SHOREWALL-MASQ(5) | [FIXME: manual] | SHOREWALL-MASQ(5) |
NAME¶
masq - Shorewall Masquerade/SNAT definition fileSYNOPSIS¶
/etc/shorewall/masq
DESCRIPTION¶
Use this file to define dynamic NAT (Masquerading) and to define Source NAT (SNAT).Outgoing interfacelist. This may be a
comma-separated list of interface names. This is usually your internet
interface. If ADD_SNAT_ALIASES=Yes in shorewall.conf[3](5), you may add
":" and a digit to indicate that you want the alias added
with that name (e.g., eth0:0). This will allow the alias to be displayed with
ifconfig. That is the only use for the alias name; it may not appear in any
other place in your Shorewall configuration.
Each interface must match an entry in shorewall-interfaces[4](5).
Shorewall allows loose matches to wildcard entries in
shorewall-interfaces[4](5). For example, ppp0 in this file will match a
shorewall-interfaces[4](5) entry that defines ppp+.
Where more that one internet provider share a single interface[5], the
provider is specified by including the provider name or number in parentheses:
In that case, you will want to specify the interfaces's address for that
provider in the ADDRESS column.
The interface may be qualified by adding the character ":" followed by
a comma-separated list of destination host or subnet addresses to indicate
that you only want to change the source IP address for packets being sent to
those particular destinations. Exclusion is allowed (see
shorewall-exclusion[6](5)) as are ipset names preceded by a plus sign
'+';
If you wish to inhibit the action of ADD_SNAT_ALIASES for this entry then
include the ":" but omit the digit:
Normally Masq/SNAT rules are evaluated after those for one-to-one NAT (defined
in shorewall-nat[7](5)). If you want the rule to be applied before
one-to-one NAT rules, prefix the interface name with "+":
This feature should only be required if you need to insert rules in this file
that preempt entries in shorewall-nat[7](5).
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.
SOURCE (Formerly called SUBNET) -
{interface[:exclusion]|address[,address][exclusion]}
eth0(Avvanta)
eth0(Avvanta): eth2::192.0.2.32/27
+eth0 +eth0:192.0.2.32/27 +eth0:2
Set of hosts that you wish to masquerade. You
can specify this as an address (net or host) or as an interface
(use of an interface is deprecated). If you give the name of an
interface, the interface must be up before you start the firewall and the
Shorewall rules compiler will warn you of that fact. (Shorewall will use your
main routing table to determine the appropriate addresses to masquerade).
In order to exclude a address of the specified SOURCE, you may append an
exclusion ("!" and a comma-separated list of IP addresses
(host or net) that you wish to exclude (see
shorewall-exclusion[6](5))). Note that a colon (":") must
appear between an interface name and the exclusion;
Example: eth1:!192.168.1.4,192.168.32.0/27
In that example traffic from eth1 would be masqueraded unless it came from
192.168.1.4 or 196.168.32.0/27
The preferred way to specify the SOURCE is to supply one or more host or network
addresses separated by comma. You may use ipset names preceded by a plus sign
(+) to specify a set of hosts.
ADDRESS (Optional) -
[-|NONAT|[address-or-address-range[,
address-or-address-range]...][:
lowport-highport][:random][:persistent]|detect|random]
If you specify an address here, SNAT will be
used and this will be the source address. If ADD_SNAT_ALIASES is set to Yes or
yes in shorewall.conf[3](5) then Shorewall will automatically add this
address to the INTERFACE named in the first column.
You may also specify a range of up to 256 IP addresses if you want the SNAT
address to be assigned from that range in a round-robin fashion by connection.
The range is specified by first.ip.in.range-last.ip.in.range.
You may follow the port range with :random in which case assignment of
ports from the list will be random. random may also be specified by
itself in this column in which case random local port assignments are made for
the outgoing connections.
Example: 206.124.146.177-206.124.146.180
You may follow the port range (or :random) with :persistent. This
is only useful when an address range is specified and causes a client to be
given the same source/destination IP pair. This feature replaces the SAME
modifier which was removed from Shorewall in version 4.4.0. Unlike
random, persistent may not be used by itself.
You may also use the special value "detect" which causes Shorewall to
determine the IP addresses configured on the interface named in the INTERFACES
column and substitute them in this column.
Finally, you may also specify a comma-separated list of ranges and/or addresses
in this column.
This column may not contain DNS Names.
Normally, Netfilter will attempt to retain the source port number. You may cause
netfilter to remap the source port by following an address or range (if any)
by ":" and a port range with the format
lowport-highport. If this is done, you must specify
"tcp" or "udp" in the PROTO column.
Examples:
If you simply place NONAT in this column, no rewriting of the source IP
address or port number will be performed. This is useful if you want
particular traffic to be exempt from the entries that follow in the file.
If you want to leave this column empty but you need to specify the next column
then place a hyphen ("-") here.
PROTO (Optional) -
{-|[!]protocol-name|[!]protocol-number}
192.0.2.4:5000-6000 :4000-5000
If you wish to restrict this entry to a
particular protocol then enter the protocol name (from protocols(5)) or number
here.
PORT(S) (Optional) -
[[!]port-name-or-number[,port-name-or-number]...]
If the PROTO column specifies TCP (6), UDP
(17), DCCP (33), SCTP (132) or UDPLITE (136) then you may list one or more
port numbers (or names from services(5)) or port ranges separated by commas.
Port ranges are of the form lowport:highport.
IPSEC (Optional) - [option[,option]...]
If you specify a value other than
"-" in this column, you must be running kernel 2.6 and your kernel
and iptables must include policy match support.
Comma-separated list of options from the following. Only packets that will be
encrypted via an SA that matches these options will have their source address
changed.
reqid=number
MARK - [!]value[/mask][:C]
where number is specified using
setkey(8) using the 'unique: number option for the SPD level.
spi=<number>
where number is the SPI of the SA used
to encrypt/decrypt packets.
proto=ah|esp|ipcomp
IPSEC Encapsulation Protocol
mss=number
sets the MSS field in TCP packets
mode=transport|tunnel
IPSEC mode
tunnel-src=address[/mask]
only available with mode=tunnel
tunnel-dst=address[/mask]
only available with mode=tunnel
strict
Means that packets must match all rules.
next
Separates rules; can only be used with
strict
yes
When used by itself, causes all traffic that
will be encrypted/encapsulated to match the rule.
Defines a test on the existing packet or
connection mark. The rule will match only if the test returns true.
If you don't want to define a test but need to specify anything in the following
columns, place a "-" in this field.
!
USER/GROUP (Optional) -
[!][user-name-or-number][:group-name-or-number][+program-name]
Inverts the test (not equal)
value
Value of the packet or connection mark.
mask
A mask to be applied to the mark before
testing.
:C
Designates a connection mark. If omitted, the
packet mark's value is tested.
Only locally-generated connections will match
if this column is non-empty.
When this column is non-empty, the rule matches only if the program generating
the output is running under the effective user and/or group
specified (or is NOT running under that id if "!" is given).
Examples:
joe
SWITCH - [!]switch-name
program must be run by joe
:kids
program must be run by a member of the 'kids'
group
!:kids
program must not be run by a member of the
'kids' group
+upnpd
#program named upnpd
Important
The ability to specify a program name was removed from Netfilter in kernel
version 2.6.14.
Added in Shorewall 4.5.1 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. switch-name 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:
/proc/net/nf_condition/switch-name
echo 0 >
/proc/net/nf_condition/switch-name
Switch settings are retained over shorewall restart./proc/net/nf_condition/switch-name
EXAMPLES¶
Example 1:You have a simple masquerading setup where
eth0 connects to a DSL or cable modem and eth1 connects to your local network
with subnet 192.168.0.0/24.
Your entry in the file will be:
Example 2:
#INTERFACE SOURCE eth0 192.168.0.0/24
You add a router to your local network to
connect subnet 192.168.1.0/24 which you also want to masquerade. You then add
a second entry for eth0 to this file:
Example 3:
#INTERFACE SOURCE eth0 192.168.1.0/24
You have an IPSEC tunnel through ipsec0 and
you want to masquerade packets coming from 192.168.1.0/24 but only if these
packets are destined for hosts in 10.1.1.0/24:
Example 4:
#INTERFACE SOURCE ipsec0:10.1.1.0/24 196.168.1.0/24
You want all outgoing traffic from
192.168.1.0/24 through eth0 to use source address 206.124.146.176 which is NOT
the primary address of eth0. You want 206.124.146.176 to be added to eth0 with
name eth0:0.
Example 5:
#INTERFACE SOURCE ADDRESS eth0:0 192.168.1.0/24 206.124.146.176
You want all outgoing SMTP traffic entering
the firewall from 172.20.1.0/29 to be sent from eth0 with source IP address
206.124.146.177. You want all other outgoing traffic from 172.20.1.0/29 to be
sent from eth0 with source IP address 206.124.146.176.
Warning
The order of the above two rules is significant!
Example 6:
#INTERFACE SOURCE ADDRESS PROTO PORT(S) eth0 172.20.1.0/29 206.124.146.177 tcp smtp eth0 172.20.1.0/29 206.124.146.176
Connections leaving on eth0 and destined to
any host defined in the ipset myset should have the source IP address
changed to 206.124.146.177.
#INTERFACE SOURCE ADDRESS eth0:+myset[dst] - 206.124.146.177
FILES¶
/etc/shorewall/masqSEE ALSO¶
http://shorewall.net/configuration_file_basics.htm#Pairs shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5), shorewall-exclusion(5), shorewall-hosts(5), shorewall_interfaces(5), shorewall-ipsets(5), shorewall-maclist(5), shorewall-nat(5), shorewall-netmap(5), shorewall-params(5), shorewall-policy(5), shorewall-providers(5), shorewall-proxyarp(5), shorewall-rtrules(5), shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5), shorewall-secmarks(5), shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5), shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)NOTES¶
- 1.
- shorewall-rtrules
- 2.
- shorewall-tcrules
- 3.
- shorewall.conf
- 4.
- shorewall-interfaces
- 5.
- more that one internet provider share a single interface
- 6.
- shorewall-exclusion
- 7.
- shorewall-nat
06/28/2012 | [FIXME: source] |