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PCAP-FILTER(7)									   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 destina-
	      tion 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 net-
	      work  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  net-
	      work 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 qual-
	      ified 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 equiva-
	      lent to:
		   len >= length.

       ip proto protocol
	      True if the packet is an IPv4 packet (see ip(4P)) of protocol type protocol.   Pro-
	      tocol  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 net-
	      mask 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 Ether-
	      net; 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(3PCAP) 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 sub-
	      type 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 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 [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 expres-
	      sion  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 encoun-
	      tered 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 [session_id]
	      True if the packet is a PPP-over-Ethernet Session packet	(Ethernet  type  0x8864).
	      If [session_id] is specified, only true if the packet has the specified session_id.
	      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 0x27 && ip
	      filters IPv4 protocols encapsulated in PPPoE session id 0x27.

       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-encap-
	      sulated packet.

       llc    True if the packet is an ATM packet, for SunATM on Solaris, and is an  LLC-encapsu-
	      lated 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 sig-
	      naling 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  cir-
	      cuit (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 sig-
	      naling 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 opera-
	      tions.  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 val-
	      ues.  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-ire-
	      qreply, 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(3PCAP)

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)
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