summaryrefslogtreecommitdiffstats
path: root/doc/manual/conntrack-tools.tmpl
blob: 08b5b953340fc2ba957821e0a5f036760a34c4ff (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE book PUBLIC "-//OASIS//DTD DocBook XML V4.1.2//EN"
	"http://www.oasis-open.org/docbook/xml/4.1.2/docbookx.dtd" []>

<book id="conntrack-tools-how-to">
 <bookinfo>
  <title>The conntrack-tools user manual</title>
  
  <authorgroup>
   <author>
    <firstname>Pablo</firstname>
    <surname>Neira Ayuso</surname>
    <affiliation>
     <address>
      <email>pablo@netfilter.org</email>
     </address>
    </affiliation>
   </author>
  </authorgroup>

  <copyright>
   <year>2008-2011</year>
   <holder>Pablo Neira Ayuso</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, no Front-Cover Texts, and no Back-Cover Texts.
   A copy of the license is included in the section entitled "GNU
   Free Documentation License".
   </para>
  </legalnotice>

  <releaseinfo>
  This document details how to install and configure the
  <ulink url="http://conntrack-tools.netfilter.org">conntrack-tools</ulink>
  &gt;= 0.9.15. This software is under development, for that reason, it is
  likely that this document will evolve in the future to cover new features
  and changes.</releaseinfo>

 </bookinfo>

 <toc></toc>

 <chapter id="introduction"><title>Introduction</title>

  <para>This document should be a kick-off point to install and configure the 
  <ulink url="http://conntrack-tools.netfilter.org">conntrack-tools</ulink>.
  If you find any error or imprecision in this document, please send an email
  to the author, it will be appreciated.</para>

  <para>In this document, the author assumes that the reader is familiar with firewalling concepts and iptables in general. If this is not your case, I suggest you to read the iptables documentation before going ahead. Moreover, the reader must also understand the difference between <emphasis>stateful</emphasis> and <emphasis>stateless</emphasis> firewalls. If this is not your case, I strongly suggest you to read the article <ulink url="http://people.netfilter.org/pablo/docs/login.pdf">Netfilter's Connection Tracking System</ulink> published in <emphasis>:login; the USENIX magazine</emphasis>. That document contains a general description that should help to clarify the concepts.</para>

<para>If you do not fulfill the previous requirements, this documentation is likely to be a source of frustration. Probably, you wonder why I'm insisting on these prerequisites too much, the fact is that if your iptables rule-set is <emphasis>stateless</emphasis>, it is very likely that the <emphasis>conntrack-tools</emphasis> will not be of any help for you. You have been warned!</para>

 </chapter>
 <chapter id="what"><title>What are the conntrack-tools?</title>

  <para>The conntrack-tools are a set of free software tools for GNU/Linux that allow system administrators interact, from user-space, with the in-kernel <ulink url="http://people.netfilter.org/pablo/docs/login.pdf">Connection Tracking System</ulink>, which is the module that enables stateful packet inspection for iptables. Probably, you did not hear about this module so far. However, if any of the rules of your rule-set use the <emphasis>state</emphasis> or <emphasis>ctstate</emphasis> iptables matches, you are indeed using it.
  
  </para>

<para>The <ulink url="http://conntrack-tools.netfilter.org">conntrack-tools</ulink> package contains two programs:</para>

  <itemizedlist>
   <listitem>
  	<para><emphasis>conntrack</emphasis> is command line interface conntrack provides a more flexible interface to the connnection tracking system than /proc/net/ip_conntrack. With conntrack, you can show, delete and update the existing state entries; and you can also listen to flow events.</para>
   </listitem>
   <listitem>
  	<para><emphasis>conntrackd</emphasis> is the user-space connection tracking daemon. This daemon can be used to deploy fault-tolerant GNU/Linux firewalls but you can also use it to collect flow-based statistics of the firewall use.</para>
   </listitem>
  </itemizedlist>

  <para>Although the name of both tools is very similar - and you can blame me for that, I'm not a marketing guy - they are used for very different tasks.</para>

 </chapter>

 <chapter id="requirements"><title>Requirements</title>

  <para>You have to install the following software in order to get the <emphasis>conntrack-tools</emphasis> working. Make sure that you have installed them correctly before going ahead:</para>

  <itemizedlist>
   <listitem>
  	<para><ulink url="http://www.kernel.org">Linux kernel</ulink> version &gt;= 2.6.18 that, at least, has support for:</para>
	<itemizedlist>
	 <listitem>
	 	<para>Connection Tracking System.</para>
		<itemizedlist>
		 <listitem>
		 <para>CONFIG_NF_CONNTRACK=m</para>
		 </listitem>
		 <listitem>
		 <para>CONFIG_NF_CONNTRACK_IPV4=m</para>
		 </listitem>
		 <listitem>
		 <para>CONFIG_NF_CONNTRACK_IPV6=m (if your setup supports IPv6)</para>
		 </listitem>
		</itemizedlist>
	 </listitem>
	 <listitem>
		<para>nfnetlink: the generic messaging interface for Netfilter.</para>
		<itemizedlist>
		 <listitem>
		 <para>CONFIG_NETFILTER_NETLINK=m</para>
		 </listitem>
		</itemizedlist>
	 </listitem>
	 <listitem>
		<para>nf_conntrack_netlink: the messaging interface for the Connection Tracking System.</para>
		<itemizedlist>
		 <listitem>
		 <para>CONFIG_NF_CT_NETLINK=m</para>
		 </listitem>
		</itemizedlist>
	 </listitem>
	 <listitem>
		<para>connection tracking event notification API: the flow-based event notification interface.</para>
		<itemizedlist>
		 <listitem>
		 <para>CONFIG_NF_CONNTRACK_EVENTS=y</para>
		 </listitem>
		</itemizedlist>
	 </listitem>
	</itemizedlist>
   <note><title>Verifying kernel support</title>
    <para>
     Make sure you have loaded <emphasis>nf_conntrack</emphasis>, <emphasis>nf_conntrack_ipv4</emphasis> (if your setup also supports IPv6, <emphasis>nf_conntrack_ipv6</emphasis>) and <emphasis>nf_conntrack_netlink</emphasis>.
    </para>
   </note>
   </listitem>
   <listitem>
   	<para>libnfnetlink: the netfilter netlink library use the official release available in <ulink url="http://www.netfilter.org">netfilter.org</ulink></para>
   </listitem>
   <listitem>
   	<para>libnetfilter_conntrack: the netfilter netlink library use the official release available in <ulink url="http://www.netfilter.org">netfilter.org</ulink></para>
   </listitem>
  </itemizedlist>
 </chapter>

 <chapter id="Installation"><title>Installation</title>

   <para>To compile and install the <emphasis>conntrack-tools</emphasis> run the following commands:</para>
   <programlisting>
	(non-root)$ tar xvjf conntrack-tools-x.x.x.tar.bz2
	(non-root)$ cd conntrack-tools-x.x.x
	(non-root)$ ./configure --prefix=/usr
	(non-root)$ make
	(root)    # make install</programlisting>

<note><title>Fedora Users</title>
  <para>If you are installing the libraries in /usr/local/, do not forget to do the following things:</para>
   <itemizedlist>
     <listitem><para>PKG_CONFIG_PATH=/usr/local/lib/pkgconfig; export PKG_CONFIG_PATH</para></listitem>
     <listitem><para>Add `/usr/local/lib' to your /etc/ld.so.conf file and run `ldconfig'</para></listitem>
   </itemizedlist>
   <para>Check `ldd' for trouble-shooting, read <ulink url="http://tldp.org/HOWTO/Program-Library-HOWTO/shared-libraries.html">this</ulink> for more information on how libraries work.</para>
</note>

<note><title>Verifying kernel support</title>
 <para>To check that the modules are enabled in the kernel, run <emphasis>`conntrack -E'</emphasis> and generate traffic, you should see flow events reporting new connections and updates.
 </para>
</note>

 </chapter>

 <chapter id="conntrack"><title>Using conntrack: the command line interface</title>

 <para>The <emphasis>/proc/net/ip_conntrack</emphasis> interface is very limited as it only allows you to display the existing flows, their state and other information:</para>

 <programlisting>
 # cat /proc/net/ip_conntrack
 tcp      6 431982 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=34846 dport=993 packets=169 bytes=14322 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=34846 packets=113 bytes=34787 [ASSURED] mark=0 secmark=0 use=1
 tcp      6 431698 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=34849 dport=993 packets=244 bytes=18723 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=34849 packets=203 bytes=144731 [ASSURED] mark=0 secmark=0 use=1
 </programlisting>

<para>The command line tool <emphasis>conntrack</emphasis> can be used to display the same information:</para>
 <programlisting>
 # conntrack -L
 tcp      6 431982 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=34846 dport=993 packets=169 bytes=14322 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=34846 packets=113 bytes=34787 [ASSURED] mark=0 secmark=0 use=1
 tcp      6 431698 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=34849 dport=993 packets=244 bytes=18723 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=34849 packets=203 bytes=144731 [ASSURED] mark=0 secmark=0 use=1
conntrack v0.9.7 (conntrack-tools): 2 flow entries have been shown.
 </programlisting>

<para>You can natively filter the output without using <emphasis>grep</emphasis>:</para>
<programlisting>
 # conntrack -L -p tcp --dport 34856
 tcp      6 431982 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=34846 dport=993 packets=169 bytes=14322 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=34846 packets=113 bytes=34787 [ASSURED] mark=0 secmark=0 use=1
conntrack v0.9.7 (conntrack-tools): 1 flow entries have been shown.
 </programlisting>

<para>Update the mark based on a selection, this allows you to change the mark of an entry without using the CONNMARK target:</para>
<programlisting>
 # conntrack -U -p tcp --dport 3486 --mark 10
 tcp      6 431982 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=34846 dport=993 packets=169 bytes=14322 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=34846 packets=113 bytes=34787 [ASSURED] mark=1 secmark=0 use=1
conntrack v0.9.7 (conntrack-tools): 1 flow entries has been updated.
 </programlisting>

<para>Delete one entry, this can be used to block traffic if:</para>
<itemizedlist>
 <listitem><para>You have a stateful rule-set that blocks traffic in INVALID state.</para></listitem>
 <listitem><para>You have set <emphasis>/proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_loose</emphasis> or <emphasis>/proc/sys/net/netfilter/nf_conntrack_tcp_loose</emphasis>, depending on your kernel version, to zero.</para></listitem>
</itemizedlist>

<programlisting>
 # conntrack -D -p tcp --dport 3486
 tcp      6 431982 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=34846 dport=993 packets=169 bytes=14322 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=34846 packets=113 bytes=34787 [ASSURED] mark=1 secmark=0 use=1
conntrack v0.9.7 (conntrack-tools): 1 flow entries has been deleted.
 </programlisting>

<para>Display the connection tracking events:</para>
<programlisting>
 # conntrack -E
     [NEW] udp      17 30 src=192.168.2.100 dst=192.168.2.1 sport=57767 dport=53 [UNREPLIED] src=192.168.2.1 dst=192.168.2.100 sport=53 dport=57767
  [UPDATE] udp      17 29 src=192.168.2.100 dst=192.168.2.1 sport=57767 dport=53 src=192.168.2.1 dst=192.168.2.100 sport=53 dport=57767
     [NEW] tcp      6 120 SYN_SENT src=192.168.2.100 dst=66.102.9.104 sport=33379 dport=80 [UNREPLIED] src=66.102.9.104 dst=192.168.2.100 sport=80 dport=33379
  [UPDATE] tcp      6 60 SYN_RECV src=192.168.2.100 dst=66.102.9.104 sport=33379 dport=80 src=66.102.9.104 dst=192.168.2.100 sport=80 dport=33379
  [UPDATE] tcp      6 432000 ESTABLISHED src=192.168.2.100 dst=66.102.9.104 sport=33379 dport=80 src=66.102.9.104 dst=192.168.2.100 sport=80 dport=33379 [ASSURED]
</programlisting>

<para>You can also display the existing flows in XML format, filter the output based on the NAT handling applied, etc.</para>

</chapter>

 <chapter id="settingup"><title>Setting up conntrackd: the daemon</title>

 <para>The daemon <emphasis>conntrackd</emphasis> supports two working modes:</para>

 <itemizedlist> 
  <listitem>
   <para><emphasis>State table synchronization</emphasis>: the daemon can be used to synchronize the connection tracking state table between several firewall replicas. This can be used to deploy fault-tolerant stateful firewalls. This is the main feature of the daemon.</para>
  </listitem>
  <listitem>
   <para><emphasis>Flow-based statistics collection</emphasis>: the daemon can be used to collect flow-based statistics. This feature is similar to what <ulink url="http://www.netfilter.org/projects/ulogd/">ulogd-2.x</ulink> provides.</para>
  </listitem>
 </itemizedlist>

 <sect1 id="sync"><title>State table synchronization</title>

 <sect2 id="sync-requirements"><title>Requirements</title>

 <para>In order to get <emphasis>conntrackd</emphasis> working in synchronization mode, you have to fulfill the following requirements:</para>

 <orderedlist>
 <listitem>
 <para>A <emphasis>high availability manager</emphasis> like <ulink url="http://www.keepalived.org">keepalived</ulink> that manages the virtual IPs of the 
 firewall cluster, detects errors, and decide when to migrate the virtual IPs
 from one firewall replica to another. Without it, <emphasis>conntrackd</emphasis> will not work appropriately.</para>

 <para>The state synchronization setup requires a working installation of <ulink url="http://www.keepalived.org">keepalived</ulink>, preferibly a recent version. Check if your distribution comes with a recent packaged version. Otherwise, you may compile it from the sources.
 </para>

 <para>
 There is a very simple example file in the <emphasis>conntrackd</emphasis>
 sources to setup a simple HA cluster with keepalived (see the file 
 keepalived.conf under the doc/sync/ directory). This file can be used to 
 set up a simple VRRP cluster composed of two machines that hold the virtual
 IPs 192.168.0.100 on eth0 and 192.168.1.100 on eth1.</para>

 <para>If you are not familiar with <emphasis>keepalived</emphasis>, please
 read the official documentation available at the keepalived website 
 (<ulink url="http://www.keepalived.org">http://www.keepalived.org</ulink>).</para>

<para>If you use a different high availability manager, make sure it works correctly before going ahead.</para>

 </listitem>

 <listitem>
 <para>A dedicated link. The dedicated link between the firewalls is used
 to transmit and receive the state information. The use of a dedicated link
 is mandatory for security reasons as someone may pick the state information
 that is transfered between the firewalls.</para>
 </listitem>

 <listitem>
 <para>A well-formed stateful rule-set. Otherwise you are likely to experience
 problems during the fail-over. An example of a well-formed stateful iptables
 rule-set is available in the <ulink url="http://conntrack-tools.netfilter.org/testcase.html">conntrack-tools website</ulink>.</para>
 </listitem>

 <listitem>
  <para>If your Linux kernel is &lt; 2.6.22, you have to disable TCP window
  tracking:
   <programlisting>
    # echo 1 > /proc/sys/net/ipv4/netfilter/ip_conntrack_tcp_be_liberal
   </programlisting>
  </para>
 </listitem>

 </orderedlist>

 </sect2>

 <sect2 id="sync-configure"><title>Configuring the daemon</title>

 <para>The daemon <emphasis>conntrackd</emphasis> in synchronization mode 
 supports up to three replication approaches:</para>

 <itemizedlist>
  <listitem>
   <para><emphasis>notrack</emphasis>: this approach is the most simple as 
   it is based on a best effort replication protocol, ie. unreliable
   protocol. This protocol sends and receives the state information
   without performing any specific checking.
   </para>
  </listitem>
  <listitem>
   <para><emphasis>ft-fw</emphasis>: this approach is based on a reliable 
   protocol that performs message tracking. Thus, the protocol can recover
   from message loss, re-ordering and corruption.</para>
  </listitem>
  <listitem>
   <para><emphasis>alarm</emphasis>: this approach is spamming. It is based 
   on a alarm-based protocol that periodically re-sends the flow state to
   the backup firewall replicas. This protocol consumes a lot of bandwidth
   but it resolves synchronization problems fast.</para>
  </listitem>
 </itemizedlist>

 <para>The three existing approaches are soft real-time asynchronous 
 replication protocols that are aimed to have negligible impact in terms
 of latency and bandwidth throughput in the stateful firewall filtering.</para>

 <para>To configure <emphasis>conntrackd</emphasis> in any of the existing
 synchronization modes, you have to copy the example configuration file to
 the directory /etc/conntrackd/ on every firewall replica. Note that 
 <emphasis>_type_</emphasis> is the synchronization type selected.</para>

<programlisting>
 (conntrack-tools-x.x.x)# cp doc/_type_/conntrackd.conf /etc/conntrackd/conntrackd.conf
</programlisting>

<para>
 Do not forget to edit the files before going ahead. There are several
 parameters that you have to tune to adapt the example configuration file
 to your setup.
</para>

<note><title>Configuration file location</title>
 <para>If you don't want to put the config file under /etc/conntrackd/, just tell conntrackd where to find it passing the option -C.</para>
</note>

</sect2>

<sect2 id="sync-pb"><title>Active-Backup setup</title>

 <note><title>Stateful firewall architectures</title>
  <para>A good reading to extend the information about firewall architectures is <ulink url="http://1984.lsi.us.es/~pablo/docs/intcomp09.pdf">Demystifying cluster-based fault-tolerant firewalls</ulink> published in IEEE Internet Computing magazine.
  </para>
 </note>

 <para>In the Active-Backup setup, one of the stateful firewall replicas 
 filters traffic and the other acts as backup. If you use this approach, 
 you have to copy the script <emphasis>primary-backup.sh</emphasis> to:
 </para>

<programlisting>
 (conntrack-tools-x.x.x)# cp doc/sync/primary-backup.sh /etc/conntrackd/
</programlisting>

 <para>The HA manager invokes this script when a transition happens, ie. If
 a stateful firewall replica:</para>

 <itemizedlist>
  <listitem>
   <para>becomes active to recover the filtering.</para>
  </listitem>
  <listitem>
   <para>becomes backup.</para>
  </listitem>
  <listitem>
   <para>hits failure (this is available if the HA manager has a failure state, which is true for <ulink url="http://www.keepalived.org">keepalived</ulink>.</para>
  </listitem>
 </itemizedlist>

 <para>The script is simple, and it contains the different actions that 
 <emphasis>conntrackd</emphasis> performs to recover the filtering or
 purge obsolete entries from the state table, among others. The script is
 commented, you can have a look at it if you need further information.</para>

</sect2>

<sect2 id="sync-aa"><title>Active-Active setup</title>

 <para>The Active-Active setup consists of having more than one stateful
 firewall replicas actively filtering traffic. Thus, we reduce the resource
 waste that implies to have a backup firewall which does nothing.</para>

 <para>We can classify the type of Active-Active setups in several
 families:</para>

 <itemizedlist>
  <listitem>
   <para><emphasis>Symmetric path routing</emphasis>: The stateful firewall
   replicas share the workload in terms of flows, ie. the packets that are
   part of a flow are always filtered by the same firewall.</para>
   </listitem>
   <listitem>
   <para><emphasis>Asymmetric multi-path routing</emphasis>: The packets that 
   are part of a flow can be filtered by whatever stateful firewall in the
   cluster. Thus, every flow-states have to be propagated to all the firewalls
   in the cluster as we do not know which one would be the next to filter a
   packet. This setup goes against the design of stateful firewalls as we
   define the filtering policy based on flows, not in packets anymore.
   </para>
  </listitem>
 </itemizedlist>

 <para>As for 0.9.8, the design of <emphasis>conntrackd</emphasis> allows you
 to deploy an symmetric Active-Active setup based on a static approach. 
 For example, assume that you have two virtual IPs, vIP1 and vIP2, and two
 firewall replicas, FW1 and FW2. You can give the virtual vIP1 to the
 firewall FW1 and the vIP2 to the FW2.
 </para>

 <para>Unfortunately, you will have to wait for the support for the
 Active-Active setup based on dynamic approach, ie. a workload sharing setup
 without directors that allow the stateful firewall share the filtering.</para>

 <para>On the other hand, the asymmetric scenario may work if your setup 
 fulfills several strong assumptions. However, in the opinion of the author
 of this work, the asymmetric setup goes against the design of stateful
 firewalls and <emphasis>conntrackd</emphasis>. Therefore, you have two
 choices here: you can deploy an Active-Backup setup or go back to your
 old stateless rule-set (in that case, the conntrack-tools will not be
 of any help anymore, of course).</para>

</sect2>

<sect2 id="sync-launch"><title>Launching conntrackd</title>

 <para>
 Once you have configured <emphasis>conntrackd</emphasis>, you can run in 
 <emphasis>console mode</emphasis> which is an interactive mode, in that case 
 type 'conntrackd' as root.</para>
 
 <programlisting>(root)# conntrackd</programlisting>

 <para>If you want to run <emphasis>conntrackd</emphasis> in <emphasis>daemon
 mode</emphasis>, then type:</para>

 <programlisting>(root)# conntrackd -d</programlisting>

 <para>You can verify that conntrackd is running by checking the log messages 
 via <emphasis>ps</emphasis>. Moreover, if <emphasis>conntrackd</emphasis> is
 running fine, you can dump the current status of the daemon:</para>

 <programlisting>
 # conntrackd -s
 cache internal:
 current active connections:                4
 connections created:                       4    failed:            0
 connections updated:                       0    failed:            0
 connections destroyed:                     0    failed:            0

 cache external:
 current active connections:                0
 connections created:                       0    failed:            0
 connections updated:                       0    failed:            0
 connections destroyed:                     0    failed:            0

 traffic processed:
                    0 Bytes                         0 Pckts

 multicast traffic:
                  352 Bytes sent                    0 Bytes recv
                   22 Pckts sent                    0 Pckts recv
                    0 Error send                    0 Error recv

 multicast sequence tracking:
                    0 Pckts mfrm                    0 Pckts lost
 </programlisting>

 <para>This command displays the number of entries in the internal and
 external cache:</para>

 <itemizedlist>
  <listitem>
   <para>The internal cache contains the states that this firewall replica is filtering, ie. this is a cache of the kernel state table.
   </para>
  </listitem>
  <listitem>
   <para>The external cache contains the states that the other firewall replica is filtering.
   </para>
  </listitem>
 </itemizedlist>

 <para>You can dump the internal cache with the following command:</para>

 <programlisting>
 # conntrackd -i
 tcp      6 ESTABLISHED src=192.168.2.100 dst=139.174.175.20 sport=58491 dport=993 src=139.174.175.20 dst=192.168.2.100 sport=993 dport=58491 [ASSURED] mark=0 secmark=0 [active since 536s]
 tcp      6 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=38211 dport=993 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=38211 [ASSURED] mark=0 secmark=0 [active since 536s]
 tcp      6 ESTABLISHED src=192.168.2.100 dst=123.59.27.117 sport=38209 dport=993 src=123.59.27.117 dst=192.168.2.100 sport=993 dport=38209 [ASSURED] mark=0 secmark=0 [active since 536s]
 tcp      6 TIME_WAIT src=192.168.2.100 dst=74.125.45.166 sport=42593 dport=80 src=74.125.45.166 dst=192.168.2.100 sport=80 dport=42593 [ASSURED] [active since 165s]
 tcp      6 ESTABLISHED src=192.168.2.100 dst=139.174.175.20 sport=37962 dport=993 src=139.174.175.20 dst=192.168.2.100 sport=993 dport=37962 [ASSURED] mark=0 secmark=0 [active since 536s]
 </programlisting>

 <para>You can dump the external cache with the following command:</para>

 <programlisting># conntrackd -e</programlisting>

 <para>If the replication works fine, <emphasis>conntrackd -s</emphasis>
 displays the active's internal cache should display the same number of
 entries than the backup's external cache and vice-versa.</para>

 <para>To verify that the recovery works fine, if you trigger a fail-over,
 the log files should display the following information:</para>

 <programlisting>
 [Thu Sep 18 18:03:02 2008] (pid=9759) [notice] committing external cache
 [Thu Sep 18 18:03:02 2008] (pid=9759) [notice] Committed 1545 new entries</programlisting>

 <para>This means that the state entries have been injected into the kernel correctly.</para>

</sect2>

<sect2 id="sync-options"><title>Other configuration options</title>

 <para>The daemon allows several configuration options that you may want to
 enable. This section contains some information about them.</para>

<sect3 id="sync-disable-external"><title>Disabling external cache</title>

 <para>It is possible to disable the external cache. Thus,
 <emphasis>conntrackd</emphasis> directly injects the flow-states into the
 in-kernel Connection Tracking System of the backup firewall. You can do it
 by enabling the <emphasis>DisableExternalCache</emphasis> option in the
 <emphasis>conntrackd.conf</emphasis> configuration file:
 </para>

 <programlisting>
Sync {
	Mode FTFW {
		 [...]
		 DisableExternalCache Off
	}
}
 </programlisting>

 <para>You can also use this option with the NOTRACK and ALARM modes. This
 increases CPU consumption in the backup firewall but now you do not need
 to commit the flow-states during the master failures since they are already
 in the in-kernel Connection Tracking table. Moreover, you save memory in
 the backup firewall since you do not need to store the foreign flow-states
 anymore.
 </para>

</sect3>

<sect3 id="sync-disable-internal"><title>Disabling internal cache</title>

 <para>You can also disable the internal cache by means of the
 <emphasis>DisableInternalCache</emphasis> option in the
 <emphasis>conntrackd.conf</emphasis> configuration file:
 </para>

 <programlisting>
Sync {
	Mode NOTRACK {
		 [...]
		 DisableInternalCache Off
	}
}
 </programlisting>

 <para>However, this option is only available for the NOTRACK mode. This
 mode provides unreliable flow-state synchronization between firewalls.
 Thus, if flow-states are lost during the synchronization, the protocol
 provides no way to recover them.</para>

</sect3>

<sect3 id="sync-transport-protocol">
<title>Using UDP, TCP or multicast for flow-state synchronization</title>

 <para>You can use up to three different transport layer protocols to
 synchronize flow-state changes between the firewalls: UDP, TCP and
 Multicast. UDP and multicast are unreliable but together with the FT-FW
 mode provide partial reliable flow-state synchronization.
 </para>

 <para>The preferred choice is FT-FW over UDP, or multicast alternatively.
 TCP introduces latency in the flow-state synchronization due to the
 congestion control. Under flow-state message are lost, the FIFO delivery
 becomes also a problem since the backup firewall quickly gets out of
 sync. For that reason, its use is discouraged. Note that using TCP only
 makes sense with the NOTRACK mode.
 </para>

</sect3>

<sect3 id="sync-redundant-link"><title>Redundant dedicated links</title>

 <para>You can set redundant dedicated links without using bonding, you have
 to configure as many redundant links as you want in the configuration file.
 In case of failure of the master dedicated link, conntrackd failovers to one
 of the backups. An example of this configuration is the following:
 </para>

 <programlisting>
Sync {
	Mode FTFW {
		 [...]
	}
	# default master dedicated link
        UDP Default {
                IPv4_address 192.168.2.1
                IPv4_Destination_Address 192.168.2.2
                Port 3780
                Interface eth3
                SndSocketBuffer 24985600
                RcvSocketBuffer 24985600
                Checksum on
        }
	# backup dedicated link
        UDP {
               IPv4_address 192.168.1.3
               IPv4_Destination_Address 192.168.1.4
               Port 3780
               Interface eth2
               SndSocketBuffer 24985600
               RcvSocketBuffer 24985600
               Checksum on
        }
	[...]
}
 </programlisting>

</sect3>

</sect2>

<sect2 id="sync-trouble"><title>Troubleshooting</title>

 <para>Problems with <emphasis>conntrackd</emphasis>? The following list 
 of questions should help for troubleshooting:</para>

 <qandaset>

  <qandaentry>
   <question>
    <para>
    I see <emphasis>packets lost</emphasis> in <emphasis>conntrackd -s</emphasis>
    </para>
   </question>
   <answer>
    <para>
    You can rise the value of <emphasis>McastRcvSocketBuffer</emphasis> and <emphasis>McastRcvSocketBuffer</emphasis>, if the problem is due to buffer overruns in the multicast sender or the receiver, the problem should disapear.
    </para>
   </answer>
  </qandaentry>
 
  <qandaentry>
   <question>
    <para>
    The log messages report that the <emphasis>maximum netlink socket buffer has been reached</emphasis>.
    </para>
   </question>
   <answer>
    <para>
    You can increase the values of <emphasis>SocketBufferSize</emphasis> and <emphasis>SocketBufferSizeMaxGrown</emphasis>.
    </para>
   </answer>
  </qandaentry>

 <qandaentry>
   <question>
    <para>
    I see <emphasis>can't open multicast server</emphasis> in the log messages
    </para>
   </question>
   <answer>
    <para>
    Make sure that the <emphasis>IPv4_interface</emphasis> clause has the IP of the dedicated link.
    </para>
   </answer>
  </qandaentry>

 <qandaentry>
   <question>
    <para>
    Can I use <ulink url="http://www.backhand.org/wackamole/">wackamole</ulink>, heartattack or any other HA manager?
    </para>
   </question>
   <answer>
    <para>
    Absolutely, you can. But before reporting issues, make sure that your HA manager is not the source of the problems.
    </para>
   </answer>
  </qandaentry>

 <qandaentry>
   <question>
    <para>
    Does conntrackd support TCP flow-recovery with window tracking enabled?
    </para>
   </question>
   <answer>
    <para>
    Yes, but you require a Linux kernel &gt;= 2.6.36 and the conntrack-tools &gt;= 0.9.15. To enable it, check the TCPWindowTracking clause in the example configuration files.
    </para>
   </answer>
  </qandaentry>

 <qandaentry>
   <question>
    <para>
    Does conntrackd support the H.323 and SIP connection tracking helpers?
    </para>
   </question>
   <answer>
    <para>
    No. This is not implemented yet, sorry. If you are interested in
    sponsoring this support, please contact me.
    </para>
   </answer>
  </qandaentry>

  <qandaentry>
   <question>
    <para>
    Is there any way to set up a more verbose mode in the log message for debugging?
    </para>
   </question>
   <answer>
    <para>
    No, but conntrackd provides lots of information that you can look up in
    runtime via -s option.</para>

    <para>You can check network statistics to find anomalies:</para>
    <programlisting>
    # conntrackd -s network
    network statistics:
        recv:
                Malformed messages:                        0
                Wrong protocol version:                    0
                Malformed header:                          0
                Malformed payload:                         0
                Bad message type:                          0
                Truncated message:                         0
                Bad message size:                          0
        send:
                Malformed messages:                        0

sequence tracking statistics:
        recv:
                Packets lost:                          42726
                Packets before:                            0

UDP traffic (active device=eth3):
              564232 Bytes sent              1979844 Bytes recv
                2844 Pckts sent                 8029 Pckts recv
                   0 Error send                    0 Error recv
    </programlisting>

    <para>You can check cache statistics:</para>
    <programlisting>
cache:internal  active objects:                    0
        active/total entries:                      0/           0
        creation OK/failed:                    11068/           0
                no memory available:               0
                no space left in cache:            0
        update OK/failed:                       4128/           0
                entry not found:                   0
        deletion created/failed:               11068/           0
                entry not found:                   0

cache:external  active objects:                    0
        active/total entries:                      0/           0
        creation OK/failed:                    10521/           0
                no memory available:               0
                no space left in cache:            0
        update OK/failed:                       8832/           0
                entry not found:                   0
        deletion created/failed:               10521/           0
                entry not found:                   0
    </programlisting>

    <para>You can check runtime miscelaneous statistics:</para>
    <programlisting>
daemon uptime: 14 min

netlink stats:
        events received:                       24736
        events filtered:                           0
        events unknown type:                       0
        catch event failed:                        0
        dump unknown type:                         0
        netlink overrun:                           0
        flush kernel table:                        1
        resync with kernel table:                  0
        current buffer size (in bytes):      8000000

runtime stats:
        child process failed:                      0
                child process segfault:            0
                child process termsig:             0
        select failed:                             0
        wait failed:                               0
        local read failed:                         0
        local unknown request:                     0
    </programlisting>

    <para>You can check dedicated link statistics:</para>
    <programlisting>
UDP traffic device=eth3 status=RUNNING role=ACTIVE:
              566848 Bytes sent              1982612 Bytes recv
                3018 Pckts sent                 8203 Pckts recv
                   0 Error send                    0 Error recv
    </programlisting>

    <para>You can check network queue statistics:</para>
    <programlisting>
allocated queue nodes:                     1

queue txqueue:
current elements:                          0
maximum elements:                 2147483647
not enough space errors:                   0

queue errorq:
current elements:                          0
maximum elements:                        128
not enough space errors:                   0

queue rsqueue:
current elements:                          1
maximum elements:                     131072
not enough space errors:                   0
    </programlisting>
   </answer>
  </qandaentry>

 </qandaset>

</sect2>

</sect1>

</chapter>

</book>