Messages in this thread | | | Subject | Re: [PATCH net] virtio-net: unbreak cusmed packet for small buffer XDP | From | Jason Wang <> | Date | Wed, 28 Jun 2017 11:40:30 +0800 |
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On 2017年06月28日 11:31, Michael S. Tsirkin wrote: > On Wed, Jun 28, 2017 at 10:45:18AM +0800, Jason Wang wrote: >> On 2017年06月28日 10:17, Michael S. Tsirkin wrote: >>> On Wed, Jun 28, 2017 at 10:14:34AM +0800, Jason Wang wrote: >>>> On 2017年06月28日 10:02, Michael S. Tsirkin wrote: >>>>> On Wed, Jun 28, 2017 at 09:54:03AM +0800, Jason Wang wrote: >>>>>> We should allow csumed packet for small buffer, otherwise XDP_PASS >>>>>> won't work correctly. >>>>>> >>>>>> Fixes commit bb91accf2733 ("virtio-net: XDP support for small buffers") >>>>>> Signed-off-by: Jason Wang<jasowang@redhat.com> >>>>> The issue would be VIRTIO_NET_HDR_F_DATA_VALID might be set. >>>>> What do you think? >>>> I think it's safe. For XDP_PASS, it work like in the past. >>> That's the part I don't get. With DATA_VALID csum in packet is wrong, XDP >>> tools assume it's value. >> DATA_VALID is CHECKSUM_UNCESSARY on the host, and according to the comment >> in skbuff.h >> >> >> " >> * The hardware you're dealing with doesn't calculate the full checksum >> * (as in CHECKSUM_COMPLETE), but it does parse headers and verify >> checksums >> * for specific protocols. For such packets it will set >> CHECKSUM_UNNECESSARY >> * if their checksums are okay. skb->csum is still undefined in this case >> * though. A driver or device must never modify the checksum field in the >> * packet even if checksum is verified. >> " >> >> The csum is correct I believe? >> >> Thanks > That's on input. But I think for tun it's output, where that is equivalent > to CHECKSUM_NONE > >
Yes, but the comment said:
" CKSUM_NONE: * * The skb was already checksummed by the protocol, or a checksum is not * required. * * CHECKSUM_UNNECESSARY: * * This has the same meaning on as CHECKSUM_NONE for checksum offload on * output. * "
So still correct I think?
Thanks
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