames(-1)
+	if err != nil {
+		return nil, err
+	}
+	sort.Strings(ns)
+
+	return ns, nil
+}
+
+var typeEthernet = []byte{49, 10}
+
+// isEthernet returns true if the network interface is Ethernet.
+// '/sys/class/net/type' with 1 is Ethernet 10Mbps, 772 is Loopback device.
+// https://github.com/torvalds/linux/blob/master/include/uapi/linux/if_arp.h
+func isEthernet(name string) bool {
+	path := filepath.Join(sysClassNet, name, "type")
+	f, err := os.Open(path)
+	if err != nil {
+		return false
+	}
+	defer f.Close()
+
+	b, err := ioutil.ReadAll(f)
+	if err != nil {
+		return false
+	}
+	return bytes.Equal(typeEthernet, b)
+}
diff --git a/pkg/netutil/isolate_linux_test.go b/pkg/netutil/isolate_linux_test.go
new file mode 100644
index 000000000000..f957a15acdc8
--- /dev/null
+++ b/pkg/netutil/isolate_linux_test.go
@@ -0,0 +1,25 @@
+// Copyright 2016 The etcd 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 netutil
+
+import "testing"
+
+func TestGetEthernet(t *testing.T) {
+	eths, err := getEthernet()
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Log(eths)
+}