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PCAP-FILTER(7)     FreeBSD Miscellaneous Information Manual     PCAP-FILTER(7)

NAME
       pcap-filter - packet filter syntax

DESCRIPTION
       pcap_compile() 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 supplied to pcap_loop(),
       pcap_dispatch(), pcap_next(), or pcap_next_ex().

       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.  For some link layers, such as SLIP
              and the ``cooked'' Linux capture mode used for the ``any''
              device and for some other device types, the inbound and outbound
              qualifiers can be used to specify a desired direction.

       proto  proto qualifiers restrict the match to a particular protocol.
              Possible protos are: ether, fddi, tr, wlan, ip, ip6, arp, rarp,
              decnet, 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' (except the latter is not legal
              syntax), `net bar' means `(ip or arp or rarp) net bar' and `port
              53' means `(tcp or udp) port 53'.

       [`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 described below.

       More complex filter expressions are built up by using the words and, or
       and not 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 host
              True if the IPv4/v6 destination field of the packet is host,
              which may be either an address or a name.

       src host host
              True if the IPv4/v6 source field of the packet is host.

       host host
              True if either the IPv4/v6 source or destination of the packet
              is host.

              Any of the above host expressions can be prepended with the
              keywords, ip, arp, rarp, or ip6 as in:
                   ip host host
              which is equivalent to:
                   ether proto \ip and host host
              If host is a name with multiple IP addresses, each address will
              be checked for a match.

       ether dst ehost
              True if the Ethernet destination address is ehost.  Ehost may be
              either a name from /etc/ethers or a number (see ethers(3N) for
              numeric format).

       ether src ehost
              True if the Ethernet source address is ehost.

       ether host ehost
              True if either the Ethernet source or destination address is
              ehost.

       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-Ethernet-address resolution mechanism
              (/etc/ethers, etc.).  (An equivalent expression is
                   ether host ehost and not host host
              which can be used with either names or numbers for host /
              ehost.)  This syntax does not work in IPv6-enabled configuration
              at this moment.

       dst net net
              True if the IPv4/v6 destination address of the packet has a
              network number of net.  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 net
              True if the IPv4/v6 source address of the packet has a network
              number of net.

       net net
              True if either the IPv4/v6 source or destination address of the
              packet has a network number of net.

       net net mask netmask
              True if the IPv4 address matches net with the specific netmask.
              May be qualified with src or dst.  Note that this syntax is not
              valid for IPv6 net.

       net net/len
              True if the IPv4/v6 address matches net with a netmask len bits
              wide.  May be qualified with src or dst.

       dst port port
              True if the packet is ip/tcp, ip/udp, ip6/tcp or ip6/udp and has
              a destination port value of port.  The port can be a number or a
              name used in /etc/services (see tcp(4P) and udp(4P)).  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 port
              True if the packet has a source port value of port.

       port port
              True if either the source or destination port of the packet is
              port.

       dst portrange port1-port2
              True if the packet is ip/tcp, ip/udp, ip6/tcp or ip6/udp and has
              a destination port value between port1 and port2.  port1 and
              port2 are interpreted in the same fashion as the port parameter
              for port.

       src portrange port1-port2
              True if the packet has a source port value between port1 and
              port2.

       portrange port1-port2
              True if either the source or destination port of the packet is
              between port1 and port2.

              Any of the above port or port range expressions can be prepended
              with the keywords, tcp or udp, as in:
                   tcp src port port
              which matches only tcp packets whose source port is port.

       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)) of protocol
              type protocol.  Protocol can be a number or one of the names
              icmp, icmp6, igmp, igrp, pim, ah, esp, vrrp, udp, or tcp.  Note
              that the identifiers tcp, udp, and icmp are also keywords and
              must be escaped via backslash (\), which is \\ in the C-shell.
              Note that this primitive does not chase the protocol header
              chain.

       ip6 proto protocol
              True if the packet is an IPv6 packet of protocol type protocol.
              Note that this primitive does not chase the protocol header
              chain.

       proto protocol
              True if the packet is an IPv4 or IPv6 packet of protocol type
              protocol.  Note that this primitive does not chase the protocol
              header chain.

       tcp, udp, icmp
              Abbreviations for:
                   proto p
              where p 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.  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 primitive is complex and cannot be optimized by
              the BPF optimizer code, so this can be somewhat slow.

       ip protochain protocol
              Equivalent to ip6 protochain protocol, but this is for IPv4.

       protochain protocol
              True if the packet is an IPv4 or IPv6 packet of protocol type
              protocol.  Note that this primitive chases the protocol 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 available, 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 ip, ip6, arp, rarp, atalk, aarp,
              decnet, sca, lat, mopdl, moprc, iso, stp, ipx, or netbeui.  Note
              these identifiers are also keywords and must be escaped via
              backslash (\).

              [In the case of FDDI (e.g., `fddi protocol arp'), Token Ring
              (e.g., `tr protocol arp'), and IEEE 802.11 wireless LANS (e.g.,
              `wlan protocol 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 filter 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 exceptions 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 AppleTalk 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 p
              where p is one of the above protocols.

       lat, moprc, mopdl
              Abbreviations for:
                   ether proto p
              where p is one of the above protocols.  Note that not all
              applications using pcap(3) currently know how to parse these
              protocols.

       decnet src host
              True if the DECNET source address is host, which may be an
              address of the form ``10.123'', or a DECNET host name.  [DECNET
              host name support is only available on ULTRIX systems that are
              configured to run DECNET.]

       decnet dst host
              True if the DECNET destination address is host.

       decnet host host
              True if either the DECNET source or destination address is host.

       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)).

       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)).

       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)).

       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)).

       ruleset name
              Synonomous 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)).

       subrulenum num
              Synonomous 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)), nat, rdr, binat and scrub (applies only to packets
              logged by OpenBSD's or FreeBSD's pf(4)).

       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_types 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_subtypes 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_subtypes are:
              ps-poll, rts, cts, ack, cf-end and cf-end-ack.

              If the specified wlan_type is data, then valid wlan_subtypes
              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 dir
              True if the IEEE 802.11 frame direction matches the specified
              dir.  Valid directions are: nods, tods, fromds, dstods, or a
              numeric value.

       vlan [vlan_id]
              True if the packet is an IEEE 802.1Q VLAN packet.  If [vlan_id]
              is specified, only true if the packet has the specified vlan_id.
              Note that the first vlan keyword encountered in expression
              changes the decoding offsets for the remainder of expression on
              the assumption that the packet is a VLAN packet.  The vlan
              [vlan_id] expression may be used more than once, to filter on
              VLAN hierarchies.  Each use of that expression 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 protocols encapsulated in VLAN 300 encapsulated
              within any higher order VLAN.

       mpls [label_num]
              True if the packet is an MPLS packet.  If [label_num] is
              specified, only true is the packet has the specified label_num.
              Note that the first mpls keyword encountered in expression
              changes the decoding offsets for the remainder of expression on
              the assumption that the packet is a MPLS-encapsulated IP packet.
              The mpls [label_num] expression may be used more than once, to
              filter on MPLS hierarchies.  Each use of that expression
              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 label.

       pppoed True if the packet is a PPP-over-Ethernet Discovery packet
              (Ethernet type 0x8863).

       pppoes True if the packet is a PPP-over-Ethernet Session packet
              (Ethernet type 0x8864).  Note that the first pppoes keyword
              encountered in expression changes the decoding offsets for the
              remainder of expression on the assumption that the packet is a
              PPPoE session packet.

              For example:
                   pppoes && ip
              filters IPv4 protocols encapsulated in PPPoE.

       iso proto protocol
              True if the packet is an OSI packet of protocol type protocol.
              Protocol can be a number or one of the names clnp, esis, or
              isis.

       clnp, esis, isis
              Abbreviations for:
                   iso proto p
              where p 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 identifier 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 expression changes the tests done in the
              remainder of 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.

       llc    True if the packet is an ATM packet, for SunATM on Solaris, and
              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 signaling circuit (VPI=0 & VCI=2).

       sc     True if the packet is an ATM packet, for SunATM on Solaris, and
              is on a signaling circuit (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 circuit 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 message.

       expr relop expr
              True if the relation holds, where relop is one of >, <, >=, <=,
              =, !=, and expr is an arithmetic expression composed of integer
              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.  To access data inside the packet, use the following syntax:
                   proto [ expr : size ]
              Proto is one of ether, fddi, tr, wlan, ppp, slip, link, ip, arp,
              rarp, tcp, udp, icmp, ip6 or radio, and indicates the protocol
              layer for the index operation.  (ether, fddi, wlan, tr, ppp,
              slip and link 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 protocol 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.  The length operator, indicated by the keyword len, gives
              the length of the packet.

              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
              datagrams.  This check is implicitly applied to the tcp and udp
              index operations.  For instance, 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), icmpcode
              (ICMP 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 TCP flags field values are available: tcp-fin,
              tcp-syn, tcp-rst, tcp-push, tcp-ack, tcp-urg.

       Primitives may be combined using:

              A parenthesized group of primitives and operators (parentheses
              are special to the Shell and must be escaped).

              Negation (`!' or `not').

              Concatenation (`&&' or `and').

              Alternation (`||' or `or').

       Negation has 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 example,
            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 IP 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 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 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 exercise for the reader.)
              tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)

       To select IP packets longer than 576 bytes sent through gateway snup:
              gateway snup and ip[2:2] > 576

       To select IP 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

SEE ALSO
       pcap(3)

BUGS
       Please send problems, bugs, questions, desirable enhancements, etc. to:

              tcpdump-workers@lists.tcpdump.org

       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.

       Arithmetic expression against transport layer headers, like tcp[0],
       does not work against IPv6 packets.  It only looks at IPv4 packets.

                                6 January 2008                  PCAP-FILTER(7)

NAME | DESCRIPTION | EXAMPLES | SEE ALSO | BUGS

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