Inliniac

Dave Remien of NitroSecurity created a patch that “implements a relatively simple form of (IPV4) load balancing” between multiple Snort_inline processes using Nfqueue. Here is what it does:

1. Load balancing. The bottom half of the source and dest addresses are added together, and mod’d with the number of “load-balancing” snorts you desire to run. This means that traffic stays with a particular snort, so that state is maintained.

2. Because you can run many snorts (presumably on many CPUs), you can now take advantage of that super-hooty 16way box and those 10 gig NICs you just got your hands on…

3. The snort at the “magicqueue” is a back-up snort - normally no traffic is sent to it, but in the event that one of the “load-balancing” snorts isn’t present, the traffic for that “load-balancing” snort gets sent to the “backup” snort.

And even more, read that here.

I haven’t tried this myself, but it sure looks cool. Try it by checking out the latest SVN code for Snort_inline. Then follow the instructions from README.NFQUEUE.

Big thanks to Dave Remien & NitroSecurity for this contribution!

Snort_inline was just updated to Snort 2.8.3 in SVN. Please give it a try. It hasn’t seen much testing so far, so be careful when putting it on production servers.

Get the code from SVN like this:

svn co https://snort-inline.svn.sourceforge.net/svnroot/snort-inline/trunk

Check it out!

This morning I updated our Snort_inline codebase with SourceFire’s just released 2.8.2.1 version. See the original changelogs here: 2.8.1, 2.8.2, 2.8.2.1.

Also Richard Bejtlich and Nr have good posts about the improvements of the last versions. See Richards post about a fixed frag3 vulnerability here and see Nr’s post here.

Please note that our SVN code has seen limited testing so far, so be careful! Please report any issues!

Today I’ve spent some time on updating the Snort_inline source to the latest 2.8.2.rc1. The updating went quite smooth, so I hope no big issues pop up. Like before, trying out this code can be done by checking out SVN like this:

svn co https://snort-inline.svn.sourceforge.net/svnroot/snort-inline/trunk

This will save the source to the directory ‘trunk’. In the directory ‘trunk’, run ’sh autojunk.sh’ and then configure, make, make install…

A while ago I wrote about porting Snort_inline to 2.8.0.1. That worked well, however we are still trying to resolve some issues. Especially in stickydrop, that is just broken right now. Also, SourceFire released 2.8.0.2 last week, so we need to update to that too.

First however, I will be traveling to California this week. I will be meeting Will there, so I’ll try to get him to fix that damn code

When using Snort_inline with NFQ support, it’s likely that at some point you’ve seen messages like these on the console: packet recv contents failure: No buffer space available. When the messages are appearing Snort_inline slows down significantly. I’ve been trying to find out why.

There are a number of setting that influence NFQ performance. One of them is the NFQ queue maximum length. This is a value in packets. Snort_inline takes an argument to modify the buffer length: –queue-maxlen 5000 (note: there are two dashes before queue-maxlen).

That’s not enough though. The following settings increase the buffer that NFQ seems to use for it’s queue. Since I’ve set it this high, I haven’t been able to get a single read error anymore:

sysctl -w net.core.rmem_default=’8388608′
sysctl -w net.core.wmem_default=’8388608′

The values are in bytes. The following values increase buffers for tcp traffic.

sysctl -w net.ipv4.tcp_wmem=’1048576 4194304 16777216′
sysctl -w net.ipv4.tcp_rmem=’1048576 4194304 16777216′

For more details see this page: http://www-didc.lbl.gov/TCP-tuning/linux.html

Setting these values fixed all my NFQ related slowdowns. The values probably work for ip_queue as well. If you use other values, please put them in a comment below.

Thanks to Dave Remien for helping me track this down!

Not many people have native IPv6 connectivity and use some form of tunneling. For this reason Nitro Security asked me to develop a Snort preprocessor to unwrap various tunnels. This resulted in the preprocessor ‘ip6tunnel’, which I uploaded to Snort_inline’s SVN yesterday. The preprocessor is capable of unwrapping IPv6-in-IPv4, IPv6-in-IPv6, IPv4-in-IPv6, IPv4-in-IPv4 and finally IPv6-over-UDP. The latter is used by Freenet6.

I chose to develop it as a preprocessor because this allows Snort to inspect both the original packet and the tunnel packet(s). The preprocessor supports recursive unwrapping. The recursion depth is limited to 3 by default, but can be configured differently. Get the preprocessor from Snort_inline’s SVN by checking out the latest trunk:

svn co https://snort-inline.svn.sourceforge.net/svnroot/snort-inline/trunk

Then have a look at doc/README.IP6TUNNEL for configuration options.

Once again thanks to the great people of Nitro Security. I think it’s great to see this company giving back to the community!

I’ve just committed an update to Snort_inline’s SVN. It brings it to the Snort 2.8.0.1 level. It supports both IPv4 and IPv6 on IPQ and NFQ. I have not been able to test IPFW on IPv6, so I don’t think that will work currently.

This update removes the libdnet dependency and replaces it with libnet 1.1. To be able to send ICMPv6 unreachable packets you will need the libnet 1.1 patch I wrote a while ago. You can find that here. Get the latest Snort_inline by checking out SVN:

svn co https://snort-inline.svn.sourceforge.net/svnroot/snort-inline/trunk

Consider the code to be of beta quality for now, so be careful with it. Please report any problems with it!

Again, a big thank you to NitroSecurity for funding this work!

The last week I’ve been working on bringing Snort_inline to the Snort 2.8.0.1 level, including it’s IPv6 support. I’m almost ready to commit it to SVN, there are just some issues I need to fix in the inline specific code. The code will get rid of libdnet and use libnet 1.1 for sending reset/reject packets for both IPv4 and IPv6. After committing I will start working on getting the IPv6 features I wrote for NitroSecurity into this tree. This includes more matches, tunnel decoding (including for example the freenet6 tunnel, etc). So stay tuned!

A while ago I wrote about why the TCP window scaling normalization in Snort_inline was broken by design. I also wrote about a new solution I was working on and testing that would be uploaded to SVN soon. I just committed the patch to SVN. What it does is add two new options to stream4:

norm_window: normalize the TCP window (disabled by default). This is to protect Snort_inline from being forced to queue too many packets.
max_win_size: maximum size of the scaled TCP window. Packets increasing the window beyond the limit are modified.

This option is disabled by default, and the old wscale normalization code is removed, as are the options that configured it. It runs fine on my gateway, without noticeable slowdowns, but I haven’t done any benchmarking so far. Please try this and let me know how it works for you!