[SunHELP] ping a port

[Kovalev, Ivan]

 Adam,

Understood.

Regarding "ping server" stuff, here is what I found in Stevens book. Chapter
6 and 7 from Volume1 talk about ICMP and ping in details. Stevens uses the
term "ping server" in a sence host being pinged. He gaves a table listing
all ICMP messages and who processes them. Good portion is handled directly
by the kernel (as oppposite to user processes), and that includes redirects
and echo requests (but echo reply is listed as being handled by user
process). I am not sure if it is the same thread (that would make sence) or
not. Some conditions (destination unreachable and parameter problem) have
just UNIX message corresponding to this condition. It looks to me they are
also handled by the kernel (?).

And Thomas, yes, knowledge might be dangerous, but I trust it will be
handled properly in your hands ;-) .

Ivan 

-----Original Message-----
From: Adam Kropelin
To: sunhelp at sunhelp.org
Sent: 9/22/01 11:04 PM
Subject: Re: [SunHELP] ping a port

Yes, that's basically what I meant by "The network stack is what
responds to
a PING (really an ICMP echo request packet), not any particular
application".

I think there is unlikely to be anything dedicated to the job of
listening
for and responding to pings, i.e., a "ping server". Stevens is the
expert,
for sure, but I expect it's just a terminology issue. I'm fairly certain
that there is basically one piece of kernel code that looks at what sort
of
ICMP packet has arrived and deals with it appropriately. A redirect, for
instance, would result in a temporary change to the routing table, while
an
echo request begets an echo reply. I would be very surprised if there is
a
kernel thread dedicated to being a "ping server". If there is, I'd like
to
understand why.

--Adam

----- Original Message -----
From: "Kovalev, Ivan" <Ivan.Kovalev at tfn.com>
To: "'Thomas Cameron '" <archimage at linux-magic.com>;
<sunhelp at sunhelp.org>
Sent: Saturday, September 22, 2001 12:09 PM
Subject: RE: [SunHELP] ping a port


> A little correction to Adam's reply: "...ping server is normally part
of
the
> kernel's ICMP implementation" (Stevens)
>
> -----Original Message-----
> From: Thomas Cameron
> To: sunhelp at sunhelp.org
> Sent: 9/22/01 12:54 AM
> Subject: Re: [SunHELP] ping a port
>
> Thanks for the clarification.  I wasn't sure what exactly to call the
> ICMP connection other than "port," but I thought that wasn't quite
> right.
>
> TC
>
> Adam Kropelin wrote:
>
> > AFAIK, there is no such thing as a port in ICMP. ICMP packets are
> > demultiplexed by IP based on the value of the protocol field in the
IP
>
> > header. The network stack is what responds to a PING (really an ICMP
> > echo request packet), not any particular application.
> >
> > --Adam


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