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Subject: Re: ctrl-c doesn't reliably kill ping
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References: <56E6F25A.7070000@gmx.de> <56E75B3E.7020102@farance.com>
From: Marco Atzeri <marco.atzeri@gmail.com>
Message-ID: <56E95EA2.8070800@gmail.com>
Date: Wed, 16 Mar 2016 14:24:50 +0100
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On 15/03/2016 01:45, Frank Farance wrote:
> I have been having this problem with "ping".  If I "ping" a location
> that doesn't exist, then "ping" just hangs and cannot be killed via
> "kill -KILL [pid]".
>
>
> Back to the problem, so when I type
>
> $ ping some.unknown.host
>

I do not succeed to replicate.
CTRL-C works fine for me

$ type ping
ping is hashed (/usr/bin/ping)

$ ping 172.21.1.254
PING 172.21.1.254 (172.21.1.254): 56 data bytes

----172.21.1.254 PING Statistics----
4 packets transmitted, 0 packets received, 100.0% packet loss

or I have not a biased DNS answer.

> according to "ping", the hostname resolves to 90.242.140.21 (as per the
> explanation above), but I cannot kill "ping".  I tried "ping" with a
> limited packet size and count so, in theory, "ping" would die on its own
> after 10 packets, such as:
>
> $ ping some.unknown.host 50 10
>
> but it still hangs rather than timing out.  If I ping to some actual IP
> address that is unresponsive (route-able to the last subnet, but dies on
> the floor at the end), then I can kill via ctrl-c.  My only solution to
> the hanging "ping" is to kill the terminal window.
>
> Any suggestions on:
>
> - Why "ping" behaves this way?
> - How to avoid this problem?
>
> Thanks, in advance.

cygwin ping is based on very old source from a time where people was not
cheating on protocol answer.

http://ftp.arl.mil/mike/ping.html
(the author passed away 16 years ago..)

can you send me a strace to see where the program is stacking ?
No promise to find a solution but I will look on it.

Regards
Marco


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