BenV's notes

A while ago a friend hinted me of this printer. We were both looking for a somewhat affordable network laser printer, color preferred. However, I was wondering if this thing would work properly under linux. (continue reading…)

So yesterday at work I ran into the famous ssh MAC failure like this:

wouter@wouter-laptop:~:0> rsync -varP ./vmware/ wouter@192.168.1.2:/archive/archive2/programs/vmware/
Password:
sending incremental file list
./
Keys
116 100% 0.00kB/s 0:00:00 (xfer#1, to-check=8/10)
linux/
linux/VMware-server-2.0.1-156745.i386.tar.gz
32768 0% 800.00kB/s 0:10:11 Received disconnect from 192.168.1.2: 2: Corrupted MAC on input.

rsync: writefd_unbuffered failed to write 4 bytes to socket [sender]: Broken pipe (32)
rsync: connection unexpectedly closed (53 bytes received so far) [sender]
rsync error: error in rsync protocol data stream (code 12) at io.c(600) [sender=3.0.6]


No, that has nothing to do with Apple/Mac computers or Media Access Control, it’s
part of the SSH protocol (and others) called Messenge Authentication Code. This blog has a nice explanation: Jan Pechanec on SSH messages.

Funny thing, my brother also had this exact issue with the same kind of laptop. Well…. in his case it was putty failing his connection from a windows machine to this laptop.
The reason? Same as ever, checksum offloading.
You can check if your card does this with the ethtool program:

wouter@wouter-laptop:~:0> sudo ethtool -k eth0
Offload parameters for eth0:
Cannot get device flags: Operation not supported
rx-checksumming: on
tx-checksumming: on
scatter-gather: on
tcp-segmentation-offload: off
udp-fragmentation-offload: off
generic-segmentation-offload: on
generic-receive-offload: off
large-receive-offload: off


And the fix for this:

wouter@wouter-laptop:~:85> sudo ethtool -K eth0 tx off

Fixed.

” Wait, what does Pokemon OS have to do with this?”
Well, isn’t that obvious? It’s supposed to magically work, and it doesn’t! 😉
Probably more a kernel thing though… oh well.

Or… not. Oh, the pokemon reference comes from the brilliant webcomic XKCD.

Usually I have little problems getting stuff to work on it, but as hardware gets older and support gets worse thing get more interesting.
First things first: I have no issues with ubuntu, they’re doing great work. In fact, the machine worked fine after installation, except for I can’t live with 800×600, so I wanted a better video driver.
Needless to say that means NON OPEN SOURCE GARBAGE FROM NVIDIA (ATI is just as bad btw). Although their binary driver usually ‘works’, you’re royally screwed if your system doesn’t meet their requirements. (continue reading…)