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IPClassifier

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Tom Barbette edited this page Aug 6, 2018 · 2 revisions

IPClassifier Element Documentation

NAME

IPClassifier — Click element; classifies IP packets by contents

SYNOPSIS

IPClassifier(PATTERN_1, ..., PATTERN_N)

Ports: 1 input, any number of outputs
Processing: push

DESCRIPTION

Classifies IP packets according to tcpdump-like patterns. The IPClassifier has N outputs, each associated with the corresponding pattern from the configuration string. The input packets must have their IP header annotation set; CheckIPHeader and MarkIPHeader do this.

Patterns are built from pattern primitives. The primitives IPClassifier understands are:

  • ip proto PROTO — PROTO is an IP protocol name (see below) or a valid IP protocol number. Matches packets of the given protocol.
  • [SRCORDST] host IPADDR — IPADDR is an IP address and SRCORDST is 'src', 'dst', 'src or dst', or 'src and dst'. (If SRCORDST is missing, 'src or dst' is assumed.) Matches packets sent to and/or from the given address.
  • [SRCORDST] net NETADDR — NETADDR is an IP network address (either CIDR-style 'IPADDR/BITS' or 'IPADDR mask MASK') and SRCORDST is as above. Matches packets sent to and/or from the given network.
  • [SRCORDST] [tcp | udp] port PORT — PORT is a TCP or UDP port name (see below) or number and SRCORDST is as above. Matches packets sent to and/or from the given TCP or UDP port. If you leave out 'tcp' or 'udp', then either TCP or UDP is accepted.
  • ip vers VERSION — VERSION is a value between 0 and 15. Matches IP packets with the given version.
  • ip hl HL — HL is a value between 0 and 15. Matches IP packets with the given header length.
  • ip id ID — ID is a value between 0 and 65535. Matches IP packets with the given IP ID.
  • ip tos TOS — TOS is a value between 0 and 255. Matches IP packets with the given TOS value.
  • ip dscp DSCP — DSCP is a value between 0 and 63. Matches IP packets with the given DSCP value (the upper 6 bits of TOS).
  • ip ect — Matches IP packets with ECN Capable Transport turned on.
  • ip ce — Matches IP packets with ECN Congestion Experienced set.
  • ip ttl TTL — TTL is a value between 0 and 255. Matches IP packets with the given TTL value.
  • ip frag — Matches fragmented IP packets (that is, packets with the more-fragments bit set and/or a nonzero fragment offset).
  • ip unfrag — Equivalent to 'not ip frag'.
  • tcp opt TCPOPT — TCPOPT is a TCP option name (see below). Matches TCP packets with the given option.
  • tcp win TCPWIN — TCPWIN is a TCP receive window length. Matches TCP packets with the given window length. Note that window scaling is not applied.
  • icmp type TYPE — TYPE is a value between 0 and 255 or an ICMP type name (see below). Matches ICMP packets with the given ICMP type.
  • ip[POS:LEN] VALUE — Matches packets whose IP header field starting at byte position POS, and going on for LEN bytes, equals VALUE. You can say ip[POS] instead of ip[POS:1].
  • transp[POS:LEN] VALUE — Like ip[POS:LEN], but for transport header fields. You can also give particular transport protocols, such as tcp[POS:LEN].
  • [SRCORDST] ether host ETH — Matches packets whose source and/or destination Ethernet address matches ETH. The packet's MAC header annotation must be set.
  • true — Matches every packet.
  • false — Matches no packets.

These primitives can be combined with the connectives 'and', 'or', and 'not' (synonyms '&&', '||', and '!'), with the ternary operator '?:' (the colon must be surrounded by spaces!), and with parentheses. For example, '(dst port www or dst port ssh) and tcp opt syn'.

All primitives except tcp opt accept an optional OPERATION, '==' or '!=', which can occur before the actual option. If no OPERATION is specified, '==' is assumed. 'src host == 10.0.0.10' matches packets whose source host is 10.0.0.10; 'src host != 10.0.0.10' matches packets whose source host is not 10.0.0.10. Directives with integer values also support the '<', '>', '<=', and '>=' operations.

For port and icmp type directives, 'DIRECTIVE != VALUE' is not the same as 'not (DIRECTIVE == VALUE)'. For example, 'src tcp port != 5' matches TCP packets whose source port is not 5, while '!(src tcp port == 5)' matches non-TCP packets as well. (The 'src tcp port != 5' option is effectively equivalent to 'tcp and not src tcp port 5'.) Similarly, 'icmp type != 4' will not match non-ICMP packets. The same goes for the '<', '>', '<=', and '>=' relations.

Most primitives also accept bitmasks: 'DIRECTIVE & MASK [[OP] VALUE]'. For instance, 'src tcp port & 10 == 8'.

The port, icmp type, and tcp opt directives will only match first fragments.

You can omit a lot of this syntax. For example, instead of 'ip proto tcp', you can just say 'tcp'; and similarly for 'port www' (just say 'www'), 'tcp opt syn' (just say 'syn'), 'net 10.0.0.0/24' (just say '10.0.0.0/24'), and 'ip unfrag' (just say 'unfrag'). You can often eliminate repetitive qualifiers, too: 'src port 80 or 81' is the same as 'src port 80 or src port 81'.

A pattern consisting entirely of "-", "any", or "all" matches every packet.

The patterns are scanned in order, and the packet is sent to the output corresponding to the first matching pattern. Thus more specific patterns should come before less specific ones. You will get a warning if no packet will ever match a pattern. Usually, this is because an earlier pattern is more general, or because your pattern is contradictory ('src port www and src port ftp').

NOTES

Valid IP port names: 'echo', 'discard', 'daytime', 'chargen', 'ftp-data', 'ftp', 'ssh', 'telnet', 'smtp', 'domain', 'dns', 'bootps', 'bootpc', 'tftp', 'finger', 'www', 'pop3', 'sunrpc', 'auth', 'nntp', 'ntp', 'netbios-ns', 'netbios-dgm', 'netbios-ssn', 'snmp', 'snmp-trap', 'irc', 'imap3', 'https', 'rip', 'route', 'imaps', 'pop3s'

Valid IP protocol names: 'icmp', 'igmp', 'ipip', 'tcp', 'udp'

Valid TCP options: 'syn', 'fin', 'ack', 'rst', 'psh', 'urg'

Valid ICMP type names: 'echo-reply', 'unreachable', 'sourcequench', 'redirect', 'echo', 'routeradvert', 'routersolicit', 'timeexceeded', 'parameterproblem', 'timestamp', 'timestamp-reply', 'inforeq', 'inforeq-reply', 'maskreq', 'maskreq-reply'

This element correctly handles IP packets with options.

[tcp | udp] port, icmp type, tcp opt, and tcp win directives can only be true on the first fragment of a fragmented packet.

Every IPClassifier element has an equivalent corresponding IPFilter element and vice versa. Use the element whose syntax is more convenient for your needs.

EXAMPLES

For example,

  IPClassifier(10.0.0.0/24 and syn,
               10.0.0.0/24 and fin ack,
               10.0.0.0/24 and tcp,
               -);

creates an element with four outputs. The first three outputs are for TCP packets from net 10.0.0.x. SYN packets are sent to output 0, FIN packets with the ACK bit set to output 1, and all other TCP packets to output 2. The last output is for all other IP packets, and non-TCP packets from net 10.0.0.x.

  IPClassifier(dst tcp port 8000 or 8080,
               dst tcp port > 1023,
               tcp);

creates an element with three outputs. The first output is for TCP packets destined for port 8000 or 8080; the second output is for TCP packets destined for any other user port (that is, port > 1023); and the third output is for all other TCP packets. Non-TCP packets are dropped.

ELEMENT HANDLERS

  • program (read-only) — Returns a human-readable definition of the program the IPClassifier element is using to classify packets. At each step in the program, four bytes of packet data are ANDed with a mask and compared against four bytes of classifier pattern.
  • pattern0 (read/write) — Returns or sets the element's pattern 0. There are as many pattern handlers as there are output ports.

SEE ALSO

Classifier, IPFilter, CheckIPHeader, MarkIPHeader, CheckIPHeader2, tcpdump

Generated by click-elem2man from ../elements/ip/ipclassifier.hh:6 on 2018/08/06.

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