/proc/sys/net/* proliferation

Richard Gooch (rgooch@atnf.CSIRO.AU)
Thu, 11 Sep 1997 09:44:43 +1000

Hi, all. I'll admit that it's very nice having runtime control over
the various networking options, but one things that bothers me is that
things which used to work suddenly stop working because the default is
off. For example, running a bootp server under 2.0.30 worked fine, but
when I booted 2.1.5[45] it stopped working and I got an error about
martians invading. OK, so I read
Documentation/networking/ip-sysctl.txt to see if there was something I
should configure, and sure enough I found "ip_bootp_agent" is off by
default. Enabling it worked fine.
I've noticed the same thing for IP forwarding and SYN cookies.

The problem I see here is that many of these options default to
off. Why is that? Considering that the default was on with the 2.0.x
series when the option was not runtime configurable, should not the
default remain the same? Not only is it annoying to have to read the
documentation and edit the system boot scripts (for those who know
this particular trap), but it can be a real trap for sysadmins who
boot a 2.1.x kernel and a few days later (say when someone reboots
their bootp client) some user asks why xxx doesn't work anymore. The
sysadmin scratches his head thinking that nothing has been changed
today. Must be a faulty network cable...

Is there a good reason why these options aren't enabled by default?