[PATCH 0/3][Yakkety][SRU] virtio: fix xmit packet flag settings

Jay Vosburgh jay.vosburgh at canonical.com
Wed Apr 19 23:41:44 UTC 2017

BugLink: https://bugs.launchpad.net/bugs/1683947

	Beginning with fd2a0437dc33 ("virtio_net: introduce
virtio_net_hdr_{from,to}_skb"), virtio_net incorrectly sets
packets are modified prior to transmission (e.g., by NAT), they are
dropped by the receving virtio.  I suspect (but have not confirmed
experimentally) that this is because the checksum is incorrect after NAT
modifies the packet, but the checksum is not recomputed.

	Patch 1/3, 3e9e40e74753 ("virtio_net: Simplify call sites for
virtio_net_hdr_{from, to}_skb()."), is a prerequisite to permit patch 3/3,
6391a4481ba0, to apply more easily and end up with the final code closer
to mainline.

	Patch 2/3, 501db511397f ("virtio: don't set
VIRTIO_NET_HDR_F_DATA_VALID on xmit") was found by bisect to initially
resolve the issue.

	Patch 3/3, 6391a4481ba0 ("virtio-net: restore
VIRTIO_HDR_F_DATA_VALID on receiving") is a follow-on to 501db511397f for
the complete fix.

	As the issue was introduced during 4.8-rc and resolved before 4.10
release, this bug exists only in the Ubuntu Yakkety 4.8 kernel series.


	-Jay Vosburgh, jay.vosburgh at canonical.com

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