1PCAP-FILTER(7) Miscellaneous Information Manual PCAP-FILTER(7)
2
6 pcap-filter - packet filter syntax
7
9 pcap_compile(3PCAP) is used to compile a string into a filter program.
10 The resulting filter program can then be applied to some stream of
11 packets to determine which packets will be supplied to
12 pcap_loop(3PCAP), pcap_dispatch(3PCAP), pcap_next(3PCAP), or
13 pcap_next_ex(3PCAP).
14 The filter expression consists of one or more primitives. Primitives
16 usually consist of an id (name or number) preceded by one or more qual‐
17 ifiers. There are three different kinds of qualifier:
18 type type qualifiers say what kind of thing the id name or number
20 refers to. Possible types are host, net, port and portrange.
21 E.g., `host foo', `net 128.3', `port 20', `portrange 6000-6008'.
22 If there is no type qualifier, host is assumed.
23 dir dir qualifiers specify a particular transfer direction to and/or
25 from id. Possible directions are src, dst, src or dst, src and
26 dst, ra, ta, addr1, addr2, addr3, and addr4. E.g., `src foo',
27 `dst net 128.3', `src or dst port ftp-data'. If there is no dir
28 qualifier, `src or dst' is assumed. The ra, ta, addr1, addr2,
29 addr3, and addr4 qualifiers are only valid for IEEE 802.11 Wire‐
30 less LAN link layers.
31 proto proto qualifiers restrict the match to a particular protocol.
33 Possible protocols are: ether, fddi, tr, wlan, ip, ip6, arp,
34 rarp, decnet, sctp, tcp and udp. E.g., `ether src foo', `arp
35 net 128.3', `tcp port 21', `udp portrange 7000-7009', `wlan
36 addr2 0:2:3:4:5:6'. If there is no proto qualifier, all proto‐
37 cols consistent with the type are assumed. E.g., `src foo'
38 means `(ip or arp or rarp) src foo', `net bar' means `(ip or arp
39 or rarp) net bar' and `port 53' means `(tcp or udp or sctp) port
40 53' (note that these examples use invalid syntax to illustrate
41 the principle).
42 [fddi is actually an alias for ether; the parser treats them identi‐
44 cally as meaning ``the data link level used on the specified network
45 interface''. FDDI headers contain Ethernet-like source and destination
46 addresses, and often contain Ethernet-like packet types, so you can
47 filter on these FDDI fields just as with the analogous Ethernet fields.
48 FDDI headers also contain other fields, but you cannot name them ex‐
49 plicitly in a filter expression.
50 Similarly, tr and wlan are aliases for ether; the previous paragraph's
52 statements about FDDI headers also apply to Token Ring and 802.11 wire‐
53 less LAN headers. For 802.11 headers, the destination address is the
54 DA field and the source address is the SA field; the BSSID, RA, and TA
55 fields aren't tested.]
56 In addition to the above, there are some special `primitive' keywords
58 that don't follow the pattern: gateway, broadcast, less, greater and
59 arithmetic expressions. All of these are described below.
60 More complex filter expressions are built up by using the words and, or
62 and not (or equivalently: `&&', `||' and `!' respectively) to combine
63 primitives. E.g., `host foo and not port ftp and not port ftp-data'.
64 To save typing, identical qualifier lists can be omitted. E.g., `tcp
65 dst port ftp or ftp-data or domain' is exactly the same as `tcp dst
66 port ftp or tcp dst port ftp-data or tcp dst port domain'.
67 Allowable primitives are:
69 dst host hostnameaddr
71 True if the IPv4/v6 destination field of the packet is host‐
72 nameaddr, which may be either an address or a name.
73 src host hostnameaddr
75 True if the IPv4/v6 source field of the packet is hostnameaddr.
76 host hostnameaddr
78 True if either the IPv4/v6 source or destination of the packet
79 is hostnameaddr.
80 Any of the above host expressions can be prepended with the key‐
82 words, ip, arp, rarp, or ip6 as in:
83 ip host hostnameaddr
84 which is equivalent to:
85 ether proto \ip and host hostnameaddr
86 If hostnameaddr is a name with multiple IPv4/v6 addresses, each
87 address will be checked for a match.
88 ether dst ethernameaddr
90 True if the Ethernet destination address is ethernameaddr. eth‐
91 ernameaddr may be either a name from /etc/ethers or a numerical
92 MAC address of the form "xx:xx:xx:xx:xx:xx",
93 "xx.xx.xx.xx.xx.xx", "xx-xx-xx-xx-xx-xx", "xxxx.xxxx.xxxx",
94 "xxxxxxxxxxxx", or various mixes of ':', '.', and '-', where
95 each "x" is a hex digit (0-9, a-f, or A-F).
96 ether src ethernameaddr
98 True if the Ethernet source address is ethernameaddr.
99 ether host ethernameaddr
101 True if either the Ethernet source or destination address is
102 ethernameaddr.
103 gateway host
105 True if the packet used host as a gateway. I.e., the Ethernet
106 source or destination address was host but neither the IP source
107 nor the IP destination was host. Host must be a name and must
108 be found both by the machine's host-name-to-IP-address resolu‐
109 tion mechanisms (host name file, DNS, NIS, etc.) and by the ma‐
110 chine's host-name-to-Ethernet-address resolution mechanism
111 (/etc/ethers, etc.). (An equivalent expression is
112 ether host ethernameaddr and not host hostnameaddr
113 which can be used with either names or numbers for hostnameaddr
114 / ethernameaddr.) This syntax does not work in IPv6-enabled
115 configuration at this moment.
116 dst net netnameaddr
118 True if the IPv4/v6 destination address of the packet has a net‐
119 work number of netnameaddr. Net may be either a name from the
120 networks database (/etc/networks, etc.) or a network number. An
121 IPv4 network number can be written as a dotted quad (e.g.,
122 192.168.1.0), dotted triple (e.g., 192.168.1), dotted pair (e.g,
123 172.16), or single number (e.g., 10); the netmask is
124 255.255.255.255 for a dotted quad (which means that it's really
125 a host match), 255.255.255.0 for a dotted triple, 255.255.0.0
126 for a dotted pair, or 255.0.0.0 for a single number. An IPv6
127 network number must be written out fully; the netmask is
128 ff:ff:ff:ff:ff:ff:ff:ff, so IPv6 "network" matches are really
129 always host matches, and a network match requires a netmask
130 length.
131 src net netnameaddr
133 True if the IPv4/v6 source address of the packet has a network
134 number of netnameaddr.
135 net netnameaddr
137 True if either the IPv4/v6 source or destination address of the
138 packet has a network number of netnameaddr.
139 net netaddr mask netmask
141 True if the IPv4 address matches netaddr with the specific net‐
142 mask. May be qualified with src or dst. Note that this syntax
143 is not valid for IPv6 netaddr.
144 net netaddr/len
146 True if the IPv4/v6 address matches netaddr with a netmask len
147 bits wide. May be qualified with src or dst.
148 dst port portnamenum
150 True if the packet is IPv4/v6 TCP, UDP or SCTP and has a desti‐
151 nation port value of portnamenum. The portnamenum can be a num‐
152 ber or a name used in /etc/services (see tcp(4P) and udp(4P)).
153 If a name is used, both the port number and protocol are
154 checked. If a number or ambiguous name is used, only the port
155 number is checked (e.g., `dst port 513' will print both tcp/lo‐
156 gin traffic and udp/who traffic, and `port domain' will print
157 both tcp/domain and udp/domain traffic).
158 src port portnamenum
160 True if the packet has a source port value of portnamenum.
161 port portnamenum
163 True if either the source or destination port of the packet is
164 portnamenum.
165 dst portrange portnamenum1-portnamenum2
167 True if the packet is IPv4/v6 TCP, UDP or SCTP and has a desti‐
168 nation port value between portnamenum1 and portnamenum2 (both
169 inclusive). portnamenum1 and portnamenum2 are interpreted in
170 the same fashion as the portnamenum parameter for port.
171 src portrange portnamenum1-portnamenum2
173 True if the packet has a source port value between portnamenum1
174 and portnamenum2 (both inclusive).
175 portrange portnamenum1-portnamenum2
177 True if either the source or destination port of the packet is
178 between portnamenum1 and portnamenum2 (both inclusive).
179 Any of the above port or port range expressions can be prepended
181 with the keywords, tcp, udp or sctp, as in:
182 tcp src port portnamenum
183 which matches only TCP packets whose source port is portnamenum.
184 less length
186 True if the packet has a length less than or equal to length.
187 This is equivalent to:
188 len <= length
189 greater length
191 True if the packet has a length greater than or equal to length.
192 This is equivalent to:
193 len >= length
194 ip proto protocol
196 True if the packet is an IPv4 packet (see ip(4P)) of protocol
197 type protocol. Protocol can be a number or one of the names
198 recognized by getprotobyname(3) (as in e.g. `getent(1) proto‐
199 cols'), typically from an entry in /etc/protocols, for example:
200 ah, esp, eigrp (only in Linux, FreeBSD, NetBSD, DragonFly BSD,
201 and macOS), icmp, igmp, igrp (only in OpenBSD), pim, sctp, tcp,
202 udp or vrrp. Note that most of these example identifiers are
203 also keywords and must be escaped via backslash (\). Note that
204 this primitive does not chase the protocol header chain.
205 icmp Abbreviation for:
207 ip proto 1
208 ip6 proto protocol
210 True if the packet is an IPv6 packet of protocol type protocol.
211 (See `ip proto' above for the meaning of protocol.) Note that
212 the IPv6 variant of ICMP uses a different protocol number, named
213 ipv6-icmp in AIX, FreeBSD, illumos, Linux, macOS, NetBSD, Open‐
214 BSD, Solaris and Windows. Note that this primitive does not
215 chase the protocol header chain.
216 icmp6 Abbreviation for:
218 ip6 proto 58
219 proto protocol
221 True if the packet is an IPv4 or IPv6 packet of protocol type
222 protocol. (See `ip proto' above for the meaning of protocol.)
223 Note that this primitive does not chase the protocol header
224 chain.
225 ah, esp, pim, sctp, tcp, udp
227 Abbreviations for:
228 proto \protocol
229 where protocol is one of the above protocols.
230 ip6 protochain protocol
232 True if the packet is IPv6 packet, and contains protocol header
233 with type protocol in its protocol header chain. (See `ip
234 proto' above for the meaning of protocol.) For example,
235 ip6 protochain 6
236 matches any IPv6 packet with TCP protocol header in the protocol
237 header chain. The packet may contain, for example, authentica‐
238 tion header, routing header, or hop-by-hop option header, be‐
239 tween IPv6 header and TCP header. The BPF code emitted by this
240 primitive is complex and cannot be optimized by the BPF opti‐
241 mizer code, and is not supported by filter engines in the ker‐
242 nel, so this can be somewhat slow, and may cause more packets to
243 be dropped.
244 ip protochain protocol
246 Equivalent to ip6 protochain protocol, but this is for IPv4.
247 (See `ip proto' above for the meaning of protocol.)
248 protochain protocol
250 True if the packet is an IPv4 or IPv6 packet of protocol type
251 protocol. (See `ip proto' above for the meaning of protocol.)
252 Note that this primitive chases the protocol header chain.
253 ether broadcast
255 True if the packet is an Ethernet broadcast packet. The ether
256 keyword is optional.
257 ip broadcast
259 True if the packet is an IPv4 broadcast packet. It checks for
260 both the all-zeroes and all-ones broadcast conventions, and
261 looks up the subnet mask on the interface on which the capture
262 is being done.
263 If the subnet mask of the interface on which the capture is be‐
265 ing done is not available, either because the interface on which
266 capture is being done has no netmask or because the capture is
267 being done on the Linux "any" interface, which can capture on
268 more than one interface, this check will not work correctly.
269 ether multicast
271 True if the packet is an Ethernet multicast packet. The ether
272 keyword is optional. This is shorthand for `ether[0] & 1 != 0'.
273 ip multicast
275 True if the packet is an IPv4 multicast packet.
276 ip6 multicast
278 True if the packet is an IPv6 multicast packet.
279 ether proto protocol
281 True if the packet is of ether type protocol. Protocol can be a
282 number or one of the names aarp, arp, atalk, decnet, ip, ip6,
283 ipx, iso, lat, loopback, mopdl, moprc, netbeui, rarp, sca or
284 stp. Note these identifiers (except loopback) are also keywords
285 and must be escaped via backslash (\).
286 [In the case of FDDI (e.g., `fddi proto \arp'), Token Ring
288 (e.g., `tr proto \arp'), and IEEE 802.11 wireless LANs (e.g.,
289 `wlan proto \arp'), for most of those protocols, the protocol
290 identification comes from the 802.2 Logical Link Control (LLC)
291 header, which is usually layered on top of the FDDI, Token Ring,
292 or 802.11 header.
293 When filtering for most protocol identifiers on FDDI, Token
295 Ring, or 802.11, the filter checks only the protocol ID field of
296 an LLC header in so-called SNAP format with an Organizational
297 Unit Identifier (OUI) of 0x000000, for encapsulated Ethernet; it
298 doesn't check whether the packet is in SNAP format with an OUI
299 of 0x000000. The exceptions are:
300 iso the filter checks the DSAP (Destination Service Access
302 Point) and SSAP (Source Service Access Point) fields of
303 the LLC header;
304 stp and netbeui
306 the filter checks the DSAP of the LLC header;
307 atalk the filter checks for a SNAP-format packet with an OUI of
309 0x080007 and the AppleTalk etype.
310 In the case of Ethernet, the filter checks the Ethernet type
312 field for most of those protocols. The exceptions are:
313 iso, stp, and netbeui
315 the filter checks for an 802.3 frame and then checks the
316 LLC header as it does for FDDI, Token Ring, and 802.11;
317 atalk the filter checks both for the AppleTalk etype in an Eth‐
319 ernet frame and for a SNAP-format packet as it does for
320 FDDI, Token Ring, and 802.11;
321 aarp the filter checks for the AppleTalk ARP etype in either
323 an Ethernet frame or an 802.2 SNAP frame with an OUI of
324 0x000000;
325 ipx the filter checks for the IPX etype in an Ethernet frame,
327 the IPX DSAP in the LLC header, the 802.3-with-no-LLC-
328 header encapsulation of IPX, and the IPX etype in a SNAP
329 frame.
330 ip, ip6, arp, rarp, atalk, aarp, decnet, iso, stp, ipx, netbeui
332 Abbreviations for:
333 ether proto \protocol
334 where protocol is one of the above protocols.
335 lat, moprc, mopdl
337 Abbreviations for:
338 ether proto \protocol
339 where protocol is one of the above protocols. Note that not all
340 applications using pcap(3PCAP) currently know how to parse these
341 protocols.
342 decnet src decnetaddr
344 True if the DECnet source address is decnetaddr, which may be an
345 address of the form ``10.123'', or a DECnet host name. [DECnet
346 host name support is only available on ULTRIX systems that are
347 configured to run DECnet.]
348 decnet dst decnetaddr
350 True if the DECnet destination address is decnetaddr.
351 decnet host decnetaddr
353 True if either the DECnet source or destination address is dec‐
354 netaddr.
355 llc True if the packet has an 802.2 LLC header. This includes:
357 Ethernet packets with a length field rather than a type field
359 that aren't raw NetWare-over-802.3 packets;
360 IEEE 802.11 data packets;
362 Token Ring packets (no check is done for LLC frames);
364 FDDI packets (no check is done for LLC frames);
366 LLC-encapsulated ATM packets, for SunATM on Solaris.
368 llc type
370 True if the packet has an 802.2 LLC header and has the specified
371 type. type can be one of:
372 i Information (I) PDUs
374 s Supervisory (S) PDUs
376 u Unnumbered (U) PDUs
378 rr Receiver Ready (RR) S PDUs
380 rnr Receiver Not Ready (RNR) S PDUs
382 rej Reject (REJ) S PDUs
384 ui Unnumbered Information (UI) U PDUs
386 ua Unnumbered Acknowledgment (UA) U PDUs
388 disc Disconnect (DISC) U PDUs
390 sabme Set Asynchronous Balanced Mode Extended (SABME) U PDUs
392 test Test (TEST) U PDUs
394 xid Exchange Identification (XID) U PDUs
396 frmr Frame Reject (FRMR) U PDUs
398 inbound
400 Packet was received by the host performing the capture rather
401 than being sent by that host. This is only supported for cer‐
402 tain link-layer types, such as SLIP and the ``cooked'' Linux
403 capture mode used for the ``any'' device and for some other de‐
404 vice types.
405 outbound
407 Packet was sent by the host performing the capture rather than
408 being received by that host. This is only supported for certain
409 link-layer types, such as SLIP and the ``cooked'' Linux capture
410 mode used for the ``any'' device and for some other device
411 types.
412 ifname interface
414 True if the packet was logged as coming from the specified in‐
415 terface (applies only to packets logged by OpenBSD's or Free‐
416 BSD's pf(4)).
417 on interface
419 Synonymous with the ifname modifier.
420 rnr num
422 True if the packet was logged as matching the specified PF rule
423 number (applies only to packets logged by OpenBSD's or FreeBSD's
424 pf(4)).
425 rulenum num
427 Synonymous with the rnr modifier.
428 reason code
430 True if the packet was logged with the specified PF reason code.
431 The known codes are: match, bad-offset, fragment, short,
432 normalize, and memory (applies only to packets logged by Open‐
433 BSD's or FreeBSD's pf(4)).
434 rset name
436 True if the packet was logged as matching the specified PF rule‐
437 set name of an anchored ruleset (applies only to packets logged
438 by OpenBSD's or FreeBSD's pf(4)).
439 ruleset name
441 Synonymous with the rset modifier.
442 srnr num
444 True if the packet was logged as matching the specified PF rule
445 number of an anchored ruleset (applies only to packets logged by
446 OpenBSD's or FreeBSD's pf(4)).
447 subrulenum num
449 Synonymous with the srnr modifier.
450 action act
452 True if PF took the specified action when the packet was logged.
453 Known actions are: pass and block and, with later versions of
454 pf(4), nat, rdr, binat and scrub (applies only to packets logged
455 by OpenBSD's or FreeBSD's pf(4)).
456 wlan ra ehost
458 True if the IEEE 802.11 RA is ehost. The RA field is used in
459 all frames except for management frames.
460 wlan ta ehost
462 True if the IEEE 802.11 TA is ehost. The TA field is used in
463 all frames except for management frames and CTS (Clear To Send)
464 and ACK (Acknowledgment) control frames.
465 wlan addr1 ehost
467 True if the first IEEE 802.11 address is ehost.
468 wlan addr2 ehost
470 True if the second IEEE 802.11 address, if present, is ehost.
471 The second address field is used in all frames except for CTS
472 (Clear To Send) and ACK (Acknowledgment) control frames.
473 wlan addr3 ehost
475 True if the third IEEE 802.11 address, if present, is ehost.
476 The third address field is used in management and data frames,
477 but not in control frames.
478 wlan addr4 ehost
480 True if the fourth IEEE 802.11 address, if present, is ehost.
481 The fourth address field is only used for WDS (Wireless Distri‐
482 bution System) frames.
483 type wlan_type
485 True if the IEEE 802.11 frame type matches the specified
486 wlan_type. Valid wlan_types are: mgt, ctl and data.
487 type wlan_type subtype wlan_subtype
489 True if the IEEE 802.11 frame type matches the specified
490 wlan_type and frame subtype matches the specified wlan_subtype.
491 If the specified wlan_type is mgt, then valid wlan_subtypes are:
493 assoc-req, assoc-resp, reassoc-req, reassoc-resp, probe-req,
494 probe-resp, beacon, atim, disassoc, auth and deauth.
495 If the specified wlan_type is ctl, then valid wlan_subtypes are:
497 ps-poll, rts, cts, ack, cf-end and cf-end-ack.
498 If the specified wlan_type is data, then valid wlan_subtypes
500 are: data, data-cf-ack, data-cf-poll, data-cf-ack-poll, null,
501 cf-ack, cf-poll, cf-ack-poll, qos-data, qos-data-cf-ack,
502 qos-data-cf-poll, qos-data-cf-ack-poll, qos, qos-cf-poll and
503 qos-cf-ack-poll.
504 subtype wlan_subtype
506 True if the IEEE 802.11 frame subtype matches the specified
507 wlan_subtype and frame has the type to which the specified
508 wlan_subtype belongs.
509 dir direction
511 True if the IEEE 802.11 frame direction matches the specified
512 direction. Valid directions are: nods, tods, fromds, dstods, or
513 a numeric value.
514 vlan [vlan_id]
516 True if the packet is an IEEE 802.1Q VLAN packet. If the op‐
517 tional vlan_id is specified, only true if the packet has the
518 specified vlan_id. Note that the first vlan keyword encountered
519 in an expression changes the decoding offsets for the remainder
520 of the expression on the assumption that the packet is a VLAN
521 packet. The `vlan [vlan_id]` keyword may be used more than
522 once, to filter on VLAN hierarchies. Each use of that keyword
523 increments the filter offsets by 4.
524 For example:
526 vlan 100 && vlan 200
527 filters on VLAN 200 encapsulated within VLAN 100, and
528 vlan && vlan 300 && ip
529 filters IPv4 protocol encapsulated in VLAN 300 encapsulated
530 within any higher order VLAN.
531 mpls [label_num]
533 True if the packet is an MPLS packet. If the optional label_num
534 is specified, only true if the packet has the specified la‐
535 bel_num. Note that the first mpls keyword encountered in an ex‐
536 pression changes the decoding offsets for the remainder of the
537 expression on the assumption that the packet is a MPLS-encapsu‐
538 lated IP packet. The `mpls [label_num]` keyword may be used
539 more than once, to filter on MPLS hierarchies. Each use of that
540 keyword increments the filter offsets by 4.
541 For example:
543 mpls 100000 && mpls 1024
544 filters packets with an outer label of 100000 and an inner label
545 of 1024, and
546 mpls && mpls 1024 && host 192.9.200.1
547 filters packets to or from 192.9.200.1 with an inner label of
548 1024 and any outer label.
549 pppoed True if the packet is a PPP-over-Ethernet Discovery packet (Eth‐
551 ernet type 0x8863).
552 pppoes [session_id]
554 True if the packet is a PPP-over-Ethernet Session packet (Ether‐
555 net type 0x8864). If the optional session_id is specified, only
556 true if the packet has the specified session_id. Note that the
557 first pppoes keyword encountered in an expression changes the
558 decoding offsets for the remainder of the expression on the as‐
559 sumption that the packet is a PPPoE session packet.
560 For example:
562 pppoes 0x27 && ip
563 filters IPv4 protocol encapsulated in PPPoE session id 0x27.
564 geneve [vni]
566 True if the packet is a Geneve packet (UDP port 6081). If the
567 optional vni is specified, only true if the packet has the spec‐
568 ified vni. Note that when the geneve keyword is encountered in
569 an expression, it changes the decoding offsets for the remainder
570 of the expression on the assumption that the packet is a Geneve
571 packet.
572 For example:
574 geneve 0xb && ip
575 filters IPv4 protocol encapsulated in Geneve with VNI 0xb. This
576 will match both IPv4 directly encapsulated in Geneve as well as
577 IPv4 contained inside an Ethernet frame.
578 iso proto protocol
580 True if the packet is an OSI packet of protocol type protocol.
581 Protocol can be a number or one of the names clnp, esis, or
582 isis.
583 clnp, esis, isis
585 Abbreviations for:
586 iso proto \protocol
587 where protocol is one of the above protocols.
588 l1, l2, iih, lsp, snp, csnp, psnp
590 Abbreviations for IS-IS PDU types.
591 vpi n True if the packet is an ATM packet, for SunATM on Solaris, with
593 a virtual path identifier of n.
594 vci n True if the packet is an ATM packet, for SunATM on Solaris, with
596 a virtual channel identifier of n.
597 lane True if the packet is an ATM packet, for SunATM on Solaris, and
599 is an ATM LANE packet. Note that the first lane keyword encoun‐
600 tered in an expression changes the tests done in the remainder
601 of the expression on the assumption that the packet is either a
602 LANE emulated Ethernet packet or a LANE LE Control packet. If
603 lane isn't specified, the tests are done under the assumption
604 that the packet is an LLC-encapsulated packet.
605 oamf4s True if the packet is an ATM packet, for SunATM on Solaris, and
607 is a segment OAM F4 flow cell (VPI=0 & VCI=3).
608 oamf4e True if the packet is an ATM packet, for SunATM on Solaris, and
610 is an end-to-end OAM F4 flow cell (VPI=0 & VCI=4).
611 oamf4 True if the packet is an ATM packet, for SunATM on Solaris, and
613 is a segment or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 |
614 VCI=4)).
615 oam True if the packet is an ATM packet, for SunATM on Solaris, and
617 is a segment or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 |
618 VCI=4)).
619 metac True if the packet is an ATM packet, for SunATM on Solaris, and
621 is on a meta signaling circuit (VPI=0 & VCI=1).
622 bcc True if the packet is an ATM packet, for SunATM on Solaris, and
624 is on a broadcast signaling circuit (VPI=0 & VCI=2).
625 sc True if the packet is an ATM packet, for SunATM on Solaris, and
627 is on a signaling circuit (VPI=0 & VCI=5).
628 ilmic True if the packet is an ATM packet, for SunATM on Solaris, and
630 is on an ILMI circuit (VPI=0 & VCI=16).
631 connectmsg
633 True if the packet is an ATM packet, for SunATM on Solaris, and
634 is on a signaling circuit and is a Q.2931 Setup, Call Proceed‐
635 ing, Connect, Connect Ack, Release, or Release Done message.
636 metaconnect
638 True if the packet is an ATM packet, for SunATM on Solaris, and
639 is on a meta signaling circuit and is a Q.2931 Setup, Call Pro‐
640 ceeding, Connect, Release, or Release Done message.
641 expr1 relop expr2
643 True if the relation holds. Relop is one of {>, <, >=, <=, =,
644 ==, !=} (where = means the same as ==). Each of expr1 and expr2
645 is an arithmetic expression composed of integer constants (ex‐
646 pressed in standard C syntax), the normal binary operators {+,
647 -, *, /, %, &, |, ^, <<, >>}, a length operator, and special
648 packet data accessors. Note that all comparisons are unsigned,
649 so that, for example, 0x80000000 and 0xffffffff are > 0.
650 The % and ^ operators are currently only supported for filtering
652 in the kernel on particular operating systems (for example:
653 FreeBSD, Linux with 3.7 and later kernels, NetBSD); on all other
654 systems (for example: AIX, illumos, Solaris, OpenBSD), if those
655 operators are used, filtering will be done in user mode, which
656 will increase the overhead of capturing packets and may cause
657 more packets to be dropped.
658 The length operator, indicated by the keyword len, gives the
660 length of the packet.
661 To access data inside the packet, use the following syntax:
663 proto [ expr : size ]
664 Proto is one of arp, atalk, carp, decnet, ether, fddi, icmp,
665 icmp6, igmp, igrp, ip, ip6, lat, link, mopdl, moprc, pim, ppp,
666 radio, rarp, sca, sctp, slip, tcp, tr, udp, vrrp or wlan, and
667 indicates the protocol layer for the index operation. (ether,
668 fddi, link, ppp, slip, tr and wlan all refer to the link layer.
669 radio refers to the "radio header" added to some 802.11 cap‐
670 tures.) Note that tcp, udp and other upper-layer protocol types
671 only apply to IPv4, not IPv6 (this will be fixed in the future).
672 The byte offset, relative to the indicated protocol layer, is
673 given by expr. Size is optional and indicates the number of
674 bytes in the field of interest; it can be either one, two, or
675 four, and defaults to one.
676 For example, `ether[0] & 1 != 0' catches all multicast traffic.
678 The expression `ip[0] & 0xf != 5' catches all IPv4 packets with
679 options. The expression `ip[6:2] & 0x1fff = 0' catches only un‐
680 fragmented IPv4 datagrams and frag zero of fragmented IPv4 data‐
681 grams. This check is implicitly applied to the tcp and udp in‐
682 dex operations. For instance, tcp[0] always means the first
683 byte of the TCP header, and never means the first byte of an in‐
684 tervening fragment.
685 Some offsets and field values may be expressed as names rather
687 than as numeric values. The following protocol header field
688 offsets are available: icmptype (ICMP type field), icmp6type
689 (ICMPv6 type field), icmpcode (ICMP code field), icmp6code
690 (ICMPv6 code field) and tcpflags (TCP flags field).
691 The following ICMP type field values are available:
693 icmp-echoreply, icmp-unreach, icmp-sourcequench, icmp-redirect,
694 icmp-echo, icmp-routeradvert, icmp-routersolicit, icmp-timxceed,
695 icmp-paramprob, icmp-tstamp, icmp-tstampreply, icmp-ireq,
696 icmp-ireqreply, icmp-maskreq, icmp-maskreply.
697 The following ICMPv6 type field values are available:
699 icmp6-destinationunreach, icmp6-packettoobig,
700 icmp6-timeexceeded, icmp6-parameterproblem, icmp6-echo,
701 icmp6-echoreply, icmp6-multicastlistenerquery,
702 icmp6-multicastlistenerreportv1, icmp6-multicastlistenerdone,
703 icmp6-routersolicit, icmp6-routeradvert, icmp6-neighborsolicit,
704 icmp6-neighboradvert, icmp6-redirect, icmp6-routerrenum,
705 icmp6-nodeinformationquery, icmp6-nodeinformationresponse,
706 icmp6-ineighbordiscoverysolicit, icmp6-ineighbordiscoveryadvert,
707 icmp6-multicastlistenerreportv2,
708 icmp6-homeagentdiscoveryrequest, icmp6-homeagentdiscoveryreply,
709 icmp6-mobileprefixsolicit, icmp6-mobileprefixadvert,
710 icmp6-certpathsolicit, icmp6-certpathadvert,
711 icmp6-multicastrouteradvert, icmp6-multicastroutersolicit,
712 icmp6-multicastrouterterm.
713 The following TCP flags field values are available: tcp-fin,
715 tcp-syn, tcp-rst, tcp-push, tcp-ack, tcp-urg, tcp-ece, tcp-cwr.
716 Primitives may be combined using:
718 A parenthesized group of primitives and operators.
720 Negation (`!' or `not').
722 Concatenation (`&&' or `and').
724 Alternation (`||' or `or').
726 Negation has the highest precedence. Alternation and concatenation
728 have equal precedence and associate left to right. Note that explicit
729 and tokens, not juxtaposition, are now required for concatenation.
730 If an identifier is given without a keyword, the most recent keyword is
732 assumed. For example,
733 not host vs and ace
734 is short for
735 not host vs and host ace
736 which should not be confused with
737 not (host vs or ace)
738
740 To select all packets arriving at or departing from `sundown':
741 host sundown
742 To select traffic between `helios' and either `hot' or `ace':
744 host helios and (hot or ace)
745 To select all IPv4 packets between `ace' and any host except `helios':
747 ip host ace and not helios
748 To select all traffic between local hosts and hosts at Berkeley:
750 net ucb-ether
751 To select all FTP traffic through Internet gateway `snup':
753 gateway snup and (port ftp or ftp-data)
754 To select IPv4 traffic neither sourced from nor destined for local
756 hosts (if you gateway to one other net, this stuff should never make it
757 onto your local net).
758 ip and not net localnet
759 To select the start and end packets (the SYN and FIN packets) of each
761 TCP conversation that involves a non-local host.
762 tcp[tcpflags] & (tcp-syn|tcp-fin) != 0 and not src and dst net localnet
763 To select the TCP packets with flags RST and ACK both set. (i.e. se‐
765 lect only the RST and ACK flags in the flags field, and if the result
766 is "RST and ACK both set", match)
767 tcp[tcpflags] & (tcp-rst|tcp-ack) == (tcp-rst|tcp-ack)
768 To select all IPv4 HTTP packets to and from port 80, i.e. print only
770 packets that contain data, not, for example, SYN and FIN packets and
771 ACK-only packets. (IPv6 is left as an exercise for the reader.)
772 tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)
773 To select IPv4 packets longer than 576 bytes sent through gateway
775 `snup':
776 gateway snup and ip[2:2] > 576
777 To select IPv4 broadcast or multicast packets that were not sent via
779 Ethernet broadcast or multicast:
780 ether[0] & 1 = 0 and ip[16] >= 224
781 To select all ICMP packets that are not echo requests/replies (i.e.,
783 not ping packets):
784 icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply
785 icmp6[icmp6type] != icmp6-echo and icmp6[icmp6type] != icmp6-echoreply
786
788 The ICMPv6 type code names, as well as the tcp-ece and tcp-cwr TCP flag
789 names became available in libpcap 1.9.0.
790 The geneve keyword became available in libpcap 1.8.0.
792
794 pcap(3PCAP)
795
797 To report a security issue please send an e-mail to
798 security@tcpdump.org.
799 To report bugs and other problems, contribute patches, request a fea‐
801 ture, provide generic feedback etc please see the file CONTRIBUTING.md
802 in the libpcap source tree root.
803 Filter expressions on fields other than those in Token Ring headers
805 will not correctly handle source-routed Token Ring packets.
806 Filter expressions on fields other than those in 802.11 headers will
808 not correctly handle 802.11 data packets with both To DS and From DS
809 set.
810 `ip6 proto' should chase header chain, but at this moment it does not.
812 `ip6 protochain' is supplied for this behavior. For example, to match
813 IPv6 fragments: `ip6 protochain 44'
814 Arithmetic expression against transport layer headers, like tcp[0],
816 does not work against IPv6 packets. It only looks at IPv4 packets.
817 19 November 2022 PCAP-FILTER(7)