linux-kernel - Re: Small MSS in vmxnet3

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Message-ID: <CANpxKHEDD+fjQiH=DrHPWTm6CMkT78Tcbk2sVfPydO9+M2-FQA@mail.gmail.com>
Date:   Mon, 25 Sep 2023 20:57:11 +1000
From:   Naruto Nguyen <narutonguyen2018@...il.com>
To:     kernel derkeiler <linux-kernel@...r.kernel.org>,
        kernelnewbies <kernelnewbies@...nelnewbies.org>
Subject: Re: Small MSS in vmxnet3

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@...il.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