PPT Universitas Padjadjaran

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Open Source Routing, Firewalls and Traffic Shaping

Russell Sutherland

Computing and Networking Services University of Toronto

[email protected]

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Reference URLs for Tree Huggers

 This presentation

– http://madhaus.cns.utoronto.ca/~russ/canheit2004/

 Routing

– http://www.quagga.net/

– http://www.xorp.net/

– http://latrc.org/

 Traffic Shaping

– Linux http://tcng.sourceforge.net/

– FreeBSD http://info.iet.unipi.it/~luigi/ip_dummynet/

 Packet Filtering

– Linux (iptables) http://www.netfilter.org/

– FreeBSD (ipfw) http://www.freebsd.org/

– OpenBSD (pf) http://www.benzedrine.cx/pf.html

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Routing Chronology

 1984 BSD 4.2 ships with routed (RIPv1)

 1986 Fuzz Ball PDP-11 NSFNet Routers

 1988 Age of dedicated routing machines

– Cisco, Proteon, Wellfleet, ACC

 1992 Gated Consortium Formed

 1996 GNU Zebra

 2002 Quagga, XORP

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Quagga Routing Architecture

 Modular Design

 One process per protocol

– bgpd, ospfd, ripd

 One main controlling process

– zebra

 Extensible

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Quagga Architecture Diagram

bgpd

ospfd ripd

zebra

Unix Kernel Routing Table

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Quagga Routing Protocols

 RIPv1, RIPv2, RIPng

 OSPFv2, OSPFv3

 BGP-4, BGP+

 BGP route server and reflector

 IPv6

 Supported RFCs

– 1058 RIPv1, 2453 RIPv2, 2080 RIPng – 2328 OSPFv2, 2740 OSPF for Ipv6

– 1771 BGPv4, 1965, 1997, 2545 BGPv6, 2796 BGP Route Reflection, 2858 Multiprotocol extensions, 2842 Capabilities Advertisement

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Quagga Supported Platforms

 GNU Linux

– Debian, RedHat, SuSE, Slackware – Kernels 2.2.x - 2.4.x

 FreeBSD

– versions 4.x and 5.x

 OpenBSD

– version 3.x

 NetBSD

– version 1.4

 Solaris

– 2.6 and version 7

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Hardware Requirements

 CPU Intel 2.0 – 3.0 Ghz

 Memory 512MB

 Disks 18GB

– RAID-1 (optional) – SCSI or IDE

 Ethernet Interfaces

– 2 x 10/100 Intel, 2 x 10/100/100 Broadcom

 Redundancy

– hot spare serves as backup to N production units

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Scottish Economics

 Router Prices

– Cisco Mid-size

 7204VxR, Catalyst 3550

 $15k – $32k

– Extreme

 Alpine 3800

 $31k - $38k

– Foundry

 BigIron 4000

 $16k

– Intel 2.x Ghz server

 Dell 2650, IBM x335

 $2.5k - $3.5k

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Network Topology

Internal

External

Cogent A [100Mbps]

Cogent B [100Mbps]

C4 [1000Mbps]

Skye

Mull

Jura

Bute McL

1. UofT A 2. UofT B 3. ResNet

Touchdown Network 1000 Mbps

Traffic Shaper

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Network Routing Policy

 Three classes of traffic (based on src IP)

– ResNet – UofT A – UofT B

 ResNet

– to (via TS) Skye to Cogent A – No C4 transit !!!

 UofT A

– to C4 if dst IP == C4 otherwise via Skye to Cog A

 UofT B

– to C4 if dst IP == C4 otherwise via Mull to CogB

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Network Packet Filtering Policies

 Drop all packets with

– spoofed (non UofT) source IP addresses – non-routable destination addresses

 0.0.0.0/8, 10.0.0.0/8, 127.0.0.0/8

 169.254.0.0/16, 172.16.0.0/12, 192.168/16

 etc.

– nasty tcp/udp M$ worm ports (Blaster, Welchia, etc.)

 67, 68, 69, 135, 137, 139

 161, 162

 445, 593, 707, 1433, 1434, 3127, 4444

– non-assigned UofT subnets

 Allow everything else

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Network Traffic Shaping Policies

 All traffic from a local Redhat ftp site to the outside world gets a 50 kbps pipe

 Peer to peer traffic to and from UofT A&B gets a 256 kpbs full duplex pipe

– KaZaa 1214

– eDonkey 466[12]

– BitTorrent 6881-6889

 ResNet traffic gets conditioned by a dedicated Traffic Shaper (Packeteer)

 Everything else flows freely

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Routing Protocols and Configuration

 Jura

– runs OSPF on int. intf. with other UofT routers – runs BGP on external interface with C4 peer – contains all UofT and C4 specific routes

 Mull

– runs OSPF on int. intf. with other UofT routers

– runs BGP on external interface with Cogent B peer – advertises UofTB routes

– defaults points to Cogent B

 Skye

– same setup as Mull but with Cogent A – advertises UofTA and ResNet routes

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Quagga Routing Configuration

 Command line interface similar to Cisco IOS

C4# conf t

C4(config)# interface eth2

C4(config-if)# description dummy interface C4(config-if)# ip address 10.1.2.3/24

C4(config-if)# exit C4(config)# exit C4#

C4# conf t

C4(config)# router bgp 328

C4(config-router)# bgp router-id 10.1.1.10 C4(config-router)# network 10.1.1.0/24 C4(config-router)# redistribute static

C4(config-router)# neighbor 10.1.1.1 remote-as 999 C4(config-router)# exit

C4(config)# exit C4#

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Quagga Operation

# show ip route

Codes: K - kernel route, C – connected, S – static, O -OSPF B – BGP, > - selected route, * FIB route

S>* 0.0.0.0/0 [10/0] via 128.100.96.194, disc0

B>* 6.1.0.0/16 [20/0] via 205.211.94.97, yk0, 01w4d03h B>* 6.2.0.0/22 [20/0] via 205.211.94.97, yk0, 01w4d03h B>* 6.3.0.0/18 [20/0] via 205.211.94.97, yk0, 01w4d03h

# show bgp neighbors

BGP neighbor is 205.211.94.97, remote AS 549, local AS 239, external link BGP version 4, remote router ID 205.211.94.253

BGP state = Established, up for 01w4d22h

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FreeBSD ipfw Packet Filtering

 Native packet filtering interface

 Implemented as a multifunction user command

 The packet passed to the firewall is

compared against each of the rules in the firewall ruleset.

 When a match is found, the action corresponding to the matching rule is performed and the search terminates.

 General syntax

– ipfw [rule number] action [log] body

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ipfw examples

 Drop all www traffic from a network

– ipfw add deny tcp from 12.12.12.0/24 to www.ubc.ca 80

 Drop all telnet traffic from a bad host

– ipfw add deny tcp from bad.host.com to my.host.com 23

 Throw away RFC 1918 networks

– ipfw add deny all from 10.0.0.0/8 to any in via fxp0

– ipfw add deny all from 172.16.0.0/12 to any in via fxp0 – ipfw add deny all from 192.168.0.0/16 to any in via fxp0

 Allow ssh

– ipfw add allow tcp from any to any 22 in via fxp0 setup keep-state

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ipfw actions

 allow | accept | pass | permit

– Allow packets that match rule. The search ends.

 deny | drop

– Discard packets that match rule. The search ends.

 fwd | forward ipaddr[,port]

– Change the next-hop on matching pckts to ipaddr

 pipe N

– Pass packet to a dummynet(4) for bandwidth limitation. [ conditionally end or continue ]

 count

– Update counters for all packets that match rule.

The search continues with the next rule

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Traffic Control Concepts I

 Set of mechanisms to condition net traffic

 Examples

– raise priority of some kinds of traffic – limit the rate at which traffic is sent

– block undesirable traffic (same as packet filtering)

 TC is done at the network interface

– ingress (traffic entering an interface)

 limited set of functions (classifying, dropping)

– egress (traffic leaving an interface)

 full range of functions available

 queueing

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Traffic Control Concepts II

Queueing

Classification Scheduling

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Traffic Control Concepts III

 Classification

– looks at packet content and assigns each to one or more classes.

 Queueing

– stuffs incoming packets into storage silos based on class

 Scheduling

– transmitting packets in queues based upon priority

 Queueing and Scheduling are often combined into queuing disciplines

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Traffic Control Concepts IV

 Common Queueing Disciplines

– simple drop tail (FIFO)

 stores and emits packets in order which they arrive

– Random Early Detection (RED)

 starts dropping packets already before reaching maximum queue size

– Token Bucket Filter (TBF)

 shapers that emits packets at a fixed rate

– Priority Scheduler (PQ)

 emits packets in higher priority classes before packets in lower priority classes

– Weighted Fair Queueing (WFQ)

 assigns an independent queue for each flow

 a weight can be defined for each queue

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FreeBSD Dummynet Features

 Integrated with ipfw to classify packets

 Can be used equally well on egress/ingress

 Abstractions/features

– pipes

 fixed bandwidth channels

 variable queue size, delays, random packet loss

– queues

 queues of packets

 weighted

 share bandwidth of pipe they are associated with proportionally to their weight

 WF2Q+ used for queuing discipline

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Dummynet Examples

 Limit WWW traffic to 100Mbps

 ipfw pipe 1 config bw 100Mbit/s

 ipfw add pipe 1 ip from any to any dst-port 80

 Prefer ssh to telnet traffic

 ipfw pipe 2 config bw 256kbit/s

 ipfw queue 1 config pipe 2 weight 7

 ipfw queue 2 config pipe 2 weight 3

 ipfw add queue 1 ip from any to any dst-port 22

 ipfw add queue 2 ip from any to any dst-port 23

 Rate limit each network host's upload rate

 ipfw pipe 3 config mask src-ip 0x000000ff bw 16kbit/s queue 8Kbytes

 ipfw add pipe 3 ip from 12.18.123.0/24 to any out via xl0

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Routing Policy Using ipfw

 All ResNet traffic forwarded directly to Skye

– ipfw add fwd $skye from $resnet to any in recv $uoft_if

 Block spoofed packets

– ipfw add allow all from $uoftnet to any in recv $uoft_if – ipfw add deny in recv $uoft_if

 Block bad packets (M$ worms etc.)

– for i in 67-69 135-139 161 162 445 593 707 4444

 do

– ipfw add deny udp from any to any $i – ipfw add deny tcp from any to any $i

 done

 C4 traffic follows specific routes from BGP

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Routing Policy Using ipfw Cont.

 Block all traffic to non-defined UofT addrs

– ipfw add deny all from any to $uoftnet out xmit $def_if

 Partition UofT A/B traffic to Skye/Mull

– add fwd $skye all from $uoftA to any out xmit $def_if – add fwd $mull all from $uoftB to any out xmit $def_if

 Traffic Shaping

– limit RH ftp server

 ipfw pipe 1 config bw 50Kbit/s

 ipfw add pipe 1 ip from $rhftp to any in recv $uoftif

– limit peer to peer

 ipfw pipe 2 config bw 256 Kbit/s

 ipfw add pipe 2 ip from $uoftA to any dst_port 1214,4661,4662

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Linux Packet Filtering: iptables

 Similar to ipfw in functionality and use

 User based command line interface

 Syntax

– iptables rule-action table name conditions action

 Very rich set of conditions and actions

 Extensible modular actions

 More complicated in concept than ipfw or pf

 hierarchy: tables -> chains -> rules

 three default tables with default policies

– filter, nat, mangle

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Linux iptables Anatomy Ingress

P^REROUTING

QOS Ingress

I^NPUT R^OUTING and RPDB

Contrack mangle IMQ nat

Network Interface

F^ORWARD I^NPUT

mangle filter

L^OCAL P^ROCESSES

mangle filter

R^EMOTE I^P A^DDR

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Linux iptables Anatomy Egress

POSTROUTING

QOS Egress Network Interface

nat IMQ

L^OCAL P^ROCESSES

REMOTE IP ADDR

mangle contrack

mangle nat filter

O^UTPUT R^OUTING

OUTPUT

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iptables examples

 Drop all www traffic from a network

 iptables -A FORWARD -p tcp –dport 80 -s 12.12.12.0/24 -d www.ubc.ca -j DROP

 Drop all telnet traffic from a bad host

 iptables -A INPUT -p tcp -s bad.host.com -d my.host.com –- dport 23 -j DROP

 Throw away RFC 1918 networks from inside

 iptables -A FORWARD -s 10.0.0.0/8 -i eth0 -j DROP

 iptables -A INPUT -s 10.0.0.0/8 -i eth0 -j DROP

 iptables -t mangle -A PREROUTING -s 172.16.0.0/12 -i eth0 -j DROP

 Allow ssh and keep state

 iptables -A FORWARD -p tcp –dport 22 -i fxp0 -m state -–state NEW,ESTABLISHED -j ACCEPT

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Linux Routing – Multiple Tables

 Multiple routing/forwarding tables

 Three fixed prefined tables

– local – main – default

 Each table is assigned a priority number

– 0 local – 32766 main – 32767 default

 match is sought starting with highest priority tables (local -> main -> default)

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Linux Routing Policy Database

Traditional Routing Routing Policy Database (RPDB)

Destination IP Address Destination IP Address Type of Service Source IP Address

Type of Service Iptables FW mark

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Linux Traffic Control: tc

 Uses queueing disciplines for managing bandwidth

 Largely concerned with data being sent rather than received.

 Classless queueing disciplines

– reschedule, drop or delay – applied to the bulk interface – pfifo_fast

 default, can't be changed

– TBF (Token Bucket Filter)

 passes traffic up to a fixed rate

 drops the rest

 allows short burst in excess of fixed rate

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tc: Classless qdiscs

 SFQ (Stocastic Fair Queueing)

– Traffic split into large number of FIFO queues, one per flow

– Traffic gets sent/serviced in a round robin fashion, giving each flow a chance to sent its data.

– Leads to fair behaviour

– prevents one flow from hogging all the bandwidth

– only really useful when the link is full

 RED (Random Early Detection)

– drops packets statistically before queues are full – leads to a congested link to slow more gracefully – helps TCP applications find their fair speed

faster

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tc: Classful qdiscs

 Used when different types of traffic need different treatment.

 CBQ (Class Based Queueing)

– very complicated to set up and tune

 PRIO

– classify and traffic into a number of bands each with its own priority.

 u32

– used as the tool to classify the traffic into sub queues

– based on actual offset of information in the IP header

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Linux: tcng

 tc syntax is very complicated both in setting up the qdisc's and classification

 tc qdisc add dev eth0 root handle 1:0 prio

 tc qdisc add dev eth0 parent 1:0 protocol ip u32 match ip protocol 6 ff match tcp dst 50 ffff classid 1:1

 tc qdisc add dev eth0 parent 1:3 handle 30: sfq

 tc filter add dev eth0 parent 1:0 protocol ip prio 1 u32 match ip sport 80 0xffff flowid 1:3

 tcng was created as a higher level tool

– simple to configure

– more natural language to set up classes and qdisc – compiles to tc or “C”

– comes with a simulator

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tcng: Example Input

dev “eth0” { egress {

class (<$high>) if tcp_port == 80;

class (<$low>) if 1;

prio {

$high = class {

tbf(limit 10kB, rate 20kbps, burst 2kB, mtu 1500B);

$low = class {

fifo(limit 30kB) }

} }

}

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tcng: Example Output

tc qdisc add dev eth0 handle 1:0 root dsmark indices 4 default_index 0 tc qdisc add dev eth0 handle 2:0 parent 1:0 prio

tc qdisc add dev eth0 handle 3:0 parent 2:1 tbf burst 2048 limit 10240 mtu 1500 rate 2500bps

tc qdisc add dev eth0 handle 4:0 parent 2:2 bfifo limit 30720

tc filter add dev eth0 parent 2:0 protocol all prio 1 tcindex mask 0x3 shift 0

tc filter add dev eth0 parent 2:0 protocol all prio 1 handle 2 tcindex classid 2:2

tc filter add dev eth0 parent 2:0 protocol all prio 1 handle 1 tcindex classid 2:1

tc filter add dev eth0 parent 1:0 protocol all prio 1 handle 1:0:0 u32 divisor 1

tc filter add dev eth0 parent 1:0 protocol all prio 1 u32 match u8 0x6 0xff at 9 offset at 0 mask 0f00 shift 6 eat link 1:0:0

tc filter add dev eth0 parent 1:0 protocol all prio 1 handle 1:0:1 u32 ht 1:0:0 match u16 0x50 0xffff at 2 classid 1:1

tc filter add dev eth0 parent 1:0 protocol all prio 1 u32 match u32 0x0 0x0 at 0 classid 1:2

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Routing Policy Using Linux

 Routing Tables

– 0: from all lookup local

– 100: from 142.151.0.0/16 lookup resnet – 1000: from all lookup main

– 2000: from 142.150.0.0/16 lookup uoftA – 32767: from all lookup default

 resnet contains a single default to syke

 uoftA contains a default to skye

 default contains a default to mull

 main contains all the C4 routes

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Linux Traffic Shaping Policy

dev eth1 { egress {

class ( <$rhftp> ) if ip_src == 128.100.17.10;

class ( <$p2p> ) if ( (tcp_dport == 1214 ||

tcp_dport == 4661 || tcp_dport == 4662) &&

ip_src:16 == 128.100.0.0 );

class ( <$high> ) if 1 ; htb () {

class ( rate 100Mbps , ceil 100Mbps ) {

$rhftp = class ( rate 50kbps, ceil 75kbps );

$p2p = class ( rate 256kbps, ceil 325kbps );

$high = class ( rate 90Mbps, ceil 100Mbps );

} }

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OpenBSD packet filtering

 pf runs as the native packet filtering engine

 similar in syntax to ipfw

 traffic shaping (ALTQ) integrated with pf

 BSD only supports one main routing table

 pf (like ipfw) supports a forwarding action to explicitly forward a packet

 URLs

– www.openbsd.org

– www.csl.sony.co.jp/person/kjc/software.html – www.benzedrene.cx/pf.html

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Results and Conclusions

 OSS Routers in service for > 18 months

 Scaled easily from 1 to 3 machines

 Currently running

– FreeBSD 4.x, 5.x, dummynet, ipfw

 Will be moving to Linux in next 3 months

 Standard network monitoring via SNMP

 CPU running < 40%

 OSS is a viable option for policy based routing and shaping at the edge