From mboxrd@z Thu Jan 1 00:00:00 1970 From: Richard Weinberger Subject: Re: Netfilter: New target: RLOG Date: Thu, 19 Jan 2012 10:21:40 +0100 Message-ID: <4F17E0A4.9040004@linutronix.de> References: <1326926610-17830-1-git-send-email-rw@linutronix.de> <20120119091248.GA32391@1984> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: netfilter-devel@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, rostedt@goodmis.org To: Pablo Neira Ayuso Return-path: In-Reply-To: <20120119091248.GA32391@1984> Sender: linux-kernel-owner@vger.kernel.org List-Id: netfilter-devel.vger.kernel.org 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