Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP checksum definition

[Jerin Jacob <jerin.jacob@caviumnetworks.com>]

-----Original Message-----
> Date: Wed, 3 Oct 2018 21:00:37 +0300
> From: Andrew Rybchenko <arybchenko@solarflare.com>
> To: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> CC: Wenzhuo Lu <wenzhuo.lu@intel.com>, Jingjing Wu <jingjing.wu@intel.com>,
>  Bernard Iremonger <bernard.iremonger@intel.com>, John McNamara
>  <john.mcnamara@intel.com>, Marko Kovacevic <marko.kovacevic@intel.com>,
>  Thomas Monjalon <thomas@monjalon.net>, Ferruh Yigit
>  <ferruh.yigit@intel.com>, Olivier Matz <olivier.matz@6wind.com>,
>  dev@dpdk.org, shahafs@mellanox.com, "Ananyev, Konstantin"
>  <konstantin.ananyev@intel.com>
> Subject: Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP
>  checksum definition
> User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
>  Thunderbird/52.9.1
> 
> On 03.10.2018 20:12, Jerin Jacob wrote:
> > -----Original Message-----
> > > Date: Wed, 3 Oct 2018 13:27:13 +0530
> > > From: Jerin Jacob <jerin.jacob@caviumnetworks.com>
> > > To: Andrew Rybchenko <arybchenko@solarflare.com>
> > > CC: Wenzhuo Lu <wenzhuo.lu@intel.com>, Jingjing Wu <jingjing.wu@intel.com>,
> > >   Bernard Iremonger <bernard.iremonger@intel.com>, John McNamara
> > >   <john.mcnamara@intel.com>, Marko Kovacevic <marko.kovacevic@intel.com>,
> > >   Thomas Monjalon <thomas@monjalon.net>, Ferruh Yigit
> > >   <ferruh.yigit@intel.com>, Olivier Matz <olivier.matz@6wind.com>,
> > >   dev@dpdk.org, shahafs@mellanox.com, "Ananyev, Konstantin"
> > >   <konstantin.ananyev@intel.com>
> > > Subject: Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP
> > >   checksum definition
> > > User-Agent: Mutt/1.10.1 (2018-07-13)
> > > 
> > > External Email
> > > 
> > > -----Original Message-----
> > > > Date: Wed, 3 Oct 2018 10:34:52 +0300
> > > > From: Andrew Rybchenko <arybchenko@solarflare.com>
> > > > To: Jerin Jacob <jerin.jacob@caviumnetworks.com>, Wenzhuo Lu
> > > >   <wenzhuo.lu@intel.com>, Jingjing Wu <jingjing.wu@intel.com>, Bernard
> > > >   Iremonger <bernard.iremonger@intel.com>, John McNamara
> > > >   <john.mcnamara@intel.com>, Marko Kovacevic <marko.kovacevic@intel.com>,
> > > >   Thomas Monjalon <thomas@monjalon.net>, Ferruh Yigit
> > > >   <ferruh.yigit@intel.com>, Olivier Matz <olivier.matz@6wind.com>
> > > > CC: dev@dpdk.org, shahafs@mellanox.com, "Ananyev, Konstantin"
> > > >   <konstantin.ananyev@intel.com>
> > > > Subject: Re: [dpdk-dev] [PATCH v2 1/4] ethdev: add Rx offload outer UDP
> > > >   checksum definition
> > > > User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
> > > >   Thunderbird/60.0
> > > > 
> > > > 
> > > > On 10/2/18 10:24 PM, Jerin Jacob wrote:
> > > > 
> > > > Introduced DEV_RX_OFFLOAD_OUTER_UDP_CKSUM Rx offload flag and
> > > > PKT_RX_EL4_CKSUM_BAD mbuf ol_flags to detect outer UDP checksum
> > > > failure.
> > > > 
> > > > - To use hardware Rx outer UDP checksum offload, the user needs to
> > > > configure DEV_RX_OFFLOAD_OUTER_UDP_CKSUM offload flags in slowpath.
> > > > 
> > > > - Driver updates the PKT_RX_EL4_CKSUM_BAD mbuf ol_flag on checksum failure
> > > > similar to the outer L3 PKT_RX_EIP_CKSUM_BAD flag.
> > > > 
> > > > Signed-off-by: Jerin Jacob <jerin.jacob@caviumnetworks.com><mailto:jerin.jacob@caviumnetworks.com>
> > > > 
> > > > 1. I'm not sure that it is OK that mbuf and ethdev changes go in one patch.
> > > >     It seems typically mbuf changes go separately and mbuf changes should
> > > >     be applied to main dpdk repo.
> > > 
> > > I don't have strong opinion on this. If there are no other objection, I
> > > will split the patch further as mbuf and ethdev as you pointed out.
> > > 
> > > > 2. I'd like to see thought why single bit is used for outer L2 checksum when
> > > >     2 bits (UNKNOWN, BAD, GOOD, NONE) are used for PKT_RX_L4_CKSUM.
> > > >     May be it is OK, but it would be useful to state explicitly why it is decided
> > > >     to go this way.
> > > I am following the scheme similar to OUTER IP checksum where we have only
> > > one bit filed(PKT_RX_EIP_CKSUM_BAD). I will mention in the git commit.
> > > 
> > > 
> > > > 3. PKT_RX_L4_CKSUM_MASK description says nothing if it is inner or outer.
> > > >     May be it is not directly related to changeset, but I think it would be really
> > > >     useful to clarify it.
> > > I will update the comment.
> > Hi Andrew,
> > 
> > I looked at the other definitions in mbuf.h, according the documentation,
> > If nothing is mentioned it is treated as inner if the packet is
> > tunneled else it is outer most. So I would like avoid confusion by
> > adding "inner" in the exiting PKT_RX_L4_CKSUM_MASK comment.
> > Technically it is not correct to say "inner" if the packet is not
> > tunneled. So I am untouching the exiting comment.
> > 
> 
> Yes, it is incorrect to say that it is inner. How does application find
> how to treat PKT_RX_L4_CKSUM (inner or outer)?
> Should it rely on packet type provided in mbuf?

AFAIK, Finding is it a tunneled packet or not is through ptype or SW has
to parse the packet. For example, testpmd chooses later method using
"csum parse-tunnel on <port>" to detect the presence of the tunnel.

> Is it specified/mentioned somewhere?

I don't know. It it not directly related to this change set, Olivier may know
additional details.

> 
> Andrew.