[dpdk-dev] [PATCH v2 1/5] ethdev: introduce Tx generic tunnel offloads

[Xueming(Steven) Li]

Hi Thomas,

Yes, would update in next version, thanks for reminding.

Regards,
Xueming

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas at monjalon.net]
> Sent: Wednesday, January 31, 2018 4:21 AM
> To: Xueming(Steven) Li <xuemingl at mellanox.com>
> Cc: Ananyev, Konstantin <konstantin.ananyev at intel.com>; Olivier MATZ
> <olivier.matz at 6wind.com>; dev at dpdk.org; Wu, Jingjing
> <jingjing.wu at intel.com>; Shahaf Shuler <shahafs at mellanox.com>; Yongseok
> Koh <yskoh at mellanox.com>; Yigit, Ferruh <ferruh.yigit at intel.com>
> Subject: Re: [dpdk-dev] [PATCH v2 1/5] ethdev: introduce Tx generic tunnel
> offloads
> 
> Xueming,
> 
> We already discussed privately some time ago about this API.
> You got some questions from me, from Olivier and from Konstantin.
> The next version should answer the questions asked.
> 
> When defining an API, the doxygen documentation must explain precisely
> what must be set, when and why.
> The documentation must be sufficient to allow users using it, and to allow
> PMD writers to implement it.
> 
> I think it cannot be properly reviewed until we clearly understand the API
> and the HW requirements/expectations.
> 
> Hope this helps to understand what is expected for integrating such API.
> 
> 
> 30/01/2018 18:54, Xueming(Steven) Li:
> 
> > > > > > > > > > > > This patch introduce new TX offloads flag for
> > > > > > > > > > > > devices that support tunnel agnostic checksum and
> TSO offloads.
> > > > > > > > > > > >
> > > > > > > > > > > > The support from the device is for inner and outer
> > > > > > > > > > > > checksums on IPV4/TCP/UDP and TSO for *any packet
> > > > > > > > > > > > with the following
> > > > > > > format*:
> > > > > > > > > > > >
> > > > > > > > > > > > < some headers > / [optional IPv4/IPv6] /
> > > > > > > > > > > > [optional TCP/UDP] / <some
> > > > > > > > > > > > headers> / [optional inner IPv4/IPv6] / [optional
> > > > > > > > > > > > headers> TCP/UDP]
> > > > > > > > > > > >
> > > > > > > > > > > > For example the following packets can use this
> feature:
> > > > > > > > > > > >
> > > > > > > > > > > > 1. eth / ipv4 / udp / VXLAN / ip / tcp 2. eth /
> > > > > > > > > > > > ipv4 / GRE / MPLS /
> > > > > > > > > > > > ipv4 / udp
> > > > > > > > > > >
> > > > > > > > > > > So in terms of usage - what is the difference with
> > > > > > > > > > > current TSO
> > > > > > > types?
> > > > > > > > > > > Konstantin
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > Traditionally, HW only recognize "known" tunnel type,
> > > > > > > > > > do TSO calculation based on L3/L4 headers known to
> > > > > > > > > > tunnel type. For example, it must be
> > > > > > > > > > L2 header after VXLAN, then L3. While this Generic
> > > > > > > > > > offloading provides inner/outer L3/L4 header info(len
> > > > > > > > > > and
> > > > > > > > > > offset) to HW, and thus tunnel info become less
> important.
> > > > > > > > > > Please note the MPLS over GRE tunnel in last example
> above.
> > > > > > > > >
> > > > > > > > > Ok, but I wonder when the user would like to do TSO on
> > > > > > > > > tunnel packet, for this offload - would he need to do
> > > > > > > > > something differently from what he has to do now:
> > > > > > > > > raise PKT_TX_TCP_SEG and related flags, raise
> > > > > > > > > appropriate
> > > > > > > > > PKT_TX_TUNNEL_* flag, fill l2_len, l3_len,
> > > > > > > l4_len,tso_segsz,outer_l2_len,outer_l3_len?
> > > > > > > > >
> > > > > > > >
> > > > > > > > Yes, these fields are sufficient except PKT_TX_TUNNEL_*,
> > > > > > > > major target of this new feature is to support "unknown"
> > > > > > > > tunnel offloading, it
> > > > > > > supports "known"
> > > > > > > > tunnel type as well.
> > > > > > >
> > > > > > > Ok, but user would still need to set some flag to indicate
> > > > > > > that this is a tunnel packet, and he wants TSO over it, right?
> > > > > > > For pre-defined tunnel types it can be one of
> > > > > > > PKT_TX_TUNNEL_* (which actually means that user still have
> > > > > > > to know tunnel type
> > > > > > > anyway?) But for some not defined tunnel type - what it would
> be?
> > > > > > > Konstantin
> > > > > > >
> > > > > >
> > > > > > As this feature target to TX path, Outer length as tunnel
> > > > > > indication, leave it empty if tunnel not defined.
> > > > >
> > > > > Sorry, I didn't get it.
> > > > > We need to let PMD know that it is a tunnel packet, right?
> > > > > So we do need to raise PKT_TX_TUNNEL_* flag.
> > > > >
> > > >
> > > > In my current code, mbuf.outer_l2_len is used to test tunnel packet.
> > > > Agree a new tunnel flag would be better.
> > > >
> > > > > >
> > > > > > But I think it good to define something like:
> > > > > >  	PKT_TX_TUNNEL_GENERIC = PKT_TX_TUNNEL_MASK
> > > > >
> > > > > Yes, that's an option, I would probably name it
> PKT_TX_TUNNEL_UNKNOWN.
> > > > >
> > > > > > And a new flag PKT_TX_OUTER_UDP, how do you think?
> > > > >
> > > > > Not sure why do we need it?
> > > > > HW still needs to know outer_l4_type to be able to work correctly?
> > > >
> > > > For tunnel type like vxlan, if outer UDP present, hw has to update
> > > > UDP length field for each TSO packet segment.
> > >
> > > I understand that, but I thought that HW is smart enough to parse
> > > the header and recognize outer L3/L4 type  - as it is a 'generic'
> > > tunneling (sorry I am not familiar with MLX HW at all).
> >
> > It might be useful if the outer encapsulation not regular, for example
> MPLS.
> >
> > > From what you saying - that assumption was wrong and user still
> > > need to provide some packet-type info at  least about outer headers,
> right?
> > > So what else need to be set?
> > > Probably PKT_TX_OUTER_IPV*, might be something else?
> >
> > Sorry for the confusion, besides optional outer UDP type, still need
> > PKT_TX_IPV4/6 and PKT_TX_OUTER_IPV4/6