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Web Server Crash




     We had a web server crash, this time with an OOPS pointing to a NULL
pointer dereference.  This can happen if something exhausts memory and the
kernel is unable to malloc memory and gets a NULL pointer.

     We were under a denial of service attack at the time, this one however was
not aimed at our web server but rather one of the machines at my home, however,
it was of sufficient intensity to overload the router.

     The router being overloaded was unable to take all the data from the
webserver fast enough and that in turn causes memory to be consumed by buffers.
There are some parameters that, if properly adjusted, would maintain a minimal
amount of memory necessary for proper operation however, the only way to really
test whether enough the settings are adequate is an event like this.

     The attack has ended, everything is back up.  This machine has 50% more
CPU cycles than the web server it replaced, but it still doesn't have enough
memory and I'm still really looking for a better replacement (I have in mind
something along the lines of a Netra V210 which would maintain binary
compatibility but supports up to 8GB of RAM, 2GB is the max on the current
platform).

     I am also going to take a look at the configuration of the router to see
if there is a way I can limit the buffers it uses for the T1 to my house so
that such an attack won't exhaust the routers buffers.

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