Small MSS in vmxnet3

Small MSS in vmxnet3

[Naruto Nguyen]

Hello everyone,

Recently I found that packets sent from vmxnet3 driver on guest have
MSS value set to very small size, some 10 bytes, some 25 bytes MSS.
The vmxnet3 NIC enables TSO. Could you let me know any possible reason
that the packets are fragmented with very small MSS.and is it normal?.
Any way to avoid this small MSS or it's just normal.

In addition, when enabling debug for vmxnet3, in function
vmxnet3_tq_xmit, it has a printout

netdev_dbg(adapter->netdev,
"txd[%u]: SOP 0x%Lx 0x%x 0x%x\n",
(u32)(ctx.sop_txd -
tq->tx_ring.base), le64_to_cpu(gdesc->txd.addr),
le32_to_cpu(gdesc->dword[2]), le32_to_cpu(gdesc->dword[3]));

could you suggest an easier way to extract the MSS value from this output?

Thanks,
Kind regards, Naruto

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Re: Small MSS in vmxnet3

[Naruto Nguyen]

Hello,
could you please let me know any ideas?

Thank you,
Kind regards,
Bao

On Sat, 23 Sept 2023 at 12:12, Naruto Nguyen <narutonguyen2018@gmail.com> wrote:
>
> Hello everyone,
>
> Recently I found that packets sent from vmxnet3 driver on guest have
> MSS value set to very small size, some 10 bytes, some 25 bytes MSS.
> The vmxnet3 NIC enables TSO. Could you let me know any possible reason
> that the packets are fragmented with very small MSS.and is it normal?.
> Any way to avoid this small MSS or it's just normal.
>
> In addition, when enabling debug for vmxnet3, in function
> vmxnet3_tq_xmit, it has a printout
>
> netdev_dbg(adapter->netdev,
> "txd[%u]: SOP 0x%Lx 0x%x 0x%x\n",
> (u32)(ctx.sop_txd -
> tq->tx_ring.base), le64_to_cpu(gdesc->txd.addr),
> le32_to_cpu(gdesc->dword[2]), le32_to_cpu(gdesc->dword[3]));
>
> could you suggest an easier way to extract the MSS value from this output?
>
> Thanks,
> Kind regards, Naruto

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