Shorewall Traffic AccountingTomEastep2003-2009Thomas M. EastepPermission 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
GNU Free Documentation
License.This article applies to Shorewall 4.0 and
later. If you are running a version of Shorewall earlier than Shorewall
4.0.0 then please see the documentation for that
release.Accounting BasicsShorewall accounting rules are described in the file
/etc/shorewall/accounting. By
default, the accounting rules are placed in a chain called
accounting and can thus be displayed using
shorewall[-lite] show -x accounting. All traffic passing
into, out of, or through the firewall traverses the accounting chain
including traffic that will later be rejected by interface options such as
tcpflags and maclist.The columns in the accounting file are described in shorewall-accounting (5)
and shorewall6-accounting
(5).In all columns except ACTION and CHAIN, the values -,
any and all are treated as
wild-cards.The accounting rules are evaluated in the Netfilter
filter table. This is the same environment where the
rules file rules are evaluated and in this environment,
DNAT has already occurred in inbound packets and SNAT has not yet occurred
on outbound packets.Accounting rules are not stateful -- each rule only handles traffic
in one direction. For example, if eth0 is your Internet interface, and you
have a web server in your DMZ connected to eth1, then to count HTTP
traffic in both directions requires two rules: #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
# PORT PORT
DONE - eth0 eth1 tcp 80
DONE - eth1 eth0 tcp - 80Associating a counter with a chain allows for nice reporting. For
example: #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
# PORT PORT
web:COUNT - eth0 eth1 tcp 80
web:COUNT - eth1 eth0 tcp - 80
web:COUNT - eth0 eth1 tcp 443
web:COUNT - eth1 eth0 tcp - 443
DONE webNow shorewall show web (or
shorewall-lite show web for Shorewall Lite users) will
give you a breakdown of your web traffic: [root@gateway shorewall]# shorewall show web
Shorewall-1.4.6-20030821 Chain web at gateway.shorewall.net - Wed Aug 20 09:48:56 PDT 2003
Counters reset Wed Aug 20 09:48:00 PDT 2003
Chain web (4 references)
pkts bytes target prot opt in out source destination
11 1335 tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
18 1962 tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:80
0 0 tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
0 0 tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:443
29 3297 RETURN all -- * * 0.0.0.0/0 0.0.0.0/0
[root@gateway shorewall]#Here is a slightly different example: #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
# PORT PORT
web - eth0 eth1 tcp 80
web - eth1 eth0 tcp - 80
web - eth0 eth1 tcp 443
web - eth1 eth0 tcp - 443
COUNT web eth0 eth1
COUNT web eth1 eth0Now shorewall show web (or
shorewall-lite show web for Shorewall Lite users)
simply gives you a breakdown by input and output: [root@gateway shorewall]# shorewall show accounting web
Shorewall-1.4.6-20030821 Chains accounting web at gateway.shorewall.net - Wed Aug 20 10:27:21 PDT 2003
Counters reset Wed Aug 20 10:24:33 PDT 2003
Chain accounting (3 references)
pkts bytes target prot opt in out source destination
8767 727K web tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
0 0 web tcp -- eth0 eth1 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
11506 13M web tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:80
0 0 web tcp -- eth1 eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:443
Chain web (4 references)
pkts bytes target prot opt in out source destination
8767 727K all -- eth0 eth1 0.0.0.0/0 0.0.0.0/0
11506 13M all -- eth1 eth0 0.0.0.0/0 0.0.0.0/0
[root@gateway shorewall]#Here's how the same example would be constructed on an HTTP server
with only one interface (eth0).READ THE ABOVE CAREFULLY -- IT SAYS SERVER. If you want to account for web browsing,
you have to reverse the rules below. #ACTION CHAIN SOURCE DESTINATION PROTOCOL DEST SOURCE
# PORT PORT
web - eth0 - tcp 80
web - - eth0 tcp - 80
web - eth0 - tcp 443
web - - eth0 tcp - 443
COUNT web eth0
COUNT web - eth0Note that with only one interface, only the SOURCE (for input rules)
or the DESTINATION (for output rules) is specified in each rule.Here's the output: [root@mail shorewall]# shorewall show accounting web Shorewall-1.4.7
Chains accounting web at mail.shorewall.net - Sun Oct 12 10:27:21 PDT 2003
Counters reset Sat Oct 11 08:12:57 PDT 2003
Chain accounting (3 references)
pkts bytes target prot opt in out source destination
8767 727K web tcp -- eth0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:80
11506 13M web tcp -- * eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:80
0 0 web tcp -- eth0 * 0.0.0.0/0 0.0.0.0/0 tcp dpt:443
0 0 web tcp -- * eth0 0.0.0.0/0 0.0.0.0/0 tcp spt:443
Chain web (4 references)
pkts bytes target prot opt in out source destination
8767 727K all -- eth0 * 0.0.0.0/0 0.0.0.0/0
11506 13M all -- * eth0 0.0.0.0/0 0.0.0.0/0
[root@mail shorewall]#For an example of integrating Shorewall Accounting with MRTG, see
http://www.nightbrawler.com/code/shorewall-stats/.Accounting with BridgesThe structure of the accounting rules changes slightly when there
are bridges defined in the
Shorewall configuration. Because of the restrictions imposed by Netfilter
in kernel 2.6.21 and later, output accounting rules must be segregated
from forwarding and input rules. To accomplish this separation,
Shorewall-perl creates two accounting chains:accounting - for input and
forwarded traffic.accountout - for output
traffic.If the CHAIN column contains -, then:If the SOURCE column in a rule includes the name of the firewall
zone (e.g., $FW), then the default chain to insert the rule into is
accountout only.Otherwise, if the DEST in the rule is any or all or
0.0.0.0/0, then the rule is added to both accounting and accountout.Otherwise, the rule is added to accounting only.Sectioned Accounting RulesTraditionally, the root of the Shorewall accounting rules has been
the accounting chain. Having a single
root chain has drawbacks:Many rules are traversed needlessly (they could not possibly
match traffic).At any time, the Netfilter team could begin generating errors
when loading those same rules.MAC addresses may not be used in the accounting rules.The accounting chain cannot be
optimized when OPTIMIZE_ACCOUNTING=Yes.The rules may be defined in any order so the rules compiler must
post-process the ruleset to ensure that there are no loops and to
alert the user to unreferenced chains.Beginning with Shorewall 4.4.18, the accounting structure can be
created with three root chains:accountin: Rules that are valid
in the INPUT chain (may not specify
an output interface).accountout: Rules that are
valid in the OUTPUT chain (may not specify an input interface or a MAC
address).accounting: Other rules.The new structure is enabled by sectioning the accounting file in a
manner similar to the rules
file. The sections are INPUT,
OUTPUT and FORWARD and must appear in that order (although any
of them may be omitted). The first non-commentary record in the accounting
file must be a section header when sectioning is used. Beginning with Shorewall 4.4.20, the ACCOUNTING_TABLE setting was
added to shorewall.conf and shorewall6.conf. That setting determines the
Netfilter table (filter or mangle) where the accounting rules are added.
When ACCOUNTING_TABLE=mangle is specified, the available sections are
PREROUTING, INPUT, OUTPUT,
FORWARD and POSTROUTING.Section headers have the form:section-nameWhen sections are enabled:You must jump to a user-defined accounting chain before you can
add rules to that chain.This eliminates loops and unreferenced chains.You may not specify an output interface in the PREROUTING and INPUT sections.In the OUTPUT and POSTROUTING sections:You may not specify an input interfaceYou may not jump to a chain defined in the INPUT or PREROUTING sections that specifies an input
interfaceYou may not specify a MAC addressYou may not jump to a chain defined in the INPUT or PREROUTING section that specifies specifies
a MAC address.The default value of the CHAIN column is:accountin in the INPUT sectionaccounout in the OUTPUT sectionaccountfwd in the FORWARD sectionaccountpre in the PREROUTING sectionaccountpost in the
POSTROUTING sectionTraffic addressed to the firewall goes through the rules defined
in the INPUT section.Traffic originating on the firewall goes through the rules
defined in the OUTPUT section.Traffic being forwarded through the firewall goes through the
rules from the FORWARD sections.Here is a sample sectioned file that used Per-IP Accounting.In this example, the dmz net corresponds to a vserver zone so
lives on the firewall itself.#ACTION CHAIN SOURCE DESTINATION PROTO DEST SOURCE USER/ MARK IPSEC
# PORT(S) PORT(S) GROUP
SECTION INPUT
ACCOUNT(fw-net,$FW_NET) - COM_IF
ACCOUNT(dmz-net,$DMZ_NET) - COM_IF
SECTION OUTPUT
ACCOUNT(fw-net,$FW_NET) - - COM_IF
ACCOUNT(dmz-net,$DMZ_NET) - - COM_IF
SECTION FORWARD
ACCOUNT(loc-net,$INT_NET) - COM_IF INT_IF
ACCOUNT(loc-net,$INT_NET) - INT_IF COM_IF
Integrating Shorewall Accounting with CollectdSergiusz Pawlowicz has written a nice article that shows how to
integrate Shorewall Accounting with collectd to produce nice graphs of
traffic activity. The article may be found at http://collectd.org/wiki/index.php/Plugin:IPTables.Per-IP AccountingShorewall 4.4.17 added support for per-IP accounting using the
ACCOUNT target. That target is only available when xtables-addons is
installed. This support has been successfully tested with xtables-addons
1.32 on:Fedora 14Debian SqueezeOpenSuSE 11.3and xtables-addons Version 1.21 on:Debian LennyInformation about xtables-addons installation may be found at here.Per-IP accounting is configured in shorewall-accounting (5)
(it is currently not supported in IPv6). In the ACTION column,
enter:ACCOUNT(table,network)wheretable is the name of an accounting
table (you choose the name). All rules specifying the same table will
have their per-IP counters accumulated in that table.network is an IPv4 network in CIDR
notation. The network can be as large as a /8 (class A).One nice feature of per-IP accounting is that the counters survive
shorewall restart. This has a downside, however. If you
change the network associated with an accounting table, then you must
shorewall stop; shorewall start to have a successful
restart (counters will be cleared).Example: Suppose your WAN interface is eth0 and your LAN interface
is eth1 with network 172.20.1.0/24. To account for all traffic between the
WAN and LAN interfaces:#ACTION CHAIN SOURCE DEST ...
ACCOUNT(net-loc,172.20.1.0/24) - eth0 eth1
ACCOUNT(net-loc,172.20.1.0/24) - eth1 eth0This will create a net-loc table
for counting packets and bytes for traffic between the two
interfaces.The table is dumped using the iptaccount utility
(part of xtables-addons):iptaccount [-f] -l net-locExample:gateway:~# iptaccount -l net-loc
libxt_ACCOUNT_cl userspace accounting tool v1.3
Showing table: net-loc
Run #0 - 3 items found
IP: 172.20.1.105 SRC packets: 115 bytes: 131107 DST packets: 68 bytes: 20045
IP: 172.20.1.131 SRC packets: 47 bytes: 12729 DST packets: 38 bytes: 25304
IP: 172.20.1.145 SRC packets: 20747 bytes: 2779676 DST packets: 27050 bytes: 32286071
Finished.
gateway:~#For each local IP address with non-zero counters, the packet and
byte count for both incoming traffic (IP is DST) and outgoing traffic (IP
is SRC) are listed. The -f option causes the table to be flushed (reset
all counters to zero) after printing.For a command synopsis:iptaccount --help/sbin/shorewall also supports a show
ipa command (from my own gateway just after I flushed the
counters using iptaccount -f -l.:gateway:~# shorewall show ipa
Shorewall 4.4.18-Beta1 per-IP Accounting at gateway - Thu Feb 10 13:28:37 PST 2011
Showing table: loc-net
IP: 172.20.1.146 SRC packets: 9 bytes: 574 DST packets: 9 bytes: 770
Showing table: dmz-net
IP: 70.90.191.124 SRC packets: 243 bytes: 23726 DST packets: 248 bytes: 39036
IP: 70.90.191.125 SRC packets: 73 bytes: 10640 DST packets: 73 bytes: 4846
Showing table: fw-net
IP: 70.90.191.121 SRC packets: 0 bytes: 0 DST packets: 4 bytes: 243
IP: 70.90.191.122 SRC packets: 11 bytes: 1338 DST packets: 8 bytes: 5465
IP: 70.90.191.123 SRC packets: 42 bytes: 4604 DST packets: 44 bytes: 10662
gateway:~#