RND(tech)

disabling NetBIOS over TCP/IP in Windows via DHCPD

khanh@khanh.net (Khanh) — Thu, 27 May 2010 08:31:40 -0700

This is scarce information on the Internet, so I'm reposting!

NetBIOS can be disabled now that it's fairly ancient networking. You're using TCP/IP and DNS right?
I don't use Microsoft DHCP or DNS servers, so finding the information to set this is hard to come by. To disable NetBIOS over TCP/IP in an ISC DHCP server, add the following to your dhcpd.conf:

option vendor-encapsulated-options 01:04:00:00:00:02;

It's that easy!

enabling OS X screen sharing remotely in Terminal

khanh@khanh.net (Khanh) — Thu, 08 Oct 2009 19:40:56 -0700

short and simple for 10.5 (Leopard)

sudo sh -c "/bin/echo -n enabled > /Library/Preferences/com.apple.ScreenSharing.launchd"

slightly different for 10.6 (Snow Leopard)

sudo sh -c "/bin/echo -n enabled > /private/etc/ScreenSharing.launchd"

rm the file to disable it. launchd polls regularyly, so after you "enable" the service, it'll be loaded by the time you check for the open port with netstat -an

burning files larger than 4GB with linux!

khanh@khanh.net (Khanh) — Fri, 01 May 2009 19:51:18 -0700

Burning files larger than 4GB seems to be a tricky thing in most programs. Lets say for example, you have a DV file that's 6GB. You should be able to fit it on a dual layer DVD without issue, but most burning programs fail to handle it.

Linux seems to work wonders for me on the command line. If I figure out something in Mac or Windows, I'll let you know, but I don't have access to a dual layer burner on either of those OSes at this time.

In Linux, you can make the appropriate ISO image with either:

mkisofs -r -R -J -l -allow-limited-size -udf -o largefile.iso largefile.ext

or use:

genisoimage -allow-limited-size -udf -o largefile.iso largefile.ext

Once the ISO is generated, you could burn with growisofs -Z /dev/dvd=largefile.iso or move the ISO to Mac or Windows...

AT&T 3G Speedtests

khanh@khanh.net (Khanh) — Sun, 22 Mar 2009 12:33:22 -0700

I haven't been writing much lately due to a busy schedule!

Anyway, I recently borrowed one of those AT&T 3G LaptopConnect cards. It's a Sierra Wireless AirCard 881. Compared to the speeds I've been getting with my AT&T Tilt (tethered via USB), it didn't hold up as well as I expected:

AT&T Tilt (HTC) tethered via USB:

AT&T Sierra Wireless LaptopConnect Card (AirCard 881):

And although this isn't really for comparison to the AT&T test, it seems Cablevision (Optimum Online) has been steadily increasing my bandwidth at home, even out in the middle of nowhere!

Super Mario Bros Fish Tank

khanh@khanh.net (Khanh) — Sun, 08 Feb 2009 20:42:44 -0700

Well, not quite totally a Mario Bros fish tank. However, I think the backdrop I made came out awesome.

eh, wordle...

khanh@khanh.net (Khanh) — Wed, 04 Feb 2009 11:36:47 -0700

Wordle generated and interesting graphic of the blog today...

If you look at it hard enough, it's slightly 3D!

Then there was this, more relaxed graphic:

Finished Final Fantasy IV Again!

khanh@khanh.net (Khanh) — Sun, 11 Jan 2009 16:03:49 -0700

If you don't keep up with the blog, I've been re-living the Final Fantasy saga again. I've been playing them in order, and depending on how I feel after Final Fantasy VIII, I may stop or go on to Final Fantasy IX.

In any event, it took me nearly a year of on-again-off-again playing (totaling just under 43 hours of game time):

This story was one of my favorites too. Final Fantasy IV (orginally released as Final Fantasy II on SNES in America) was the first to have all of the original elements of the Final Fantasy we know and love. It's the five-member party, the near-active battle system, classic music, summons, fat chocobo, etc. Yes, and this is the one where you go to the moon. Contrary to popular belief, you don't have to have a level 70 party to complete it. I was fine with my mid-60 level party. Of course, higher would have helped more, but you can defeat Zeromus just fine. As you can see, in addition to Cecil, I brought along Palom, Porom, Cid, and Yang. Yang just uses his "power" for double attacks. Cecil just attacks since his white mage curaga is useless for healing even one person on a turn. Which means, you'll rely on Porom's more powerful curaja or full-life (instead of wasting a turn on a phoenix down, then curing). Next to Yang's attack, Cid's standard attack was important. Cecil is still fairly weak comparatively in the attack department. He's your standard RPG main character (who's always a knight or a fighter) so you have no choice but to bring him along in this case. The majority of your attack will be dealt by Palom. You could have brough Rydia and her summonses, but whatever. Palom has meteor which is probably just as powerful, although not as pretty to watch. Palom will hit for 9999 hit points, but your party will be countered with similar magic from Zeromus. Watch out for that Big Bang attack of his!

Now on to Final Fantasy V!

Star Wars Coffee!

khanh@khanh.net (Khanh) — Fri, 21 Nov 2008 09:40:09 -0700

Star Wars mugs always make coffee taste good!

using openSSH as a layer-2 ethernet bridge (VPN)

khanh@khanh.net (Khanh) — Tue, 18 Nov 2008 21:11:40 -0700

Consider the following network setup (which I live with by the way):

[main LAN] <-----------------------------------------------------> [remote datacenter LAN]
(192.168.0.0/16) <-------- leased point-to-point ------------> (192.168.0.0/16)

Both locations also have separate connections to the public Internet with different public IP subnets. However, for this discussion it's not necessary to have different public IP subnets. Under normal circumstances the local LAN and the remote LAN are the same logical LAN via the magic of the leased point to point line.

However, today that p2p connection broke (physically between the two locations, out of our control). This outage lasted several hours, but brought out an interesting use of SSH tunneling for ethernet bridging aka Layer-2 VPN or tunneling. For this to work, you'll need to have at least openSSH 4.3, a somewhat recent linux distro and the bridge-utils package for your distro. This also assumes you have a basic knowledge of IP and the linux command line. I use openSuSE 11.0, but this should work for almost any similar linux.

Let's say for example, the main location has a linux box (router1) with two NICs:
eth0: 1.1.1.1 (the public interface)
eth1: unassigned IP, but connected to your LAN (192.168.0.0/16 in my case)

On the other box, at the remote location (router2) we also have two NICs:
eth0: 2.2.2.2 (the public interface)
eth1: unassigned IP, but connected to your LAN (192.168.0.0/16 in my case)

Both routers should be set with it's public IP gateway as the default route, working DNS, etc. You'll want to enable IP forwarding (consult your specific distro) and in my case, I disabled the distro's firewall. On the remote side (consider it the "server"), you'll need to edit your sshd config to allow remote root logins and tunnels via SSH.

/etc/ssh/sshd_config:
PermitRootLogin yes
PermitTunnel yes

The root login is necessary to allow ssh to create the TAP devices for the bridge. Because of that, you'll also want to add your local side's IPs to /etc/hosts.allow for the sshd process. Now, on the local side (IP 1.1.1.1, which you might consider the client now) you'll want to "su root" and do the following:

ssh -o Tunnel=ethernet -f -w 0:0 2.2.2.2 true

The -o switch sets client options on the command line. We're specifying the tunnel type as ethernet (bridge) as opposed to point-to-point, which it'll do by default (for Layer-3 type VPN routing). The -f switch just forks ssh in the background so we're returned to our "client's" command line and not remote's. Since we've done that, ssh will expect a remote command of some kind, so we'll just run "true", effectively doing nothing. The -w 0:0 switch actually sets up our tap devices on either side as tap0. You can do -w 1:1 for tap1, -w 0:1 for tap0 on one side and tap1 on the other, etc.

On both sides now, you should be able to see via ifconfig -a your eth0, eth1 and tap0 devices. Make sure to call ifconfig with -a, or you'll only see interfaces with defined IPs. Now that the two boxes are connected via the public Internet to each other via SSH, you can finally start to establish the bridge interface. Now we'll use the bridge-utils binary to create a bridge interface called br0:

brctl addbr br0
brctl addif br0 eth1
brctl addif br0 tap0

Then you'll want to bring up all of your interfaces, if they aren't already:

ifconfig eth1 up
ifconfig tap0 up
ifconfig br0 up

Doing so will create the br0 interface, then bridge your eth1 and tap0 together and bring up the interfaces. Don't forget, YOU MUST RUN THE brctl and ifconfig COMANDS ON BOTH SIDES!!! Once you've done this, you can check the remote side to see if it knows about the MAC addresses (from Layer-2) on the local side:

brctl showmacs br0

This will report on the known MAC address from the ARP protocol. Depending on your network, you'll see a few or many. Depending on your setup, you can get a DHCP address on the "other side" of the tunnel now or configure an appropriate IP and ping across as if you were on the same physical broadcast domain!

As a final note, there's always a downside. TCP encapsulated TCP is bad and will put a STRAIN on your hardware. Make sure it's decent for the amount of anticipated traffic and use only as a quick and dirty solution or a temporary measure. The following is good reading for why this is not a long-term, permanent solution:
http://sites.inka.de/~W1011/devel/tcp-tcp.html

Election 2008 flash widget thingy

khanh@khanh.net (Khanh) — Mon, 03 Nov 2008 19:39:30 -0700

Election 2008 flash widget thingy!

RAWR! Bowser Pumpkin!!!

khanh@khanh.net (Khanh) — Sun, 02 Nov 2008 15:55:20 -0700

RAWR! Bowser Pumpkin!!!

no power :(

khanh@khanh.net (Khanh) — Mon, 27 Oct 2008 11:28:23 -0700

This has only a little to do with technology, but the power was out all weekend due to a bad storm we just had. So, I fired up the generator and played some Nintendo-style Uno. Apparently, it's a good time!

Gallagher's take on the English language and Final Fantasy IV

khanh@khanh.net (Khanh) — Thu, 23 Oct 2008 20:18:36 -0700

So I had completely forgot about my quest to relive the Final Fantasy sagas, again, finally. Over a year ago I had finished Final Fantasy I and II, gave up on III due to a technicality, and started Final Fantasy IV. Actually, it was just over a year ago to the day that I started, but somehow got lost in life work and other things. Anyway, I'm picking it back up again and apparently, I'm on the moon and close to the end. Blah.

Along the lines of my last post, I rediscovered some of my old stand-up comedy favorites on YouTube. That site is such a ridiculous waste of bandwidth sometimes, but there are some gems. This has little to nothing to do with technology, but it's one of my favorite Gallaghers. It's somewhat hard to find, but a classic of his take on school and the English language.

Eddie Izzard on Computers

khanh@khanh.net (Khanh) — Sat, 18 Oct 2008 23:02:13 -0700

RND(tech)

disabling NetBIOS over TCP/IP in Windows via DHCPD

enabling OS X screen sharing remotely in Terminal

burning files larger than 4GB with linux!

AT&T 3G Speedtests

Super Mario Bros Fish Tank

eh, wordle...

Finished Final Fantasy IV Again!

Star Wars Coffee!

using openSSH as a layer-2 ethernet bridge (VPN)

more MythTV and Intel G33 video performance

Election 2008 flash widget thingy

RAWR! Bowser Pumpkin!!!

no power :(

Gallagher's take on the English language and Final Fantasy IV

Eddie Izzard on Computers