[RFC] per-containers tcp buffer limitation

Matthew Helsley matt.helsley at gmail.com
Sat Aug 27 16:39:11 PDT 2011


On Thu, Aug 25, 2011 at 11:27 AM, Daniel Wagner <wagi at monom.org> wrote:

> Hi Chris,
>
> On 08/25/2011 05:05 PM, Chris Friesen wrote:
> > On 08/25/2011 06:55 AM, Daniel Wagner wrote:
> >
> >> I'd like to solve a use case where it is necessary to count all bytes
> >> transmitted and received by an application [1]. So far I have found two
> >> unsatisfying solution for it. The first one is to hook into libc and
> >> count the bytes there. I don't think I have to say I don't like this.
> >
> > Is there any particular reason you can't use LD_PRELOAD to interpose a
> > library to do the statistics monitoring?
>
> This is certainly possible to do for any dynamic linked application. I
> think it wouldn't work for static linked ones. Currently I don't know if
> I have to face such application on the project I am on. The reason why I
> am not so a big fan is that using the LD_PRELOAD trick seems very
> hackish to me.
>

LD_PRELOAD is widely regarded as a debugging and tracing method -- it's not
usually suitable for implementing features. Why? Because there's nothing
stopping an application from resetting LD_PRELOAD and re-exec'ing to escape
the measurements and limitations such a preload implements. Plus naive use
of LD_PRELOAD could easily interfere with other things that use it. For
example what if you want to use DMTCP with this?

Cheers,
    -Matt


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