Open Source Routing, Firewalls and Traffic Shaping
Russell SutherlandComputing and Networking ServicesUniversity of [email protected]
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
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
Quagga Routing Architecture
Modular Design
One process per protocol– bgpd, ospfd, ripd
One main controlling process– zebra
Extensible
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
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
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
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 - $3.5k
Network Topology
Internal
External
Cogent A [100Mbps]
Cogent B [100Mbps]
C4 [1000Mbps]
Skye
Mull
Jura
Bute
McL
1. UofT A2. UofT B3. ResNet
Touchdown Network1000 Mbps
Traffic Shaper
Network Routing Policy
Three classes of traffic (based on src IP)– ResNet– UofT A– UofT B
ResNet– to (via TS) Skye to Cogent A– No C4 transit !!!
UofT A– to C4 if dst IP == C4 otherwise via Skye to Cog A
UofT B– to C4 if dst IP == C4 otherwise via Mull to CogB
Network Packet Filtering Policies
Drop all packets with– spoofed (non UofT) source IP addresses– non-routable destination addresses
0.0.0.0/8, 10.0.0.0/8, 127.0.0.0/8 169.254.0.0/16, 172.16.0.0/12, 192.168/16 etc.
– nasty tcp/udp M$ 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
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
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
Quagga Routing Configuration
Command line interface similar to Cisco IOSC4# conf tC4(config)# interface eth2C4(config-if)# description dummy interfaceC4(config-if)# ip address 10.1.2.3/24C4(config-if)# exitC4(config)# exitC4#
C4# conf tC4(config)# router bgp 328C4(config-router)# bgp router-id 10.1.1.10C4(config-router)# network 10.1.1.0/24C4(config-router)# redistribute staticC4(config-router)# neighbor 10.1.1.1 remote-as 999C4(config-router)# exitC4(config)# exitC4#
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
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
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
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
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
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
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
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
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
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
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
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
Linux iptables Anatomy Ingress
PREROUTING
QOS Ingress
INPUT ROUTING and RPDB
ContrackmangleIMQnat
Network Interface
FORWARDINPUT
manglefilter
LOCAL PROCESSES
manglefilter
REMOTE IP ADDR
Linux iptables Anatomy Egress
POSTROUTING
QOS Egress
Network Interface
nat
IMQ
LOCAL PROCESSES
REMOTE IP ADDR
mangle
contrackmanglenatfilter
OUTPUT ROUTING
OUTPUT
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
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)
Linux Routing Policy Database
Traditional Routing Routing Policy Database(RPDB)
Destination IP Address Destination IP AddressType of Service Source IP Address
Type of ServiceIptables FW mark
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
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
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
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
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);
$low = class {
fifo(limit 30kB)
}
}
}
}
tcng: Example Output
tc qdisc add dev eth0 handle 1:0 root dsmark indices 4 default_index 0
tc qdisc add dev eth0 handle 2:0 parent 1:0 prio
tc qdisc add dev eth0 handle 3:0 parent 2:1 tbf burst 2048 limit 10240 mtu
1500 rate 2500bps
tc qdisc add dev eth0 handle 4:0 parent 2:2 bfifo limit 30720
tc filter add dev eth0 parent 2:0 protocol all prio 1 tcindex mask 0x3
shift 0
tc filter add dev eth0 parent 2:0 protocol all prio 1 handle 2 tcindex
classid 2:2
tc filter add dev eth0 parent 2:0 protocol all prio 1 handle 1 tcindex
classid 2:1
tc filter add dev eth0 parent 1:0 protocol all prio 1 handle 1:0:0 u32
divisor 1
tc filter add dev eth0 parent 1:0 protocol all prio 1 u32 match u8 0x6 0xff
at 9 offset at 0 mask 0f00 shift 6 eat link 1:0:0
tc filter add dev eth0 parent 1:0 protocol all prio 1 handle 1:0:1 u32 ht
1:0:0 match u16 0x50 0xffff at 2 classid 1:1
tc filter add dev eth0 parent 1:0 protocol all prio 1 u32 match u32 0x0 0x0
at 0 classid 1:2
Routing Policy Using Linux
Routing Tables– 0: from all lookup local– 100: from 142.151.0.0/16 lookup resnet– 1000: from all lookup main– 2000: from 142.150.0.0/16 lookup uoftA– 32767: from all lookup default
resnet contains a single default to syke
uoftA contains a default to skye
default contains a default to mull
main contains all the C4 routes
Linux Traffic Shaping Policy
dev eth1 {
egress {
class ( <$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 );
}
}
}
}
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
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