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Re: [ezjail] [PATCH] "Locally configured IP" check in ezjail-admin is not 100% reliable

On 14.01.2012 20:55, Dirk Engling wrote:
> On 14.01.12 18:59, Thomas Steen Rasmussen wrote:
>> The patch below changes ezjail-admin to parse the
>> output of ifconfig instead of using ping to determine if an
>> ip address is locally configured. This will also work even if a
>> firewall is blocking pings to the IP address in question.
> Hello,
> thanks for the patch. I had something similar in place before, but I
> hesitate parsing userland tools' output as it is not standardized and
> may be subject to changes. I'd then have a hard time handling version
> differences. Also ... see your other mail for examples of parsing
> outputs to go wrong.

I agree, parsing the output of userland tools is not optimal.

I couldn't come up with anything better, so I asked on IRC
and xi on #bsdports came up with this clever idea:

[tykling@tykburk ~]$ nc -n -s -u -w 0 1 2> /dev/null
[tykling@tykburk ~]$ echo $?
[tykling@tykburk ~]$ nc -n -s -u -w 0 1 2> /dev/null
[tykling@tykburk ~]$ echo $?
[tykling@tykburk ~]$

This solves the problem in a very nice way IMO.

Best regards,

Thomas Steen Rasmussen