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From: hiro <23hiro@gmail.com>
Date: Mon, 3 Jan 2022 23:22:09 +0100
Message-ID: <CAFSF3XM_Rp_9X9BJ_fqW9d9zcMB+OVqDPLtBbut8gT1DfD2j8g@mail.gmail.com>
To: Benjamin Riefenstahl <b.riefenstahl@turtle-trading.net>
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Subject: Re: [9front] Loopback device
Reply-To: 9front@9front.org
Precedence: bulk

i think the main use case would be something like what tc is used for on li=
nux:
simulating a network link with output buffers, fragmentation, packet
drop, delay.

somebody might use it's flow-control for creating a bit of fairness on
a saturated slow link...

you're right that it isn't currently being built by default:

cpu% cd /sys/src/9/port
cpu% g =CE=BB
devloopback.c:718:      L'=CE=BB',
cpu% g loopback|grep -v devloopback.c
sdloop.c:2:  * sd loopback driver,

also try cat master in same directory.


On 1/3/22, Benjamin Riefenstahl <b.riefenstahl@turtle-trading.net> wrote:
> Hi hiro,
>
> Thanks for taking the time.
>
> hiro writes:
>> loopback is a *link*. it has two sides.
>> it's not the same as the 127.0.0.1 feature from other unixes.
>
> Ok.  But that does not answer my questions.  Why doesn't the bind
> command from the man page work?  And what *does* loopback do?
>
> Calling it a link with two sides makes it sound like a pipe.  And being
> mounted in /net makes it sound like, well, localhost, which also has two
> sides, in the sense that I can run a server on it and than connect to
> that server, all on the same host.
>
>> localhost/127.0.0.1 is not normally used on plan9.
>>
>> it doesn't make much sense on a distributed and namespaced system.
>> better use more meaningful unique IPs and hostnames and service names
>> and then use just those, together with our excellent ndb service to
>> resolve it all.
>
> I find I most often use it for testing and for other code that needs an
> IP with two sides where I do not want to hardcode, configure or find out
> the host name or host IP.
>
> Thanks, benny
>