njh / captivednsd

captivednsd, the Captive Domain Name Server, returns same authorative response to every query.

captivednsd

captivednsd, the Captive Domain Name Server, returns same authorative response to every query. The reponse to 'A' queries and 'PTR' records are passed as a parameter on the command line. The code is covered by the GNU license.

I wrote the daemon to direct people to a captive web portal, on a system that was not connected to the Internet. This meant that it was not possible to resolve the correct IP address for a host and then redirect the query using a firewall.

captivednsd is based on the source code of scdns and Busybox's dnsd:

• http://www.oao.no/filer/scdns-25.tgz
• http://www.busybox.net/cgi-bin/viewcvs.cgi/trunk/busybox/networking/dnsd.c

Usage

captivednsd [options] <ip> <host>
      -t <ttl>   Set the TTL for DNS responses (default 30).
      -p <port>  Port number to listen on (default 53).
      -b <addr>  Bind to an IP address (default 0.0.0.0).

Example

captivednsd 10.0.0.1 portal.local.

• All A requests will return IP address 10.0.0.1.
• All PTR requests will return portal.local.

captivednsd's Issues

Support reading static hosts from /etc/hosts

Add hard-coded support for looking up localhost

localhost -> 127.0.0.1
127.0.0.1 -> localhost.

Musl fix

captivedns doesn't compile under musl. The patch is simple:

diff --git a/captivednsd.c b/captivednsd.c
index 5992cf2..1c471ff 100644
--- a/captivednsd.c
+++ b/captivednsd.c
@@ -28,6 +28,7 @@
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <ctype.h>
+#include <sys/select.h>
 
 #include "captivednsd.h"

IPv6 Support