[Iftop-users] Kudos and Question

Paul Warren pdw at ex-parrot.com
Fri, 23 May 2003 17:50:39 +0100


On Fri, May 23, 2003 at 11:30:04AM -0500, Jonathan Abbey wrote:
> | Getting the hardware address is real PITA because there seem to be more
> | ways of doing it than there are platforms in the world.  Currently it's
> | only working on linux.  Can you try the attached patch, which is meant
> | to work on Solaris, and let me know how you get on.  I'm afraid I don't
> | have access to a Solaris box to test this on.
> 
> I will give this a try, thanks.
> 
> I do have another question.  When running iftop, it seems to be almost
> random which IP addresses are resolved to their DNS names, and which
> addresses appear in dotted decimal form.  This when all the hosts
> displayed, in whichever form, are properly registered in our local
> DNS.  If we do an nslookup on a host before starting iftop, that host
> seems to be properly resolved on the bar graph, but the majority go
> unresolved.

Which resolver mechanism are you using?  I'm guessing that it's fallen
back to using the single-threaded gethostbyname implementation.  This
sucks a lot, because if comes across an IP address that it can't
resolve quickly (typically it takes up to a minute to time out) then it
won't be able to resolve any more IP addresses.  If all the IP addresses
it ever encounters are in your local DNS then I'm a bit confused by
this, because the resolver thread should never stall.

In general, the best option would be to install ares, and the run:

	./configure --with-resolver=ares

You can get ares from: 
	
    ftp://athena-dist.mit.edu/pub/ATHENA/ares/

Paul