Ubuntu Manpage: conntrack - shorewall conntrack file

NAME

       conntrack - shorewall conntrack file

SYNOPSIS

       /etc/shorewall/conntrack

DESCRIPTION

The original intent of the notrack file was to exempt certain traffic from Netfilter
connection tracking. Traffic matching entries in the file were not to be tracked.

The role of the file was expanded in Shorewall 4.4.27 to include all rules that can be
added in the Netfilter raw table. In 4.5.7, the file's name was changed to conntrack.

The file supports two different column layouts: FORMAT 1, FORMAT 2, and FORMAT 3, FORMAT 1
being the default. The three differ as follows:

• in FORMAT 2 and 3, there is an additional leading ACTION column.

• in FORMAT 3, the SOURCE column accepts no zone name; rather the ACTION column allows a
SUFFIX that determines the chain(s) that the generated rule will be added to.

When an entry in the following form is encountered, the format of the following entries
are assumed to be of the specified format.
[?]FORMAT
format

where format is either 1,2 or 3.

Format 3 was introduced in Shorewall 4.5.10. The optional '?' was introduced in Shorewall
4.5.11 and ?FORMAT is the preferred form; the form without the '?' is deprecated.

Comments may be attached to Netfilter rules generated from entries in this file through
the use of COMMENT lines. These lines begin with the word COMMENT; the remainder of the
line is treated as a comment which is attached to subsequent rules until another COMMENT
line is found or until the end of the file is reached. To stop adding comments to rules,
use a line with only the word COMMENT.

Note
Beginning with Shorewall 4.5.11, ?COMMENT is a synonym for COMMENT and is preferred.

The columns in the file are as follows (where the column name is followed by a different
name in parentheses, the different name is used in the alternate specification syntax).

ACTION - {NOTRACK|CT:helper:name[(arg=val[,...])|CT:notrack|DROP}[:chain-designator]
This column is only present when FORMAT >= 2. Values other than NOTRACK or DROP
require CT Targetsupport in your iptables and kernel.

• NOTRACK or CT:notrack

Disables connection tracking for this packet.

• DROP

Added in Shorewall 4.5.10. Silently discard the packet.

• helper:name

Attach the helper identified by the name to this connection. This is more flexible
than loading the conntrack helper with preset ports.

At this writing, the available helpers are:

amanda
Requires that the amanda netfilter helper is present.

ftp
Requires that the FTP netfilter helper is present.

irc
Requires that the IRC netfilter helper is present.

netbios-ns
Requires that the netbios_ns (sic) helper is present.

RAS and Q.931
These require that the H323 netfilter helper is present.

pptp
Requires that the pptp netfilter helper is present.

sane
Requires that the SANE netfilter helper is present.

sip
Requires that the SIP netfilter helper is present.

snmp
Requires that the SNMP netfilter helper is present.

tftp
Requires that the TFTP netfilter helper is present.

May be followed by an option list of arg=val pairs in parentheses:

• ctevents=event[,...]

Only generate the specified conntrack events for this connection. Possible
event types are: new, related, destroy, reply, assured, protoinfo, helper,
mark (this is connection mark, not packet mark), natseqinfo, and secmark. If
more than one event is listed, the event list must be enclosed in parentheses
(e.g., ctevents=(new,related)).

• expevents=new

Only generate a new expectation events for this connection.

When FORMAT = 1, this column is not present and the rule is processed as if NOTRACK
had been entered in this column.

Beginning with Shorewall 4.5.10, when FORMAT = 3, this column can end with a colon
followed by a chain-designator. The chain-designator can be one of the following:

P
The rule is added to the raw table PREROUTING chain. This is the default if no
chain-designator is present.

O
The rule is added to the raw table OUTPUT chain.

PO or OP
The rule is added to the raw table PREROUTING and OUTPUT chains.

SOURCE (formats 1 and 2) – {zone[:interface][:address-list]|COMMENT}
where zone is the name of a zone, interface is an interface to that zone, and
address-list is a comma-separated list of addresses (may contain exclusion - see
shorewall-exclusion[1] (5)).

Beginning with Shorewall 4.5.7, all can be used as the zone name to mean all zones.

Beginning with Shorewall 4.5.10, all- can be used as the zone name to mean all
off-firewall zones.

SOURCE (format 3) – {-|interface[:address-list]|address-list}
Where interface is an interface to that zone, and address-list is a comma-separated
list of addresses (may contain exclusion - see shorewall-exclusion[1] (5)).

COMMENT is only allowed in format 1; the remainder of the line is treated as a comment
that will be associated with the generated rule(s).

DEST – {-|interface[:address-list]|address-list}
where address-list is a comma-separated list of addresses (may contain exclusion - see
shorewall6-exclusion[1] (5)).

PROTO – protocol-name-or-number[,...]
A protocol name from /etc/protocols or a protocol number.

Beginning with Shorewall 4.5.12, this column is labeled PROTOS and can accept a
comma-separated list of protocols. Either proto or protos is accepted in the alternate
input format.

DEST PORT(S) (dport) - port-number/service-name-list
A comma-separated list of port numbers and/or service names from /etc/services. May
also include port ranges of the form low-port:high-port if your kernel and iptables
include port range support.

SOURCE PORT(S) (sport) - port-number/service-name-list
A comma-separated list of port numbers and/or service names from /etc/services. May
also include port ranges of the form low-port:high-port if your kernel and iptables
include port range support.

Beginning with Shorewall 4.5.15, you may place '=' in this column, provided that the
DEST PORT(S) column is non-empty. This causes the rule to match when either the source
port or the destination port in a packet matches one of the ports specified in DEST
PORTS(S). Use of '=' requires multi-port match in your iptables and kernel.

USER/GROUP (user) – [user][:group]
May only be specified if the SOURCE zone is $FW. Specifies the effective user id and
or group id of the process sending the traffic.

SWITCH - [!]switch-name[={0|1}]
Added in Shorewall 4.5.10 and allows enabling and disabling the rule without requiring
shorewall restart.

The rule is enabled if the value stored in /proc/net/nf_condition/switch-name is 1.
The rule is disabled if that file contains 0 (the default). If '!' is supplied, the
test is inverted such that the rule is enabled if the file contains 0.

Within the switch-name, '@0' and '@{0}' are replaced by the name of the chain to which
the rule is a added. The switch-name (after '...' expansion) must begin with a letter
and be composed of letters, decimal digits, underscores or hyphens. Switch names must
be 30 characters or less in length.

Switches are normally off. To turn a switch on:
echo 1 >
/proc/net/nf_condition/switch-name
To turn it off again:
echo 0 >
/proc/net/nf_condition/switch-name
Switch settings are retained over shorewall restart.

When the switch-name is followed by =0 or =1, then the switch is initialized to off or
on respectively by the start command. Other commands do not affect the switch setting.

EXAMPLE

       Example 1:

           #ACTION                       SOURCE            DEST               PROTO            DEST              SOURCE              USER/GROUP
           #                                                                                   PORT(S)           PORT(S)
           CT:helper:ftp(expevents=new)  fw                -                  tcp              21

       Example 2 (Shorewall 4.5.10 or later):

       Drop traffic to/from all zones to IP address 1.2.3.4

           FORMAT 2
           #ACTION                       SOURCE             DEST               PROTO            DEST              SOURCE              USER/GROUP
           #                                                                                   PORT(S)           PORT(S)
           DROP                          all-:1.2.3.4       -
           DROP                          all                1.2.3.4

       or

           FORMAT 3
           #ACTION                       SOURCE             DEST               PROTO            DEST              SOURCE              USER/GROUP
           #                                                                                   PORT(S)           PORT(S)
           DROP:P                        1.2.3.4            -
           DROP:PO                       -                  1.2.3.4

FILES

       /etc/shorewall/notrack

NOTES