recvfrom() and Debian

[der.hans]

Am 21. Oct, 2002 schwätzte Alex Vrenios so:

> A simple approach to fault tolerance in receiving a UDP response to a query
> is to use sendto("the_query") and then recvfrom("the_response"). You, the
> client, should not trust the server, however, so you do something like the
> following:
>
>    sendto("the_query");
>    alarm(2); /* set */
>    while(1)
>    {
>       recvfrom("the_response");
>       if(alarm_didn't_go_off)
>          break;
>       sendto("the_query");
>       alarm(2); /* reset */
>    }
>    alarm(0); /* cancel */
>    /* process the response */
>
> Okay, maybe you want to add a counter so you don't spend the rest of your
> days and nights waiting for that response, but that's not the point.
>
> A particular release (2.2.18pre21 #1 Sat Nov 18 18:47:15 EST 2000 i686) of
> Debian (via the CD in Hunger's book, titled Debian GNU/Linux Bible) behaves
> oddly. Specifically, the alarm signal (SIGALRM) does -not- interrupt that
> recvfrom() call. The code sits there, never getting past the recvfrom() even
> after the alarm went off. (This was shown to be true with a puts() call)
> just after the if/break.)
>
> My search uncovered a TON of Debian+recvfrom problems, but nothing specific
> to this issue. Does anyone support my decision to condem the OS in this
> case? Is there a workaround that anyone might suggest?

Look through the debian bug reports: http://bugs.debian.org/

It might be hard to find something for the particular kernel package you're
using as it's a bit old.

Another thing is look at the kernel docs and the debian changelog.

Changelogs go in package docs, /usr/share/doc/<packagename>/.

Since it's debian, it's pretty easy to update as well :).

apt-get update && apt-get -u dist-upgrade

or just get a newer kernel.

apt-get update && apt-cache search ^kernel-image-2.2

or

apt-get update && apt-cache search ^kernel-image-2.4

then

apt-get install <kernel_package_you_choose>

ciao,

der.hans
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