Small MSS in vmxnet3

Naruto Nguyen narutonguyen2018 at
Fri Sep 22 22:12:46 EDT 2023

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

"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?

Kind regards, Naruto

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