OpenBSD Journal

PF Software: PFflowd

Contributed by jose on from the cool-tricks dept.

anonymous writes: "pfflowd converts OpenBSD PF status messages (sent via the pfsync interface) to Cisco NetFlow(tm) datagrams. These datagrams may be sent (via UDP) to a host of one's choice. Utilising the OpenBSD stateful packet filter infrastructure means that flow tracking is very fast and accurate.

That's just one of the many. It's actually cool that PF gets more supported. Does anyone know other interesting PF software?"

Wow, this is pretty cool. NetFlow is some neat stuff, and you can do a lot with the data. Cisco's website has a nice NetFlow summary. Various tools, both free and commercial, consume it and make use of the data.

(Comments are closed)

  1. By click46 () on

    I dont use NetFlow or anything like that; but I'm continuously amazed at the progress and additions made to PF.

  2. By djm () on

    It is good to see pfflowd being written about here :)

    While the guts of it are solid, it could do with an audit, some independant testing and verification that the flow records it generates are accurate. So please, download it and give it a try. You will need some sort of NetFlow collector to make sense of the records it produces. A simple perl one is here:

    I'll probably add NetFlow v.9 support before releasing this as a port - this will allow accounting of IPv6 flows and elimination of a lot of information that isn't currently collected by pf.

    pf is a very nice framework to hack on - its design is very easy to understand, even for a kernel neophyte such as I.

    1. By Anonymous Coward () on

      This is killer - I love the idea. I will definitely be fooling around with this when I get some -current action happening.

  3. By Blake () blake at two one one two dot net on mailto:blake at two one one two dot net

    /usr/ports/net/ntop is a nice tool with lots of bells and whistles for collecting/reporting this data.

    1. By Rick () on appears unreachable. Can you confirm the link is good?

      1. By djm () on

        yes, but my isp is having issues

    2. By G () on

      and it is to old to eat any NetFlow data

  4. By Anonymous Coward () on

    On Damien's pfflowd's page, I noticed the mentioning of synproxy. This is going to be a big thing in terms of synflood prevention.

    Any one knows how it works? Is it using syn cookie?

    1. By Petr R. () on

      No, it intercepts SYN packet going to protected server and aswers SA instead of that server. If , and only if ACK comes back, it will "proxy" connection to protected server.

    2. By Anonymous Coward () on

      This is not about using SYN Cookies, this is using more memory on Cisco or pf instead of adjusting system to handle load of syn flood

    3. By Anonymous Coward () on

      Thanks for the above replies. I know how synproxy works, I just don't know how it recognize the ACK as being part of a previous SYN and SYN/ACK ...

      Syncookie is using a crypto hash to recognize it, I was just wondering how pf's synproxy does it.

      1. By Above Anonymous C. () on

        i guess pf state is (noticeably) smaller than socket with its buffers

      2. By Anonymous Coward () on

        pf uses a state entry for it, but doesn't pass any packets to the proxied host until the handshake is done. -current also has adaptive timeout scaling -- the timeouts decrease as the number of state entries rise, on a scale you specify. Since you can specify both the intial TCP timeout and scaling on a per-rule basis, the entire thing should work pretty well.

        Skim the current man page for more.

  5. By Anonymous Coward () on

    does anybody know free tools to make use of netflow data?

    1. By jose () on

      osu has a flow-tools toolset that does, and caida's cflowd can do some netflow versions. i'm not a fan at all of ntop, i found it to be unstable, buggy, and pretty crufty code.

      1. By G () on

        ntop crashes within gd, -w works well without pictures and huge hash buffer

      2. By jose () on

        i should ad that flow-tools is in ports, and i have an unofficial port of cflowd here:

        it's been a while since i updated it, so it may be a bit outdated, but it should help you get started. others have used it with reported success..

        lastly, several companies (including the one i work for) make commercial flow based security and monitoring solutions. we go well beyond what you can do with free stuff in terms of performance and features .. :) we're very proud of that.

    2. By bb () on

      Yeap, I've been using Netflowmet ( variation on Netramet ) in a production environment. SO far successfully. Very flexible tool

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