Re: [dpdk-dev] Where is the padding code in DPDK?

[Sam <batmanustc@gmail.com>]

OK, then shortly speaking, DPDK will NOT care about padding.
NIC will care about padding while send and recv with NIC.
kernel will care about while send and recv with vhostuser port.

Is that right?


Burakov, Anatoly <anatoly.burakov@intel.com> 于2018年11月13日周二 下午5:29写道：

> On 13-Nov-18 7:16 AM, Sam wrote:
> > Hi all,
> >
> > As we know, ethernet frame must longer then 64B.
> >
> > So if I create rte_mbuf and fill it with just 60B data, will
> > rte_eth_tx_burst add padding data, let the frame longer then 64B
> >
> > If it does, where is the code?
> >
>
> Others can correct me if i'm wrong here, but specifically in case of
> 64-byte packets, these are the shortest valid packets that you can send,
> and a 64-byte packet will actually carry only 60 bytes' worth of packet
> data, because there's a 4-byte CRC frame at the end (see Ethernet frame
> format). If you enabled CRC offload, then your NIC will append the 4
> bytes at transmit. If you haven't, then it's up to each individual
> driver/NIC to accept/reject such a packet because it can rightly be
> considered malformed.
>
> In addition, your NIC may add e.g. VLAN tags or other stuff, again
> depending on hardware offloads that you have enabled in your TX
> configuration, which may push the packet size beyond 64 bytes while
> having only 60 bytes of actual packet data.
>
> --
> Thanks,
> Anatoly
>