[nycbug-talk] To ping or not to ping, that is the question...

[Ray Lai]

On Sat, Jul 08, 2006 at 07:11:22AM -0400, Isaac Levy wrote:
> Hey All,
> 
> I'm trying to ping. :)
> 
> Ok, so the situation is this- I'm attempting to determine weather or  
> not a box is 'live', using some kind of external network probe  
> (ping), hopefully determining if the box is up within 10 seconds or  
> so- so my program can decide to do other things.
> 
> With that, the ping utility was not really designed to accommodate  
> this need, on several counts:
> 
> Inside the box:
> - to my knowledge, (and digging through the man pages), ping cannot  
> bind itself to a particular network interface, which is a problem on  
> boxes with multiple interfaces, with IP's all on the same subnet.   
> (ping just finds the first IP route, and pings out on that interface.

NetBSD and OpenBSD's ping allows this with the -I flag.  FreeBSD's
allows it with the -S flag.

> Outside the box:
> - to my knowledge, (and digging through the man pages), ping does not  
> have any options which let the utility return some sort of boolean  
> value for weather or not a packet was returned.

It returns 0 if a packet was received and other values otherwise,
depending on the operating system.  You'll probably want to use the
-c flag.

-Ray-

> If I'm wrong on either of these points, I'd love for someone to tell  
> me different- it would get me out of some tedious work here...
> 
> (sidenote- I know the implications of my question are a bit heavy,  
> insomuch as there's *so much* that can happen to make a given ping  
> fail, network latency, tons of factors... so using ping to determine  
> weather a box is 'up' is more of an ontological debate than a simple  
> yes or no answer...)
> 
> --
> What I'm planning on doing, to solve my problem(s), is to write a  
> small utility into my application which creates a network socket on a  
> specified network interface, and pings from an IP assigned to it-  
> returning boolean values to my program, so it can decide what to do  
> (a fail-over type application).  This can be done pretty simply in  
> Python (or similar), I'd just rather use a core system utility and  
> keep it all in nice portable shell scripts...
> 
> Is this a sane idea, or are there some other ping type utilities out  
> there that people know and love to do the same thing?  (Note- I'm not  
> looking for some kind of Nagios/etc... type solution, I'm looking for  
> a small stable widget to incorporate into my program).
> 
> Any thoughts, urls, chiding, anything- much appreciated...
> (Arp related tools would also be a fine solution here, since I'm  
> really focused on layer 2 [or perhps 3, IP], not services on the  
> upper layers...)