DNS Mail Server Lookup from C?

JohnGraham · 02-14-2010, 04:49 AM

Hi there,

I'm trying to do dns lookups from C using getaddrinfo(), but I can't find out how to set the query type to MX instead of the default A - can anyone help me out?

Thanks

John G

paulsm4 · 02-14-2010, 03:40 PM

Hi -

If you really want to query low-level DNS stuff like MX records, perhaps your best bet might be to write some scripts for "dig" or "nslookup", and have your C program a) invoke the script, and b) parse the results.

Another alternative might be "man 3 resolver". This documents APIs like "res_mkquery" and "res_search".

'Hope that helps .. PSM

ForzaItalia2006 · 02-14-2010, 05:53 PM

Maybe, you find the following API interesting as well:

man 3 gethostbyaddr
man 3 gethostbyname

This will resolve a hostname by following the configuration in /etc/nsswitch.conf, e.g. via the hosts file or the dns server. The advantage is that you don't have to care about the DNS specifics/details.

Hope that helps,

- Andi -