NFS lockup when copying a "special" file

Sean McNeil sean at
Thu Jul 13 19:31:46 UTC 2006

On Thu, 2006-07-13 at 21:09 +0200, Oliver Lehmann wrote:
> Sean McNeil wrote:
> >
> > I used to have a similar problem and tracked it down to my NIC and
> > hardware checksums.  Would this happen to be an if_re device?  Can you
> > give ifconfig info and if hardware checksums are on, try your test with
> > them turned off (RXCSUM and TXCSUM).  You can try different combos of
> > these if turning off both helps.
> Yeah, it is indeed an on-board if_re:
> re0: <RealTek 8169S Single-chip Gigabit Ethernet> port 0xe800-0xe8ff mem 0xcfffff00-0xcfffffff irq 16 at device 11.0 on pci0
> miibus0: <MII bus> on re0
> rgephy0: <RTL8169S/8110S media interface> on miibus0
> rgephy0:  10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseTX, 1000baseTX-FDX, auto
> re0: Ethernet address: 00:11:09:cf:e2:e1
> re0: [FAST]
> olivleh1 at kartoffel olivleh1> ifconfig
>         options=18<VLAN_MTU,VLAN_HWTAGGING>
>         inet6 fe80::211:9ff:fecf:e2e1%re0 prefixlen 64 scopeid 0x1 
>         inet netmask 0xffffff00 broadcast
>         ether 00:11:09:cf:e2:e1
>         media: Ethernet autoselect (100baseTX <full-duplex>)
>         status: active
> lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
>         inet6 ::1 prefixlen 128 
>         inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3 
>         inet netmask 0xff000000 
> olivleh1 at kartoffel olivleh1> uname -a
> FreeBSD 6.1-STABLE FreeBSD 6.1-STABLE #0: Fri Jul  7 18:40:18 CEST 2006     olivleh1 at  amd64
> How can I disable checksum offloading?

man ifconfig:
     -rxcsum, -txcsum
             If the driver supports user-configurable checksum offloading,
             disable receive (or transmit) checksum offloading on the inter-
             face.  These settings may not always be independent of each

So, just do an

ifconfig re0 -rxcsum -txcsum

But it would appear that they are already disabled.  This is the exact
same device that I had issues with and I thought receive only hw
checksums were disabled by default.  ifconfig shows that they are both
off.  You would have seen them in the options field if on. i.e.


Maybe try setting one of them on?  Try "ifconfig re0 txcsum".

How about on the other side? The checksum offloading problem exists for
i386 and amd64 versions of the if_re driver.  What does the NFS server
have for a NIC and what is the OS/ifconfig settings?  I seem to recall
the problem was with RXCSUM.

What is most likely occurring is either the box writing to the NFS
server has a packet with an improperly calculated checksum or the
checksum on the receive side is calculated incorrectly.  This leaves it
stuck trying to resend that bad packet over and over.

>From your original email it appears that the amd64 box is sending to an
NFS server.  The other possibility is that, perhaps, you have your
firewall setup on your amd64 box is such a way that it is messing up the

The NFS client is less likely to be the problem than one of the above.


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