Re: [dpdk-dev] [PATCH v2 1/3] ethdev: add new RSS types for IPv6 prefix

["Zhang, Qi Z" <qi.z.zhang@intel.com>]

> -----Original Message-----
> From: Thomas Monjalon <thomas@monjalon.net>
> Sent: Wednesday, July 8, 2020 8:26 PM
> To: Xing, Beilei <beilei.xing@intel.com>; Zhang, Qi Z <qi.z.zhang@intel.com>
> Cc: dev@dpdk.org; Guo, Jia <jia.guo@intel.com>; Guo, Junfeng
> <junfeng.guo@intel.com>; Su, Simei <simei.su@intel.com>; Yigit, Ferruh
> <ferruh.yigit@intel.com>; arybchenko@solarflare.com;
> viacheslavo@mellanox.com; jerinj@marvell.com;
> ajit.khaparde@broadcom.com; orika@mellanox.com
> Subject: Re: [dpdk-dev] [PATCH v2 1/3] ethdev: add new RSS types for IPv6
> prefix
> 
> 08/07/2020 14:05, Zhang, Qi Z:
> > From: Thomas Monjalon <thomas@monjalon.net>
> > > 08/07/2020 13:10, Zhang, Qi Z:
> > > > From: Thomas Monjalon <thomas@monjalon.net>
> > > > > 08/07/2020 11:45, Zhang, Qi Z:
> > > > > > On 2020/7/7 19:06, Thomas Monjalon wrote:
> > > > > > > 16/06/2020 10:16, Junfeng Guo:
> > > > > > >> This patch defines new RSS offload types for IPv6 prefix
> > > > > > >> with 32, 48,
> > > > > > >> 64 bits of both SRC and DST IPv6 address.
> > > > > > >>
> > > > > > >> Signed-off-by: Junfeng Guo <junfeng.guo@intel.com>
> > > > > > >> ---
> > > > > > >>   lib/librte_ethdev/rte_ethdev.h | 51
> > > > > ++++++++++++++++++++++++++++++++++
> > > > > > >>   1 file changed, 51 insertions(+)
> > > > > > >>
> > > > > > >> diff --git a/lib/librte_ethdev/rte_ethdev.h
> > > > > > >> b/lib/librte_ethdev/rte_ethdev.h index 631b146bd..5a7ba36d8
> > > > > > >> 100644
> > > > > > >> --- a/lib/librte_ethdev/rte_ethdev.h
> > > > > > >> +++ b/lib/librte_ethdev/rte_ethdev.h
> > > > > > >> @@ -538,6 +538,9 @@ struct rte_eth_rss_conf {
> > > > > > >>   #define ETH_RSS_L4_DST_ONLY        (1ULL << 60)
> > > > > > >>   #define ETH_RSS_L2_SRC_ONLY        (1ULL << 59)
> > > > > > >>   #define ETH_RSS_L2_DST_ONLY        (1ULL << 58)
> > > > > > >> +#define ETH_RSS_L3_PRE32           (1ULL << 57)
> > > > > > >> +#define ETH_RSS_L3_PRE48           (1ULL << 56)
> > > > > > >> +#define ETH_RSS_L3_PRE64           (1ULL << 55)
> > > > > > >
> > > > > > > PRE32, 48 and 64 are not obvious.
> > > > > > > Why is it needed?
> > > > > >
> > > > > > there is typical usage for NAT64, which use 32 bit prefix for
> > > > > > IPv6 addresses, in this case flows over IPv4 and IPv6 will
> > > > > > result in the same hash value, as well as 48, 64, which also
> > > > > > have some corresponding use cases,
> > > > > > > At least, please add comments for the values of this API.
> > > > > >
> > > > > > sure, we will add more comments.
> [...]
> > > > > > 32, 48, 64 are typical usage, and consider suffix pair we may
> > > > > > add later, it will cost 6 bits so far we still have 27 bit
> > > > > > left,  so it looks like will not be a problem in following couple
> releases.
> > > > >
> > > > > Having some space left is not a reason to waste it :) If I
> > > > > understand well, there is no standard for this API.
> > > > > You are assigning some bits to some usage.
> > > > > I don't find it generic and flexible enough.
> > > >
> > > > Actually IPv6 address prefix is in spec, please check below RFC.
> > > > https://tools.ietf.org/html/rfc6052#page-5
> > >
> > > Quoting the RFC:
> > > "
> > >    the prefix shall be either the "Well-Known Prefix"
> > >    or a "Network-Specific Prefix" unique to the organization
> > >    deploying the address translators.
> > >    The prefixes can only have one of the following lengths:
> > >    32, 40, 48, 56, 64, or 96.
> > >    (The Well-Known Prefix is 96 bits long, and can only be used
> > >    in the last form of the table.)
> > > "
> > >
> > > So 40 and 56 are missing.
> >
> > Yes, like to add and lets accelerate the progress to abandon the old
> > APIs :)
> 
> Please could list which part of the existing API you would like to deprecate in
> future?

I think it's a new version of rte_flow_action_rss, we need a more generic way to describe the RSS input set of a flow
But not just a 64 bits type, then all ETH_RSS_xxx will be decoupled from rte_flow.

> 
> 
> > > > So probably we are not wasting bits here, since this is a typical
> > > > usage that DPDK can provide.
> > > > Of cause more description is needed in the code here.
> > > >
> > > > > If you want to limit the size of the match, we should have a
> > > > > generic syntax to choose how many bits of the IPv6 address are
> > > > > taken into account for RSS. Or maybe an IPv6 mask.
> > > >
> > > > Yes, I believe at some moment, a more generic solution is
> > > > mandatory, And I think that will not work if we stick on the 64
> > > > bits, new API need to be introduced and old one should be
> > > > abandoned
> > > >
> > > > >
> > > > > > but anyway use 64 bits to represent RSS inputset can't meet
> > > > > > the coming complex RSS usage, we may need to figure out some
> > > > > > new APIs and
> > > > > abandon
> > > > > > the old one.
> > > > > > A stacked protocol layer with bit field selector in each layer
> > > > > > is under consideration, hope we can contribute some RFC at
> > > > > > some
> > > moment.
> > > > > > also feel free let us know your thought.
> > > > >
> > > > > My thought is to discuss how to fit this need in future and
> > > > > avoid adding few bits of temporary workaround.
> > > > > API definition is serious and we must avoid temporary half solutions.
> 
>