Full Code of tylertreat/comcast for AI

Repository: tylertreat/comcast
Branch: master
Commit: 145d02155cff
Files: 13
Total size: 52.6 KB

Directory structure:
gitextract_m1qezx1i/

├── .gitignore
├── .travis.yml
├── LICENSE
├── Makefile
├── README.md
├── comcast.go
├── go.mod
└── throttler/
    ├── ipfw.go
    ├── pfctl.go
    ├── pfctl_test.go
    ├── tc.go
    ├── tc_test.go
    └── throttler.go

================================================
FILE CONTENTS
================================================

================================================
FILE: .gitignore
================================================
# Compiled Object files, Static and Dynamic libs (Shared Objects)
*.o
*.a
*.so

# Folders
_obj
_test

# Architecture specific extensions/prefixes
*.[568vq]
[568vq].out

*.cgo1.go
*.cgo2.c
_cgo_defun.c
_cgo_gotypes.go
_cgo_export.*

_testmain.go

*.exe
*.test
*.prof


================================================
FILE: .travis.yml
================================================
language: golang

go:
  - 1.8.x
  - 1.9.x
  - 1.10.x
  - 1.11.x

script:
  - go test -v ./throttler/...


================================================
FILE: LICENSE
================================================
Apache License
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                        http://www.apache.org/licenses/

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================================================
FILE: Makefile
================================================
BINARY="comcast"
VERSION=1.0.0
BUILD=`date +%FT%T%z`
DIR=bin

PACKAGES=`go list ./... | grep -v /vendor/`
VETPACKAGES=`go list ./... | grep -v /vendor/ | grep -v /examples/`
GOFILES=`find . -name "*.go" -type f -not -path "./vendor/*"`

default:
	@mkdir ${DIR}
	@go build -o ${DIR}/${BINARY} -tags=jsoniter

list:
	@echo ${PACKAGES}
	@echo ${VETPACKAGES}
	@echo ${GOFILES}

fmt:
	@gofmt -s -w ${GOFILES}

fmt-check:
	@diff=?(gofmt -s -d $(GOFILES)); \
	if [ -n "$$diff" ]; then \
		echo "Please run 'make fmt' and commit the result:"; \
		echo "$${diff}"; \
		exit 1; \
	fi;

install:
	@govendor sync -v

test:
	@go test -cpu=1,2,4 -v -tags integration ./...

vet:
	@go vet $(VETPACKAGES)


clean:
	@if [ -f${DIR}/${BINARY} ] ; then rm -rf ${DIR} ; fi

.PHONY: default fmt fmt-check install test vet docker clean




================================================
FILE: README.md
================================================
# Comcast

Testing distributed systems under hard failures like network partitions and instance termination is critical, but it's also important we test them under [less catastrophic conditions](http://www.bravenewgeek.com/sometimes-kill-9-isnt-enough/) because this is what they most often experience. Comcast is a tool designed to simulate common network problems like latency, bandwidth restrictions, and dropped/reordered/corrupted packets.

It works by wrapping up some system tools in a portable(ish) way. On BSD-derived systems such as OSX, we use tools like `ipfw` and `pfctl` to inject failure. On Linux, we use `iptables` and `tc`. Comcast is merely a thin wrapper around these controls. Windows support may be possible with `wipfw` or even the native network stack, but this has not yet been implemented in Comcast and may be at a later date.

## Installation

```
$ go install github.com/tylertreat/comcast@latest
```

### Path addition may be needed

In unix-like systems, after installing comcast with go, it may be needed to add it to the `PATH`. Go installs by default in `$HOME/go/bin`.
```
$ export PATH=$PATH:$HOME/go/bin
```

## Usage

On Linux, Comcast supports several options: device, latency, target/default bandwidth, packet loss, protocol, and port number.

```
$ comcast --device=eth0 --latency=250 --target-bw=1000 --default-bw=1000000 --packet-loss=10% --target-addr=8.8.8.8,10.0.0.0/24 --target-proto=tcp,udp,icmp --target-port=80,22,1000:2000
```

On OSX, Comcast will check for `pfctl` support (as of Yosemite), which supports the same options as above. If `pfctl` is not available, it will use `ipfw` instead, which supports device, latency, target bandwidth, and packet-loss options.

On BSD (with `ipfw`), Comcast currently supports only: device, latency, target bandwidth, and packet loss. 

```
$ comcast --device=eth0 --latency=250 --target-bw=1000 --packet-loss=10%
```

This will add 250ms of latency, limit bandwidth to 1Mbps, and drop 10% of packets to the targetted (on Linux) destination addresses using the specified protocols on the specified port numbers (slow lane). The default bandwidth specified will apply to all egress traffic (fast lane). To turn this off, run the following:

```
$ comcast --stop
```

By default, comcast will determine the system commands to execute, log them to stdout, and execute them. The `--dry-run` flag will skip execution.

## I don't trust you, this code sucks, I hate Go, etc.

If you don't like running code that executes shell commands for you (despite it being open source, so you can read it and change the code) or want finer-grained control, you can run them directly instead. Read the man pages on these things for more details.

### Linux

On Linux, you can use `iptables` to drop incoming and outgoing packets.

```
$ iptables -A INPUT -m statistic --mode random --probability 0.1 -j DROP
$ iptables -A OUTPUT -m statistic --mode random --probability 0.1 -j DROP
```

Alternatively, you can use `tc` which supports some additional options.

```
$ tc qdisc add dev eth0 root netem delay 50ms 20ms distribution normal
$ tc qdisc change dev eth0 root netem reorder 0.02 duplicate 0.05 corrupt 0.01
```

To reset:

```
$ tc qdisc del dev eth0 root netem
```

### BSD/OSX

To shape traffic in BSD-derived systems, create an `ipfw` pipe and configure it. You can control incoming and outgoing traffic separately for any specific host or network.

```
$ ipfw add 1 pipe 1 ip from me to any
$ ipfw add 2 pipe 1 ip from any to me
$ ipfw pipe 1 config delay 500ms bw 1Mbit/s plr 0.1
```

To reset:

```
$ ipfw delete 1
```

*Note: `ipfw` was removed in OSX Yosemite in favor of `pfctl`.*

## Network Condition Profiles

Here's a list of network conditions with values that you can plug into Comcast. Please add any more that you may come across.

Name | Latency | Bandwidth | Packet-loss
:-- | --: | --: | --:
GPRS (good) | 500 | 50 | 2
EDGE (good) | 300 | 250 | 1.5
3G/HSDPA (good) | 250 | 750 | 1.5
DIAL-UP (good) | 185 | 40 | 2
DSL (poor) | 70 | 2000 | 2
DSL (good) | 40 | 8000 | 0.5
WIFI (good) | 40 | 30000 | 0.2
Starlink | 20 | - | 2.5


================================================
FILE: comcast.go
================================================
package main

import (
	"flag"
	"fmt"
	"net"
	"os"
	"strconv"
	"strings"

	"github.com/tylertreat/comcast/throttler"
)

const version = "1.0.0"

func main() {
	// TODO: Add support for other options like packet reordering, duplication, etc.
	var (
		device      = flag.String("device", "", "Interface (device) to use (defaults to eth0 where applicable)")
		stop        = flag.Bool("stop", false, "Stop packet controls")
		latency     = flag.Int("latency", -1, "Latency to add in ms")
		targetbw    = flag.Int("target-bw", -1, "Target bandwidth limit in kbit/s (slow-lane)")
		defaultbw   = flag.Int("default-bw", -1, "Default bandwidth limit in kbit/s (fast-lane)")
		packetLoss  = flag.String("packet-loss", "0", "Packet loss percentage (e.g. 0.1%)")
		targetaddr  = flag.String("target-addr", "", "Target addresses, (e.g. 10.0.0.1 or 10.0.0.0/24 or 10.0.0.1,192.168.0.0/24 or 2001:db8:a::123)")
		targetport  = flag.String("target-port", "", "Target port(s) (e.g. 80 or 1:65535 or 22,80,443,1000:1010)")
		targetproto = flag.String("target-proto", "tcp,udp,icmp", "Target protocol TCP/UDP (e.g. tcp or tcp,udp or icmp)")
		dryrun      = flag.Bool("dry-run", false, "Specifies whether or not to actually commit the rule changes")
		//icmptype  = flag.String("icmp-type", "", "icmp message type (e.g. reply or reply,request)") //TODO: Maybe later :3
		vers = flag.Bool("version", false, "Print Comcast's version")
	)
	flag.Parse()

	if *vers {
		fmt.Printf("Comcast version %s\n", version)
		return
	}

	targetIPv4, targetIPv6 := parseAddrs(*targetaddr)

	throttler.Run(&throttler.Config{
		Device:           *device,
		Stop:             *stop,
		Latency:          *latency,
		TargetBandwidth:  *targetbw,
		DefaultBandwidth: *defaultbw,
		PacketLoss:       parseLoss(*packetLoss),
		TargetIps:        targetIPv4,
		TargetIps6:       targetIPv6,
		TargetPorts:      parsePorts(*targetport),
		TargetProtos:     parseProtos(*targetproto),
		DryRun:           *dryrun,
	})
}

func parseLoss(loss string) float64 {
	val := loss
	if strings.Contains(loss, "%") {
		val = loss[:len(loss)-1]
	}
	l, err := strconv.ParseFloat(val, 64)
	if err != nil {
		fmt.Println("Incorrectly specified packet loss:", loss)
		os.Exit(1)
	}
	return l
}

func parseAddrs(addrs string) ([]string, []string) {
	adrs := strings.Split(addrs, ",")
	parsedIPv4 := []string{}
	parsedIPv6 := []string{}

	if addrs != "" {
		for _, adr := range adrs {
			ip := net.ParseIP(adr)
			if ip != nil {
				if ip.To4() != nil {
					parsedIPv4 = append(parsedIPv4, adr)
				} else {
					parsedIPv6 = append(parsedIPv6, adr)
				}
			} else { //Not a valid single IP, could it be a CIDR?
				parsedIP, net, err := net.ParseCIDR(adr)
				if err == nil {
					if parsedIP.To4() != nil {
						parsedIPv4 = append(parsedIPv4, net.String())
					} else {
						parsedIPv6 = append(parsedIPv6, net.String())
					}
				} else {
					fmt.Println("Incorrectly specified target IP or CIDR:", adr)
					os.Exit(1)
				}
			}
		}
	}

	return parsedIPv4, parsedIPv6
}

func parsePorts(ports string) []string {
	prts := strings.Split(ports, ",")
	parsed := []string{}

	if ports != "" {
		for _, prt := range prts {
			if strings.Contains(prt, ":") {
				if validRange(prt) {
					parsed = append(parsed, prt)
				} else {
					fmt.Println("Incorrectly specified port range:", prt)
					os.Exit(1)
				}
			} else { //Isn't a range, check if just a single port
				if validPort(prt) {
					parsed = append(parsed, prt)
				} else {
					fmt.Println("Incorrectly specified port:", prt)
					os.Exit(1)
				}
			}
		}
	}

	return parsed
}

func parsePort(port string) int {
	prt, err := strconv.Atoi(port)
	if err != nil {
		return 0
	}

	return prt
}

func validPort(port string) bool {
	prt := parsePort(port)
	return prt > 0 && prt < 65536
}

func validRange(ports string) bool {
	pr := strings.Split(ports, ":")

	if len(pr) == 2 {
		if !validPort(pr[0]) || !validPort(pr[1]) {
			return false
		}

		if portHigher(pr[0], pr[1]) {
			return false
		}
	} else {
		return false
	}

	return true
}

func portHigher(prt1, prt2 string) bool {
	p1 := parsePort(prt1)
	p2 := parsePort(prt2)

	return p1 > p2
}

func parseProtos(protos string) []string {
	ptcs := strings.Split(protos, ",")
	parsed := []string{}

	if protos != "" {
		for _, ptc := range ptcs {
			p := strings.ToLower(ptc)
			if p == "udp" ||
				p == "tcp" ||
				p == "icmp" {
				parsed = append(parsed, p)
			} else {
				fmt.Println("Incorrectly specified protocol:", p)
				os.Exit(1)
			}
		}
	}

	return parsed
}


================================================
FILE: go.mod
================================================
module github.com/tylertreat/comcast

go 1.15

require github.com/tylertreat/comcast v1.0.1


================================================
FILE: throttler/ipfw.go
================================================
package throttler

import (
	"strconv"
)

const (
	ipfwAddPipe  = `sudo ipfw add 1 pipe 1 ip from any to any via `
	ipfwTeardown = `sudo ipfw delete 1`
	ipfwConfig   = `sudo ipfw pipe 1 config`
	ipfwExists   = `sudo ipfw list | grep "pipe 1"`
	ipfwCheck    = `sudo ipfw list`
)

type ipfwThrottler struct {
	c commander
}

func (i *ipfwThrottler) setup(c *Config) error {
	cmd := ipfwAddPipe + c.Device
	err := i.c.execute(cmd)
	if err != nil {
		return err
	}

	configCmd := i.buildConfigCommand(c)
	err = i.c.execute(configCmd)
	return err
}

func (i *ipfwThrottler) teardown(_ *Config) error {
	err := i.c.execute(ipfwTeardown)
	return err
}

func (i *ipfwThrottler) exists() bool {
	if dry {
		return false
	}
	err := i.c.execute(ipfwExists)
	return err == nil
}

func (i *ipfwThrottler) check() string {
	return ipfwCheck
}

func (i *ipfwThrottler) buildConfigCommand(c *Config) string {
	cmd := ipfwConfig

	if c.Latency > 0 {
		cmd = cmd + " delay " + strconv.Itoa(c.Latency) + "ms"
	}

	if c.TargetBandwidth > 0 {
		cmd = cmd + " bw " + strconv.Itoa(c.TargetBandwidth) + "Kbit/s"
	}

	if c.PacketLoss > 0 {
		cmd = cmd + " plr " + strconv.FormatFloat(c.PacketLoss/100, 'f', 4, 64)
	}

	return cmd
}


================================================
FILE: throttler/pfctl.go
================================================
package throttler

import (
	"fmt"
	"strconv"
	"strings"
)

const (
	// TODO: use printf in favour of echo due to shell portability issues
	pfctlCreateAnchor    = `(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`
	pfctlTeardown        = `sudo pfctl -f /etc/pf.conf`
	dnctl                = `sudo dnctl pipe 1 config`
	pfctlCreateDummynet  = `echo $'dummynet in on %s all pipe 1'`
	pfctlExecuteInline   = `%s | sudo pfctl -a mop -f - `
	pfctlEnableFirewall  = `sudo pfctl -E`
	pfctlEnableFwRegex   = `pf enabled`
	pfctlDisableFirewall = `sudo pfctl -d`
	pfctlDisbleFwRegex   = `pf disabled`
	pfctlIsEnabled       = `sudo pfctl -sa | grep -i enabled`
	dnctlIsConfigured    = `sudo dnctl show`
	pfctlIsEnabledRegex  = `Enabled`
	dnctlTeardown        = `sudo dnctl -q flush`
)

type pfctlThrottler struct {
	c commander
}

// Execute a command and check that any matching line in the result contains 'match'
func (i *pfctlThrottler) executeAndParse(cmd string, match string) bool {
	lines, err := i.c.executeGetLines(cmd)

	if err != nil {
		return false
	}

	for _, line := range lines {
		if strings.Contains(line, match) {
			return true
		}
	}
	return false
}

func (i *pfctlThrottler) setup(c *Config) error {
	// Enable firewall
	err := i.c.execute(pfctlEnableFirewall)
	if err != nil {
		return fmt.Errorf("Could not enable firewall using: `%s`. Error: %s", pfctlEnableFirewall, err.Error())
	}

	// Add the dummynet and anchor
	err = i.c.execute(pfctlCreateAnchor)
	if err != nil {
		return fmt.Errorf("Could not create anchor rule for dummynet using: `%s`. Error: %s", pfctlCreateAnchor, err.Error())
	}

	// Add 'execute' portion of the command
	input := fmt.Sprintf(pfctlCreateDummynet, c.Device)
	cmd := fmt.Sprintf(pfctlExecuteInline, input)

	err = i.c.execute(cmd)
	if err != nil {
		return fmt.Errorf("Could not create dummynet using: `%s`. Error: %s", input, err.Error())
	}

	// Apply the shaping etc.
	for _, cmd := range i.buildConfigCommand(c) {
		err = i.c.execute(cmd)
		if err != nil {
			return err
		}
	}

	return nil
}

func (i *pfctlThrottler) teardown(_ *Config) error {

	// Reset firewall rules, leave it running
	err := i.c.execute(pfctlTeardown)
	if err != nil {
		return fmt.Errorf("Could not remove firewall rules using: `%s`. Error: %s", pfctlTeardown, err.Error())
	}

	// Turn off the firewall, discarding any rules
	err = i.c.execute(pfctlDisableFirewall)
	if err != nil {
		return fmt.Errorf("Could not disable firewall using: `%s`. Error: %s", pfctlDisableFirewall, err.Error())
	}

	// Disable dnctl rules
	err = i.c.execute(dnctlTeardown)
	if err != nil {
		return fmt.Errorf("Could not disable dnctl rules using: `%s`. Error: %s", dnctlTeardown, err.Error())
	}

	return nil
}

func (i *pfctlThrottler) isFirewallRunning() bool {
	return i.executeAndParse(pfctlIsEnabled, pfctlIsEnabledRegex)
}
func (i *pfctlThrottler) exists() bool {
	if dry {
		return false
	}
	return i.executeAndParse(dnctlIsConfigured, "port") || i.isFirewallRunning()
}

func (i *pfctlThrottler) check() string {
	return pfctlIsEnabled
}

func addProtosToCommands(cmds []string, protos []string) []string {
	commands := make([]string, 0)

	for _, cmd := range cmds {
		for _, proto := range protos {
			commands = append(commands, fmt.Sprintf("%s proto %s", cmd, proto))
		}
	}

	return commands
}
func addPortsToCommand(cmd string, ports []string) []string {
	commands := make([]string, 0)

	for _, port := range ports {
		commands = append(commands, fmt.Sprintf("%s dst-port %s", cmd, port))
		commands = append(commands, fmt.Sprintf("%s src-port %s", cmd, port))
	}

	return commands
}

// Takes care of the annoying differences between ipv4 and ipv6
func addIpsAndProtoToCommands(ipVersion int, cmds []string, ips []string, protos []string) []string {

	commands := make([]string, 0)

	for _, cmd := range cmds {
		for _, ip := range ips {
			srcIpFlag := "src-ip"
			dstIpFlag := "dst-ip"
			if ipVersion == 6 {
				srcIpFlag = "src-ip6"
				dstIpFlag = "dst-ip6"
			}

			commands = append(commands, addProtoToCommands(ipVersion, fmt.Sprintf("%s %s %s", cmd, srcIpFlag, ip), protos)...)
			commands = append(commands, addProtoToCommands(ipVersion, fmt.Sprintf("%s %s %s", cmd, dstIpFlag, ip), protos)...)
		}
	}

	return commands
}

func addProtoToCommands(ipVersion int, cmd string, protos []string) []string {
	commands := make([]string, 0)
	for _, proto := range protos {
		if ipVersion == 6 {
			if proto == "icmp" {
				proto = "ipv6-icmp"
			}
		}
		commands = append(commands, fmt.Sprintf("%s proto %s", cmd, proto))
	}
	return commands
}

func (i *pfctlThrottler) buildConfigCommand(c *Config) []string {

	cmd := dnctl

	// Add all non tcp version dependent stuff first...
	if c.Latency > 0 {
		cmd = cmd + " delay " + strconv.Itoa(c.Latency) + "ms"
	}

	if c.TargetBandwidth > 0 {
		cmd = cmd + " bw " + strconv.Itoa(c.TargetBandwidth) + "Kbit/s"
	}

	if c.PacketLoss > 0 {
		cmd = cmd + " plr " + strconv.FormatFloat(c.PacketLoss/100, 'f', 4, 64)
	}

	// Add Mask keyword if we have pipe qualifiers
	if len(c.TargetPorts) > 0 || len(c.TargetProtos) > 0 || len(c.TargetIps) > 0 || len(c.TargetIps6) > 0 {
		cmd = cmd + " mask "
	}

	// Expand commands with ports
	commands := []string{cmd}

	if len(c.TargetPorts) > 0 {
		commands = addPortsToCommand(cmd, c.TargetPorts)
	}

	if len(c.TargetIps) == 0 && len(c.TargetIps6) == 0 {
		if len(c.TargetProtos) > 0 {
			return addProtosToCommands(commands, c.TargetProtos)
		}
		return commands
	}

	// create and combine the ipv4 and ipv6 IPs with the protocol version specific keywords
	return append(addIpsAndProtoToCommands(4, commands, c.TargetIps, c.TargetProtos), addIpsAndProtoToCommands(6, commands, c.TargetIps6, c.TargetProtos)...)
}


================================================
FILE: throttler/pfctl_test.go
================================================
package throttler

import (
	"testing"
)

func TestPfctlDefaultConfigCommand(t *testing.T) {

	r := newCmdRecorder()
	th := &pfctlThrottler{r}
	c := defaultTestConfig
	c.PacketLoss = 0
	c.TargetIps = []string{}
	c.TargetIps6 = []string{}
	c.TargetBandwidth = -1
	c.TargetPorts = []string{}
	c.TargetProtos = []string{"tcp,udp,icmp"}

	th.setup(&c)
	r.verifyCommands(t, []string{
		"sudo pfctl -E",
		`(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`,
		`echo $'dummynet in all pipe 1' | sudo pfctl -a mop -f - `,
		`sudo dnctl pipe 1 config mask  proto tcp,udp,icmp`,
	})
}

func TestPfctlThrottleOnlyConfigCommand(t *testing.T) {

	var c = Config{
		Device:           "eth0",
		Stop:             false,
		Latency:          -1,
		TargetBandwidth:  -1,
		DefaultBandwidth: 20000,
		PacketLoss:       0.1,
	}
	r := newCmdRecorder()
	th := &pfctlThrottler{r}

	th.setup(&c)
	r.verifyCommands(t, []string{
		"sudo pfctl -E",
		`(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`,
		`echo $'dummynet in all pipe 1' | sudo pfctl -a mop -f - `,
		`sudo dnctl pipe 1 config plr 0.0010`,
	})
}
func TestPfctlNoIPThrottleConfigCommand(t *testing.T) {

	var c = Config{
		Device:           "eth0",
		Stop:             false,
		Latency:          -1,
		TargetBandwidth:  -1,
		DefaultBandwidth: 20000,
		PacketLoss:       0.1,
		TargetProtos:     []string{"tcp"},
	}
	r := newCmdRecorder()
	th := &pfctlThrottler{r}

	th.setup(&c)
	r.verifyCommands(t, []string{
		"sudo pfctl -E",
		`(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`,
		`echo $'dummynet in all pipe 1' | sudo pfctl -a mop -f - `,
		`sudo dnctl pipe 1 config plr 0.0010 mask  proto tcp`,
	})
}

func TestPfctlPacketSetup(t *testing.T) {

	r := newCmdRecorder()
	th := &pfctlThrottler{r}
	c := defaultTestConfig
	c.PacketLoss = 0.5

	th.setup(&c)
	r.verifyCommands(t, []string{
		"sudo pfctl -E",
		`(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`,
		`echo $'dummynet in all pipe 1' | sudo pfctl -a mop -f - `,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 src-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 dst-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 src-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 dst-ip 10.10.10.10 proto tcp`,
	})
}

func TestPfctlProtoSetup(t *testing.T) {

	r := newCmdRecorder()
	th := &pfctlThrottler{r}
	c := defaultTestConfig
	c.PacketLoss = 0.5
	c.TargetProtos = []string{"tcp", "udp", "icmp"}

	th.setup(&c)
	r.verifyCommands(t, []string{
		"sudo pfctl -E",
		`(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`,
		`echo $'dummynet in all pipe 1' | sudo pfctl -a mop -f - `,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 src-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 src-ip 10.10.10.10 proto udp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 src-ip 10.10.10.10 proto icmp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 dst-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 dst-ip 10.10.10.10 proto udp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  dst-port 80 dst-ip 10.10.10.10 proto icmp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 src-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 src-ip 10.10.10.10 proto udp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 src-ip 10.10.10.10 proto icmp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 dst-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 dst-ip 10.10.10.10 proto udp`,
		`sudo dnctl pipe 1 config plr 0.0050 mask  src-port 80 dst-ip 10.10.10.10 proto icmp`,
	})
}

func TestPfctlMultiplePortsAndIps(t *testing.T) {
	r := newCmdRecorder()
	th := &pfctlThrottler{r}
	cfg := defaultTestConfig
	cfg.TargetIps = []string{"1.1.1.1", "2.2.2.2"}
	cfg.TargetPorts = []string{"80", "8080"}
	cfg.TargetProtos = []string{"tcp"}
	th.setup(&cfg)
	r.verifyCommands(t, []string{
		"sudo pfctl -E",
		`(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`,
		`echo $'dummynet in all pipe 1' | sudo pfctl -a mop -f - `,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 80 src-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 80 dst-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 80 src-ip 2.2.2.2 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 80 dst-ip 2.2.2.2 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 80 src-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 80 dst-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 80 src-ip 2.2.2.2 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 80 dst-ip 2.2.2.2 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 8080 src-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 8080 dst-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 8080 src-ip 2.2.2.2 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  dst-port 8080 dst-ip 2.2.2.2 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 8080 src-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 8080 dst-ip 1.1.1.1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 8080 src-ip 2.2.2.2 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0010 mask  src-port 8080 dst-ip 2.2.2.2 proto tcp`,
	})
}

func TestPfctlMixedIPv6Setup(t *testing.T) {
	r := newCmdRecorder()
	th := &pfctlThrottler{r}
	cfg := defaultTestConfig
	cfg.TargetProtos = []string{"icmp", "tcp"}
	cfg.PacketLoss = 0.2
	cfg.TargetIps6 = []string{"2001:db8::1"}
	th.setup(&cfg)
	r.verifyCommands(t, []string{
		`sudo pfctl -E`,
		`(cat /etc/pf.conf && echo "dummynet-anchor \"mop\"" && echo "anchor \"mop\"") | sudo pfctl -f -`,
		`echo $'dummynet in all pipe 1' | sudo pfctl -a mop -f - `,

		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 src-ip 10.10.10.10 proto icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 src-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 dst-ip 10.10.10.10 proto icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 dst-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 src-ip 10.10.10.10 proto icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 src-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 dst-ip 10.10.10.10 proto icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 dst-ip 10.10.10.10 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 src-ip6 2001:db8::1 proto ipv6-icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 src-ip6 2001:db8::1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 dst-ip6 2001:db8::1 proto ipv6-icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  dst-port 80 dst-ip6 2001:db8::1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 src-ip6 2001:db8::1 proto ipv6-icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 src-ip6 2001:db8::1 proto tcp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 dst-ip6 2001:db8::1 proto ipv6-icmp`,
		`sudo dnctl pipe 1 config plr 0.0020 mask  src-port 80 dst-ip6 2001:db8::1 proto tcp`,
	})
}


================================================
FILE: throttler/tc.go
================================================
package throttler

import (
	"fmt"
	"os/exec"
	"strconv"
	"strings"
	"syscall"
)

const (
	tcRootQDisc    = `dev %s handle 10: root`
	tcRootExtra    = `default 1`
	tcDefaultClass = `dev %s parent 10: classid 10:1`
	tcTargetClass  = `dev %s parent 10: classid 10:10`
	tcNetemRule    = `dev %s parent 10:10 handle 100:`
	tcRate         = `rate %vkbit`
	tcDelay        = `delay %vms`
	tcLoss         = `loss %v%%`
	tcAddClass     = `sudo tc class add`
	tcDelClass     = `sudo tc class del`
	tcAddQDisc     = `sudo tc qdisc add`
	tcDelQDisc     = `sudo tc qdisc del`
	iptAddTarget   = `sudo %s -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10`
	iptDelTarget   = `sudo %s -D POSTROUTING -t mangle -j CLASSIFY --set-class 10:10`
	iptDestIP      = `-d %s`
	iptProto       = `-p %s`
	iptDestPorts   = `--match multiport --dports %s`
	iptDestPort    = `--dport %s`
	iptDelSearch   = `class 0010:0010`
	iptList        = `sudo %s -S -t mangle`
	ip4Tables      = `iptables`
	ip6Tables      = `ip6tables`
	iptDel         = `sudo %s -t mangle -D`
	tcExists       = `sudo tc qdisc show | grep "netem"`
	tcCheck        = `sudo tc -s qdisc`
)

type tcThrottler struct {
	c commander
}

func (t *tcThrottler) setup(cfg *Config) error {
	err := addRootQDisc(cfg, t.c) //The root node to append the filters
	if err != nil {
		return err
	}

	err = addDefaultClass(cfg, t.c) //The default class for all traffic that isn't classified
	if err != nil {
		return err
	}

	err = addTargetClass(cfg, t.c) //The class that the network emulator rule is assigned
	if err != nil {
		return err
	}

	err = addNetemRule(cfg, t.c) //The network emulator rule that contains the desired behavior
	if err != nil {
		return err
	}

	return addIptablesRules(cfg, t.c) //The network emulator rule that contains the desired behavior
}

func addRootQDisc(cfg *Config, c commander) error {
	//Add the root QDisc
	root := fmt.Sprintf(tcRootQDisc, cfg.Device)
	strs := []string{tcAddQDisc, root, "htb", tcRootExtra}
	cmd := strings.Join(strs, " ")

	return c.execute(cmd)
}

func addDefaultClass(cfg *Config, c commander) error {
	//Add the default Class
	def := fmt.Sprintf(tcDefaultClass, cfg.Device)
	rate := ""

	if cfg.DefaultBandwidth > 0 {
		rate = fmt.Sprintf(tcRate, cfg.DefaultBandwidth)
	} else {
		rate = fmt.Sprintf(tcRate, 1000000)
	}

	strs := []string{tcAddClass, def, "htb", rate}
	cmd := strings.Join(strs, " ")

	return c.execute(cmd)
}

func addTargetClass(cfg *Config, c commander) error {
	//Add the target Class
	tar := fmt.Sprintf(tcTargetClass, cfg.Device)
	rate := ""

	if cfg.TargetBandwidth > -1 {
		rate = fmt.Sprintf(tcRate, cfg.TargetBandwidth)
	} else {
		rate = fmt.Sprintf(tcRate, 1000000)
	}

	strs := []string{tcAddClass, tar, "htb", rate}
	cmd := strings.Join(strs, " ")

	return c.execute(cmd)
}

func addNetemRule(cfg *Config, c commander) error {
	//Add the Network Emulator rule
	net := fmt.Sprintf(tcNetemRule, cfg.Device)
	strs := []string{tcAddQDisc, net, "netem"}

	if cfg.Latency > 0 {
		strs = append(strs, fmt.Sprintf(tcDelay, cfg.Latency))
	}

	if cfg.TargetBandwidth > -1 {
		strs = append(strs, fmt.Sprintf(tcRate, cfg.TargetBandwidth))
	}

	if cfg.PacketLoss > 0 {
		strs = append(strs, fmt.Sprintf(tcLoss, strconv.FormatFloat(cfg.PacketLoss, 'f', 2, 64)))
	}

	cmd := strings.Join(strs, " ")

	return c.execute(cmd)
}

func addIptablesRules(cfg *Config, c commander) error {
	var err error
	if len(cfg.TargetIps) == 0 && len(cfg.TargetIps6) == 0 {
		if err == nil {
			err = addIptablesRulesForAddrs(cfg, c, ip4Tables, cfg.TargetIps)
		}
		if err == nil {
			err = addIptablesRulesForAddrs(cfg, c, ip6Tables, cfg.TargetIps6)
		}
		return err
	}
	if err == nil && len(cfg.TargetIps) > 0 {
		err = addIptablesRulesForAddrs(cfg, c, ip4Tables, cfg.TargetIps)
	}
	if err == nil && len(cfg.TargetIps6) > 0 {
		err = addIptablesRulesForAddrs(cfg, c, ip6Tables, cfg.TargetIps6)
	}
	return err
}

func addIptablesRulesForAddrs(cfg *Config, c commander, command string, addrs []string) error {
	rules := []string{}
	ports := ""

	if len(cfg.TargetPorts) > 0 {
		if len(cfg.TargetPorts) > 1 {
			prts := strings.Join(cfg.TargetPorts, ",")
			ports = fmt.Sprintf(iptDestPorts, prts)
		} else {
			ports = fmt.Sprintf(iptDestPort, cfg.TargetPorts[0])
		}
	}

	addTargetCmd := fmt.Sprintf(iptAddTarget, command)

	if len(cfg.TargetProtos) > 0 {
		for _, ptc := range cfg.TargetProtos {
			proto := fmt.Sprintf(iptProto, ptc)
			rule := addTargetCmd + " " + proto

			if ptc != "icmp" {
				if ports != "" {
					rule += " " + ports
				}
			}

			rules = append(rules, rule)
		}
	} else {
		rules = []string{addTargetCmd}
	}

	if len(addrs) > 0 {
		iprules := []string{}
		for _, ip := range addrs {
			dest := fmt.Sprintf(iptDestIP, ip)
			if len(rules) > 0 {
				for _, rule := range rules {
					r := rule + " " + dest
					iprules = append(iprules, r)
				}
			} else {
				iprules = append(iprules, dest)
			}
		}
		if len(iprules) > 0 {
			rules = iprules
		}
	}

	for _, rule := range rules {
		if err := c.execute(rule); err != nil {
			return err
		}
	}

	return nil
}

func (t *tcThrottler) teardown(cfg *Config) error {
	if err := delIptablesRules(cfg, t.c); err != nil {
		return err
	}

	// The root node to append the filters
	if err := delRootQDisc(cfg, t.c); err != nil {
		return err
	}
	return nil
}

func delIptablesRules(cfg *Config, c commander) error {
	iptablesCommands := []string{ip4Tables, ip6Tables}

	for _, iptablesCommand := range iptablesCommands {
		if !c.commandExists(iptablesCommand) {
			continue
		}
		lines, err := c.executeGetLines(fmt.Sprintf(iptList, iptablesCommand))
		if err != nil {
			// ignore exit code 3 from iptables, which might happen if the system
			// has the ip6tables command, but no IPv6 capabilities
			werr, ok := err.(*exec.ExitError)
			if !ok {
				return err
			}
			status, ok := werr.Sys().(syscall.WaitStatus)
			if !ok {
				return err
			}
			if status.ExitStatus() == 3 {
				continue
			}
			return err
		}

		delCmdPrefix := fmt.Sprintf(iptDel, iptablesCommand)

		for _, line := range lines {
			if strings.Contains(line, iptDelSearch) {
				cmd := strings.Replace(line, "-A", delCmdPrefix, 1)
				err = c.execute(cmd)
				if err != nil {
					return err
				}
			}
		}
	}
	return nil
}

func delRootQDisc(cfg *Config, c commander) error {
	//Delete the root QDisc
	root := fmt.Sprintf(tcRootQDisc, cfg.Device)

	strs := []string{tcDelQDisc, root}
	cmd := strings.Join(strs, " ")

	return c.execute(cmd)
}

func (t *tcThrottler) exists() bool {
	if dry {
		return false
	}
	err := t.c.execute(tcExists)
	return err == nil
}

func (t *tcThrottler) check() string {
	return tcCheck
}


================================================
FILE: throttler/tc_test.go
================================================
package throttler

import (
	"testing"
)

type cmdRecorder struct {
	commands     []string
	responses    map[string][]string
	cmdBlackList []string
}

func newCmdRecorder() *cmdRecorder {
	return &cmdRecorder{[]string{}, map[string][]string{}, []string{}}
}

func (r *cmdRecorder) execute(cmd string) error {
	r.commands = append(r.commands, cmd)
	return nil
}

func (r *cmdRecorder) executeGetLines(cmd string) ([]string, error) {
	r.execute(cmd)
	if responses, found := r.responses[cmd]; found {
		return responses, nil
	}
	return []string{}, nil
}

func (r *cmdRecorder) commandExists(cmd string) bool {
	for _, blackListed := range r.cmdBlackList {
		if blackListed == cmd {
			return false
		}
	}
	return true
}

func (r *cmdRecorder) verifyCommands(t *testing.T, expected []string) {
	if len(expected) != len(r.commands) {
		for i, cmd := range expected {
			t.Logf("Expected (%d): %s", i, cmd)
		}
		for i, cmd := range r.commands {
			t.Logf("Actual   (%d): %s", i, cmd)
		}

		t.Fatalf("Expected to see %d commands, got %d", len(expected), len(r.commands))
	}

	for i, cmd := range expected {
		if actual := r.commands[i]; actual != cmd {
			t.Fatalf("Expected to see command `%s`, got `%s`", cmd, actual)
		}
	}
}

var defaultTestConfig = Config{
	Device:           "eth0",
	Stop:             false,
	Latency:          -1,
	TargetBandwidth:  -1,
	DefaultBandwidth: 20000,
	PacketLoss:       0.1,
	TargetIps:        []string{"10.10.10.10"},
	TargetPorts:      []string{"80"},
	TargetProtos:     []string{"tcp"},
	DryRun:           false,
}

func TestTcPacketLossSetup(t *testing.T) {
	r := newCmdRecorder()
	th := &tcThrottler{r}
	cfg := defaultTestConfig
	cfg.Device = "eth1"
	cfg.PacketLoss = 0.2
	th.setup(&cfg)
	r.verifyCommands(t, []string{
		"sudo tc qdisc add dev eth1 handle 10: root htb default 1",
		"sudo tc class add dev eth1 parent 10: classid 10:1 htb rate 20000kbit",
		"sudo tc class add dev eth1 parent 10: classid 10:10 htb rate 1000000kbit",
		"sudo tc qdisc add dev eth1 parent 10:10 handle 100: netem loss 0.20%",
		"sudo iptables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10 -p tcp --dport 80 -d 10.10.10.10",
	})
}

func TestTcWildcardIps(t *testing.T) {
	r := newCmdRecorder()
	th := &tcThrottler{r}
	cfg := defaultTestConfig
	cfg.TargetIps = []string{}
	cfg.TargetPorts = []string{}
	cfg.TargetProtos = []string{}
	cfg.PacketLoss = -1
	th.setup(&cfg)
	r.verifyCommands(t, []string{
		"sudo tc qdisc add dev eth0 handle 10: root htb default 1",
		"sudo tc class add dev eth0 parent 10: classid 10:1 htb rate 20000kbit",
		"sudo tc class add dev eth0 parent 10: classid 10:10 htb rate 1000000kbit",
		"sudo tc qdisc add dev eth0 parent 10:10 handle 100: netem",
		"sudo iptables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10",
		"sudo ip6tables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10",
	})
}

func TestTcMultiplePortsAndIps(t *testing.T) {
	r := newCmdRecorder()
	th := &tcThrottler{r}
	cfg := defaultTestConfig
	cfg.TargetIps = []string{"1.1.1.1", "2.2.2.2"}
	cfg.TargetPorts = []string{"80", "8080"}
	cfg.TargetProtos = []string{"tcp", "udp"}
	th.setup(&cfg)
	r.verifyCommands(t, []string{
		"sudo tc qdisc add dev eth0 handle 10: root htb default 1",
		"sudo tc class add dev eth0 parent 10: classid 10:1 htb rate 20000kbit",
		"sudo tc class add dev eth0 parent 10: classid 10:10 htb rate 1000000kbit",
		"sudo tc qdisc add dev eth0 parent 10:10 handle 100: netem loss 0.10%",
		"sudo iptables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10 -p tcp --match multiport --dports 80,8080 -d 1.1.1.1",
		"sudo iptables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10 -p udp --match multiport --dports 80,8080 -d 1.1.1.1",
		"sudo iptables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10 -p tcp --match multiport --dports 80,8080 -d 2.2.2.2",
		"sudo iptables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10 -p udp --match multiport --dports 80,8080 -d 2.2.2.2",
	})
}

func TestTcMixedIPv6Setup(t *testing.T) {
	r := newCmdRecorder()
	th := &tcThrottler{r}
	cfg := defaultTestConfig
	cfg.Device = "eth1"
	cfg.PacketLoss = 0.2
	cfg.TargetIps6 = []string{"2001:db8::1"}
	th.setup(&cfg)
	r.verifyCommands(t, []string{
		"sudo tc qdisc add dev eth1 handle 10: root htb default 1",
		"sudo tc class add dev eth1 parent 10: classid 10:1 htb rate 20000kbit",
		"sudo tc class add dev eth1 parent 10: classid 10:10 htb rate 1000000kbit",
		"sudo tc qdisc add dev eth1 parent 10:10 handle 100: netem loss 0.20%",
		"sudo iptables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10 -p tcp --dport 80 -d 10.10.10.10",
		"sudo ip6tables -A POSTROUTING -t mangle -j CLASSIFY --set-class 10:10 -p tcp --dport 80 -d 2001:db8::1",
	})
}

func TestTcTeardown(t *testing.T) {
	r := newCmdRecorder()
	th := &tcThrottler{r}
	r.responses = map[string][]string{
		"sudo iptables -S -t mangle": {
			"-P PREROUTING ACCEPT",
			"-P INPUT ACCEPT",
			"-P FORWARD ACCEPT",
			"-P OUTPUT ACCEPT",
			"-P POSTROUTING ACCEPT",
			"-A POSTROUTING -d 10.10.10.10 -p tcp -m tcp --dport 80 -j CLASSIFY --set-class 0010:0010",
		},
		"sudo ip6tables -S -t mangle": {
			"-P PREROUTING ACCEPT",
			"-P INPUT ACCEPT",
			"-P FORWARD ACCEPT",
			"-P OUTPUT ACCEPT",
			"-P POSTROUTING ACCEPT",
		},
	}
	th.teardown(&defaultTestConfig)
	r.verifyCommands(t, []string{
		"sudo iptables -S -t mangle",
		"sudo iptables -t mangle -D POSTROUTING -d 10.10.10.10 -p tcp -m tcp --dport 80 -j CLASSIFY --set-class 0010:0010",
		"sudo ip6tables -S -t mangle",
		"sudo tc qdisc del dev eth0 handle 10: root",
	})
}

func TestTcTeardownNoIpTables(t *testing.T) {
	r := newCmdRecorder()
	th := &tcThrottler{r}
	th.teardown(&defaultTestConfig)
	r.verifyCommands(t, []string{
		"sudo iptables -S -t mangle",
		"sudo ip6tables -S -t mangle",
		"sudo tc qdisc del dev eth0 handle 10: root",
	})
}

func TestTcIPv6Teardown(t *testing.T) {
	r := newCmdRecorder()
	th := &tcThrottler{r}
	r.responses = map[string][]string{
		"sudo iptables -S -t mangle": {},
		"sudo ip6tables -S -t mangle": {
			"-P PREROUTING ACCEPT",
			"-P INPUT ACCEPT",
			"-P FORWARD ACCEPT",
			"-P OUTPUT ACCEPT",
			"-P POSTROUTING ACCEPT",
			"-A POSTROUTING -d 2001:db8::1 -p tcp -m tcp --dport 80 -j CLASSIFY --set-class 0010:0010",
		},
	}
	config := defaultTestConfig

	th.teardown(&config)
	r.verifyCommands(t, []string{
		"sudo iptables -S -t mangle",
		"sudo ip6tables -S -t mangle",
		"sudo ip6tables -t mangle -D POSTROUTING -d 2001:db8::1 -p tcp -m tcp --dport 80 -j CLASSIFY --set-class 0010:0010",
		"sudo tc qdisc del dev eth0 handle 10: root",
	})
}

func TestTcTeardownNoIPv6(t *testing.T) {
	r := newCmdRecorder()
	r.cmdBlackList = []string{"ip6tables"}
	th := &tcThrottler{r}
	r.responses = map[string][]string{
		"sudo iptables -S -t mangle": {
			"-P PREROUTING ACCEPT",
			"-P INPUT ACCEPT",
			"-P FORWARD ACCEPT",
			"-P OUTPUT ACCEPT",
			"-P POSTROUTING ACCEPT",
			"-A POSTROUTING -d 10.10.10.10 -p tcp -m tcp --dport 80 -j CLASSIFY --set-class 0010:0010",
		},
	}

	th.teardown(&defaultTestConfig)
	r.verifyCommands(t, []string{
		"sudo iptables -S -t mangle",
		"sudo iptables -t mangle -D POSTROUTING -d 10.10.10.10 -p tcp -m tcp --dport 80 -j CLASSIFY --set-class 0010:0010",
		"sudo tc qdisc del dev eth0 handle 10: root",
	})
}


================================================
FILE: throttler/throttler.go
================================================
package throttler

import (
	"bufio"
	"errors"
	"fmt"
	"os"
	"os/exec"
	"runtime"
)

const (
	linux           = "linux"
	darwin          = "darwin"
	freebsd         = "freebsd"
	windows         = "windows"
	checkOSXVersion = "sw_vers -productVersion"
	ipfw            = "ipfw"
	pfctl           = "pfctl"
)

// Config specifies options for configuring packet filter rules.
type Config struct {
	Device           string
	Stop             bool
	Latency          int
	TargetBandwidth  int
	DefaultBandwidth int
	PacketLoss       float64
	TargetIps        []string
	TargetIps6       []string
	TargetPorts      []string
	TargetProtos     []string
	DryRun           bool
}

type throttler interface {
	setup(*Config) error
	teardown(*Config) error
	exists() bool
	check() string
}

type commander interface {
	execute(string) error
	executeGetLines(string) ([]string, error)
	commandExists(string) bool
}

type dryRunCommander struct{}

type shellCommander struct{}

var dry bool

func setup(t throttler, cfg *Config) {
	if t.exists() {
		fmt.Println("It looks like the packet rules are already setup")
		os.Exit(1)
	}

	if err := t.setup(cfg); err != nil {
		fmt.Println("I couldn't setup the packet rules:", err.Error())
		os.Exit(1)
	}

	fmt.Println("Packet rules setup...")
	fmt.Printf("Run `%s` to double check\n", t.check())
	fmt.Printf("Run `%s --device %s --stop` to reset\n", os.Args[0], cfg.Device)
}

func teardown(t throttler, cfg *Config) {
	if !t.exists() {
		fmt.Println("It looks like the packet rules aren't setup")
		os.Exit(1)
	}

	if err := t.teardown(cfg); err != nil {
		fmt.Println("Failed to stop packet controls")
		os.Exit(1)
	}

	fmt.Println("Packet rules stopped...")
	fmt.Printf("Run `%s` to double check\n", t.check())
	fmt.Printf("Run `%s` to start\n", os.Args[0])
}

// Run executes the packet filter operation, either setting it up or tearing
// it down.
func Run(cfg *Config) {
	dry = cfg.DryRun
	var t throttler
	var c commander

	if cfg.DryRun {
		c = &dryRunCommander{}
	} else {
		c = &shellCommander{}
	}

	switch runtime.GOOS {
	case freebsd:
		if cfg.Device == "" {
			fmt.Println("Device not specified, unable to default to eth0 on FreeBSD.")
			os.Exit(1)
		}

		t = &ipfwThrottler{c}
	case darwin:
		// Avoid OS version pinning and choose based on what's available
		if c.commandExists(pfctl) {
			t = &pfctlThrottler{c}
		} else if c.commandExists(ipfw) {
			t = &ipfwThrottler{c}
		} else {
			fmt.Println("Could not determine an appropriate firewall tool for OSX (tried pfctl, ipfw), exiting")
			os.Exit(1)
		}

		if cfg.Device == "" {
			cfg.Device = "eth0"
		}

	case linux:
		if cfg.Device == "" {
			cfg.Device = "eth0"
		}

		t = &tcThrottler{c}
	default:
		fmt.Printf("I don't support your OS: %s\n", runtime.GOOS)
		os.Exit(1)
	}

	if !cfg.Stop {
		setup(t, cfg)
	} else {
		teardown(t, cfg)
	}
}

func (c *dryRunCommander) execute(cmd string) error {
	fmt.Println(cmd)
	return nil
}

func (c *dryRunCommander) executeGetLines(cmd string) ([]string, error) {
	fmt.Println(cmd)
	return []string{}, nil
}

func (c *dryRunCommander) commandExists(cmd string) bool {
	return true
}

func (c *shellCommander) execute(cmd string) error {
	fmt.Println(cmd)
	return exec.Command("/bin/sh", "-c", cmd).Run()
}

func (c *shellCommander) executeGetLines(cmd string) ([]string, error) {
	lines := []string{}
	child := exec.Command("/bin/sh", "-c", cmd)

	out, err := child.StdoutPipe()
	if err != nil {
		return []string{}, err
	}

	err = child.Start()
	if err != nil {
		return []string{}, err
	}

	scanner := bufio.NewScanner(out)

	for scanner.Scan() {
		lines = append(lines, scanner.Text())
	}
	if err := scanner.Err(); err != nil {
		return []string{}, errors.New(fmt.Sprint("Error reading standard input:", err))
	}

	err = child.Wait()
	if err != nil {
		return []string{}, err
	}

	return lines, nil
}

func (c *shellCommander) commandExists(cmd string) bool {
	_, err := exec.LookPath(cmd)
	return err == nil
}