darkstat-3.0.719 patched to query and display Autonomous System numbers
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This is a copy of the darkstat network traffic analyzer which has been patched to support Autonomous System Numbers.

After cloning this repo, build as usual: ./configure, make, make install. (Got compiler errors?)

Or, you can apply the patch to an existing source tree and compile.

To enable ASN support, use the new --with-asn command line option. darkstat will query the Team Cymru IP to ASN DNS service to determine the AS Number of each IPv4 host. The AS Numbers are displayed in darkstat's web interface, both as a new column in the "hosts" list and also on the host detail pages.

Host summary page with AS numbers displayed

In order to reduce DNS query load, an effort is made to skip AS Number lookups for IP addresses in certain reserved ranges (RFC1918, multicast, etc.). IPv6 hosts are also skipped for the time being. The ASN column will display "(none)" or "(unsupported)" for these hosts.

ASN support adds a second child thread to darkstat, mirroring the behavior of the main DNS resolution thread. In testing, there was no noticeable additional overhead from the extra process; it only does anything when you load the web interface.

This build has been tested on several Linux 2.6 kernels and on FreeBSD 11.1. Feedback from users of other operating systems is welcome.


The following files are new (italic) or modified from the original source:

  • Makefile.in
  • asn.c
  • asn.h
  • configure
  • configure.ac
  • darkstat.8.in
  • darkstat.c
  • dns.c
  • hosts_db.c
  • hosts_db.h
  • opt.h

You can review the patch to see what's changed.


IPv4 only

At present, AS Numbers will only be looked up for IPv4 hosts.


Querying for DNS TXT resource records uses several functions from the resolver library. Modern unix-based operating systems support these functions either natively or through libresolv.

Linux users will need to link against libresolv. I've tried to make the configure script detect this automatically. If you receive errors like this when compiling,

asn.o: In function `ip4_lookup_asn':
asn.c:420: undefined reference to `__res_nquery'
asn.c:451: undefined reference to `ns_initparse'
asn.c:461: undefined reference to `ns_parserr'
asn.c:462: undefined reference to `ns_sprintrr'
collect2: ld returned 1 exit status
make: *** [darkstat] Error 1

...open the Makefile and append -lresolv to the LIBS = line, then recompile.

Google's name servers (,

Enabling ASN lookups will nearly double the number of DNS queries generated by darkstat. Google's public name servers are rate limited, and may refuse your queries for awhile when you send a rapid burst of traffic. If you use Google DNS, and darkstat shows a lot of "(none)" where you know there should be valid data, this is likely due to a Google rate limit. Consider using your ISP's DNS servers or running one of your own.


  • Support IPv6 addresses.

  • Maybe refactor the ASN into an integer (I know!) and support sorting by it.