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

       The filter expression consists of one or more  primitives.   Primitives
       usually consist of an id (name or number) preceded by one or more qual-
       ifiers.  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 Wire-
              less 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 identi-
       cally 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 wire-
       less  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 (or equivalently: `&&', `||' and `!' respectively)  to  combine
       primitives.   E.g.,  `host foo and not port ftp and not port ftp-data'.
       To save typing, identical qualifier lists can be omitted.   E.g.,  `tcp
       dst  port  ftp  or  ftp-data or domain' is exactly the same as `tcp dst
       port ftp or tcp dst port ftp-data or tcp dst port domain'.

       Allowable primitives are:

       dst host 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 key-
              words, 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 IPv4 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 resolu-
              tion 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 net-
              work  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 IPv4 TCP, IPv4 UDP, IPv6 TCP or IPv6 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 IPv4 TCP, IPv4 UDP, IPv6 TCP or IPv6 UDP
              and has a destination port value between port1 and  port2  (both
              inclusive).  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 (both inclusive).

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

              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 \protocol
              where protocol is one of the above protocols.

       ip6 protochain protocol
              True if the packet is IPv6 packet, and contains protocol  header
              with type protocol in its protocol header chain.  For example,
                   ip6 protochain 6
              matches any IPv6 packet with TCP protocol header in the protocol
              header chain.  The packet may contain, for example,  authentica-
              tion  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  cap-
              ture  is being done on the Linux "any" interface, which can cap-
              ture on more than one interface, this check will not  work  cor-
              rectly.

       ether multicast
              True  if  the packet is an Ethernet multicast packet.  The ether
              keyword is optional.  This is shorthand for `ether[0] & 1 != 0'.

       ip multicast
              True if the packet is an IPv4 multicast packet.

       ip6 multicast
              True if the packet is an IPv6 multicast packet.

       ether proto protocol
              True if the packet is of ether type protocol.  Protocol can be a
              number or one of the names aarp, arp, atalk,  decnet,  ip,  ip6,
              ipx,  iso,  lat,  loopback,  mopdl, moprc, netbeui, rarp, sca or
              stp.  Note these identifiers (except loopback) are also keywords
              and must be escaped via backslash (\).

              [In  the  case  of  FDDI  (e.g.,  `fddi proto \arp'), Token Ring
              (e.g., `tr proto \arp'), and IEEE 802.11  wireless  LANs  (e.g.,
              `wlan  proto  \arp'),  for most of those protocols, the protocol
              identification comes from the 802.2 Logical Link  Control  (LLC)
              header, which is usually layered on top of the FDDI, Token Ring,
              or 802.11 header.

              When filtering for most  protocol  identifiers  on  FDDI,  Token
              Ring, or 802.11, the 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 Eth-
                     ernet  frame  and for a SNAP-format packet as it does for
                     FDDI, Token Ring, and 802.11;

              aarp   the filter checks for the AppleTalk ARP etype  in  either
                     an  Ethernet  frame or an 802.2 SNAP frame with an OUI of
                     0x000000;

              ipx    the filter checks for the IPX etype in an Ethernet frame,
                     the  IPX  DSAP  in the LLC header, the 802.3-with-no-LLC-
                     header encapsulation of IPX, and the IPX etype in a  SNAP
                     frame.

       ip, ip6, arp, rarp, atalk, aarp, decnet, iso, stp, ipx, netbeui
              Abbreviations for:
                   ether proto \protocol
              where protocol is one of the above protocols.

       lat, moprc, mopdl
              Abbreviations for:
                   ether proto \protocol
              where protocol is one of the above protocols.  Note that not all
              applications using pcap(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.

       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  cer-
              tain  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, normal-
              ize,  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 rule-
              set  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 Distri-
              bution 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  the
              optional  vlan_id  is specified, only true if the packet has the
              specified vlan_id.  Note that the first vlan keyword encountered
              in  an expression changes the decoding offsets for the remainder
              of the expression on the assumption that the packet  is  a  VLAN
              packet.   The  `vlan  [vlan_id]`  keyword  may be used more than
              once, to filter on VLAN hierarchies.  Each use of  that  keyword
              increments the filter offsets by 4.

              For example:
                   vlan 100 && vlan 200
              filters on VLAN 200 encapsulated within VLAN 100, and
                   vlan && vlan 300 && ip
              filters  IPv4  protocol  encapsulated  in  VLAN 300 encapsulated
              within any higher order VLAN.

       mpls [label_num]
              True if the packet is an MPLS packet.  If the optional label_num
              is  specified,  only  true  if  the  packet  has  the  specified
              label_num.  Note that the first mpls keyword encountered  in  an
              expression changes the decoding offsets for the remainder of the
              expression on the assumption that the packet is a  MPLS-encapsu-
              lated  IP  packet.   The  `mpls [label_num]` keyword may be used
              more than once, to filter on MPLS hierarchies.  Each use of that
              keyword increments the filter offsets by 4.

              For example:
                   mpls 100000 && mpls 1024
              filters packets with an outer label of 100000 and an inner label
              of 1024, and
                   mpls && mpls 1024 && host 192.9.200.1
              filters packets to or from 192.9.200.1 with an  inner  label  of
              1024 and any outer label.

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

       pppoes [session_id]
              True if the packet is a PPP-over-Ethernet Session packet (Ether-
              net type 0x8864).  If the optional session_id is specified, only
              true if the packet has the specified session_id.  Note that  the
              first  pppoes  keyword  encountered in an expression changes the
              decoding offsets for the remainder  of  the  expression  on  the
              assumption that the packet is a PPPoE session packet.

              For example:
                   pppoes 0x27 && ip
              filters IPv4 protocol encapsulated in PPPoE session id 0x27.

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

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

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

       clnp, esis, isis
              Abbreviations for:
                   iso proto \protocol
              where protocol is one of the above protocols.

       l1, l2, iih, lsp, snp, csnp, psnp
              Abbreviations for IS-IS PDU types.

       vpi n  True if the packet is an ATM packet, for SunATM on Solaris, with
              a virtual path 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 encoun-
              tered in an expression changes the tests done in  the  remainder
              of  the expression on the assumption that the packet is either a
              LANE emulated Ethernet packet or a LANE LE Control  packet.   If
              lane  isn't  specified,  the tests are done under the assumption
              that the packet is an LLC-encapsulated packet.

       oamf4s True if the packet is an ATM packet, for SunATM on Solaris,  and
              is a segment OAM F4 flow cell (VPI=0 & VCI=3).

       oamf4e True  if the packet is an ATM packet, for SunATM on Solaris, and
              is an end-to-end OAM F4 flow cell (VPI=0 & VCI=4).

       oamf4  True if the packet is an ATM packet, for SunATM on Solaris,  and
              is  a  segment  or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 |
              VCI=4)).

       oam    True if the packet is an ATM packet, for SunATM on Solaris,  and
              is  a  segment  or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 |
              VCI=4)).

       metac  True if the packet is an ATM packet, for SunATM on Solaris,  and
              is on a meta signaling circuit (VPI=0 & VCI=1).

       bcc    True  if the packet is an ATM packet, for SunATM on Solaris, and
              is on a broadcast 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 Proceed-
              ing, 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 Pro-
              ceeding, 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, rela-
              tive 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
              (ICMPv6  type  field),  icmpcode  (ICMP  code  field), icmp6code
              (ICMPv6 code field) and tcpflags (TCP flags field).

              The following ICMP type field values are available: icmp-echore-
              ply,  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 ICMPv6 type fields are  available:  icmp6-destina-
              tionrunreach,       icmp6-packettoobig,      icmp6-timeexceeded,
              icmp6-parameterproblem, icmp6-echo, icmp6-echoreply,  icmp6-mul-
              ticastlistenerquery, icmp6-multicastlistenerreportv1, icmp6-mul-
              ticastlistenerdone,   icmp6-routersolicit,   icmp6-routeradvert,
              icmp6-neighborsolicit,   icmp6-neighboradvert,   icmp6-redirect,
              icmp6-routerrenum, icmp6-nodeinformationquery,  icmp6-nodeinfor-
              mationresponse,  icmp6-ineighbordiscoverysolicit,  icmp6-ineigh-
              bordiscoveryadvert, icmp6-multicastlistenerreportv2, icmp6-home-
              agentdiscoveryrequest,            icmp6-homeagentdiscoveryreply,
              icmp6-mobileprefixsolicit, icmp6-mobileprefixadvert, icmp6-cert-
              pathsolicit,  icmp6-certpathadvert, icmp6-multicastrouteradvert,
              icmp6-multicastroutersolicit, icmp6-multicastrouterterm.

              The following TCP flags field  values  are  available:  tcp-fin,
              tcp-syn,  tcp-rst, tcp-push, tcp-ack, tcp-urg, tcp-ece, tcp-cwr.

       Primitives may be combined using:

              A parenthesized group of primitives and operators.

              Negation (`!' or `not').

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

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

       Negation has the highest  precedence.   Alternation  and  concatenation
       have  equal precedence and associate left to right.  Note that explicit
       and tokens, not juxtaposition, are now required for concatenation.

       If an identifier is given without a keyword, the most recent keyword is
       assumed.  For 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 IPv4 packets between `ace' and any host except `helios':
              ip host ace and not helios

       To select all traffic between local hosts and hosts at Berkeley:
              net ucb-ether

       To select all FTP traffic through Internet gateway `snup':
              gateway snup and (port ftp or ftp-data)

       To  select  IPv4  traffic  neither  sourced from nor destined for local
       hosts (if you gateway to one other net, this stuff should never make it
       onto your local net).
              ip and not net localnet

       To  select  the start and end packets (the SYN and FIN packets) of each
       TCP conversation that involves a non-local host.
              tcp[tcpflags] & (tcp-syn|tcp-fin) != 0 and not src and dst net localnet

       To select the TCP packets with flags  RST  and  ACK  both  set.   (i.e.
       select only the RST and ACK flags in the flags field, and if the result
       is "RST and ACK both set", match)
              tcp[tcpflags] & (tcp-rst|tcp-ack) == (tcp-rst|tcp-ack)

       To select all IPv4 HTTP packets to and from port 80,  i.e.  print  only
       packets  that  contain  data, not, for example, SYN and FIN packets and
       ACK-only packets.  (IPv6 is left as an exercise for the reader.)
              tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)

       To select IPv4 packets longer  than  576  bytes  sent  through  gateway
       `snup':
              gateway snup and ip[2:2] > 576

       To  select  IPv4  broadcast or multicast packets that were not sent via
       Ethernet broadcast or multicast:
              ether[0] & 1 = 0 and ip[16] >= 224

       To select all ICMP packets that are not  echo  requests/replies  (i.e.,
       not ping packets):
              icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply
              icmp6[icmp6type] != icmp6-echo and icmp6[icmp6type] != icmp6-echoreply


SEE ALSO

       pcap(3)


BUGS

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

       To report bugs and other problems, contribute patches, request  a  fea-
       ture,  provide generic feedback etc please see the file CONTRIBUTING.md
       in the libpcap source tree root.

       Filter expressions on fields other than those  in  Token  Ring  headers
       will not correctly handle source-routed Token Ring packets.

       Filter  expressions  on  fields other than those in 802.11 headers will
       not correctly handle 802.11 data packets with both To DS  and  From  DS
       set.

       `ip6  proto' should chase header chain, but at this moment it does not.
       `ip6 protochain' is supplied for this behavior.  For example, to  match
       IPv6 fragments: `ip6 protochain 44'

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



                                6 February 2021                 pcap-filter(7)

libpcap 1.10.1 - Generated Fri Jun 11 14:53:35 CDT 2021
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