Re: [dpdk-dev] [PATCH v8 10/10] app/testpmd:test VxLAN Tx checksum offload

["Liu, Jijiang" <jijiang.liu@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> Sent: Thursday, November 13, 2014 1:26 AM
> To: Liu, Jijiang
> Cc: dev@dpdk.org; Olivier MATZ
> Subject: Re: [dpdk-dev] [PATCH v8 10/10] app/testpmd:test VxLAN Tx checksum
> offload
> 
> 2014-11-11 05:29, Liu, Jijiang:
> > From: Olivier MATZ
> > > On 11/10/2014 07:03 AM, Liu, Jijiang wrote:
> > > > > - if PKT_TX_VXLAN_CKSUM is not set (legacy use case), then the
> > > > >    driver use l2_len and l3_len to offload inner IP/UDP/TCP checksums.
> > > >
> > > > If the flag is not set, and imply that it is not VXLAN packet,
> > > > and do TX checksum offload as regular packet.
> > > >
> > > > > - if PKT_TX_VXLAN_CKSUM is set, then the driver has to use
> > > > >    inner_l{23}_len instead of l{23}_len for the same operation.
> > > >
> > > > Your understanding is not fully correct.
> > > > The l{23}_len is still used for TX checksum offload, please refer
> > > > to
> > > > i40e_txd_enable_checksum()  implementation.
> > >
> > > This fields are part of public mbuf API. You cannot say to refer to
> > > i40e PMD code to understand how to use it.
> > >
> > > > > Adding PKT_TX_VXLAN_CKSUM changes the semantic of l2_len and
> l3_len.
> > > > > To fix this, I suggest to remove the new fields inner_l{23}_len
> > > > > then add outer_l{23}_len instead. Therefore, the semantic of
> > > > > l2_len and l3_len would not change, and a driver would always
> > > > > use the same field for a specific offload.
> > > >
> > > > Oh...
> > >
> > > Does it mean you agree?
> >
> > I don't agree to change inner_l{23}_len the name.
> > The reason is that using the "inner" word means incoming packet is tunneling
> packet or encapsulation packet.
> > if we add "outer"{2,3}_len, which will cause confusion when processing non-
> tunneling packet.
> 
> Sorry Jijiang, maybe I don't understand what you are saying, but I think you
> missed something. Let me explain the problem.
> 
> For PKT_TX_IP_CKSUM, we must set l{2,3}_len.
> When PKT_TX_VXLAN_CKSUM is set, PKT_TX_IP_CKSUM is related to inner IP,
> right?
First of all, I want to explain that what PKT_TX_VXLAN_CKSUM meaning is,  when the flag is set, driver know that it need set TX checksum for whole packet, not only for inner part. 

So When PKT_TX_VXLAN_CKSUM is set, PKT_TX_IP_CKSUM is related to inner IP,right?



> So we must set inner_l{2,3}_len.
> It means that PKT_TX_IP_CKSUM requires different fields to be set, depending of
> PKT_TX_VXLAN_CKSUM. That's what Olivier calls a semantic change.
> It's not acceptable for an API.
> 
> PKT_TX_IP_CKSUM should always be related to l{2,3}_len.
> When PKT_TX_VXLAN_CKSUM is set, we should add outer_l{2,3}_len.
> 
> Please, correct me if I'm wrong or fix the API.
> 
> Thanks
> --
> Thomas