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    SubjectRe: Netfilter: New target: RLOG
    On 19.01.2012 10:12, Pablo Neira Ayuso wrote:
    > Hi Richard,
    > On Wed, Jan 18, 2012 at 11:43:25PM +0100, Richard Weinberger wrote:
    >> RLOG is a new log target, it works like LOG with the exception that it writes to ring buffers.
    >> It makes use of Steven Rostedt's ring_buffer subsystem.
    >> I've used Steve's ring buffer because it allows concurrent writes. IOW it's very fast.
    >> For more details see: Documentation/trace/ring-buffer-design.txt.
    >> Each ring buffer is represented as a pipe-like file in /proc/net/netfilter/xt_RLOG/.
    >> You can read from it with and program you like (cat, syslog, etc...).
    >> The default size is 1MiB. With this size it can store approximately 5000 messages.
    >> - Why not LOG?
    >> I like the LOG target a lot but I really hat it when it floods my kernel syslog.
    >> dmesg becomes useless.
    >> Writing all log messages to a file using syslogd also not always the best solution.
    >> Most of the time my firewall logs just waste disk space.
    >> Compared with Steve's ring_buffer, the kernel syslog is rather slow.
    >> Especially when the firewall logs very much syslog becomes a bottleneck.
    >> As we all know printk() is not fast.
    >> - Why not ULOG/NFLOG?
    >> Because it cannot replace LOG.
    >> Details like PHYSIN and PHYSOUT are not available form the packet headers.
    >> Also on many Linux systems ulogd is not available/supported.
    > We only include physin and phyout if netfilter bridge is enabled. I
    > may be missing anything but, why can these be useful if bridging is not
    > enabled?

    Of course they are only useful if bridging enabled.
    In nearly all of my use-cases I'm using bridging (KVM, LXC, ...).

    >> - Why RLOG?
    >> Using RLOG you can have many ring buffers with all kind of logs.
    >> If your firewall goes nuts you don't have to mess you rule-set with adding
    >> new LOG rules to find out what's going on.
    >> Just install a few RLOG rules with small buffer sized and read them if you don't
    >> know what's going on.
    >> If you make you firewall rule-set per default verbose using LOG or NFLOG it will
    >> generate lot's of useless messages which you'll never ever read.
    >> With RLOG you can bypass this problem.
    >> On my firewall I record only useful data to the disk. Everything else goes into RLOG.
    >> If your firewall is really busy and you want to log nearly everything, c
    >> reate a big ring buffer and read from is using your favorite userspace tool.
    >> In case the buffer fills faster than the userspace consumes it, RLOG will warn you.
    >> I'd also possible to resize the buffer.
    > I still think this can be useful.
    > But, why don't you add this to the LOG target as an extension instead
    > of yet another target?

    Yeah, I could add --ring, --ring-size and --add-timestamp to LOG.
    What about a rlog_common.o which can be used by ipt_LOG and ip6t_LOG?


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