Re: preventing route cache overflow

Gianni Tedesco
2003-02-27T13:10:31Z

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On Thu, 2003-02-27 at 12:50, Patrick Michael Kane wrote:
> We recently had a server come under attack. Some script monkeys
> started generating a bunch of pings and SYNs from a huge variety of
> spoofed addresses (mostly in 43.0.0.0/8 and 44.0.0.0/8, for those that
> are interested).
>
> There were so many forged packets that the destination cache began to
> overflow hundreds or thousands of times per second ("kernel: dst cache
> overflow"). This had a huge negative impact on server performance.

Was this just syslog doing lots of write()+fsync() ? What kernel
version?

You should not get those messages that often in your logs, they should
be ratelimited:

linux-2.4.19/net/ipv4/route.c:598:
if (net_ratelimit())
printk(KERN_WARNING "dst cache overflow\n");

--
// Gianni Tedesco (gianni at scaramanga dot co dot uk)
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