From bright@wintelcom.net Tue Jun 13 17:04:32 2000
Date: Tue, 13 Jun 2000 17:23:37 -0700
From: Alfred Perlstein <bright@wintelcom.net>
To: hackers@freebsd.org
Subject: big patch: rlimits, accept filters and kblob.
Message-ID: <20000613172336.S18462@fw.wintelcom.net>
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Hey guys, I have some patches here which implement a number of things.

1) fixes dangerous races in per-uid limiting code

2) 2 accept filters which will not mark a socket as completed for accept()
   until either:
   1) there is data available to be read
   2) there is an http request in the socketbuffer

3) kblob, a kernel hack for preloading data into the kernel to send out
   on multiple descriptors, very similar to sendfile but more lightweight
   and pretty useful for serving many small chunks of data over stream
   sockets.

I'd really like to commit this stuff pretty soon after i polish it up
just a bit more...  but I'd like some guidance for the polishing part.

Here's some implementation details about kblob:

A pointer to an address and a length is given to a syscall which creates
a file referernce as a kblob.  Then there is kblobsend which works in
the same manner as sendfile except that instead of a vnode it expects a
kblob fd.

I know the conerns about users exahusting KVM via kblobs, and I'd like
some feedback, some options come to mind:

1) kblobs not in the default kernel (don't like this)
2) kblobs limited via a sysctl for max per uid.
3) default entries in /etc/login.conf for 0.

I've already implemented rlimits so #3 seems pretty attractive.

You can grab the code at:
  http://people.freebsd.org/~alfred/kblob/kblob.diff
to be applied via 'patch' from /usr/src 

and:
  http://people.freebsd.org/~alfred/kblob/kern_blob.c
which needs to go into src/sys/kern

you also need "options KBLOB" in your kernel config.

Engineers at Yahoo provided the http accept filter and my delayed
accept filter is a stripped down version of it, really cool stuff!

Questions, comments, suggestions, flames?

Manpages will be written up and patched soon after commit.

-- 
-Alfred Perlstein - [bright@wintelcom.net|alfred@freebsd.org]


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