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