kubernetes/pkg/util/bandwidth/linux.go

/*
Copyright 2015 The Kubernetes Authors All rights reserved.

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 bandwidth

import (
	"bufio"
	"bytes"
	"encoding/hex"
	"fmt"
	"net"
	"strings"

	"k8s.io/kubernetes/pkg/api/resource"
	"k8s.io/kubernetes/pkg/util"
	"k8s.io/kubernetes/pkg/util/exec"

	"github.com/golang/glog"
)

// tcShaper provides an implementation of the BandwidthShaper interface on Linux using the 'tc' tool.
// In general, using this requires that the caller posses the NET_CAP_ADMIN capability, though if you
// do this within an container, it only requires the NS_CAPABLE capability for manipulations to that
// container's network namespace.
// Uses the hierarchical token bucket queueing discipline (htb), this requires Linux 2.4.20 or newer
// or a custom kernel with that queueing discipline backported.
type tcShaper struct {
	e     exec.Interface
	iface string
}

func NewTCShaper(iface string) BandwidthShaper {
	shaper := &tcShaper{
		e:     exec.New(),
		iface: iface,
	}
	shaper.initializeInterface()
	return shaper
}

func (t *tcShaper) execAndLog(cmdStr string, args ...string) error {
	glog.V(6).Infof("Running: %s %s", cmdStr, strings.Join(args, " "))
	cmd := t.e.Command(cmdStr, args...)
	out, err := cmd.CombinedOutput()
	glog.V(6).Infof("Output from tc: %s", string(out))
	return err
}

func (t *tcShaper) nextClassID() (int, error) {
	data, err := t.e.Command("tc", "class", "show", "dev", t.iface).CombinedOutput()
	if err != nil {
		return -1, err
	}

	scanner := bufio.NewScanner(bytes.NewBuffer(data))
	classes := util.StringSet{}
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		// skip empty lines
		if len(line) == 0 {
			continue
		}
		parts := strings.Split(line, " ")
		// expected tc line:
		// class htb 1:1 root prio 0 rate 1000Kbit ceil 1000Kbit burst 1600b cburst 1600b
		if len(parts) != 14 {
			return -1, fmt.Errorf("unexpected output from tc: %s (%v)", scanner.Text(), parts)
		}
		classes.Insert(parts[2])
	}

	// Make sure it doesn't go forever
	for nextClass := 1; nextClass < 10000; nextClass++ {
		if !classes.Has(fmt.Sprintf("1:%d", nextClass)) {
			return nextClass, nil
		}
	}
	// This should really never happen
	return -1, fmt.Errorf("exhausted class space, please try again")
}

// Convert a CIDR from text to a hex representation
// Strips any masked parts of the IP, so 1.2.3.4/16 becomes hex(1.2.0.0)/ffffffff
func hexCIDR(cidr string) (string, error) {
	ip, ipnet, err := net.ParseCIDR(cidr)
	if err != nil {
		return "", err
	}
	ip = ip.Mask(ipnet.Mask)
	hexIP := hex.EncodeToString([]byte(ip.To4()))
	hexMask := ipnet.Mask.String()
	return hexIP + "/" + hexMask, nil
}

func (t *tcShaper) findCIDRClass(cidr string) (class, handle string, err error) {
	data, err := t.e.Command("tc", "filter", "show", "dev", t.iface).CombinedOutput()
	if err != nil {
		return "", "", err
	}

	hex, err := hexCIDR(cidr)
	if err != nil {
		return "", "", err
	}
	spec := fmt.Sprintf("match %s", hex)

	scanner := bufio.NewScanner(bytes.NewBuffer(data))
	filter := ""
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if len(line) == 0 {
			continue
		}
		if strings.HasPrefix(line, "filter") {
			filter = line
			continue
		}
		if strings.Contains(line, spec) {
			parts := strings.Split(filter, " ")
			// expected tc line:
			// filter parent 1: protocol ip pref 1 u32 fh 800::800 order 2048 key ht 800 bkt 0 flowid 1:1
			if len(parts) != 19 {
				return "", "", fmt.Errorf("unexpected output from tc: %s %d (%v)", filter, len(parts), parts)
			}
			return parts[18], parts[9], nil
		}
	}
	return "", "", fmt.Errorf("Failed to find cidr: %s on interface: %s", cidr, t.iface)
}

func makeKBitString(rsrc resource.Quantity) string {
	return fmt.Sprintf("%dkbit", (rsrc.Value() / 1000))
}

func (t *tcShaper) makeNewClass(rate string) (int, error) {
	class, err := t.nextClassID()
	if err != nil {
		return -1, err
	}
	if err := t.execAndLog("tc", "class", "add", "dev", t.iface, "parent", "1:", "classid", fmt.Sprintf("1:%d", class), "htb", "rate", rate); err != nil {
		return -1, err
	}
	return class, nil
}

func (t *tcShaper) Limit(cidr string, upload, download resource.Quantity) (err error) {
	var downloadClass, uploadClass int
	if downloadClass, err = t.makeNewClass(makeKBitString(download)); err != nil {
		return err
	}
	if uploadClass, err = t.makeNewClass(makeKBitString(upload)); err != nil {
		return err
	}

	if err := t.execAndLog("tc", "filter", "add", "dev", t.iface, "protocol", "ip", "parent", "1:0", "prio", "1", "u32", "match", "ip", "dst", cidr, "flowid", fmt.Sprintf("1:%d", downloadClass)); err != nil {
		return err
	}
	if err := t.execAndLog("tc", "filter", "add", "dev", t.iface, "protocol", "ip", "parent", "1:0", "prio", "1", "u32", "match", "ip", "src", cidr, "flowid", fmt.Sprintf("1:%d", uploadClass)); err != nil {
		return err
	}
	return nil
}

func (t *tcShaper) initializeInterface() error {
	return t.execAndLog("tc", "qdisc", "add", "dev", t.iface, "root", "handle", "1:", "htb", "default", "30")
}

func (t *tcShaper) Reset(cidr string) error {
	class, handle, err := t.findCIDRClass(cidr)
	if err != nil {
		return err
	}
	if err := t.execAndLog("tc", "filter", "del", "dev", t.iface, "parent", "1:", "proto", "ip", "prio", "1", "handle", handle, "u32"); err != nil {
		return err
	}
	return t.execAndLog("tc", "class", "del", "dev", t.iface, "parent", "1:", "classid", class)
}