Re: hw/net/cadence_gem: TX checksum offload does not work for fragmented packets

[Jason Wang]

On 2020/4/26 下午2:57, Bin Meng wrote:
> Hi Jason,
>
> On Tue, Apr 21, 2020 at 10:31 PM Bin Meng <address@hidden> wrote:
> > Hi,
> >
> > The cadence_gem does the TX checksum offload by:
> >
> >                  /* Is checksum offload enabled? */
> >                  if (s->regs[GEM_DMACFG] & GEM_DMACFG_TXCSUM_OFFL) {
> >                      net_checksum_calculate(tx_packet, total_bytes);
> >                  }
> >
> > However this will only work for non-fragmented packets. For fragmented
> > packets, it just corrupts the packets by inserting wrong checksum to
> > the fist fragment, or corrupts the data to be sent in other fragments
> > than the first one.
> >
> > Any idea of how to solve this cleanly?
> I suspect this is a common issue for all NIC models in QEMU. Could you
> please comment?
>
> Regards,
> Bin


I think maybe you can have a look at how it was done by e1000e which 
uses NetTxPkt structure. (E.g net_tx_pkt_update_ip_checksum()).

In the future, we may consider to convert the metadata that just uses 
NetTxPkt structure, but it's a non-trivial changes.

Thanks