Occasionally people are testing some kind of top secret device with tcpreplay and can’t tell me how it works or what it does or share their pcap file (because it has some kind of exploit or something like that I guess), but expect me to help them figure out why it can’t “see” the traffic tcpreplay sends. That’s a lot like asking your car mechanic to fix your car, but you won’t let them look at it because you’ve modified the engine to run on tap water and don’t want the mechanic to figure out your secret. As you might imagine, this is both very frustrating and a huge waste of my time.

Simply put, if you see the traffic in Wireshark or tcpdump, but your device under test can’t see it, then it’s most likely either a) bug in your product, b) you’ve miss-configured tcpreplay or c) you’ve got a bad pcap. You’ve pretty much ruled out a bug in tcpreplay at that point. Hence if you want help with determining if it’s A, B or C you’re going to have to give me your pcap, tell me what your product does and some basics about how it works under the hood. Honestly, I wouldn’t consider any of this at the company secrets level unless you’re hacking directly in kernel-space and are completely avoiding the well known socket API’s, but that’s your call.

Anyways, if you’re unable to tell the whole world on this mailing list the above, then your other option is to hire me as a consultant (for a price) at which point I’d be happy to sign an NDA to keep your secrets and we can work off list. Other then that, your best bet is to try and figure it out on your own, but please don’t ask me or the list for help to your problem.

Thanks,
Aaron

For my food and smoker temp measuring needs, I picked up 3 food safe probes from Thermoworks for $8/ea. Unfortunately, the probes come with no technical documentation and my email to the company requesting information was ignored. Contrary to my initial thoughts, these probes are not the same as those sold by Maverick or Amwei. I was however able to determine they are NTC thermistors and some searches turned up a way to convert the resistor readings into actual temperatures.

I did a lot of research on the web, and ended up having to piece together a lot of information to get something that actually works. Once you know what to do, it’s more tedious then anything, but getting that knowledge seems to be challenging.

To do calibrate an unknown thermistor, you first take a series of measurements of the resistance at different temperatures. There’s no need to provide power to the thermistor or hook anything up to it. The more measurements the better, and you want to read 10% above and below your necessary usable range for best accuracy. For measuring meat and smoker temps that means about 60-325F + 10%. Using a refrigerator, electric water pot for boiling water and a convection oven I was able to take a series of temperature readings using commercially calibrated thermometers and read the resulting resistance values using a multimeter. The real trick is to use temperature sources which are as stable as possible so your readings are stable and accurate. The whole process took me a few hours and ended up setting off the smoke alarms, but in the end I had a fair bit of data for processing.

If you do this, you’ll quickly realize that thermistors are not at all linear, so you can’t easily interpolate missing values. But there is an equation you can use called the Steinhart-Hart Equation to calculate the unique curve of a thermistor. To use the Stenhart-Hart equation (“S/H” for now on) you take your temp/resistance readings and do some math to generate four coefficients which are then used in a different equation to convert resistance values into to temp values.

There’s a fair bit of math involved, but there is the thermistor project on SourceForge which has C/Java code to do all the work for you. Look at the included simu.txt file for an example table showing temp values (in Centigrade) in the first column and resistance in the second column- space delimited. Run the coeff tool to generate the four coefficients needed for later. Here’s the simu.txt file I used:

3.6     640000
4       620000
14.3    383333
17      350000
80.3    24767
83.6    21433
90      17940
92      16133
100     13033
107.2   9627
115.6   7783
126.7   5857
137.8   4440
142.8   3923
149.4   3247
168.3   1988
190.6   1176
199.4   997
210     774
232.2   645

And the resulting coefficients:

a[0] = 1.211111230054231e-04
a[1] = 3.762691542377820e-04
a[2] = -1.735716635603824e-05
a[3] = 6.538964941154940e-07

Once you have these coefficients, it’s relatively straight forward to use the S/H equation to convert any resistance value (at least within the range you measured) into a temperature. For the Arduino, I ended up using the
Thermistor4 library which seems to give me good results.

Wiring up a thermistor is pretty simple. Connect it to +5V and run it through a resistor acting as a voltage divider and then to an analog pin on your Arduino board. For best results you will want to measure the actual voltage since voltage regulators are very rarely exactly 5.0V and measure the resistor since those are usually +/-5% and plug that into the Thermistor4 library.

Instead, I stopped by BRG on the way up to the track on Friday and we talked about where I was loosing time and goals I should set for myself. KC said he thought I could do a 2:02 and I think I laughed. I mean, drop 3 seconds in a weekend? Riiiiight. Seemed like a big step at this point. But I’ve learned to listen to KC and so I told him I’d push harder this round in practice and try to build off that in the races. Honestly, I would of been happy with just improving my times at all.

Saturday was really hot, but enjoyed hanging out with Quinton, Ben and Andre. I think I drank close to two gallons of water/gatorade trying to stay hydrated in the 100 degree heat. Once again, I was having a hard time getting down to my race pace in practice, doing a bunch of 2:10-09′s with a few 08′s. I know this really holds me back, because when I work with Jim and Dave at Catalyst Reaction on suspension setup, you can’t really setup the bike for how it will behave when you’re going 4sec a lap faster. I had Chris and the gang at CT Racing put a new Pirelli rear on at lunch and the bike felt a lot better through Turn 7, but my lap times didn’t really improve. Honestly, I was a bit disappointed.

Sunday morning, things were a lot cooler and I felt refreshed from sleeping 8+ hours the night before. I seemed to have finally have figured out an eating strategy which gives me plenty of energy all day without that post-lunch food coma. In morning warmup, I get into the 2:07′s- finally getting close to my race pace in practice. The cycling I’ve been doing the last month or so has helped with my stamina and so I can’t wait to get out on track again. I won’t have to wait long, because 650 Twins is the first race of the day.

I get another poor start off the line and I make it worse by getting hung out to dry on the outside of T1 and then trying to make up for it in T2 and finding myself way off line on the outside. I end up a few bike lengths behind Stephen Smith (#769) once again and quickly reply our battle in my head from last round remembering where each of us is stronger then the other. I try taking Stephen on the brakes on the inside into T10 and once again can’t make it happen. However someone crashes in 11/12 and it seems to hold Stephen up a little and so I’m able to get a much better drive out of T13 and easily make the pass on the back straight.

Just up ahead I see Charles Almy (#510). I know Charles has been faster then me all year and I hope for a tow from him to gap Stephen. I keep it relatively close for a couple of laps and then Charles starts to pull away and I end up having a pretty quiet race. I end up dropping a second off my personal best with a couple of 2:04′s and followed up with consistent 2:05′s. So far so good!

After the race I talk to Dave and Jim at Catalyst about my line through 6 because I know it’s killing my drive through one of the fastest parts of the track: turns 7 & 8. I know if I can just hit the apex in 6 I’ll have a 2:03 in the bag. Jim makes a rebound adjustment on the rear and I’m good to go. On the warm up lap of 650 Production I look for the turn in marker we talked about and burn it into my mind for the race.

Another blah launch off the line, but Patrick Murphy (#752) in the row in front of me does a nice wheelie for the crowd and Stephen Smith (#769) and I split him down the front straight. I find myself right on Charles’ tail going into Turn 1 and decide I’m not going to let him get away from me this time. And that’s when Patrick comes around me on the outside in T2- crap, that won’t help. I follow Patrick and Charles goes wide on the exit of 14 and gets a bad drive out of 15. I’m too far back to take advantage of it, but Patrick gets past Charles on the front straight. I find myself once again on Charles’ tail hoping to find an open door of my own past.

On the second lap I get a good drive out of 15 and think about drafting past Charles, but he’s good on the brakes into T1 and I know I can’t get by so I just slip back behind him on the exit. Charles gets a great drive out of Turn 2 and takes Patrick back on the outside of T3 and there’s now four of us nose to tail going through turn 3 each hoping the guy in front of us makes a mistake that we can capitalize on.

Up the hill into 5 and down the other side- I look ahead for the marks on the track that Dave and Jim talked about for T6 and that ends up helping a lot. We all get a good drive out of 6 and speed through 7, grabbing gears when the tach hits about 10,500RPM and holding the throttle wide open for as long as I dare for the entrance into Turn 8.

Turn 8 isn’t really “hard”- meaning it’s not that technical of a corner. It’s just one of those turns where you just have to turn off that part of your brain related to self preservation because you can go through there a lot faster then it seems you can. Simply put: Turn 8 takes balls.

And this is where things get confusing. Very confusing. It’s funny how when things go way wrong how quickly you start questioning yourself. At first I thought I turned in way too early- a common mistake when you start going faster and that self preservation mode kicks in and that’s what caused me to miss the apex by a mile and go way way wide. But after looking at my on board video, I know that’s not what happened at all.

What I do know is this: I turned the bike in at my turn in point and the bike rather then carving a nice corner, pretty much kept going straight. This is generally considered a bad thing at over 90mph when a turn is coming up. After passing the apex, I quickly realized I wasn’t going to make the turn stood the bike up and got on the front brake right up until I reached the dirt and then started pumping the rear brake instead. It wasn’t my first off road experience and looking back, I have to say the rear was bouncing around a lot more then I’ve grown to expect from past experiences… more on that later.

After about a second while riding along the dirt I figured I’d be ok- I’d ride it out and get back on course. About a half of a second after that, I realized that the ditch up ahead had different plans for me. Lucky, the bike didn’t fully catch the ditch and rather then flying over the bars I held on for another brief moment before deciding that I didn’t really want to be still on the bike when it fell down and so I pushed off the bike.

I landed only a few feet from where the bike stopped with the earthy flavors of dirt and dry grass in my mouth. You’d think that hitting a ditch with your front wheel at high speed and jumping off a bike would hurt. You’d be right- bruised ribs from hitting the gas tank when I hit the ditch hurt like hell, but I walked away without any other injury whatsoever (thanks again Helimot!). I might go invest in a chest protector though. :)

As we unloaded the bike off the crash truck, Jim from Catalyst gave me that look of “Dude, *WTF* is wrong with your bike?” Even though the front end had taken the brunt of the impact, it looked perfectly fine to me- as did my fairings/bellypan, gas tank and just about everything else you’d expect damaged in a crash like this. The only thing I noticed was a badly dented silencer and snapped shift rod linkage- the crash just sounded a lot worse then it really was. What I hadn’t noticed and Jim had, was that the frame had snapped where the shock linkage mounts to the frame which meant I was now the proud owner of a 650cc twin drag bike:

After further inspection, it appears that the frame had been cracked at the weld for a long time and that it finally let go in full accordance to Murphy’s Law right about the time I turned it in for turn 8. That would explain why the bike didn’t want to turn and the rear was bouncing so much once on the dirt. For the record, it’s a 1999 frame and it’s been a race bike for almost it’s entire life, so it’s hardly had an easy life. Still though, if you’ve got an SV, especially a first gen, I’d highly recommend you inspect the welds for cracks- especially at the bottom of the frame.

I looked on my lap timer to check my times, hoping to see a 2:03…

1st lap: 2:06.0. Beating my best time from last year from a standing start. Nice.

2nd lap: 2:02.6. Fuck yeah.

Anyways, the last round at Sears actually went pretty well with me putting in a series of personal best laps in the last race and so I was looking forward to coming back to Thunderhill. The bike was running great and I’ve always liked the track even if my laptimes (best a 2:06.3) haven’t been anything to brag about in the past.

For round 6 I’d be pitting with KC/BRG Racing again. Having KC available to talk about bike setup, strategy, lines and to basically kick my ass into gear has been nothing but awesome. The fact that his trailer has A/C and the temps were near 100F didn’t hurt either. :) Saturday practice was pretty uneventful, but my laps were as usual for practice pretty crappy. I’ve never been able to do anything close to race pace in practice and I pretty much hit a wall at 2:10. KC and I spent a lot of time talking about lines and what I needed to do to get my laptimes down between practice sessions and so I hoped I could bring my A-game on Sunday for the races.

My first race was 650Twins which all things considered went pretty well since I did a new personal best of 2:05.8 on the last lap and finished 19th, my best so far this year. It was only one lap, but at least I was consistent in the 2:06-7 range and so I hoped to build on that in my next race: 650 Production.

For some reason, I haven’t been getting as good starts this year as I did last, and this race was no different, but at least I was able to get the spot I lost back going into turn 1. I slotted in behind Stephen Smith (#769) who had beaten me in the last race. I had a good run on him down the hill out of T9, but couldn’t quite show him a wheel on the brakes and lost 5 or 6 bike lengths on the exit. I was however a lot stronger in T1 & 2 and thought I had him on the inside going into 3, but he shut the door on me and so I looked for my next chance.

That came at the end of lap 2 as I got a much better drive out of the T13. Stephen was about mid-track so I went to the outside, hoping I could carry more corner speed through 14 and beat him on the exit of 15 for the long front straight. Unfortunately for me, Stephen started to drift over to my line before I could show him a wheel and I had to give way to avoid a collision. I was still able to get a good drive out of 15 and was right on his tail into the first turn. I knew I was able to carry more corner speed through Turn 2 and so I set to pass him on the outside on the exit of 2 and into 3 and was able to make it stick this time. From the last race I knew Stephen would be all over me and so I put my head down and tried to get a little space. Just up ahead I saw a couple of Super Dino’s and I knew I had to get past them as quickly as possible and hope they’d hold him up. I was able to get the first one on the exit of T6 and the other on the exit of T8.

As I came over the hill, I could see two more bikes far in the distance so I took after them and found myself right on their tail a lap later coming out of the esses onto the back straight. I got the Super Dino on the brakes into T14 and caught up to Patrick Murphy (#752) coming out of T1 with two laps left. I followed Patrick for a few turns to get an idea of his lines and found myself getting a much better drive out of T9 and easily passed him before entering 10. With about 1-1/3 laps left, I pushed hard to keep Patrick at bay and finished in 8th place- my best of the year. Even better, I put in my most consistent times ever at Thunderhill with 5 laps in the 2:05-06 range… hardly fast, but at least I was improving and I knew where I was loosing time.

I ended up skipping Formula 4 since I seemed to be suffering from the heat and/or not enough food earlier in the day and it didn’t make sense to go out there and push hard when I’d already made a number of improvements. Spent the rest of the day hanging out, drinking beer and talking to all my friends before packing up for the drive home.

Seriously, wtf? How could you not notice:

1. Emails I delete from the inbox come back after a few minutes. I’ve deleted the same messages 4 or 5 times now from my inbox. I guess you figured my delete key doesn’t get enough use already?

2. Still haven’t fixed the Snow Leopard/Exchange issue where Mail.app stops downloading emails after some random period of time requiring me to restart Mail.app. The good news is I can really tell my boss I didn’t see that important email! Thank you for being my excuse!

3. Can’t quit Mail.app. Yes, it just hangs every time. Have to Force Kill it. This is great since I’m restarting Mail.app 3-5 times a day due to #2.

4. When it starts back up, it often presents me with a random email I recently sent acting like I didn’t actually send it. It’s in my Sent Mail folder… did you send it or not? It’s a mystery! We all like mysteries right?

5. How many times do I have to read an email before you mark it read? You seem to have chosen to use a random number generator for that. I guess this was designed to mess with people with alzheimer’s or something?

Outlook and Thunderbird are looking really good right now.

Unfortunately, every time I connected the GPX Pro via USB to the Windows 7 VM, I got the following error from Virtual Box:

Failed to attach the USB device <b>Unknown Device</b> to the virtual machine Windows 7
Result Code: NS_ERROR_FAILURE (0x80004005)
Component: HostUSBDevice
Interface: IHostUSBDevice {173b4b44-d268-4334-a00d-b6521c9a740a}
Callee: IConsole {515e8e8d-f932-4d8e-9f32-79a52aead882}

Long story short, this is a relatively common problem with USB devices and VirtualBox and there is a simple solution. Connect your GPX Pro to your computer and then in VirtualBox, select your Windows VM and click the Settings icon at the top. Then select Ports and USB so you see this screen:

Click the Add Filter icon on the right side, and from the drop down, select the “XT Racing GPX Pro [0101]“. A new dialog will pop up with most of the fields filled out. You need to remove all of the data except for Name and Vendor ID like this:

When you’re all done, you should see this:

Basically, this filter tells VirtualBox to not let any XT Racing product attach to the host operating system (OS X or Linux) and automatically attach to the guest operating system (Windows). So now, boot up your VM and then connect your GPX Pro and you should be good to go!

Britain, at the expense of three millions, has killed 150 Yankees this campaign, which is 20,000 pounds a head… During the same time, 60,000 children have been born in America. From these data his mathematical head will easily calculate the time and expense necessary to kill us all.

Now consider that that the TSA has a yearly budget of $7 billion ($8.2B by 2011) and didn’t stop Richard Reed, aka “The Shoe Bomber” or Umar Farouk Abdulmutallab, aka “The Underwear Bomber” or any terrorist that we know of. The entire DSA will have a budget of $43.6B next year and the costs of the wars in Iraq and Afghanistan is $1.1 trillion and growing even though you’re far more likely to die from cancer, a car accident, hot weather, railway accident, choking on your own vomit, electrocution, heart attack, drowning or even a police officer then a terrorist attack.

Hard to imagine this working out any better for us then it did the English.

I’ve been contacted by a recruiter at Google every 3-6 months for the last 4+ years or so and I’ll tell you what I tell all of them:

I have no interest in interviewing with Google ever again. I expect to be treated professionally by companies and for them to be honest with me in their communication, but that did not happen when I went through your interview/hiring process. This is not negotiable and you only get one chance.

I also tell every recruiter at Google to please put a note in your HR database to not contact me any more. Obviously that never happens or doesn’t work, because you still contact me. Honestly, I’m not sure why this is so hard to accomplish for a company which specializes in storing and retrieving information, but I do find it rather annoying having to explain myself over and over again. Hence, I’ve decided to create this post so the GoogleBot will add it to your database for you.

Have a nice day,
Aaron

UPDATE: I posted this after being contacted by a Google recruiter and so I replied with this link. He replied back, was very apologetic and promised to update their records to indicate I did not wish to be contacted again and apparently that actually worked. Success!

There’s actually a number of reasons for the change and I wanted to share the ones that were most important to me. I don’t expect everyone to like the decision, but probably most won’t care since it doesn’t really impact them. But sometimes people get all bent out of shape when a project that has been around as long as Tcpreplay (10 years? Damn, where did the time go?) changes its license so I wanted to give my side of it. The change doesn’t mean I don’t like the BSD license anymore, just that I now feel the GPL is more appropriate for the Tcpreplay Suite.

First, for those of you not familiar with the GPL and BSD, what this means for 99% of users is everything stays the same. Tcpreplay is still distributed at no cost and the source code is available for you to read, edit and redistribute. You can use Tcpreplay at no cost for personal and commercial use. The only difference is that if you redistribute Tcpreplay, you need to make the source code of Tcpreplay and any code which links to it available to anyone who asks for it. If your code runs as a separate process then you don’t need to share that. There’s no legal requirement for you to proactively send me a copy of your changes, but I would very much appreciate that.

As for why, it comes down to the following reasons:

1. Values. I still want to give Tcpreplay away for others to use and build upon, but it’s been frustrating to hear about people who have added features and then for one reason or another decide they don’t want to share those with the rest of the Tcpreplay users. This willingness to take, but not give back to the community sucks and I’d rather not allow people to continue to do that. I’ve got hundreds of hours of effort in Tcpreplay and I suppose I don’t think it’s “fair” for people to build upon it without sharing back. I’ve not only seen this with Tcpreplay, but other BSD projects- one of my previous employers added an enhancement to fragroute, distributed the new binaries to their customers, but never sent the patches back to the original author. I think my old company would of sent their changes back if the author knew about it/asked, but because there was no legal reason to do so, they never took the 5 minutes to do it.
2. Support. I’ve actually had people enhance Tcpreplay, distribute it to others and then have these users contact me for support. They couldn’t give me the code and I was stuck trying to explain to someone that even though it was my project, I couldn’t help them because I couldn’t fix the bug they were seeing.
3. Future. Tcpreplay will have a library/API in 4.0 and I hope it will become much more useful to other developers. Going GPL helps to protect the main tree from others creating incompatible forks. Yes, anyone can still fork Tcpreplay for their own purposes, but at least this way I can incorporate the good changes if they start distributing it to others. If you want to fork Tcpreplay for your own internal/personal use, go for it- I just want to limit the chances running into your libtcpreplay.so with an incompatible API getting out in the world causing problems for people.
4. Developers. I’ve discussed license choices with other existing and potential Tcpreplay developers and there appears to be a greater level of comfort with the GPL and it seemed that they would be more willing to contribute if their contributions would be GPL’d versus BSD. Honestly, I don’t expect to see a lot more people working on Tcpreplay due to the license change, but every little bit helps.

-Aaron

UPDATE: One thing I wanted to add, I chose the GPLv3 because I believe it affords better protections then v2. If you have an existing GPLv2 application and would like to incorporate any part of the Tcpreplay Suite into it, please contact me to discuss dual-licensing options.

I wasn’t originally planning on doing a beta for 3.4.5, but due to
feature creep it’s taking more time then I thought. Now that I’m done
racing for the summer, hopefully I’ll have more time to fix the
remaining open bugs & enhancements before the fall. It’s my goal that
3.4.5 will be the final 3.x release, with future enhancements being
placed in the 4.0 branch- it’s become too much of a PITA to keep
merging code between the two branches since 4.0 is really nothing like
3.x.

Anyways, this release concentrates on features & bugs users requested
or found. Special thanks goes out to Dmitriy Gerasimov who
submitted a patch for Linux TX_RING support. It’s not yet supported
on all Linux systems, but on those that it does should hopefully see
improved topspeed performance. I’d love what people’s experience is
with this feature- does it help? If so when? The other major feature
is sending two files at the same time- one out each interface. Should
hopefully be useful when replaying traffic captured via network taps.
Both features probably haven’t seen enough testing by me, but
hopefully some people are interested enough by them to try them out
and let me know how well they work.

Obligatory changelog:

08/15/2010 Version 3.4.5beta1
   - First pass at fixing 'make test' on many little-endian systems (#429)
   - Don't try to fragroute non-IPv4/v6 packets so we don't error out (#432)
   - Warn users when processing LINUX_SLL frames w/o an Ethernet source MAC (#434)
   - Initial Linux TX_RING sending support (#435)
   - Update to GNU Autoconf 2.67 (#436)
   - Add tcpcapinfo which dumps information about the pcap header/packets (#437)
   - Add --dualfile support for replaying two files at the same time (#439)
   - Fix bug where --tos=0 didn't do anything (#440)
   - Fix crash when processing CIDR data (#441)

Update: Turns out I forgot to merge the TX_RING support in. 3.4.5beta2 fixes that. Sorry for any confusion!