4.4.1 skb_warn_bad_offload+0xc5/0x110

[Wakko Warner]

Please keep me in CC.

I've been seeing the following on some of my VMs ran under qemu.  The VMs do
not have internet connectivity.  This happened when some files were accessed
via NFS to another VM (NOTE: Both VMs throw these warnings.  Both VMs are
running the exact same kernel).  The host is also throwing these warnings
and is also 4.4.1, but not the same kernel build.

The issue appears to have gone away if I issue the following on the guests
and on the host (except br0 instead of eth0 on host)
ethtool -K eth0 gso off gro off ufo off tso off

On the host, br0 does not have any interfaces enslaved except for the
interface for the VMs and also does not have an IPv4 address assigned.

[   90.067519] ------------[ cut here ]------------
[   90.067678] WARNING: CPU: 0 PID: 2258 at /usr/src/linux/dist/4.4.1-nobklcd/net/core/dev.c:2422 skb_warn_bad_offload+0xc5/0x110()
[   90.067766] virtio_net: caps=(0x00000804001f4a29, 0x0000000000000000) len=32934 data_len=32768 gso_size=1480 gso_type=2 ip_summed=0
[   90.067878] Modules linked in: nfsv3 nfsd auth_rpcgss oid_registry exportfs nfs lockd grace sunrpc ipv6 virtio_net virtio_balloon evdev unix
[   90.068206] CPU: 0 PID: 2258 Comm: kworker/0:1H Not tainted 4.4.1 #1
[   90.068258] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Debian-1.8.2-1 04/01/2014
[   90.068340] Workqueue: rpciod rpc_async_schedule [sunrpc]
[   90.068433]  ffffffff81503288 ffffffff811d455e ffff880276ffb9a0 ffffffff81041343
[   90.068575]  ffff88007b85be00 ffff880276ffb9f0 0000000000000002 ffff880276f87aac
[   90.068725]  ffff88027692c000 ffffffff810413b7 ffffffff81503498 ffffffff00000030
[   90.068846] Call Trace:
[   90.068888]  [<ffffffff811d455e>] ? dump_stack+0x47/0x69
[   90.068967]  [<ffffffff81041343>] ? warn_slowpath_common+0x73/0xa0
[   90.069068]  [<ffffffff810413b7>] ? warn_slowpath_fmt+0x47/0x50
[   90.069129]  [<ffffffff813103a5>] ? skb_warn_bad_offload+0xc5/0x110
[   90.069191]  [<ffffffff81313121>] ? __skb_gso_segment+0x71/0xc0
[   90.069250]  [<ffffffff81313460>] ? validate_xmit_skb.isra.119.part.120+0x100/0x290
[   90.069314]  [<ffffffff810848a9>] ? lock_timer_base.isra.22+0x49/0x60
[   90.069381]  [<ffffffff81313931>] ? validate_xmit_skb_list+0x31/0x50
[   90.069440]  [<ffffffff8132d3a0>] ? sch_direct_xmit+0x140/0x1e0
[   90.069497]  [<ffffffff81313be8>] ? __dev_queue_xmit+0x1c8/0x490
[   90.069555]  [<ffffffff8133e5e2>] ? ip_finish_output2+0x122/0x300
[   90.069613]  [<ffffffff812fda6d>] ? release_sock+0xfd/0x160
[   90.069671]  [<ffffffff8133fe25>] ? ip_output+0xb5/0xc0
[   90.069720]  [<ffffffff8133dab0>] ? ip_reply_glue_bits+0x50/0x50
[   90.069784]  [<ffffffff811e028b>] ? prandom_u32+0x1b/0x30
[   90.069833]  [<ffffffff8133f5f2>] ? ip_local_out+0x12/0x40
[   90.069877]  [<ffffffff81340710>] ? ip_send_skb+0x10/0x40
[   90.069922]  [<ffffffff81363760>] ? udp_send_skb+0x160/0x240
[   90.069990]  [<ffffffff81363874>] ? udp_push_pending_frames+0x34/0x50
[   90.070050]  [<ffffffff813650e4>] ? udp_sendpage+0xe4/0x150
[   90.070095]  [<ffffffff812fa4fa>] ? kernel_sendmsg+0x2a/0x40
[   90.070164]  [<ffffffffa008a233>] ? xs_send_kvec+0x83/0x90 [sunrpc]
[   90.070223]  [<ffffffff813702f3>] ? inet_sendpage+0x93/0xe0
[   90.070270]  [<ffffffffa008a3af>] ? xs_sendpages+0x16f/0x1b0 [sunrpc]
[   90.070330]  [<ffffffffa008a60e>] ? xs_udp_send_request+0x5e/0x100 [sunrpc]
[   90.070390]  [<ffffffffa0088807>] ? xprt_transmit+0x47/0x230 [sunrpc]
[   90.070449]  [<ffffffffa0086255>] ? call_transmit+0x175/0x220 [sunrpc]
[   90.070508]  [<ffffffffa008cdbb>] ? __rpc_execute+0x4b/0x290 [sunrpc]
[   90.070575]  [<ffffffff8105d123>] ? finish_task_switch+0x83/0x1b0
[   90.070653]  [<ffffffff81054ba9>] ? process_one_work+0x129/0x3f0
[   90.070711]  [<ffffffff81054eb2>] ? worker_thread+0x42/0x490
[   90.070764]  [<ffffffff81054e70>] ? process_one_work+0x3f0/0x3f0
[   90.070816]  [<ffffffff81059a98>] ? kthread+0xb8/0xd0
[   90.070860]  [<ffffffff810599e0>] ? kthread_worker_fn+0x100/0x100
[   90.070925]  [<ffffffff813a2fff>] ? ret_from_fork+0x3f/0x70
[   90.070974]  [<ffffffff810599e0>] ? kthread_worker_fn+0x100/0x100
[   90.071035] ---[ end trace ffb4f8c2d24c1959 ]---

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 million bugs.