Re: [PATCH] spidernet: Fix problem sending IP fragments

On Monday, 12. March 2007 11:44, Geert Uytterhoeven wrote:

On Mon, 12 Mar 2007, Norbert Eicker wrote:

quoted

On Monday, 12. March 2007 09:28, Geert Uytterhoeven wrote:

quoted

On Sat, 10 Mar 2007, Norbert Eicker wrote:

quoted

On Friday, 9. March 2007 17:53, Jeff Garzik wrote:

quoted

Linas Vepstas wrote:

quoted

Please apply. The rather long patch description is from the
submitter, Norbert Eicker, I don't know if that's alright,
or if I should ask to have it trimmed.

Thanks,
--linas

From: Norbert Eicker <redacted>


Signed-off-by: Norbert Eicker <redacted>
Signed-off-by: Linas Vepstas <redacted>

are you sure it can't send out fragmented IP frames?  what's
really going on here?

Pretty sure that fragmented IP frames are not send out. Here's
a small test using ttcp and tcpdump reproducing the problem (I
assume a MTU of 1500):

Hence if I understand that correctly, NFS over UDP doesn't work
at all as NFS uses 8 KiB UDP packets by default?

NFS seems to work but considering what I saw in tcpdump it uses TCP
instead of UDP. I have not yet found out why NFS seems to default
to TCP on Cell (the man-pages claims that UDP is the default).

Hmm, I just checked and for me it defaults to UDP.

quoted

If I explicitely demand to use UDP it indeed does not work at all.

And NFS over UDP works fine on my PS3 with the gelic Ethernet driver.
Ethereal (on the server side) did show fragmented packets.

Well, the gelic is a different driver, so for me it's no surprise it 
shows different behavior.

In fact from a quick inspection I would guess that it has not the bug 
that's inside the spidernet driver: The section I patched in 
spider_net.c shows up similarly around line 839 in gelic_net.c. But an 
important difference is in the lines before: It only appears in the 
else-branch of an 'if'. This one tests if ip_summed is set to 
CHECKSUM_PARTIAL.

I.e. gelic_net.c has the test that is missing in spider_net.c.

However, I remember having NFS problems when using a different NFS
server before.  I just retried using that server, and got these error
messages from

the gelic driver:
| error in received descriptor found, data_status=x70002300,
| data_error=x06100000 ERROR DESTROY:6100000
| error in received descriptor found, data_status=x70002900,
| data_error=x06100000 ERROR DESTROY:6100000

Ethereal (on the server side) did show fragmented packets with
retransmissions.

So sometimes it works, sometimes it doesn't?

The differences between the 2 NFS servers are:
  - working one runs 2.6.11, non-working one runs 2.4.17
  - working one is on the same subnet as the PS3, non-working one
isn't. - both work fine with e.g. my laptop as an NFS client
  - both have nfs-kernel-server 1:1.0.6-3.1
  - both have 3c905 Tornado Ethernet

For completeness, sometimes (1-2 times a week) I do see a similar
gelic error message when using the working NFS server, but it
recovers fine and never is a problem.

IMHO the problem I reported is not an NFS problem at all (there might be 
more problems in this arena;-)). As I have pointed out you can see the 
problem even with ttcp (or some other tool sending UDP frames larger 
than MTU - some_header_length).

Norbert
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