[Nagiosplug-devel] Antwort: Re: Feature request: extend check_ping to specify source address

[Holger Weiss]

* Andreas Ericsson <ae at op5.se> [2008-07-18 13:58]:
> Sascha.Runschke at gfkl.com wrote:
> > nagiosplug-devel-bounces at lists.sourceforge.net schrieb am 18.07.2008 
> > 09:23:03:
> >> check_icmp and ping alike mark their packets with pid, sequence-number,
> >> host-id (decided internally) etc, etc. Modifying the ip->src_addr field
> >> would cause the targeted host to send its ICMP_ECHO_REPLY packets to a
> >> different host, so check_icmp (or ping) wouldn't be able to pick them
> >> up at a later time.
> > 
> > It will work, if the local machine has 2 IP adresses and advanced source
> > policy routing is active on the gateway (or the local machine already).
> > The use of course is fairly small, since such setups are very rarely seen,
> > but obviously we found someone who does it that way ;)
> 
> Ah, ofcourse. I'm guessing the easy way is to simply bind(2) the socket
> to the address specified by -s and then send the packet in the normal
> fashion.

That's how we implemented it (plus you can specify the interface instead
of the IP address via "-s", and IMO we should also allow host names).

> As an added bonus, that would also provide typo-checking in the
> argument parsing, since it would then be impossible to specify a
> source-address that the local machine knows nothing about.

Indeed.

Holger