Bug 418691 - ath5k requires reduced MTU to work with git, rsync
ath5k requires reduced MTU to work with git, rsync
Product: Fedora
Classification: Fedora
Component: kernel (Show other bugs)
All Linux
low Severity low
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Assigned To: John W. Linville
Fedora Extras Quality Assurance
Depends On:
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Reported: 2007-12-10 14:36 EST by Adam Goode
Modified: 2008-02-19 15:43 EST (History)
3 users (show)

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Doc Type: Bug Fix
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Last Closed: 2008-02-19 15:43:04 EST
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Description Adam Goode 2007-12-10 14:36:37 EST
Description of problem:

I am using ath5k on a Thinkpad T41p.

Nearly all network traffic seems to be fine, but when I rsync or git pull, some
initial control traffic gets through and then it hangs. I must ctrl-c the program.

Setting mtu to 1498 fixes the problem for rsync.

ath5k_pci 0000:02:02.0: Atheros AR5213 chip found (MAC: 0x56, PHY: 0x41)
ath5k_pci 0000:02:02.0: RF5111 5GHz radio found (0x17)
ath5k_pci 0000:02:02.0: RF2111 2GHz radio found (0x23)

Version-Release number of selected component (if applicable):
Comment 1 John W. Linville 2007-12-10 14:47:34 EST
I doubt if it makes a difference, but please try at least -80.fc8 (the last 
round of wireless updates for .fc8):

Comment 2 Luis R. Rodriguez 2007-12-10 14:49:15 EST
Hmm, interesting. Are you forcing the driver to 11M ? Right now the driver will
get you large packet loss at higher rates. I'm curious if your issues 'also' go
away at when you force driver to 11Mbps:

iwconfig wlan0 rate 11M

Comment 3 Adam Goode 2007-12-11 12:27:35 EST
Nope, neither 11M setting nor -80.fc8 make any difference. But mtu 1498
continues to work perfectly.
Comment 4 Adam Goode 2008-01-08 15:24:48 EST
kernel -85.fc8 still has the same problem.
Comment 5 John W. Linville 2008-01-22 15:07:20 EST
Could there be an ethernet LAN using VLAN tagging somewhere between you and 
the Internet?
Comment 6 Adam Goode 2008-01-22 21:47:02 EST
I don't think so. The wireless machines are directly on the Internet.

We can ping other local addresses with another machine with this:

 ping -M do -s 1472 ...

With IP + ICMP + payload = 20 + 8 + 1472 = 1500. That works fine using ipw2200.

On the ath5k machine, if mtu is 1500, then a ping payload of 1472 or 1471
results in no remote response. Ping payload of 1470 works.
Comment 7 John W. Linville 2008-02-14 13:50:31 EST
Do you see the >1470 payload ICMP frames at the other host?  I would be 
curious to know if the frames are getting dropped on Tx or Rx.
Comment 8 Adam Goode 2008-02-15 17:06:56 EST
I have tried ping both ways. The frames are dropped only on Tx. Rx works fine.
Comment 9 Adam Goode 2008-02-19 15:30:21 EST
Seems kernel- fixes this problem! I can ping and rsync works with
MTU 1500 (the default).

I did get a panic at one point, though. Couldn't see the output since X was
running, and it hasn't happened since.
Comment 10 John W. Linville 2008-02-19 15:43:04 EST
Wow, you are quick! :-)

FWIW, I think it this patch fixes the problem:

   ath5k: correct padding in tx descriptors

I was going to ask you to test it, but you beat me to it.  Thanks for the 

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