[Bugme-new] [Bug 33972] New: Bogus UDP Fragmentation Offload packet generation
bugzilla-daemon at bugzilla.kernel.org
bugzilla-daemon at bugzilla.kernel.org
Tue Apr 26 04:46:06 PDT 2011
https://bugzilla.kernel.org/show_bug.cgi?id=33972
Summary: Bogus UDP Fragmentation Offload packet generation
Product: Networking
Version: 2.5
Kernel Version: 2.6.32.x
Platform: All
OS/Version: Linux
Tree: Mainline
Status: NEW
Severity: high
Priority: P1
Component: IPV4
AssignedTo: shemminger at linux-foundation.org
ReportedBy: tgr.kb at moo.pl
Regression: Yes
Created an attachment (id=55552)
--> (https://bugzilla.kernel.org/attachment.cgi?id=55552)
udp: Fix bogus UFO packet generation
The new UFO software fallback path fails under certain conditions with NFS and
causes partial connectivity loss due to generation of UFO packets smaller than
the MTU, which are then discarded by the software fallback path.
How to reproduce: copy a large file to an NFS mount with UFO enabled and going
through the software fallback path, e.g. on a KVM guest with virtio-net and
qdev device syntax:
-device virtio-net-pci,netdev=tap1,mac=ab:cd:ef:01:23:45 \
-netdev type=tap,id=tap1,ifname=tap1
All NFS mounts immediately stall and processes go into D state, stuck
on nfs_wait_bit_uninterruptible. There is no further communication between
the client and the server.
It has been fixed in 2.6.35-rc4 by Herbert Xu (patch for net/ipv4/ip_output.c
attached). However, it's still not in 2.6.32.x longterm (as of 2.6.32.39).
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