[Nagiosplug-devel] check_dns.c

[s lurndal]

> 
> 
> Hi,
> 
> Does anyone see any utility in rewriting check_dns.c to use gethostbyname(),
> instead of nslookup?. 

The problem with gethostbyname() is that it will not necessarily check
DNS, but rather check the host resolver configured in the /etc/nsswitch.conf[1]
file which could be NIS, NIS+, LDAP, DNS or /etc/hosts.

scott

[1] or the SVR4 network resolver configuration file.

> Also, is just just querying for an A record really enough functionality for
> a plugin which checks name servers?
> 
> Cheers
> 
> Awais
> 
> -----Original Message-----
> From: Voon, Ton [mailto:Ton.Voon at egg.com]
> Sent: Tuesday, September 30, 2003 8:55 AM
> To: 'Karl DeBisschop'
> Cc: NagiosPlug Devel
> Subject: RE: [Nagiosplug-devel] RFC: OS specific ifdefs in main plugin
> cod e
> 
> 
> > -----Original Message-----
> > From: Karl DeBisschop [mailto:karl at debisschop.net] 
> > Sent: Tuesday, September 30, 2003 5:58 AM
> > To: Ton Voon
> > Cc: NagiosPlug Devel
> > Subject: Re: [Nagiosplug-devel] RFC: OS specific ifdefs in 
> > main plugin code
> > 
> > 
> > On Mon, 2003-09-29 at 10:46, Voon, Ton wrote:
> > > Hi! Wanted to get some opinions on the latest development 
> > of the plugins.
> > > 
> > > I'm starting to use OS specific ifdefs to get system data and I was
> > > wondering if this is the right way to go. The latest 
> > version of check_swap.c
> > > has ifdefs for Solaris and AIX as they have different ways 
> > for checking
> > > swap. It could have been done via ./configure, but there 
> > are too many
> > > different possibilities (for instance, need to run 
> > different switches for
> > > individual partition checks versus a summary of swap). 
> > > 
> > > If it was done via ./configure, you'd also need to set 
> > flags to say whether
> > > to ignore first lines (some have header info, others 
> > don't), work out
> > > different format responses (some return megabytes, some 
> > return free, some
> > > return percentage).
> > > 
> > > I think all this is easier done within the code itself. Is this bad?
> > 
> > What I don't like is use of targets like #ifdef _AIX or #ifdef sun --
> > for instance, SGI IRIX also has a swap command with very 
> > similar syntax.
> > Except it is in /sbin instead of /usr/sbin. It's not at all obvious to
> > me why we needs sun-specific code, but not IRIX-specific code (or more
> > to the point, why can't we write generic code that tests whether the
> > swap command accepts the '-s' switch, and forgo the #ifdef sun.
> 
> The reason for the sun specific code is that swap -l does not report
> "allocated but not used" swap, thus giving "wrong" results on free
> (available) swap. This is only available with swap -s. There was a thread on
> this about 9 months back.
> 
> The trouble with IRIX which "also has a swap command with very similar
> syntax" is that the syntax is similar but not the same. So we would have to
> have ./configure work in parsing the output differently. But sometimes it is
> more than just the sscanf order: there is also if there is a header line, if
> the syntax returns MBs or bytes or percentage, if the results are for free,
> used or total.
> 
> I guess these could be abstracted out to a generic function, but then the
> parameters to this function will probably need to be written very
> "code-like", so why not use code?
> 
> > 
> > To use things like #ifdef sun, unless absolutely needed, would seem to
> > require perfect knowlege of all Uinx-like OS's in use, and perfect
> > knowlege of those extensions that do not yet exist.
> > 
> > Often, this is a symptom that there is a basic problem. In fact, we
> > really see this issue in 3 plugins: check_ping, check_procs, and
> > check_swap.
> > 
> > From my point of view, we should be using a C API in POSIX for these
> > functions, rather than trying to parse comannd-line utilities.
> 
> I agree, but these are not always readily available hence the hackery.
> Eventually, I guess nagiosplug is basically a command-line way of getting a
> common result from all OSes.
> 
> > 
> > Certainly we can write a check_icmp, and probably should. If we can
> > identify an apporpriate API for swap and procs, we should do the same
> > for them. If not, I am much more ready to accept OS-specific 
> > ifdefs for
> > procs than I am for swap. There are only a handful of swap variants.
> 
> I only have Solaris, AIX and Darwin knowledge and they all handle swap
> differently (Darwin doesn't even preallocated swap space - it just
> dynamically grows).
> 
> check_procs doesn't have any ifdefs, maybe because the abstration is
> better/easier. Even so, I've had to add in extra variables to ./configure
> like number of columns to get round some inconsistencies (AIX's ps does not
> have an RSS field).
> 
> > AFAICT, if there ar n varieties of Unix, there must be n+1 
> > varieties of
> > the ps command.
> > 
> 
> If we continue with the ifdef method, in future we could abstract out as we
> understand the different cases better.
> 
> Ton
> 
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