Provided by: libpcap0.8_1.9.1-2_amd64 bug

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(3PCAP),     pcap_dispatch(3PCAP),    pcap_next(3PCAP),    or
       pcap_next_ex(3PCAP).

       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 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   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 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 (\).  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, and is
              not supported 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.

       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 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
              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(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.

       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)).

       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
              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)).

       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), 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 [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.

       geneve [vni]
              True if the packet is a Geneve packet (UDP port 6081). If [vni] is specified,  only
              true  if  the  packet  has the specified vni.  Note that when the geneve keyword is
              encountered in expression, it changes the decoding offsets  for  the  remainder  of
              expression on the assumption that the packet is a Geneve packet.

              For example:
                   geneve 0xb && ip
              filters IPv4 protocols encapsulated in Geneve with VNI 0xb. This will match both IP
              directly encapsulated in Geneve as well as IP contained inside an Ethernet frame.

       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.

       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.

              The % and ^ operators are currently only supported for filtering in the  kernel  on
              Linux  with  3.7  and  later  kernels; on all other systems, if those operators are
              used, filtering will be done in user mode, which  will  increase  the  overhead  of
              capturing packets and may cause more packets to be dropped.

              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), icmp6type (ICMP v6 type field) icmpcode (ICMP code  field),  icmp6code
              (ICMP v6 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  fields  are  available:  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 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

       To report a security issue please send an e-mail to security@tcpdump.org.

       To report bugs and other problems, contribute patches, request a feature, provide  generic
       feedback etc please see the file CONTRIBUTING 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.

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

                                         5 November 2017                           PCAP-FILTER(7)