forked from extern/shorewall_code
c2558af9c8
1. Require KLUDGEFREE if existing rule uses mark match 2. Pretty up the code 3. Use MASK_BITS rather than TC_BITS when calculating the offset of EXCLUSION_MASK Signed-off-by: Tom Eastep <teastep@shorewall.net>
655 lines
27 KiB
XML
655 lines
27 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
|
|
"http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd">
|
|
<article>
|
|
<!--$Id$-->
|
|
|
|
<articleinfo>
|
|
<title>Packet Marking using /etc/shorewall/tcrules</title>
|
|
|
|
<authorgroup>
|
|
<author>
|
|
<firstname>Tom</firstname>
|
|
|
|
<surname>Eastep</surname>
|
|
</author>
|
|
</authorgroup>
|
|
|
|
<pubdate><?dbtimestamp format="Y/m/d"?></pubdate>
|
|
|
|
<copyright>
|
|
<year>2006</year>
|
|
|
|
<holder>Thomas M. Eastep</holder>
|
|
</copyright>
|
|
|
|
<legalnotice>
|
|
<para>Permission is granted to copy, distribute and/or modify this
|
|
document under the terms of the GNU Free Documentation License, Version
|
|
1.2 or any later version published by the Free Software Foundation; with
|
|
no Invariant Sections, with no Front-Cover, and with no Back-Cover
|
|
Texts. A copy of the license is included in the section entitled
|
|
<quote><ulink url="GnuCopyright.htm">GNU Free Documentation
|
|
License</ulink></quote>.</para>
|
|
</legalnotice>
|
|
</articleinfo>
|
|
|
|
<caution>
|
|
<para>This article includes information that applies to Shorewall version
|
|
3.2.5 and later. Not all features described here will be available in
|
|
earlier releases.</para>
|
|
</caution>
|
|
|
|
<section id="Marks">
|
|
<title>Packet and Connection Marks</title>
|
|
|
|
<para>Perhaps no aspect of Shorewall causes more confusion than packet
|
|
marking. This article will attempt to clear up some of that
|
|
confusion.</para>
|
|
|
|
<para>Each packet has a mark whose value is initially 0. Mark values are
|
|
stored in the <emphasis>skb</emphasis> (socket buffer) structure used by
|
|
the Linux kernel to track packets; the mark value is not part of the
|
|
packet itself and cannot be seen with <command>tcpdump</command>,
|
|
<command>ethereal</command> or any other packet sniffing program. They can
|
|
be seen in an iptables/ip6tables trace -- see the
|
|
<command>iptrace</command> command in <ulink
|
|
url="manpages/shorewall.html">shorewal</ulink>(8) and <ulink
|
|
url="manpages6/shorewall6.html">shorewall6</ulink>(8).</para>
|
|
|
|
<para>Example (output has been folded for display ):</para>
|
|
|
|
<programlisting>[11692.096077] TRACE: mangle:tcout:return:3 IN= OUT=eth0 SRC=172.20.1.130
|
|
DST=206.124.146.254 LEN=84 TOS=0x00 PREC=0x00 TTL=64
|
|
ID=0 DF PROTO=ICMP TYPE=8 CODE=0 ID=7212 SEQ=3 UID=0
|
|
GID=1000 <emphasis role="bold">MARK=0x10082</emphasis></programlisting>
|
|
|
|
<para>Each active connection (even those that are not yet in ESTABLISHED
|
|
state) has a mark value that is distinct from the packet marks. Connection
|
|
mark values can be seen using the <command>shorewall show
|
|
connections</command> command. The default connection mark value is
|
|
0.</para>
|
|
|
|
<para>Example (output has been folded for display ):</para>
|
|
|
|
<programlisting><command>shorewall show connections</command>
|
|
Shorewall 3.3.2 Connections at gateway - Mon Oct 2 09:08:18 PDT 2006
|
|
|
|
tcp 6 19 TIME_WAIT src=206.124.146.176 dst=192.136.34.98 sport=58597 dport=80
|
|
packets=23 bytes=4623 src=192.136.34.98 dst=206.124.146.176 sport=80 dport=58597
|
|
packets=23 bytes=22532 [ASSURED] <emphasis role="bold">mark=256</emphasis> use=1
|
|
…</programlisting>
|
|
|
|
<para>Packet marks are valid only while the packet is being processed by
|
|
the firewall. Once the packet has been given to a local process or sent on
|
|
to another system, the packet's mark value is no longer available.
|
|
Connection mark values, on the other hand, persist for the life of the
|
|
connection.</para>
|
|
|
|
<important>
|
|
<para>Other parts of the system such as <ulink
|
|
url="traffic_shaping.htm">Traffic Shaping</ulink> and <ulink
|
|
url="MultiISP.html">Policy Routing</ulink> cannot use connection marks —
|
|
they can only use packet marks.</para>
|
|
</important>
|
|
</section>
|
|
|
|
<section id="Programs">
|
|
<title>Packet Marking "Programs"</title>
|
|
|
|
<para>Packet marking occurs in Netfilter's <emphasis>mangle</emphasis>
|
|
table. See the <ulink url="NetfilterOverview.html">Netfilter
|
|
Overview</ulink> article.</para>
|
|
|
|
<para>You can think of entries in the tcrules file like instructions in a
|
|
program coded in a crude assembly language. The program gets executed for
|
|
each packet.</para>
|
|
|
|
<para>That is another way of saying that <emphasis role="bold">if you
|
|
don't program, you may have difficulty making full use of
|
|
Netfilter/Shorewall's Packet Marking</emphasis>.</para>
|
|
|
|
<para>Actually, the tcrules define several programs. Each program
|
|
corresponds to one of the built-in chains in the mangle table.</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>PREROUTING program — If MARK_IN_FORWARD_CHAIN=No in
|
|
<filename>shorewall.conf</filename>, then by default entries in
|
|
<filename>/etc/shorewall/tcrules</filename> are part of the PREROUTING
|
|
program. Entries specifying the ":P" suffix in the MARK column are
|
|
also part of the PREROUTING program. The PREROUTING program gets
|
|
executed for each packet entering the firewall.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>FORWARD program — If MARK_IN_FORWARD_CHAIN=Yes in
|
|
<filename>shorewall.conf</filename>, then by default entries in
|
|
<filename>/etc/shorewall/tcrules</filename> are part of the FORWARD
|
|
program. Entries specifying the ":F" suffix in the MARK column are
|
|
also part of the FORWARD program. The FORWARD program gets executed
|
|
for each packet forwarded by the firewall.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>OUTPUT program — Entries with $FW in the SOURCE column are part
|
|
of the OUTPUT program. The OUTPUT program is executed for each packet
|
|
originating on the firewall itself.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>POSTROUTING program — Entries with a class-id in the MARK column
|
|
(and that don't specify $FW in the SOURCE column) are part of the
|
|
POSTROUTING program. These rules are executed for each packet leaving
|
|
the firewall. Entries specifying the ":T" suffix in the MARK column
|
|
are also part of the POSTROUTING program (Shorewall version 3.4.0 and
|
|
later).</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>INPUT program — No entries in tcrules will add entries to this
|
|
program. It is executed for each packet that is targeted to the
|
|
firewall itself.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Note that a packet being forwarded by your firewall actually gets
|
|
processed by three different programs: PREROUTING, FORWARD and
|
|
POSTROUTING. Similarly, packets addressed to the firewall itself are
|
|
processed by two programs (PREROUTING and INPUT) while packets originating
|
|
on the firewall are likewise processed by two programs (OUTPUT and
|
|
POSTROUTING).</para>
|
|
|
|
<para>Rules in each program are <emphasis>executed</emphasis> as
|
|
follows:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>Rules are conditionally executed based on whether the current
|
|
packet matches the contents of the SOURCE, DEST, PROTO, PORT(S),
|
|
CLIENT PORT(S_, USER, TEST, LENGTH and TOS columns.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>When a rule is executed, either:</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>the current packet receives a new mark value; or</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>the connection to which the current packet belongs receives
|
|
a new mark value (":C", ":CF" or ":CP" suffix in the MARK column);
|
|
or</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>the packet is classified for traffic shaping (class-id in
|
|
the MARK column); or</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>the packet mark in the current packet is moved to the
|
|
connection mark for the connection that the current packet is part
|
|
of ("SAVE" in the MARK column); or</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>the connection mark value for the connection that the
|
|
current packet is part of is moved to the current packet's mark
|
|
("RESTORE" in the MARK column); or</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>jump to a subroutine (another chain in the mangle table).
|
|
These jumps are generated by Shorewall; or</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>exit the current subroutine ("CONTINUE" in the MARK
|
|
column).</para>
|
|
</listitem>
|
|
</orderedlist>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Unless the subroutine is exited using CONTINUE, <emphasis
|
|
role="bold">the current packet is always passed to the next tcrule in
|
|
the subroutine</emphasis>.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
</section>
|
|
|
|
<section id="Values">
|
|
<title>Mark and Mask Values</title>
|
|
|
|
<para>The mark value is held in a 32-bit field. Because packet marking is
|
|
the Netfilter <emphasis>kludge of last resort</emphasis> for solving many
|
|
hard technical problems, Shorewall reserves half of this field (16 bits)
|
|
for future use. The remainder is split into two 8-bit values:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>The low-order eight bits are used for traffic shaping marks.
|
|
These eight bits are also used for selecting among multiple providers
|
|
when HIGH_ROUTE_MARKS=No in <filename>shorewall.conf</filename>. Some
|
|
rules that deal with only these bits use a mask value of 0xff.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The next 8 bits are used for selecting among multiple providers
|
|
when HIGH_ROUTE_MARKS=Yes in <filename>shorewall.conf</filename>.
|
|
These bits are manipulated using a mask value of 0xff00.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>As hinted above, marking rules can specify both a mark value and a
|
|
mask. The mask determines the subset of the 32 bits in the mark to be used
|
|
in the operation — only those bits that are on in the mask are manipulated
|
|
when the rule is executed. For entries in tcrules, Shorewall-generated
|
|
rules use a mask value that depends on which program the rule is part of,
|
|
what the rule does, and the setting of HIGH_ROUTE_MARKS.</para>
|
|
|
|
<para>For entries in tcrules, the default mask value is 0xffff except in
|
|
these cases:</para>
|
|
|
|
<itemizedlist>
|
|
<listitem>
|
|
<para>RESTORE rules use a default mask value of 0xff.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>SAVE rules use a default mask value of 0xff.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Connection marking rules use a mask value of 0xff.</para>
|
|
</listitem>
|
|
</itemizedlist>
|
|
|
|
<para>Shorewall actually allows you to have complete control over the
|
|
layout of the 32-bit mark using the following options in <ulink
|
|
url="manpages/shorewall.conf.html">shorewall.conf</ulink> (5):</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>TC_BITS</term>
|
|
|
|
<listitem>
|
|
<para>The number of bits at the low end of the mark to be used for
|
|
traffic shaping marking. May be zero.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>PROVIDER_BITS</term>
|
|
|
|
<listitem>
|
|
<para>The number of bits in the mark to be used for provider
|
|
numbers. May be zero.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>PROVIDER_OFFSET</term>
|
|
|
|
<listitem>
|
|
<para>The offset from the right (low-order end) of the provider
|
|
number field. If non-zero, must be >= TC_BITS (Shorewall
|
|
automatically adjusts PROVIDER_OFFSET's value). PROVIDER_OFFSET +
|
|
PROVIDER_BITS must be <= 32.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>MASK_BITS</term>
|
|
|
|
<listitem>
|
|
<para>Number of bits on the right of the mark to be masked when
|
|
clearing the traffic shaping mark. Must be >= TC_BITS and <=
|
|
PROVIDER_OFFSET (if PROVIDER_OFFSET > 0)</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>The relationship between these options is shown in this
|
|
diagram.</para>
|
|
|
|
<graphic align="left" fileref="images/MarkGeometry.png" valign="top" />
|
|
|
|
<para></para>
|
|
|
|
<para>The default values of these options are determined by the settings
|
|
of other options as follows:</para>
|
|
|
|
<table>
|
|
<title>Default Values</title>
|
|
|
|
<tgroup cols="2">
|
|
<tbody>
|
|
<row>
|
|
<entry>WIDE_TC_MARKS=No, HIGH_ROUTE_MARKS=No</entry>
|
|
|
|
<entry>TC_BITS=8, PROVIDER_BITS=8, PROVIDER_OFFSET=0,
|
|
MASK_BITS=8</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>WIDE_TC_MARKS=No, HIGH_ROUTE_MARKS=Yes</entry>
|
|
|
|
<entry>TC_BITS=8, PROVIDER_BITS=8, PROVIDER_OFFSET=8,
|
|
MASK_BITS=8</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>WIDE_TC_MARKS=Yes, HIGH_ROUTE_MARKS=No</entry>
|
|
|
|
<entry>TC_BITS=14, PROVIDER_BITS=8, PROVIDER_OFFSET=0,
|
|
MASK_BITS=16</entry>
|
|
</row>
|
|
|
|
<row>
|
|
<entry>WIDE_TC_MARKS=Yes, HIGH_ROUTE_MARKS=Yes</entry>
|
|
|
|
<entry>TC_BITS=14, PROVIDER_BITS=8, PROVIDER_OFFSET=16,
|
|
MASK_BITS=16</entry>
|
|
</row>
|
|
</tbody>
|
|
</tgroup>
|
|
</table>
|
|
|
|
<para>The existence of both TC_BITS and MASK_BITS is owed to the way that
|
|
WIDE_TC_MARKS was originally implemented. Note that TC_BITS is 14 rather
|
|
than 16 when WIDE_TC_MARKS=Yes.</para>
|
|
|
|
<para>Beginning with Shorewall 4.4.12, the field between MASK_BITS and
|
|
PROVIDER_OFFSET can be used for any purpose you want.</para>
|
|
|
|
<para>Beginning with Shorewall 4.4.13, The first unused bit on the left is
|
|
used by Shorewall as an <firstterm>exclusion mark</firstterm>, allowing
|
|
exclusion in CONTINUE, NONAT and ACCEPT+ rules.</para>
|
|
</section>
|
|
|
|
<section id="Shorewall">
|
|
<title>Shorewall-defined Chains in the Mangle Table</title>
|
|
|
|
<para>Shorewall creates a set of chains in the mangle table to hold rules
|
|
defined in your <firstterm>/etc/shorewall/tcrules</firstterm> file. As
|
|
mentioned above, chains are like subroutines in the packet marking
|
|
programming language. By placing all of your rules in subroutines,
|
|
CONTINUE (which generates a Netfilter RETURN rule) can be used to stop
|
|
processing your rules while still allowing following Shorewall-generated
|
|
rules to be executed.</para>
|
|
|
|
<variablelist>
|
|
<varlistentry>
|
|
<term>tcpre</term>
|
|
|
|
<listitem>
|
|
<para>PREROUTING rules.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>tcfor</term>
|
|
|
|
<listitem>
|
|
<para>FORWARD rules.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>tcout</term>
|
|
|
|
<listitem>
|
|
<para>OUTPUT rules.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
|
|
<varlistentry>
|
|
<term>tcpost</term>
|
|
|
|
<listitem>
|
|
<para>POSTROUTING rules.</para>
|
|
</listitem>
|
|
</varlistentry>
|
|
</variablelist>
|
|
|
|
<para>Shorewall generates jumps to these chains from the built-in chains
|
|
(PREROUTING, FORWARD, etc.).</para>
|
|
</section>
|
|
|
|
<section id="Examples">
|
|
<title>An Example</title>
|
|
|
|
<para>Here's the example (slightly expanded) from the comments at the top
|
|
of the <filename>/etc/shorewall/tcrules</filename> file.</para>
|
|
|
|
<programlisting>#MARK SOURCE DEST PROTO PORT(S) CLIENT USER TEST LENGTH TOS
|
|
# PORT(S)
|
|
1 0.0.0.0/0 0.0.0.0/0 icmp echo-request #Rule 1
|
|
1 0.0.0.0/0 0.0.0.0/0 icmp echo-reply #Rule 2
|
|
1 $FW 0.0.0.0/0 icmp echo-request #Rule 3
|
|
1 $FW 0.0.0.0/0 icmp echo-reply #Rule 4
|
|
|
|
RESTORE 0.0.0.0/0 0.0.0.0/0 all - - - 0 #Rule 5
|
|
CONTINUE 0.0.0.0/0 0.0.0.0/0 all - - - !0 #Rule 6
|
|
4 0.0.0.0/0 0.0.0.0/0 ipp2p:all #Rule 7
|
|
SAVE 0.0.0.0/0 0.0.0.0/0 all - - - !0 #Rule 8
|
|
##LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE</programlisting>
|
|
|
|
<para>Let's take a look at each rule:</para>
|
|
|
|
<orderedlist>
|
|
<listitem>
|
|
<para>This straight-forward rule simply marks all 'ping' requests
|
|
passing through the firewall with mark value 1. Note that it does not
|
|
mark pings that originate on the firewall itself.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Similarly, this rule marks 'ping' replies.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>This rule marks 'ping' requests that originate on the firewall.
|
|
This rule and the next ones are part of the OUTPUT program.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Similarly, this rule marks 'ping' replies from the firewall
|
|
itself.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>Remember that even though 'ping' packets were marked in one of
|
|
the first two rules, they are still passed on to rule 5 (note that
|
|
packets marked by rules 3 and 4 are not processed by this rule since
|
|
it is in a different program). That rule moves the connection mark to
|
|
the packet mark, <emphasis>if the packet mark is still zero</emphasis>
|
|
(note the '0' in the TEST column). Without the '0' in the TEST column,
|
|
this rule would overwrite the marks assigned in the first two
|
|
rules.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If the packet mark is non-zero (note the '!0' in the TEST
|
|
column), then exit — The remaining rules will not be executed in this
|
|
case. The packet mark will be non-zero if this is a 'ping' packet, or
|
|
if the connection mark restored in rule 5 was non-zero.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>The packet mark is still zero. This rule checks to see if this
|
|
is a P2P packet and if it is, the packet mark is set to 4.</para>
|
|
</listitem>
|
|
|
|
<listitem>
|
|
<para>If the packet mark is non-zero (meaning that it was set to 4 in
|
|
rule 7), then save the value (4) in the connection. The next time that
|
|
a packet from this same connection comes through this program, rule 6
|
|
will be executed and the P2P check will be avoided.</para>
|
|
</listitem>
|
|
</orderedlist>
|
|
</section>
|
|
|
|
<section id="Show">
|
|
<title>Examining the Marking Programs on a Running System</title>
|
|
|
|
<para>You can see the tcrules in action using the <command>shorewall show
|
|
mangle</command> command.</para>
|
|
|
|
<para>The sample output from that command shown below has the following in
|
|
<filename>/etc/shorewall/providers</filename>:</para>
|
|
|
|
<programlisting>#NAME NUMBER MARK DUPLICATE INTERFACE GATEWAY OPTIONS COPY
|
|
Blarg 1 0x100 main eth3 206.124.146.254 track,balance br0,eth1
|
|
#LAST LINE -- ADD YOUR ENTRIES ABOVE THIS LINE -- DO NOT REMOVE
|
|
</programlisting>
|
|
|
|
<para>Here is <filename>/etc/shorewall/tcrules</filename>:</para>
|
|
|
|
<programlisting>#MARK SOURCE DEST PROTO PORT(S) CLIENT USER TEST
|
|
# PORT(S)
|
|
1:110 192.168.0.0/22 eth3 #Our internal nets get priority
|
|
#over the server
|
|
1:130 206.124.146.177 eth3 tcp - 873
|
|
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
|
|
</programlisting>
|
|
|
|
<para>And here is <filename>/etc/shorewall/tcdevices</filename> and
|
|
<filename>/etc/shorewall/tcclasses</filename>:</para>
|
|
|
|
<programlisting>#INTERFACE IN-BANDWITH OUT-BANDWIDTH
|
|
eth3 1.3mbit 384kbit
|
|
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
|
|
|
|
#INTERFACE MARK RATE CEIL PRIORITY OPTIONS
|
|
eth3 10 full full 1 tcp-ack,tos-minimize-delay
|
|
eth3 20 9*full/10 9*full/10 2 default
|
|
eth3 30 6*full/10 6*full/10 3
|
|
#LAST LINE -- ADD YOUR ENTRIES BEFORE THIS ONE -- DO NOT REMOVE
|
|
</programlisting>
|
|
|
|
<para>I've annotated the following output with comments beginning with
|
|
"<<<<" and ending with ">>>>". This example uses
|
|
HIGH_ROUTE_MARKS=Yes and TC_EXPERT=No in
|
|
<filename>shorewall.conf</filename>.</para>
|
|
|
|
<programlisting>gateway:~ # <command>shorewall show mangle</command>
|
|
Shorewall 3.3.2 Mangle Table at gateway - Mon Oct 2 15:07:32 PDT 2006
|
|
|
|
Counters reset Mon Oct 2 07:49:52 PDT 2006
|
|
|
|
<<<< The PREROUTING Program >>>>
|
|
|
|
Chain PREROUTING (policy ACCEPT 409K packets, 122M bytes)
|
|
pkts bytes target prot opt in out source destination
|
|
|
|
<<<< Restore the provider mark from the connection, if any >>>>
|
|
|
|
185K 77M CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 CONNMARK match !0x0/0xff00 CONNMARK restore mask 0xff00
|
|
|
|
<<<< If there is no mark in the connection and the packet came in on eth3, then jump to the <emphasis
|
|
role="bold">routemark</emphasis> chain
|
|
This rule is generated as a result of 'track' being specified in the providers file entry for eth3 >>>>
|
|
|
|
8804 1396K routemark all -- eth3 * 0.0.0.0/0 0.0.0.0/0 MARK match 0x0/0xff00
|
|
|
|
<<<< If the packet came in on eth3, jump the the <emphasis
|
|
role="bold">tcpre</emphasis> chain -- packets entering on a 'track'ed interface can have their mark set to zero there >>>>
|
|
|
|
102K 52M tcpre all -- eth3 * 0.0.0.0/0 0.0.0.0/0
|
|
|
|
<<<< Otherwise, jump to the tcpre chain if there is no current provider mark --
|
|
if we would have had TC_EXPERT=Yes, this jump would have been unconditional>>>>
|
|
|
|
215K 44M tcpre all -- * * 0.0.0.0/0 0.0.0.0/0 MARK match 0x0/0xff00
|
|
|
|
<<<< End of PREROUTING program >>>>
|
|
|
|
<<<< INPUT Program -- Shorewall generates the single rule here which turns off the provider mark in the packet after routing
|
|
The rule does that by logically ANDing the mark value with 0xff which will turn off all but the low-order 8 bits >>>>
|
|
|
|
Chain INPUT (policy ACCEPT 98238 packets, 16M bytes)
|
|
pkts bytes target prot opt in out source destination
|
|
98234 16M MARK all -- * * 0.0.0.0/0 0.0.0.0/0 MARK and 0xff
|
|
|
|
<<<< End of INPUT program >>>>
|
|
|
|
<<<< FORWARD Program -- Shorewall generates the first rule here which turns off the provider mark in the packet after routing >>>>
|
|
|
|
Chain FORWARD (policy ACCEPT 312K packets, 106M bytes)
|
|
pkts bytes target prot opt in out source destination
|
|
312K 106M MARK all -- * * 0.0.0.0/0 0.0.0.0/0 MARK and 0xff
|
|
|
|
<<<< Jump unconditionally to the <emphasis role="bold">tcfor</emphasis> chain >>>>
|
|
|
|
312K 106M tcfor all -- * * 0.0.0.0/0 0.0.0.0/0
|
|
|
|
<<<< End of FORWARD program >>>>
|
|
|
|
<<<< OUTPUT Program >>>>
|
|
|
|
Chain OUTPUT (policy ACCEPT 1462K packets, 396M bytes)
|
|
pkts bytes target prot opt in out source destination
|
|
|
|
<<<< Restore the provider mark from the connection -- this rule was generated by Shorewall because of the 'track' option >>>>
|
|
|
|
3339 615K CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 CONNMARK match !0x0/0xff00 CONNMARK restore mask 0xff00
|
|
|
|
<<<< If there is no provider mark, then jump to the <emphasis
|
|
role="bold">tcout</emphasis> chain --
|
|
if we would have had TC_EXPERT=Yes, this jump would have been unconditional >>>>
|
|
|
|
92747 28M tcout all -- * * 0.0.0.0/0 0.0.0.0/0 MARK match 0x0/0xff00
|
|
|
|
<<<< End of FORWARD program >>>>
|
|
|
|
<<<< POSTROUTING Program -- Unconditionally jump to the <emphasis
|
|
role="bold">tcpost</emphasis> chain >>>>
|
|
|
|
Chain POSTROUTING (policy ACCEPT 407K packets, 135M bytes)
|
|
pkts bytes target prot opt in out source destination
|
|
407K 135M tcpost all -- * * 0.0.0.0/0 0.0.0.0/0
|
|
|
|
<<<< End of FORWARD program >>>>
|
|
|
|
Chain <emphasis role="bold">routemark</emphasis> (1 references)
|
|
pkts bytes target prot opt in out source destination
|
|
|
|
<<<< Set connection 'track' mark for packets coming in on eth3 >>>>
|
|
|
|
8804 1396K MARK all -- eth3 * 0.0.0.0/0 0.0.0.0/0 MARK or 0x100
|
|
|
|
<<<< Save any mark added above in the connection mark >>>>
|
|
|
|
8804 1396K CONNMARK all -- * * 0.0.0.0/0 0.0.0.0/0 MARK match !0x0/0xff00 CONNMARK save mask 0xff00
|
|
|
|
Chain <emphasis role="bold">tcfor</emphasis> (1 references)
|
|
pkts bytes target prot opt in out source destination
|
|
|
|
Chain <emphasis role="bold">tcout</emphasis> (1 references)
|
|
pkts bytes target prot opt in out source destination
|
|
|
|
Chain <emphasis role="bold">tcpost</emphasis> (1 references)
|
|
pkts bytes target prot opt in out source destination
|
|
|
|
<<<< The next two rules are the entries in the /etc/shorewall/tcrules file >>>>
|
|
|
|
65061 11M CLASSIFY all -- * eth3 192.168.0.0/22 0.0.0.0/0 CLASSIFY set 1:110
|
|
2224 2272K CLASSIFY tcp -- * eth3 206.124.146.177 0.0.0.0/0 tcp spt:873 CLASSIFY set 1:130
|
|
|
|
<<<< The following rules are generated by Shorewall and classify the traffic according to the marks in /etc/shorewall/classes >>>>
|
|
|
|
0 0 CLASSIFY all -- * eth3 0.0.0.0/0 0.0.0.0/0 MARK match 0xa/0xff CLASSIFY set 1:110
|
|
0 0 CLASSIFY all -- * eth3 0.0.0.0/0 0.0.0.0/0 MARK match 0x14/0xff CLASSIFY set 1:120
|
|
0 0 CLASSIFY all -- * eth3 0.0.0.0/0 0.0.0.0/0 MARK match 0x1e/0xff CLASSIFY set 1:130
|
|
|
|
Chain <emphasis role="bold">tcpre</emphasis> (2 references)
|
|
pkts bytes target prot opt in out source destination
|
|
gateway:~ #</programlisting>
|
|
</section>
|
|
</article>
|