Mailinglist Archive: opensuse-security (757 mails)

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Re: FW: [suse-security] optimal kernel config for firewall gateway ?
On Wednesday 16 January 2002 14:38, you wrote:

> > It´s true, that you can use a 486 for Firewall, but a prefer to a P-II
> > or AMD K6-2 as minium requieremnt for 1 Mbit. The problem ist not the
> > traffic, but the syslog. We have serveral costumers, who are connected
> > with 2 mbit. If someone portscan your system or tries an dos-attack,
> > increased your system load dramaticly and the traffic stops :(
>
> The syslog.conf manpage states that if a logfile is preceded with a "-"
> (like in
>
> *.* -/var/log/allmessages
>
> ), then the syslogd will not call fsync() after a write() to this file.
> By consequence, the load will remain small.
>
> Generally, it's a good idea to fsync() all logfiles especially if
> something really urgent has been logged (like a failing disk). Typically,
> such logs are from the kernel, which leads to believe that all kernel logs
> should be synced at once. Unfortunately, firewall messages are kernel logs
> as well, and then you have to change the perspective. If your syslogd
> takes to much time to sync the data to disk, the kernel messages
> ringbuffer (/proc/kmsg) might overflow and some messages might geht lost.

Doesn't -m limit with --limit and --limit-burst help matters considerably?

Would it be a nice feature if klogd was extended, so that messages lower than
console logging level, could be matched against RE patterns, like '^IN=.*
OUT=.* MAC=' and '^APIC error on CPU', could be diverted to one of the local
syslog facilites? Pattern matching is fairly efficient with modern CPUs, and
under SuSE /var/log/messages and /var/log/firewall tends to collect far too
much duplicated rubbish and irrelevant messages.

The lack of an fscync(), explains issues with corruption in log files, I
thought that was due to ReiserFS not flushing data. It would be nice to have
really important kernel messages logged and saved immediately to help in post
morterms.

Rob


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