Messages in this thread | | | Date | Thu, 19 Jan 2012 10:21:40 +0100 | From | Richard Weinberger <> | Subject | Re: Netfilter: New target: RLOG |
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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?
Thanks, //richard
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