On 2018/11/24 上午4:01, David Miller wrote:
From: Jason Wang <jasowang@xxxxxxxxxx> Date: Thu, 22 Nov 2018 14:36:30 +0800We don't disable VIRTIO_NET_F_GUEST_CSUM if XDP was set. This means we can receive partial csumed packets with metadata kept in the vnet_hdr. This may have several side effects: - It could be overridden by header adjustment, thus is might be not correct after XDP processing. - There's no way to pass such metadata information through XDP_REDIRECT to another driver. - XDP does not support checksum offload right now. So simply disable guest csum if possible in this the case of XDP. Fixes: 3f93522ffab2d ("virtio-net: switch off offloads on demand if possible on XDP set") Reported-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> Cc: Jesper Dangaard Brouer <brouer@xxxxxxxxxx> Cc: Pavel Popa <pashinho1990@xxxxxxxxx> Cc: David Ahern <dsahern@xxxxxxxxx> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>Applied and queued up for -stable. We really should have a way to use the checksum provided if the XDP program returns XDP_PASS and does not modify the packet contents or size.
Yes, I think this may require the assistance of BPF verifier to set a flag or other. Then we can assume the metadata is safe to use.
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