Mangle

Document revision:	3 (Fri Nov 04 19:22:14 GMT 2005)
Applies to:	V2.9

General Information

Summary

The mangle facility allows to mark IP packets with special marks. These marks are used by various other router facilities to identify the packets. Additionaly, the mangle facility is used to modify some fields in the IP header, like TOS (DSCP) and TTL fields.

Specifications

Packages required: system
License required: Level1
Submenu level: /ip firewall mangle
Standards and Technologies: IP
Hardware usage: Increases with count of mangle rules

Related Documents

Mangle

Submenu level: /ip firewall mangle

Description

Mangle is a kind of 'marker' that marks packets for future processing with special marks. Many other facilities in RouterOS make use of these marks, e.g. queue trees and NAT. They identify a packet based on its mark and process it accordingly. The mangle marks exist only within the router, they are not transmitted across the network.

Property Description

action (accept | add-dst-to-address-list | add-src-to-address-list | change-mss | change-tos | change-ttl | jump | log | mark-connection | mark-packet | mark-routing | passthrough | return | strip-ipv4-options; default: accept) - action to undertake if the packet matches the rule

address-list (name) - specify the name of the address list to collect IP addresses from rules having action=add-dst-to-address-list or action=add-src-to-address-list actions. These address lists could be later used for packet matching

address-list-timeout (time; default: 00:00:00) - time interval after which the address will be removed from the address list specified by address-list parameter. Used in conjunction with add-dst-to-address-list or add-src-to-address-list actions

chain (forward | input | output | postrouting | prerouting) - specify the chain to put a particular rule into. As the different traffic is passed through different chains, always be careful in choosing the right chain for a new rule. If the input does not match the name of an already defined chain, a new chain will be created

comment (text) - free form textual comment for the rule. A comment can be used to refer the particular rule from scripts

connection-bytes (integer-integer) - match packets only if a given amount of bytes has been transfered through the particular connection

connection-limit (integer,netmask) - restrict connection limit per address or address block

connection-mark (name) - match packets marked via mangle facility with particular connection mark

connection-type (ftp | gre | h323 | irc | mms | pptp | quake3 | tftp) - match packets from related connections based on information from their connection tracking helpers. A relevant connection helper must be enabled under /ip firewall service-port

content (text) - the text packets should contain in order to match the rule

dst-address (IP address/netmask | IP address-IP address) - specify the address range an IP packet is destined to. Note that console converts entered address/netmask value to a valid network address, i.e.:1.1.1.1/24 is converted to 1.1.1.0/24

dst-address-list (name) - match destination address of a packet against user-defined address list

dst-address-type (unicast | local | broadcast | multicast) - match destination address type of the IP packet, one of the:

dst-limit (integer/time{0,1},integer,dst-address | dst-port | src-address{+},time{0,1}) - limit the packet per second (pps) rate on a per destination IP or per destination port base. As opposed to the limit match, every destination IP address / destination port has it's own limit. The options are as follows (in order of appearance):

dst-port (integer: 0..65535-integer: 0..65535{*}) - destination port number or range

hotspot (multiple choice: from-client | auth | local-dst | http) - match packets received from clients against various Hot-Spot. All values can be negated

icmp-options (integer:integer) - match ICMP Type:Code fields

in-interface (name) - interface the packet has entered the router through

ipv4-options (any | loose-source-routing | no-record-route | no-router-alert | no-source-routing | no-timestamp | none | record-route | router-alert | strict-source-routing | timestamp) - match ipv4 header options

jump-target (forward | input | output | postrouting | preroutingname) - name of the target chain to jump to, if the action=jump is used

limit (integer/time{0,1},integer) - restrict packet match rate to a given limit. Usefull to reduce the amount of log messages

log-prefix (text) - all messages written to logs will contain the prefix specified herein. Used in conjunction with action=log

new-connection-mark (name) - specify the new value of the connection mark to be used in conjunction with action=mark-connection

new-mss (integer) - specify MSS value to be used in conjunction with action=change-mss

new-packet-mark (name) - specify the new value of the packet mark to be used in conjunction with action=mark-packet

new-routing-mark (name) - specify the new value of the routing mark used in conjunction with action=mark-routing

new-tos (max-reliability | max-throughput | min-cost | min-delay | normal integer) - specify TOS value to be used in conjunction with action=change-tos

new-ttl (decrement | increment | set:integer) - specify the new TTL field value used in conjunction with action=change-ttl

nth (integer,integer: 0..15,integer{0,1}) - match a particular Nth packet received by the rule. One of 16 available counters can be used to count packets

out-interface (name) - match the interface name a packet left the router through

p2p (all-p2p | bit-torrent | direct-connect | edonkey | fasttrack | gnutella | soulseek | warez | winmx) - match packets belonging to connections of the above P2P protocols

packet-mark (name) - match the packets marked in mangle with specific packet mark

packet-size (integer: 0..65535-integer: 0..65535{0,1}) - matches packet of the specified size or size range in bytes

passthrough (yes | no; default: yes) - whether to let the packet to pass further (like action passthrough) after marking it with a given mark (property only valid if action is mark packet, connection or routing mark)

phys-in-interface (name) - matches the bridge port physical input device added to a bridge device. It is only useful if the packet has arrived through the bridge

protocol (ddp | egp | encap | ggp | gre | hmp | icmp | idrp-cmtp | igmp | ipencap | ipip | ipsec-ah | ipsec-esp | iso-tp4 | ospf | pup | rdp | rspf | st | tcp | udp | vmtp | xns-idp | xtp | integer) - matches particular IP protocol specified by protocol name or number. You should specify this setting if you want to specify ports

psd (integer,time,integer,integer) - attempts to detect TCP and UDP scans. It is advised to assign lower weight to ports with high numbers to reduce the frequency of false positives, such as from passive mode FTP transfers

random (integer: 1..99) - matches packets randomly with given propability

routing-mark (name) - matches packets marked with the specified routing mark

src-address (IP address/netmask | IP address-IP address) - specifies the address range an IP packet is originated from. Note that console converts entered address/netmask value to a valid network address, i.e.:1.1.1.1/24 is converted to 1.1.1.0/24

src-address-list (name) - matches source address of a packet against user-defined address list

src-address-type (unicast | local | broadcast | multicast) - matches source address type of the IP packet, one of the:

src-mac-address (MAC address) - source MAC address

src-port (integer: 0..65535-integer: 0..65535{*}) - source port number or range

tcp-flags (multiple choice: ack | cwr | ece | fin | psh | rst | syn | urg) - tcp flags to match

tcp-mss (integer: 0..65535) - matches TCP MSS value of an IP packet

time (time-time,sat | fri | thu | wed | tue | mon | sun{+}) - allows to create filter based on the packets' arrival time and date or, for locally generated packets, departure time and date

tos (max-reliability | max-throughput | min-cost | min-delay | normal) - specifies a match for the value of Type of Service (ToS) field of an IP header

Notes

Instead of making two rules if you want to mark a packet, connection or routing-mark and finish mangle table processing on that event (in other words, mark and simultaneously accept the packet), you may disable the set by default passthrough property of the marking rule.

Usually routing-mark is not used for P2P, since P2P traffic always is routed over a default getaway.

Application Examples

Description

The following section discusses some examples of using the mangle facility.

Peer-to-Peer Traffic Marking

To ensure the quality of service for network connection, interactive traffic types such as VoIP and HTTP should be prioritized over non-interactive, such as peer-to-peer network traffic. RouterOS QOS implementation uses mangle to mark different types of traffic first, and then place them into queues with different limits.

The following example enforces the P2P traffic will get no more than 1Mbps of the total link capacity when the link is heavily used by other traffic otherwice expanding to the full link capacity:

[admin@MikroTik] > /ip firewall mangle add chain=forward \
\... p2p=all-p2p action=mark-connection new-connection-mark=p2p_conn
[admin@MikroTik] > /ip firewall mangle add chain=forward \
\... connection-mark=p2p_conn action=mark-packet new-packet-mark=p2p
[admin@MikroTik] > /ip firewall mangle add chain=forward \
\... connection-mark=!p2p_conn action=mark-packet new-packet-mark=other
[admin@MikroTik] > /ip firewall mangle print
Flags: X - disabled, I - invalid, D - dynamic
 0   chain=forward p2p=all-p2p action=mark-connection new-connection-mark=p2p_conn

 1   chain=forward connection-mark=p2p_conn action=mark-packet new-packet-mark=p2p

 2   chain=forward packet-mark=!p2p_conn action=mark-packet new-packet-mark=other
[admin@MikroTik] >
[admin@MikroTik] > /queue tree add parent=Public packet-mark=p2p limit-at=1000000 \
\... max-limit=100000000 priority=8
[admin@MikroTik] > /queue tree add parent=Local packet-mark=p2p limit-at=1000000 \
\... max-limit=100000000 priority=8                                     
[admin@MikroTik] > /queue tree add parent=Public packet-mark=other  limit-at=1000000 \
\... max-limit=100000000 priority=1
[admin@MikroTik] > /queue tree add parent=Local packet-mark=other  limit-at=1000000 \
\... max-limit=100000000 priority=1

Mark by MAC address

To mark traffic from a known MAC address which goes to the router or through it, do the following:

[admin@MikroTik] > / ip firewall mangle add chain=prerouting \
\... src-mac-address=00:01:29:60:36:E7 action=mark-connection new-connection-mark=known_mac_conn
[admin@MikroTik] > / ip firewall mangle add chain=prerouting \
\... connection-mark=known_mac_conn action=mark-packet new-packet-mark=known_mac  
			

Change MSS

It is a well known fact that VPN links have smaller packet size due to incapsulation overhead. A large packet with MSS that exceeds the MSS of the VPN link should be fragmented prior to sending it via that kind of connection. However, if the packet has DF flag set, it cannot be fragmented and should be discarded. On links that have broken path MTU discovery (PMTUD) it may lead to a number of problems, including problems with FTP and HTTP data transfer and e-mail services.

In case of link with broken PMTUD, a decrease of the MSS of the packets coming through the VPN link solves the problem. The following example demonstrates how to decrease the MSS value via mangle:

[admin@MikroTik] > /ip firewall mangle add out-interface=pppoe-out \
\... protocol=tcp tcp-flags=syn action=change-mss new-mss=1300 chain=forward
[admin@MikroTik] > /ip firewall mangle print
Flags: X - disabled, I - invalid, D - dynamic
 0   chain=forward out-interface=pppoe-out protocol=tcp tcp-flags=syn
     action=change-mss new-mss=1300

[admin@MikroTik] >