Dear Experts,
I am seeing the error "RPC: multiple fragments per record not
supported" on my NFS server when an NFS client with an atl1c network
driver talks to it.
The server is a QNAP TS119 ARM box running Debian's 2.6.33.2 kernel.
It works reliably with other clients.
The client is a new x86 system with an "Atheros Communications AR8131
Gigabit Ethernet (rev c0)" (1969:1063). The kernel is Debian's
2.6.32-5-686 and the driver seems to be atl1c.
Typically NFS works for a few seconds and then stops, with that message
repeated on the server. Other network activity seems reliable (e.g.
HTTP, ssh, etc.)
If I use a USB-ethernet adaptor instead of the built-in gigabit it
works reliably. (The USB device is not gigabit, but I do still see the
problems if I limit the port to 100 Mbit on the switch.)
I see the problem with NFS v3 and v4. However, I only see it with
proto=tcp. By changing the NFS protocol to UDP, the problem seems to
go away [well, it has been working for about 20 minutes now without any issues].
Google finds a previous report here:
http://lkml.org/lkml/2010/1/20/198 ; the suggestion is to turn off tcp
segmentation offload, but it seems that this is not possible with my system:
# ethtool -K eth0 tso off
Cannot set device tcp segmentation offload settings: Operation not supported
I have looked at the changes to atl1c since 2.6.32
(http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=history;f=drivers/net/atl1c;h=53cd10d07d040b7bec957acb1c69bc7b44897e69;hb=HEAD)
and they seem harmless.
I wiresharked the network activity while this error was being shown,
and it did include some packets with the high-contrast colour schemes
that wireshark uses for "bad" packets. Unfortunately my laptop ran out
of battery before I could decipher these packets further.
So, is this a known issue? Do people agree that the atl1c driver is
most likely the culprit? Can I offer any further debugging?
Regards, Phil.
(Please CC me in any replies, as I'll see them sooner.)
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