PCAP-FILTER
Section: Environments, Tables, and Troff Macros (7)
Updated: 6 January 2008
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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
-
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
-
qualifiers specify a particular transfer direction to and/or from
id.
Possible directions are
src,
dst,
src or dst,
src and dst,
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
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
-
qualifiers restrict the match to a particular protocol.
Possible
protos are:
ether,
fddi,
tr,
wlan,
ip,
ip6,
arp,
rarp,
decnet,
tcp
and
udp.
E.g., `ether src foo', `arp net 128.3', `tcp port 21', `udp portrange
7000-7009', `wlan addr2 0:2:3:4:5:6'.
If there is
no proto qualifier, all protocols consistent with the type are
assumed.
E.g., `src foo' means `(ip or arp or rarp) src foo'
(except the latter is not legal syntax), `net bar' means `(ip or
arp or rarp) net bar' and `port 53' means `(tcp or udp) port 53'.
[`fddi' is actually an alias for `ether'; the parser treats them
identically as meaning ``the data link level used on the specified
network interface.'' FDDI headers contain Ethernet-like source
and destination addresses, and often contain Ethernet-like packet
types, so you can filter on these FDDI fields just as with the
analogous Ethernet fields.
FDDI headers also contain other fields,
but you cannot name them explicitly in a filter expression.
Similarly, `tr' and `wlan' are aliases for `ether'; the previous
paragraph's statements about FDDI headers also apply to Token Ring
and 802.11 wireless LAN headers. For 802.11 headers, the destination
address is the DA field and the source address is the SA field; the
BSSID, RA, and TA fields aren't tested.]
In addition to the above, there are some special `primitive' keywords
that don't follow the pattern:
gateway,
broadcast,
less,
greater
and arithmetic expressions.
All of these are described below.
More complex filter expressions are built up by using the words
and,
or
and
not
to combine primitives.
E.g., `host foo and not port ftp and not port ftp-data'.
To save typing, identical qualifier lists can be omitted.
E.g.,
`tcp dst port ftp or ftp-data or domain' is exactly the same as
`tcp dst port ftp or tcp dst port ftp-data or tcp dst port domain'.
Allowable primitives are:
- dst host host
-
True if the IPv4/v6 destination field of the packet is host,
which may be either an address or a name.
- src host host
-
True if the IPv4/v6 source field of the packet is host.
- host host
-
True if either the IPv4/v6 source or destination of the packet is host.
-
Any of the above host expressions can be prepended with the keywords,
ip, arp, rarp, or ip6 as in:
ip host host
which is equivalent to:
ether proto \ip and host host
If host is a name with multiple IP addresses, each address will
be checked for a match.
- ether dst ehost
-
True if the Ethernet destination address is ehost.
Ehost
may be either a name from /etc/ethers or a number (see
ethers(3N)
for numeric format).
- ether src ehost
-
True if the Ethernet source address is ehost.
- ether host ehost
-
True if either the Ethernet source or destination address is ehost.
- gateway host
-
True if the packet used host as a gateway.
I.e., the Ethernet
source or destination address was host but neither the IP source
nor the IP destination was host.
Host must be a name and
must be found both by the machine's host-name-to-IP-address resolution
mechanisms (host name file, DNS, NIS, etc.) and by the machine's
host-name-to-Ethernet-address resolution mechanism (/etc/ethers, etc.).
(An equivalent expression is
ether host ehost and not host host
which can be used with either names or numbers for host / ehost.)
This syntax does not work in IPv6-enabled configuration at this moment.
- dst net net
-
True if the IPv4/v6 destination address of the packet has a network
number of net.
Net may be either a name from the networks database
(/etc/networks, etc.) or a network number.
An IPv4 network number can be written as a dotted quad (e.g., 192.168.1.0),
dotted triple (e.g., 192.168.1), dotted pair (e.g, 172.16), or single
number (e.g., 10); the netmask is 255.255.255.255 for a dotted quad
(which means that it's really a host match), 255.255.255.0 for a dotted
triple, 255.255.0.0 for a dotted pair, or 255.0.0.0 for a single number.
An IPv6 network number must be written out fully; the netmask is
ff:ff:ff:ff:ff:ff:ff:ff, so IPv6 "network" matches are really always
host matches, and a network match requires a netmask length.
- src net net
-
True if the IPv4/v6 source address of the packet has a network
number of net.
- net net
-
True if either the IPv4/v6 source or destination address of the packet has a network
number of net.
- net net mask netmask
-
True if the IPv4 address matches net with the specific netmask.
May be qualified with src or dst.
Note that this syntax is not valid for IPv6 net.
- net net/len
-
True if the IPv4/v6 address matches net with a netmask len
bits wide.
May be qualified with src or dst.
- dst port port
-
True if the packet is ip/tcp, ip/udp, ip6/tcp or ip6/udp and has a
destination port value of port.
The port can be a number or a name used in /etc/services (see
tcp(4P)
and
udp(4P)).
If a name is used, both the port
number and protocol are checked.
If a number or ambiguous name is used,
only the port number is checked (e.g., dst port 513 will print both
tcp/login traffic and udp/who traffic, and port domain will print
both tcp/domain and udp/domain traffic).
- src port port
-
True if the packet has a source port value of port.
- port port
-
True if either the source or destination port of the packet is port.
- dst portrange port1-port2
-
True if the packet is ip/tcp, ip/udp, ip6/tcp or ip6/udp and has a
destination port value between port1 and port2.
port1
and
port2
are interpreted in the same fashion as the
port
parameter for
port.
- src portrange port1-port2
-
True if the packet has a source port value between port1 and
port2.
- portrange port1-port2
-
True if either the source or destination port of the packet is between
port1 and port2.
-
Any of the above port or port range expressions can be prepended with
the keywords, tcp or udp, as in:
tcp src port port
which matches only tcp packets whose source port is port.
- less length
-
True if the packet has a length less than or equal to length.
This is equivalent to:
len <= length.
- greater length
-
True if the packet has a length greater than or equal to length.
This is equivalent to:
len >= length.
- ip proto protocol
-
True if the packet is an IPv4 packet (see
ip(4P))
of protocol type protocol.
Protocol can be a number or one of the names
icmp, icmp6, igmp, igrp, pim, ah,
esp, vrrp, udp, or tcp.
Note that the identifiers tcp, udp, and icmp are also
keywords and must be escaped via backslash (\), which is \\ in the C-shell.
Note that this primitive does not chase the protocol header chain.
- ip6 proto protocol
-
True if the packet is an IPv6 packet of protocol type protocol.
Note that this primitive does not chase the protocol header chain.
- 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.
- ether broadcast
-
True if the packet is an Ethernet broadcast packet.
The ether
keyword is optional.
- ip broadcast
-
True if the packet is an IPv4 broadcast packet.
It checks for both the all-zeroes and all-ones broadcast conventions,
and looks up the subnet mask on the interface on which the capture is
being done.
-
If the subnet mask of the interface on which the capture is being done
is not available, either because the interface on which capture is being
done has no netmask or because the capture is being done on the Linux
"any" interface, which can capture on more than one interface, this
check will not work correctly.
- ether multicast
-
True if the packet is an Ethernet multicast packet.
The ether
keyword is optional.
This is shorthand for `ether[0] & 1 != 0'.
- ip multicast
-
True if the packet is an IPv4 multicast packet.
- ip6 multicast
-
True if the packet is an IPv6 multicast packet.
- ether proto protocol
-
True if the packet is of ether type protocol.
Protocol can be a number or one of the names
ip, ip6, arp, rarp, atalk, aarp,
decnet, sca, lat, mopdl, moprc,
iso, stp, ipx, or netbeui.
Note these identifiers are also keywords
and must be escaped via backslash (\).
-
[In the case of FDDI (e.g., `fddi protocol arp'), Token Ring
(e.g., `tr protocol arp'), and IEEE 802.11 wireless LANS (e.g.,
`wlan protocol arp'), for most of those protocols, the
protocol identification comes from the 802.2 Logical Link Control (LLC)
header, which is usually layered on top of the FDDI, Token Ring, or
802.11 header.
-
When filtering for most protocol identifiers on FDDI, Token Ring, or
802.11, the filter checks only the protocol ID field of an LLC header
in so-called SNAP format with an Organizational Unit Identifier (OUI) of
0x000000, for encapsulated Ethernet; it doesn't check whether the packet
is in SNAP format with an OUI of 0x000000.
The exceptions are:
-
- iso
-
the filter checks the DSAP (Destination Service Access Point) and
SSAP (Source Service Access Point) fields of the LLC header;
- stp and netbeui
-
the filter checks the DSAP of the LLC header;
- atalk
-
the filter checks for a SNAP-format packet with an OUI of 0x080007
and the AppleTalk etype.
-
In the case of Ethernet, the filter checks the Ethernet type field
for most of those protocols. The exceptions are:
-
- iso, stp, and netbeui
-
the filter checks for an 802.3 frame and then checks the LLC header as
it does for FDDI, Token Ring, and 802.11;
- atalk
-
the filter checks both for the AppleTalk etype in an Ethernet frame and
for a SNAP-format packet as it does for FDDI, Token Ring, and 802.11;
- aarp
-
the filter checks for the AppleTalk ARP etype in either an Ethernet
frame or an 802.2 SNAP frame with an OUI of 0x000000;
- ipx
-
the filter checks for the IPX etype in an Ethernet frame, the IPX
DSAP in the LLC header, the 802.3-with-no-LLC-header encapsulation of
IPX, and the IPX etype in a SNAP frame.
- 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 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.
- ip, ip6, arp, rarp, atalk, aarp, decnet, iso, stp, ipx, netbeui
-
Abbreviations for:
ether proto p
where p is one of the above protocols.
- lat, moprc, mopdl
-
Abbreviations for:
ether proto p
where p is one of the above protocols.
Note that not all applications using
pcap(3)
currently know how to parse these protocols.
- type wlan_type
-
True if the IEEE 802.11 frame type matches the specified wlan_type.
Valid wlan_types are:
mgt,
ctl
and data.
- type wlan_type subtype wlan_subtype
-
True if the IEEE 802.11 frame type matches the specified wlan_type
and frame subtype matches the specified wlan_subtype.
-
If the specified wlan_type is mgt,
then valid wlan_subtypes are:
assoc-req,
assoc-resp,
reassoc-req,
reassoc-resp,
probe-req,
probe-resp,
beacon,
atim,
disassoc,
auth and
deauth.
-
If the specified wlan_type is ctl,
then valid wlan_subtypes are:
ps-poll,
rts,
cts,
ack,
cf-end and
cf-end-ack.
-
If the specified wlan_type is data,
then valid wlan_subtypes are:
data,
data-cf-ack,
data-cf-poll,
data-cf-ack-poll,
null,
cf-ack,
cf-poll,
cf-ack-poll,
qos-data,
qos-data-cf-ack,
qos-data-cf-poll,
qos-data-cf-ack-poll,
qos,
qos-cf-poll and
qos-cf-ack-poll.
- subtype wlan_subtype
-
True if the IEEE 802.11 frame subtype matches the specified wlan_subtype
and frame has the type to which the specified wlan_subtype belongs.
- dir dir
-
True if the IEEE 802.11 frame direction matches the specified
dir.
Valid directions are:
nods,
tods,
fromds,
dstods,
or a numeric value.
- vlan [vlan_id]
-
True if the packet is an IEEE 802.1Q VLAN packet.
If [vlan_id] is specified, only true if the packet has the specified
vlan_id.
Note that the first vlan keyword encountered in expression
changes the decoding offsets for the remainder of expression on
the assumption that the packet is a VLAN packet. The vlan
[vlan_id] expression may be used more than once, to filter on VLAN
hierarchies. Each use of that expression increments the filter offsets
by 4.
-
For example:
vlan 100 && vlan 200
filters on VLAN 200 encapsulated within VLAN 100, and
vlan && vlan 300 && ip
filters IPv4 protocols encapsulated in VLAN 300 encapsulated within any
higher order VLAN.
- mpls [label_num]
-
True if the packet is an MPLS packet.
If [label_num] is specified, only true is the packet has the specified
label_num.
Note that the first mpls keyword encountered in expression
changes the decoding offsets for the remainder of expression on
the assumption that the packet is a MPLS-encapsulated IP packet. The
mpls [label_num] expression may be used more than once, to
filter on MPLS hierarchies. Each use of that expression increments the
filter offsets by 4.
-
For example:
mpls 100000 && mpls 1024
filters packets with an outer label of 100000 and an inner label of
1024, and
mpls && mpls 1024 && host 192.9.200.1
filters packets to or from 192.9.200.1 with an inner label of 1024 and
any outer label.
- pppoed
-
True if the packet is a PPP-over-Ethernet Discovery packet (Ethernet
type 0x8863).
- pppoes
-
True if the packet is a PPP-over-Ethernet Session packet (Ethernet
type 0x8864).
Note that the first pppoes keyword encountered in expression
changes the decoding offsets for the remainder of expression on
the assumption that the packet is a PPPoE session packet.
-
For example:
pppoes && ip
filters IPv4 protocols encapsulated in PPPoE.
- tcp, udp, icmp
-
Abbreviations for:
ip proto p or ip6 proto p
where p is one of the above protocols.
- iso proto protocol
-
True if the packet is an OSI packet of protocol type protocol.
Protocol can be a number or one of the names
clnp, esis, or isis.
- clnp, esis, isis
-
Abbreviations for:
iso proto p
where p is one of the above protocols.
- l1, l2, iih, lsp, snp, csnp, psnp
-
Abbreviations for IS-IS PDU types.
- vpi n
-
True if the packet is an ATM packet, for SunATM on Solaris, with a
virtual path identifier of
n.
- vci n
-
True if the packet is an ATM packet, for SunATM on Solaris, with a
virtual channel identifier of
n.
- lane
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
an ATM LANE packet.
Note that the first lane keyword encountered in expression
changes the tests done in the remainder of expression
on the assumption that the packet is either a LANE emulated Ethernet
packet or a LANE LE Control packet. If lane isn't specified, the
tests are done under the assumption that the packet is an
LLC-encapsulated packet.
- llc
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
an LLC-encapsulated packet.
- oamf4s
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
a segment OAM F4 flow cell (VPI=0 & VCI=3).
- oamf4e
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
an end-to-end OAM F4 flow cell (VPI=0 & VCI=4).
- oamf4
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
a segment or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 | VCI=4)).
- oam
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
a segment or end-to-end OAM F4 flow cell (VPI=0 & (VCI=3 | VCI=4)).
- metac
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
on a meta signaling circuit (VPI=0 & VCI=1).
- bcc
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
on a broadcast signaling circuit (VPI=0 & VCI=2).
- sc
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
on a signaling circuit (VPI=0 & VCI=5).
- ilmic
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
on an ILMI circuit (VPI=0 & VCI=16).
- connectmsg
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
on a signaling circuit and is a Q.2931 Setup, Call Proceeding, Connect,
Connect Ack, Release, or Release Done message.
- metaconnect
-
True if the packet is an ATM packet, for SunATM on Solaris, and is
on a meta signaling circuit and is a Q.2931 Setup, Call Proceeding, Connect,
Release, or Release Done message.
- expr relop expr
-
True if the relation holds, where relop is one of >, <, >=, <=, =,
!=, and expr is an arithmetic expression composed of integer
constants (expressed in standard C syntax), the normal binary operators
[+, -, *, /, &, |, <<, >>], a length operator, and special packet data
accessors. Note that all comparisons are unsigned, so that, for example,
0x80000000 and 0xffffffff are > 0.
To access
data inside the packet, use the following syntax:
proto [ expr : size ]
Proto is one of ether, fddi, tr, wlan, ppp, slip, link,
ip, arp, rarp, tcp, udp, icmp, ip6 or radio, and
indicates the protocol layer for the index operation.
(ether, fddi, wlan, tr, ppp, slip and link all refer to the
link layer. radio refers to the "radio header" added to some
802.11 captures.)
Note that tcp, udp and other upper-layer protocol types only
apply to IPv4, not IPv6 (this will be fixed in the future).
The byte offset, relative to the indicated protocol layer, is
given by expr.
Size is optional and indicates the number of bytes in the
field of interest; it can be either one, two, or four, and defaults to one.
The length operator, indicated by the keyword len, gives the
length of the packet.
For example, `ether[0] & 1 != 0' catches all multicast traffic.
The expression `ip[0] & 0xf != 5'
catches all IPv4 packets with options.
The expression
`ip[6:2] & 0x1fff = 0'
catches only unfragmented IPv4 datagrams and frag zero of fragmented
IPv4 datagrams.
This check is implicitly applied to the tcp and udp
index operations.
For instance, tcp[0] always means the first
byte of the TCP header, and never means the first byte of an
intervening fragment.
Some offsets and field values may be expressed as names rather than
as numeric values.
The following protocol header field offsets are
available: icmptype (ICMP type field), icmpcode (ICMP
code field), and tcpflags (TCP flags field).
The following ICMP type field values are available: icmp-echoreply,
icmp-unreach, icmp-sourcequench, icmp-redirect,
icmp-echo, icmp-routeradvert, icmp-routersolicit,
icmp-timxceed, icmp-paramprob, icmp-tstamp,
icmp-tstampreply, icmp-ireq, icmp-ireqreply,
icmp-maskreq, icmp-maskreply.
The following TCP flags field values are available: tcp-fin,
tcp-syn, tcp-rst, tcp-push,
tcp-ack, tcp-urg.
Primitives may be combined using:
-
A parenthesized group of primitives and operators
(parentheses are special to the Shell and must be escaped).
-
Negation (`!' or `not').
-
Concatenation (`&&' or `and').
-
Alternation (`||' or `or').
Negation has highest precedence.
Alternation and concatenation have equal precedence and associate
left to right.
Note that explicit and tokens, not juxtaposition,
are now required for concatenation.
If an identifier is given without a keyword, the most recent keyword
is assumed.
For example,
not host vs and ace
is short for
not host vs and host ace
which should not be confused with
not ( host vs or ace )
EXAMPLES
To select all packets arriving at or departing from sundown:
-
host sundown
To select traffic between helios and either hot or ace:
-
host helios and \( hot or ace \)
To select all IP packets between ace and any host except helios:
-
ip host ace and not helios
To select all traffic between local hosts and hosts at Berkeley:
-
net ucb-ether
To select all ftp traffic through internet gateway snup:
-
gateway snup and (port ftp or ftp-data)
To select traffic neither sourced from nor destined for local hosts
(if you gateway to one other net, this stuff should never make it
onto your local net).
-
ip and not net localnet
To select the start and end packets (the SYN and FIN packets) of each
TCP conversation that involves a non-local host.
-
tcp[tcpflags] & (tcp-syn|tcp-fin) != 0 and not src and dst net localnet
To select all IPv4 HTTP packets to and from port 80, i.e. print only
packets that contain data, not, for example, SYN and FIN packets and
ACK-only packets. (IPv6 is left as an exercise for the reader.)
-
tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)
To select IP packets longer than 576 bytes sent through gateway snup:
-
gateway snup and ip[2:2] > 576
To select IP broadcast or multicast packets that were
not
sent via Ethernet broadcast or multicast:
-
ether[0] & 1 = 0 and ip[16] >= 224
To select all ICMP packets that are not echo requests/replies (i.e., not
ping packets):
-
icmp[icmptype] != icmp-echo and icmp[icmptype] != icmp-echoreply
SEE ALSO
pcap(3PCAP)
AUTHORS
The original authors are:
Van Jacobson,
Craig Leres and
Steven McCanne, all of the
Lawrence Berkeley National Laboratory, University of California, Berkeley, CA.
It is currently being maintained by tcpdump.org.
The current version of libpcap is available via http:
-
http://www.tcpdump.org/
The original distribution is available via anonymous ftp:
-
ftp://ftp.ee.lbl.gov/tcpdump.tar.Z
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.
Index
- NAME
-
- DESCRIPTION
-
- EXAMPLES
-
- SEE ALSO
-
- AUTHORS
-
- BUGS
-
This document was created by
man2html,
using the manual pages.
Time: 19:49:29 GMT, April 27, 2011