Copyright © 2003-2016 Thomas M. Eastep
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2020/02/16
Table of Contents
Caution
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.
Shorewall accounting rules are described in the file
/etc/shorewall/accounting
The columns in the accounting file are described in shorewall-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 DEST PROTO DPORT SPORT USER MARK IPSEC
DONE - eth0 eth1 tcp 80
DONE - eth1 eth0 tcp - 80Associating a counter with a chain allows for nice reporting. For example:
#ACTION CHAIN SOURCE DEST PROTO DPORT SPORT USER MARK IPSEC
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 DEST PROTO DPORT SPORT USER MARK IPSEC
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).
Caution
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 DEST PROTO DPORT SPORT USER MARK IPSEC
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/.
The 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.
Traditionally, 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 (that has happened).
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
section-name
When 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 interface
You may not jump to a chain defined in the INPUT or PREROUTING sections that specifies an input interface
You may not specify a MAC address
You may not jump to a chain defined in the INPUT or PREROUTING section that specifies a MAC address.
The default value of the CHAIN column is:
accountin in the INPUT section
accounout in the OUTPUT section
accountfwd in the FORWARD section
accountpre in the PREROUTING section
accountpost in the POSTROUTING section
Traffic 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.
Caution
In this example, the dmz net corresponds to a vserver zone so lives on the firewall itself.
#ACTION CHAIN SOURCE DEST PROTO DPORT SPORT USER MARK IPSEC ?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
Sergiusz 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.
Shorewall 4.4.17 added support for per-IP accounting using the ACCOUNT target.
Per-IP accounting is configured in shorewall-accounting (5) (it is currently not supported in IPv6). In the ACTION column, enter:
ACCOUNT(table,network) |
where
table 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 PROTO DPORT SPORT USER MARK IPSEC ACCOUNT(net-loc,172.20.1.0/24) - eth0 eth1 ACCOUNT(net-loc,172.20.1.0/24) - eth1 eth0
This 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:~#
Beginning with the 3.3 kernels, Netfilter supports a form of accounting (nfacct) that is triggered by iptables rules but that survives purging and/or reloading the Netfilter ruleset. Shorewall support for this form of accounting was added in Shorewall 4.5.7.
Use of this feature requires that the nfacct utility be installed. The nfacct utility can create, delete and display nfacct objects. These named objects consist of a packet and byte counter. Packets matching those netfilter rules that use the nfacct match cause the packet and byte count in the object named in the match to be incremented.
To use nfaccnt with Shorewall, use the NFACCT target. See shorewall-accounting(5) for details.
The shorewall show nfacct command is a thin wrapper around the nfacct list command.
Beginning with Shorewall 4.6.5, it is possible to preserve
all ip[6]tables packet and byte counters over
restarts and reboots through use of the -C option. This
option is available in several commands.
- save
Causes the packet and byte counters to be saved along with the chains and rules.
- restore
Causes the packet and byte counters (if saved) to be restored along with the chains and rules.
Caution
If your iptables ruleset depends on variables that are detected at run-time, either in your params file or by Shorewall-generated code, restore will use the values that were detected when the ruleset was saved, which may be different from the current values.
- start
With Shorewall and Shorewall6, the -C option only has an effect if the
-foption is also specified. If a previously-saved configuration is restored, then the packet and byte counters (if saved) will be restored along with the chains and rules.Caution
If your iptables ruleset depends on variables that are detected at run-time, either in your params file or by Shorewall-generated code,
-Cwill use the values that were detected when the ruleset was saved, which may be different from the current values.- restart
If an existing compiled script is used (no recompilation required) and if that script generated the current running configuration, then the current netfilter configuration is reloaded as is so as to preserve the current packet and byte counters.
Caution
If your iptables ruleset depends on variables that are detected at run-time, either in your params file or by Shorewall-generated code,
-Cwill use the values that were detected when the ruleset was previously started, which may be different from the current values.
If you wish to (approximately) preserve the counters over a possibly unexpected reboot, then:
Create a cron job that periodically executes 'shorewall save
-C'.Specify the
-Cand-foptions in the STARTOPTIONS variable in either/etc/default/shorewall(/etc/default/shorewall6, etc.) or/etc/sysconfig/shorewall(/etc/sysconfig/shorewall6, etc.), whichever is supported by your distribution. Note that not all distributions include these files so you may have to create the one(s) you need.
