# PCAP-FILTER - packet filter syntax - man(7) - [phpMan] [_PCAP-FILTER_(7)](https://www.chedong.com/phpMan.php/man/PCAP-FILTER/7/markdown) Miscellaneous Information Manual [_PCAP-FILTER_(7)](https://www.chedong.com/phpMan.php/man/PCAP-FILTER/7/markdown) ## NAME pcap-filter - packet filter syntax ## DESCRIPTION [**pcap_compile**(3PCAP)](https://www.chedong.com/phpMan.php/man/pcapcompile/3PCAP/markdown) is used to compile a string into a filter program. The resulting filter program can then be applied to some stream of packets to determine which packets will be sup‐ plied to [**pcap_loop**(3PCAP)](https://www.chedong.com/phpMan.php/man/pcaploop/3PCAP/markdown), [**pcap_dispatch**(3PCAP)](https://www.chedong.com/phpMan.php/man/pcapdispatch/3PCAP/markdown), [**pcap_next**(3PCAP)](https://www.chedong.com/phpMan.php/man/pcapnext/3PCAP/markdown), or [**pcap_next_ex**(3PCAP)](https://www.chedong.com/phpMan.php/man/pcapnextex/3PCAP/markdown). The _filter_ _expression_ consists of one or more _primitives_. Primitives usually consist of an _id_ (name or number) preceded by one or more qualifiers. There are three different kinds of qualifier: _type_ _type_ qualifiers say what kind of thing the id name or number refers to. Possible types are **host**, **net**, **port **and **portrange**. E.g., `**host **foo', `**net **128.3', `**port **20', `**portrange **6000-6008'. If there is no type qualifier, **host **is assumed. _dir_ _dir_ qualifiers specify a particular transfer direction to and/or from _id_. Possible directions are **src**, **dst**, **src or dst**, **src and dst**, **ra**, **ta**, **addr1**, **addr2**, **addr3**, and **addr4**. E.g., `**src **foo', `**dst net **128.3', `**src or dst port **ftp-data'. If there is no dir qualifier, `**src or dst**' is assumed. The **ra**, **ta**, **addr1**, **addr2**, **addr3**, and **addr4** qualifiers are only valid for IEEE 802.11 Wireless LAN link layers. _proto_ _proto_ qualifiers restrict the match to a particular protocol. Possible protocols are: **ether**, **fddi**, **tr**, **wlan**, **ip**, **ip6**, **arp**, **rarp**, **decnet**, **sctp**, **tcp **and **udp**. E.g., `**ether** **src **foo', `**arp net **128.3', `**tcp port **21', `**udp portrange **7000-7009', `**wlan addr2** 0:2:3:4:5:6'. If there is no _proto_ qualifier, all protocols consistent with the type are assumed. E.g., `**src **foo' means `**(ip or arp or rarp) src **foo', `**net **bar' means `**(ip or arp or rarp) net **bar' and `**port **53' means `**(tcp or udp or sctp) port **53' (note that these examples use invalid syntax to illustrate the principle). [**fddi **is actually an alias for **ether**; the parser treats them identically as meaning ``the data link level used on the specified network interface''. FDDI headers contain Ethernet- like source and destination addresses, and often contain Ethernet-like packet types, so you can filter on these FDDI fields just as with the analogous Ethernet fields. FDDI headers also contain other fields, but you cannot name them explicitly in a filter expression. Similarly, **tr **and **wlan **are aliases for **ether**; the previous paragraph's statements about FDDI headers also apply to Token Ring and 802.11 wireless LAN headers. For 802.11 headers, the destination address is the DA field and the source address is the SA field; the BSSID, RA, and TA fields aren't tested.] In addition to the above, there are some special `primitive' keywords that don't follow the pattern: **gateway**, **broadcast**, **less**, **greater **and arithmetic expressions. All of these are de‐ scribed below. More complex filter expressions are built up by using the words **and**, **or **and **not **(or equiva‐ lently: `**&&**', `**||**' and `**!**' respectively) to combine primitives. E.g., `**host **foo **and not port** ftp **and not port **ftp-data'. To save typing, identical qualifier lists can be omitted. E.g., `**tcp dst port **ftp **or **ftp-data **or **domain' is exactly the same as `**tcp dst port **ftp **or tcp dst** **port **ftp-data **or tcp dst port **domain'. Allowable primitives are: **dst host _**hostnameaddr_ True if the IPv4/v6 destination field of the packet is _hostnameaddr_, which may be ei‐ ther an address or a name. **src host _**hostnameaddr_ True if the IPv4/v6 source field of the packet is _hostnameaddr_. **host _**hostnameaddr_ True if either the IPv4/v6 source or destination of the packet is _hostnameaddr_. Any of the above host expressions can be prepended with the keywords, **ip**, **arp**, **rarp**, or **ip6 **as in: **ip host _**hostnameaddr_ which is equivalent to: **ether proto \**ip **and host _**hostnameaddr_ If _hostnameaddr_ is a name with multiple IPv4/v6 addresses, each address will be checked for a match. **ether dst _**ethernameaddr_ True if the Ethernet destination address is _ethernameaddr_. _ethernameaddr_ may be ei‐ ther a name from /etc/ethers or a numerical MAC address of the form "xx:xx:xx:xx:xx:xx", "xx.xx.xx.xx.xx.xx", "xx-xx-xx-xx-xx-xx", "xxxx.xxxx.xxxx", "xxxxxxxxxxxx", or various mixes of ':', '.', and '-', where each "x" is a hex digit (0-9, a-f, or A-F). **ether src _**ethernameaddr_ True if the Ethernet source address is _ethernameaddr_. **ether host _**ethernameaddr_ True if either the Ethernet source or destination address is _ethernameaddr_. **gateway _**host_ True if the packet used _host_ as a gateway. I.e., the Ethernet source or destination address was _host_ but neither the IP source nor the IP destination was _host_. _Host_ must be a name and must be found both by the machine's host-name-to-IP-address resolution mechanisms (host name file, DNS, NIS, etc.) and by the machine's host-name-to-Ether‐ net-address resolution mechanism (/etc/ethers, etc.). (An equivalent expression is **ether host _**ethernameaddr_ **and not host _**hostnameaddr_ which can be used with either names or numbers for _hostnameaddr_ _/_ _ethernameaddr_.) This syntax does not work in IPv6-enabled configuration at this moment. **dst net _**netnameaddr_ True if the IPv4/v6 destination address of the packet has a network number of _net‐_ _nameaddr_. _Net_ may be either a name from the networks database (/etc/networks, etc.) or a network number. An IPv4 network number can be written as a dotted quad (e.g., 192.168.1.0), dotted triple (e.g., 192.168.1), dotted pair (e.g, 172.16), or single number (e.g., 10); the netmask is 255.255.255.255 for a dotted quad (which means that it's really a host match), 255.255.255.0 for a dotted triple, 255.255.0.0 for a dotted pair, or 255.0.0.0 for a single number. An IPv6 network number must be written out fully; the netmask is ff:ff:ff:ff:ff:ff:ff:ff, so IPv6 "network" matches are really always host matches, and a network match requires a netmask length. **src net _**netnameaddr_ True if the IPv4/v6 source address of the packet has a network number of _netnameaddr_. **net _**netnameaddr_ True if either the IPv4/v6 source or destination address of the packet has a network number of _netnameaddr_. **net _**netaddr_ **mask _**netmask_ True if the IPv4 address matches _netaddr_ with the specific _netmask_. May be qualified with **src **or **dst**. Note that this syntax is not valid for IPv6 _netaddr_. **net _**netaddr_/_len_ True if the IPv4/v6 address matches _netaddr_ with a netmask _len_ bits wide. May be qualified with **src **or **dst**. **dst port _**portnamenum_ True if the packet is IPv4/v6 TCP, UDP or SCTP and has a destination port value of _portnamenum_. The _portnamenum_ can be a number or a name used in /etc/services (see [**tcp**(4P)](https://www.chedong.com/phpMan.php/man/tcp/4P/markdown) and [**udp**(4P)](https://www.chedong.com/phpMan.php/man/udp/4P/markdown)). If a name is used, both the port number and protocol are checked. If a number or ambiguous name is used, only the port number is checked (e.g., `**dst port **513' will print both tcp/login traffic and udp/who traffic, and `**port** domain' will print both tcp/domain and udp/domain traffic). **src port _**portnamenum_ True if the packet has a source port value of _portnamenum_. **port _**portnamenum_ True if either the source or destination port of the packet is _portnamenum_. **dst portrange _**portnamenum1-portnamenum2_ True if the packet is IPv4/v6 TCP, UDP or SCTP and has a destination port value be‐ tween _portnamenum1_ and _portnamenum2_ (both inclusive). _portnamenum1_ and _portnamenum2_ are interpreted in the same fashion as the _portnamenum_ parameter for **port**. **src portrange _**portnamenum1-portnamenum2_ True if the packet has a source port value between _portnamenum1_ and _portnamenum2_ (both inclusive). **portrange _**portnamenum1-portnamenum2_ True if either the source or destination port of the packet is between _portnamenum1_ and _portnamenum2_ (both inclusive). Any of the above port or port range expressions can be prepended with the keywords, **tcp**, **udp **or **sctp**, as in: **tcp src port _**portnamenum_ which matches only TCP packets whose source port is _portnamenum_. **less _**length_ True if the packet has a length less than or equal to _length_. This is equivalent to: **len <= _**length_ **greater _**length_ True if the packet has a length greater than or equal to _length_. This is equivalent to: **len >= _**length_ **ip proto _**protocol_ True if the packet is an IPv4 packet (see [**ip**(4P)](https://www.chedong.com/phpMan.php/man/ip/4P/markdown)) of protocol type _protocol_. _Protocol_ can be a number or one of the names recognized by [**getprotobyname**(3)](https://www.chedong.com/phpMan.php/man/getprotobyname/3/markdown) (as in e.g. `[**getent**(1)](https://www.chedong.com/phpMan.php/man/getent/1/markdown) protocols'), typically from an entry in _/etc/protocols_, for example: **ah**, **esp**, **eigrp **(only in Linux, FreeBSD, NetBSD, DragonFly BSD, and macOS), **icmp**, **igmp**, **igrp **(only in OpenBSD), **pim**, **sctp**, **tcp**, **udp **or **vrrp**. Note that most of these example identifiers are also keywords and must be escaped via backslash (\). Note that this primitive does not chase the protocol header chain. **icmp **Abbreviation for: **ip proto **1 **ip6 proto _**protocol_ True if the packet is an IPv6 packet of protocol type _protocol_. (See `**ip proto**' above for the meaning of _protocol_.) Note that the IPv6 variant of ICMP uses a different protocol number, named **ipv6-icmp **in AIX, FreeBSD, illumos, Linux, macOS, NetBSD, OpenBSD, Solaris and Windows. Note that this primitive does not chase the protocol header chain. **icmp6 **Abbreviation for: **ip6 proto **58 **proto _**protocol_ True if the packet is an IPv4 or IPv6 packet of protocol type _protocol_. (See `**ip** **proto**' above for the meaning of _protocol_.) Note that this primitive does not chase the protocol header chain. **ah**, **esp**, **pim**, **sctp**, **tcp**, **udp** Abbreviations for: **proto \_**protocol_ where _protocol_ is one of the above protocols. **ip6 protochain _**protocol_ True if the packet is IPv6 packet, and contains protocol header with type _protocol_ in its protocol header chain. (See `**ip proto**' above for the meaning of _protocol_.) For example, **ip6 protochain **6 matches any IPv6 packet with TCP protocol header in the protocol header chain. The packet may contain, for example, authentication header, routing header, or hop-by-hop option header, between IPv6 header and TCP header. The BPF code emitted by this prim‐ itive is complex and cannot be optimized by the BPF optimizer code, and is not sup‐ ported by filter engines in the kernel, so this can be somewhat slow, and may cause more packets to be dropped. **ip protochain _**protocol_ Equivalent to **ip6 protochain _**protocol_, but this is for IPv4. (See `**ip proto**' above for the meaning of _protocol_.) **protochain _**protocol_ True if the packet is an IPv4 or IPv6 packet of protocol type _protocol_. (See `**ip** **proto**' above for the meaning of _protocol_.) Note that this primitive chases the proto‐ col header chain. ### ether broadcast True if the packet is an Ethernet broadcast packet. The **ether **keyword is optional. ### ip broadcast True if the packet is an IPv4 broadcast packet. It checks for both the all-zeroes and all-ones broadcast conventions, and looks up the subnet mask on the interface on which the capture is being done. If the subnet mask of the interface on which the capture is being done is not avail‐ able, either because the interface on which capture is being done has no netmask or because the capture is being done on the Linux "any" interface, which can capture on more than one interface, this check will not work correctly. ### ether multicast True if the packet is an Ethernet multicast packet. The **ether **keyword is optional. This is shorthand for `**ether[**0**] & **1 **!= **0'. ### ip multicast True if the packet is an IPv4 multicast packet. ### ip6 multicast True if the packet is an IPv6 multicast packet. **ether proto _**protocol_ True if the packet is of ether type _protocol_. _Protocol_ can be a number or one of the names **aarp**, **arp**, **atalk**, **decnet**, **ip**, **ip6**, **ipx**, **iso**, **lat**, **loopback**, **mopdl**, **moprc**, **net‐** **beui**, **rarp**, **sca **or **stp**. Note these identifiers (except **loopback**) are also keywords and must be escaped via backslash (\). [In the case of FDDI (e.g., `**fddi proto \arp**'), Token Ring (e.g., `**tr proto \arp**'), and IEEE 802.11 wireless LANs (e.g., `**wlan proto \arp**'), for most of those protocols, the protocol identification comes from the 802.2 Logical Link Control (LLC) header, which is usually layered on top of the FDDI, Token Ring, or 802.11 header. When filtering for most protocol identifiers on FDDI, Token Ring, or 802.11, the fil‐ ter checks only the protocol ID field of an LLC header in so-called SNAP format with an Organizational Unit Identifier (OUI) of 0x000000, for encapsulated Ethernet; it doesn't check whether the packet is in SNAP format with an OUI of 0x000000. The ex‐ ceptions are: **iso **the filter checks the DSAP (Destination Service Access Point) and SSAP (Source Service Access Point) fields of the LLC header; **stp **and **netbeui** the filter checks the DSAP of the LLC header; **atalk **the filter checks for a SNAP-format packet with an OUI of 0x080007 and the Ap‐ pleTalk etype. In the case of Ethernet, the filter checks the Ethernet type field for most of those protocols. The exceptions are: **iso**, **stp**, and **netbeui** the filter checks for an 802.3 frame and then checks the LLC header as it does for FDDI, Token Ring, and 802.11; **atalk **the filter checks both for the AppleTalk etype in an Ethernet frame and for a SNAP-format packet as it does for FDDI, Token Ring, and 802.11; **aarp **the filter checks for the AppleTalk ARP etype in either an Ethernet frame or an 802.2 SNAP frame with an OUI of 0x000000; **ipx **the filter checks for the IPX etype in an Ethernet frame, the IPX DSAP in the LLC header, the 802.3-with-no-LLC-header encapsulation of IPX, and the IPX etype in a SNAP frame. **ip**, **ip6**, **arp**, **rarp**, **atalk**, **aarp**, **decnet**, **iso**, **stp**, **ipx**, **netbeui** Abbreviations for: **ether proto \_**protocol_ where _protocol_ is one of the above protocols. **lat**, **moprc**, **mopdl** Abbreviations for: **ether proto \_**protocol_ where _protocol_ is one of the above protocols. Note that not all applications using [**pcap**(3PCAP)](https://www.chedong.com/phpMan.php/man/pcap/3PCAP/markdown) currently know how to parse these protocols. **decnet src _**decnetaddr_ True if the DECnet source address is _decnetaddr_, which may be an address of the form ``10.123'', or a DECnet host name. [DECnet host name support is only available on UL‐ TRIX systems that are configured to run DECnet.] **decnet dst _**decnetaddr_ True if the DECnet destination address is _decnetaddr_. **decnet host _**decnetaddr_ True if either the DECnet source or destination address is _decnetaddr_. **llc **True if the packet has an 802.2 LLC header. This includes: Ethernet packets with a length field rather than a type field that aren't raw NetWare- over-802.3 packets; IEEE 802.11 data packets; Token Ring packets (no check is done for LLC frames); FDDI packets (no check is done for LLC frames); LLC-encapsulated ATM packets, for SunATM on Solaris. **llc _**type_ True if the packet has an 802.2 LLC header and has the specified _type_. _type_ can be one of: **i **Information (I) PDUs **s **Supervisory (S) PDUs **u **Unnumbered (U) PDUs **rr **Receiver Ready (RR) S PDUs **rnr **Receiver Not Ready (RNR) S PDUs **rej **Reject (REJ) S PDUs **ui **Unnumbered Information (UI) U PDUs **ua **Unnumbered Acknowledgment (UA) U PDUs **disc **Disconnect (DISC) U PDUs **sabme **Set Asynchronous Balanced Mode Extended (SABME) U PDUs **test **Test (TEST) U PDUs **xid **Exchange Identification (XID) U PDUs **frmr **Frame Reject (FRMR) U PDUs ### inbound Packet was received by the host performing the capture rather than being sent by that host. This is only supported for certain link-layer types, such as SLIP and the ``cooked'' Linux capture mode used for the ``any'' device and for some other device types. ### outbound Packet was sent by the host performing the capture rather than being received by that host. This is only supported for certain link-layer types, such as SLIP and the ``cooked'' Linux capture mode used for the ``any'' device and for some other device types. **ifname _**interface_ True if the packet was logged as coming from the specified interface (applies only to packets logged by OpenBSD's or FreeBSD's [**pf**(4)](https://www.chedong.com/phpMan.php/man/pf/4/markdown)). **on _**interface_ Synonymous with the **ifname **modifier. **rnr _**num_ True if the packet was logged as matching the specified PF rule number (applies only to packets logged by OpenBSD's or FreeBSD's [**pf**(4)](https://www.chedong.com/phpMan.php/man/pf/4/markdown)). **rulenum _**num_ Synonymous with the **rnr **modifier. **reason _**code_ True if the packet was logged with the specified PF reason code. The known codes are: **match**, **bad-offset**, **fragment**, **short**, **normalize**, and **memory **(applies only to packets logged by OpenBSD's or FreeBSD's [**pf**(4)](https://www.chedong.com/phpMan.php/man/pf/4/markdown)). **rset _**name_ True if the packet was logged as matching the specified PF ruleset name of an anchored ruleset (applies only to packets logged by OpenBSD's or FreeBSD's [**pf**(4)](https://www.chedong.com/phpMan.php/man/pf/4/markdown)). **ruleset _**name_ Synonymous with the **rset **modifier. **srnr _**num_ True if the packet was logged as matching the specified PF rule number of an anchored ruleset (applies only to packets logged by OpenBSD's or FreeBSD's [**pf**(4)](https://www.chedong.com/phpMan.php/man/pf/4/markdown)). **subrulenum _**num_ Synonymous with the **srnr **modifier. **action _**act_ True if PF took the specified action when the packet was logged. Known actions are: **pass **and **block **and, with later versions of [**pf**(4)](https://www.chedong.com/phpMan.php/man/pf/4/markdown), **nat**, **rdr**, **binat **and **scrub **(applies only to packets logged by OpenBSD's or FreeBSD's [**pf**(4)](https://www.chedong.com/phpMan.php/man/pf/4/markdown)). **wlan ra _**ehost_ True if the IEEE 802.11 RA is _ehost_. The RA field is used in all frames except for management frames. **wlan ta _**ehost_ True if the IEEE 802.11 TA is _ehost_. The TA field is used in all frames except for management frames and CTS (Clear To Send) and ACK (Acknowledgment) control frames. **wlan addr1 _**ehost_ True if the first IEEE 802.11 address is _ehost_. **wlan addr2 _**ehost_ True if the second IEEE 802.11 address, if present, is _ehost_. The second address field is used in all frames except for CTS (Clear To Send) and ACK (Acknowledgment) control frames. **wlan addr3 _**ehost_ True if the third IEEE 802.11 address, if present, is _ehost_. The third address field is used in management and data frames, but not in control frames. **wlan addr4 _**ehost_ True if the fourth IEEE 802.11 address, if present, is _ehost_. The fourth address field is only used for WDS (Wireless Distribution System) frames. **type _**wlan_type_ True if the IEEE 802.11 frame type matches the specified _wlan_type_. Valid _wlan_type_s are: **mgt**, **ctl **and **data**. **type _**wlan_type_ **subtype _**wlan_subtype_ True if the IEEE 802.11 frame type matches the specified _wlan_type_ and frame subtype matches the specified _wlan_subtype_. If the specified _wlan_type_ is **mgt**, then valid _wlan_subtype_s are: **assoc-req**, **assoc-** **resp**, **reassoc-req**, **reassoc-resp**, **probe-req**, **probe-resp**, **beacon**, **atim**, **disassoc**, **auth** and **deauth**. If the specified _wlan_type_ is **ctl**, then valid _wlan_subtype_s are: **ps-poll**, **rts**, **cts**, **ack**, **cf-end **and **cf-end-ack**. If the specified _wlan_type_ is **data**, then valid _wlan_subtype_s are: **data**, **data-cf-ack**, **data-cf-poll**, **data-cf-ack-poll**, **null**, **cf-ack**, **cf-poll**, **cf-ack-poll**, **qos-data**, **qos-data-cf-ack**, **qos-data-cf-poll**, **qos-data-cf-ack-poll**, **qos**, **qos-cf-poll **and **qos-cf-ack-poll**. **subtype _**wlan_subtype_ True if the IEEE 802.11 frame subtype matches the specified _wlan_subtype_ and frame has the type to which the specified _wlan_subtype_ belongs. **dir _**direction_ True if the IEEE 802.11 frame direction matches the specified _direction_. Valid direc‐ tions are: **nods**, **tods**, **fromds**, **dstods**, or a numeric value. **vlan _**[vlan_id]_ True if the packet is an IEEE 802.1Q VLAN packet. If the optional _vlan_id_ is speci‐ fied, only true if the packet has the specified _vlan_id_. Note that the first **vlan** keyword encountered in an expression changes the decoding offsets for the remainder of the expression on the assumption that the packet is a VLAN packet. The `**vlan** _[vlan_id]_` keyword may be used more than once, to filter on VLAN hierarchies. Each use of that keyword increments the filter offsets by 4. For example: **vlan **100 **&& vlan **200 filters on VLAN 200 encapsulated within VLAN 100, and **vlan && vlan **300 **&& ip** filters IPv4 protocol encapsulated in VLAN 300 encapsulated within any higher order VLAN. **mpls _**[label_num]_ True if the packet is an MPLS packet. If the optional _label_num_ is specified, only true if the packet has the specified _label_num_. Note that the first **mpls **keyword en‐ countered in an expression changes the decoding offsets for the remainder of the ex‐ pression on the assumption that the packet is a MPLS-encapsulated IP packet. The `**mpls _**[label_num]_` keyword may be used more than once, to filter on MPLS hierarchies. Each use of that keyword increments the filter offsets by 4. For example: **mpls **100000 **&& mpls **1024 filters packets with an outer label of 100000 and an inner label of 1024, and **mpls && mpls **1024 **&& host **192.9.200.1 filters packets to or from 192.9.200.1 with an inner label of 1024 and any outer la‐ bel. **pppoed **True if the packet is a PPP-over-Ethernet Discovery packet (Ethernet type 0x8863). **pppoes _**[session_id]_ True if the packet is a PPP-over-Ethernet Session packet (Ethernet type 0x8864). If the optional _session_id_ is specified, only true if the packet has the specified _ses‐_ _sion_id_. Note that the first **pppoes **keyword encountered in an expression changes the decoding offsets for the remainder of the expression on the assumption that the packet is a PPPoE session packet. For example: **pppoes **0x27 **&& ip** filters IPv4 protocol encapsulated in PPPoE session id 0x27. **geneve _**[vni]_ True if the packet is a Geneve packet (UDP port 6081). If the optional _vni_ is speci‐ fied, only true if the packet has the specified _vni_. Note that when the **geneve **key‐ word is encountered in an expression, it changes the decoding offsets for the remain‐ der of the expression on the assumption that the packet is a Geneve packet. For example: **geneve **0xb **&& ip** filters IPv4 protocol encapsulated in Geneve with VNI 0xb. This will match both IPv4 directly encapsulated in Geneve as well as IPv4 contained inside an Ethernet frame. **iso proto _**protocol_ True if the packet is an OSI packet of protocol type _protocol_. _Protocol_ can be a num‐ ber or one of the names **clnp**, **esis**, or **isis**. **clnp**, **esis**, **isis** Abbreviations for: **iso proto \_**protocol_ where _protocol_ is one of the above protocols. **l1**, **l2**, **iih**, **lsp**, **snp**, **csnp**, **psnp** Abbreviations for IS-IS PDU types. **vpi _**n_ True if the packet is an ATM packet, for SunATM on Solaris, with a virtual path iden‐ tifier of _n_. **vci _**n_ True if the packet is an ATM packet, for SunATM on Solaris, with a virtual channel identifier of _n_. **lane **True if the packet is an ATM packet, for SunATM on Solaris, and is an ATM LANE packet. Note that the first **lane **keyword encountered in an expression changes the tests done in the remainder of the expression on the assumption that the packet is either a LANE emulated Ethernet packet or a LANE LE Control packet. If **lane **isn't specified, the tests are done under the assumption that the packet is an LLC-encapsulated packet. **oamf4s **True if the packet is an ATM packet, for SunATM on Solaris, and is a segment OAM F4 flow cell (VPI=0 & VCI=3). **oamf4e **True if the packet is an ATM packet, for SunATM on Solaris, and is an end-to-end OAM F4 flow cell (VPI=0 & VCI=4). **oamf4 **True if the packet is an ATM packet, for SunATM on Solaris, and is a segment or end- to-end OAM F4 flow cell (VPI=0 & (VCI=3 | VCI=4)). **oam **True if the packet is an ATM packet, for SunATM on Solaris, and is a segment or end- to-end OAM F4 flow cell (VPI=0 & (VCI=3 | VCI=4)). **metac **True if the packet is an ATM packet, for SunATM on Solaris, and is on a meta signaling circuit (VPI=0 & VCI=1). **bcc **True if the packet is an ATM packet, for SunATM on Solaris, and is on a broadcast sig‐ naling circuit (VPI=0 & VCI=2). **sc **True if the packet is an ATM packet, for SunATM on Solaris, and is on a signaling cir‐ cuit (VPI=0 & VCI=5). **ilmic **True if the packet is an ATM packet, for SunATM on Solaris, and is on an ILMI circuit (VPI=0 & VCI=16). ### connectmsg True if the packet is an ATM packet, for SunATM on Solaris, and is on a signaling cir‐ cuit and is a Q.2931 Setup, Call Proceeding, Connect, Connect Ack, Release, or Release Done message. ### metaconnect True if the packet is an ATM packet, for SunATM on Solaris, and is on a meta signaling circuit and is a Q.2931 Setup, Call Proceeding, Connect, Release, or Release Done mes‐ sage. _expr1_ _relop_ _expr2_ True if the relation holds. _Relop_ is one of {**>**, **<**, **>=**, **<=**, **=**, **==**, **!=**} (where **= **means the same as **==**). Each of _expr1_ and _expr2_ is an arithmetic expression composed of in‐ teger constants (expressed in standard C syntax), the normal binary operators {**+**, **-**, *****, **/**, **%**, **&**, **|**, **^**, **<<**, **>>**}, a length operator, and special packet data accessors. Note that all comparisons are unsigned, so that, for example, 0x80000000 and 0xffffffff are > 0. The **% **and **^ **operators are currently only supported for filtering in the kernel on par‐ ticular operating systems (for example: FreeBSD, Linux with 3.7 and later kernels, NetBSD); on all other systems (for example: AIX, illumos, Solaris, OpenBSD), if those operators are used, filtering will be done in user mode, which will increase the over‐ head of capturing packets and may cause more packets to be dropped. The length operator, indicated by the keyword **len**, gives the length of the packet. To access data inside the packet, use the following syntax: _proto_ **[ _**expr_ **: _**size_ **]** _Proto_ is one of **arp**, **atalk**, **carp**, **decnet**, **ether**, **fddi**, **icmp**, **icmp6**, **igmp**, **igrp**, **ip**, **ip6**, **lat**, **link**, **mopdl**, **moprc**, **pim**, **ppp**, **radio**, **rarp**, **sca**, **sctp**, **slip**, **tcp**, **tr**, **udp**, **vrrp **or **wlan**, and indicates the protocol layer for the index operation. (**ether**, **fddi**, **link**, **ppp**, **slip**, **tr **and **wlan **all refer to the link layer. **radio **refers to the "radio header" added to some 802.11 captures.) Note that **tcp**, **udp **and other upper-layer pro‐ tocol types only apply to IPv4, not IPv6 (this will be fixed in the future). The byte offset, relative to the indicated protocol layer, is given by _expr_. _Size_ is optional and indicates the number of bytes in the field of interest; it can be either one, two, or four, and defaults to one. For example, `**ether[**0**] & **1 **!= **0' catches all multicast traffic. The expression `**ip[**0**]** **& **0xf **!= **5' catches all IPv4 packets with options. The expression `**ip[**6:2**] & **0x1fff **=** 0' catches only unfragmented IPv4 datagrams and frag zero of fragmented IPv4 data‐ grams. This check is implicitly applied to the **tcp **and **udp **index operations. For in‐ stance, **tcp[**0**] **always means the first byte of the TCP _header_, and never means the first byte of an intervening fragment. Some offsets and field values may be expressed as names rather than as numeric values. The following protocol header field offsets are available: **icmptype **(ICMP type field), **icmp6type **(ICMPv6 type field), **icmpcode **(ICMP code field), **icmp6code **(ICMPv6 code field) and **tcpflags **(TCP flags field). The following ICMP type field values are available: **icmp-echoreply**, **icmp-unreach**, **icmp-sourcequench**, **icmp-redirect**, **icmp-echo**, **icmp-routeradvert**, **icmp-routersolicit**, **icmp-timxceed**, **icmp-paramprob**, **icmp-tstamp**, **icmp-tstampreply**, **icmp-ireq**, **icmp-ireqreply**, **icmp-maskreq**, **icmp-maskreply**. The following ICMPv6 type field values are available: **icmp6-destinationunreach**, **icmp6-packettoobig**, **icmp6-timeexceeded**, **icmp6-parameterproblem**, **icmp6-echo**, **icmp6-echoreply**, **icmp6-multicastlistenerquery**, **icmp6-multicastlistenerreportv1**, **icmp6-multicastlistenerdone**, **icmp6-routersolicit**, **icmp6-routeradvert**, **icmp6-neighborsolicit**, **icmp6-neighboradvert**, **icmp6-redirect**, **icmp6-routerrenum**, **icmp6-nodeinformationquery**, **icmp6-nodeinformationresponse**, **icmp6-ineighbordiscoverysolicit**, **icmp6-ineighbordiscoveryadvert**, **icmp6-multicastlistenerreportv2**, **icmp6-homeagentdiscoveryrequest**, **icmp6-homeagentdiscoveryreply**, **icmp6-mobileprefixsolicit**, **icmp6-mobileprefixadvert**, **icmp6-certpathsolicit**, **icmp6-certpathadvert**, **icmp6-multicastrouteradvert**, **icmp6-multicastroutersolicit**, **icmp6-multicastrouterterm**. The following TCP flags field values are available: **tcp-fin**, **tcp-syn**, **tcp-rst**, **tcp-** **push**, **tcp-ack**, **tcp-urg**, **tcp-ece**, **tcp-cwr**. Primitives may be combined using: A parenthesized group of primitives and operators. Negation (`**!**' or `**not**'). Concatenation (`**&&**' or `**and**'). Alternation (`**||**' or `**or**'). Negation has the highest precedence. Alternation and concatenation have equal precedence and associate left to right. Note that explicit **and **tokens, not juxtaposition, are now required for concatenation. If an identifier is given without a keyword, the most recent keyword is assumed. For exam‐ ple, **not host **vs **and **ace is short for **not host **vs **and host **ace which should not be confused with **not (host **vs **or **ace**)** ## EXAMPLES To select all packets arriving at or departing from `sundown': **host **sundown To select traffic between `helios' and either `hot' or `ace': **host **helios **and (**hot **or **ace**)** To select all IPv4 packets between `ace' and any host except `helios': **ip host **ace **and not **helios To select all traffic between local hosts and hosts at Berkeley: **net **ucb-ether To select all FTP traffic through Internet gateway `snup': **gateway **snup **and (port **ftp **or **ftp-data**)** To select IPv4 traffic neither sourced from nor destined for local hosts (if you gateway to one other net, this stuff should never make it onto your local net). **ip and not net **localnet To select the start and end packets (the SYN and FIN packets) of each TCP conversation that involves a non-local host. **tcp[tcpflags] & (tcp-syn|tcp-fin) != **0 **and not src and dst net **localnet To select the TCP packets with flags RST and ACK both set. (i.e. select only the RST and ACK flags in the flags field, and if the result is "RST and ACK both set", match) **tcp[tcpflags] & (tcp-rst|tcp-ack) == (tcp-rst|tcp-ack)** To select all IPv4 HTTP packets to and from port 80, i.e. print only packets that contain data, not, for example, SYN and FIN packets and ACK-only packets. (IPv6 is left as an exer‐ cise for the reader.) **tcp port **80 **and (((ip[**2:2**] - ((ip[**0**]&**0xf**)<<**2**)) - ((tcp[**12**]&**0xf0**)>>**2**)) != **0**)** To select IPv4 packets longer than 576 bytes sent through gateway `snup': **gateway **snup **and ip[**2:2**] > **576 To select IPv4 broadcast or multicast packets that were _not_ sent via Ethernet broadcast or multicast: **ether[**0**] & **1 **= **0 **and ip[**16**] >= **224 To select all ICMP packets that are not echo requests/replies (i.e., not ping packets): **icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply** **icmp6[icmp6type] != icmp6-echo and icmp6[icmp6type] != icmp6-echoreply** ## BACKWARD COMPATIBILITY The ICMPv6 type code names, as well as the **tcp-ece **and **tcp-cwr **TCP flag names became avail‐ able in libpcap 1.9.0. The **geneve **keyword became available in libpcap 1.8.0. ## SEE ALSO [**pcap**(3PCAP)](https://www.chedong.com/phpMan.php/man/pcap/3PCAP/markdown) ## BUGS To report a security issue please send an e-mail to . To report bugs and other problems, contribute patches, request a feature, provide generic feedback etc please see the file _CONTRIBUTING.md_ in the libpcap source tree root. Filter expressions on fields other than those in Token Ring headers will not correctly handle source-routed Token Ring packets. Filter expressions on fields other than those in 802.11 headers will not correctly handle 802.11 data packets with both To DS and From DS set. `**ip6 proto**' should chase header chain, but at this moment it does not. `**ip6 protochain**' is supplied for this behavior. For example, to match IPv6 fragments: `**ip6 protochain **44' Arithmetic expression against transport layer headers, like **tcp[0]**, does not work against IPv6 packets. It only looks at IPv4 packets. 19 November 2022 [_PCAP-FILTER_(7)](https://www.chedong.com/phpMan.php/man/PCAP-FILTER/7/markdown)