Re: [dpdk-dev] [PATCH v6 1/9] librte_mbuf:the rte_mbuf structure changes

[Thomas Monjalon <thomas.monjalon@6wind.com>]

2014-11-13 03:17, Liu, Jijiang:
> From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > 2014-10-23 02:23, Zhang, Helin:
> > > From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Thomas Monjalon
> > > > 2014-10-21 14:14, Liu, Jijiang:
> > > > > From: Thomas Monjalon [mailto:thomas.monjalon@6wind.com]
> > > > > > 2014-10-21 16:46, Jijiang Liu:
> > > > > > > +	uint16_t packet_type;
> > > > > >
> > > > > > Why not name it "l2_type"?
> > >
> > > 'packet_type' is for storing the hardware identified packet type upon
> > > different layers of protocols (l2, l3, l4, ...).
> > > It is quite useful for user application or middle layer software
> > > stacks, it can know what the packet type is without checking the packet too
> > much by software.
> > > Actually ixgbe already has packet types (less than 10), which is transcoded into
> > 'ol_flags'.
> > > For i40e, the packet type can represent about 256 types of packet,
> > > 'ol_flags' does not have enough bits for it anymore. So put the i40e packet types
> > into mbuf would be better.
> > > Also this field can be used for NON-Intel NICs, I think there must be
> > > the similar concepts of other NICs. And 16 bits 'packet_type' has severl
> > reserved bits for future and NON-Intel NICs.
> > 
> > Thanks Helin, that's the best description of packet_type I've seen so far.
> > It's not so clear in the commit log:
> > 	http://dpdk.org/browse/dpdk/commit/?id=73b7d59cf4f6faf
> > 
> > > > > In datasheet, this term is called packet type(s).
> > > >
> > > > That's exactly the point I want you really understand!
> > > > This is a field in generic mbuf structure, so your datasheet has no value here.
> > > >
> > > > > Personally , I think packet type is  more clear what meaning of this field is .
> > > >
> > > > You cannot add an API field without knowing what will be its generic meaning.
> > > > Please think about it and describe its scope.
> > 
> > I integrated this patch with the VXLAN patchset in the hope that you'll improve
> > the situation afterwards.
> > This is the answer you recently gave to Olivier:
> > 	http://dpdk.org/ml/archives/dev/2014-November/007599.html
> > "
> > 	Regarding adding a packet_type in mbuf, we ever had a lot of discussions
> > as follows:
> > 	http://dpdk.org/ml/archives/dev/2014-October/007027.html
> > 	http://dpdk.org/ml/archives/dev/2014-September/005240.html
> > 	http://dpdk.org/ml/archives/dev/2014-September/005241.html
> > 	http://dpdk.org/ml/archives/dev/2014-September/005274.html
> > "
> > 
> > To sum up the situation:
> > - We don't know what are the possible values of packet_type
> > - It's only filled by i40e, while other drivers use ol_flags
> > - There is no special value "unknown" which should be set by drivers
> >   not supporting this feature.
> > - Its only usage is to print a decimal value in app/test-pmd/rxonly.c
> > 
> > It's now clear that nobody cares about this part of the API.
> > So I'm going to remove packet_type from mbuf.
> > I don't want to keep something that we don't know how to use, that is not
> > consistent across drivers, and that overlap another API part (ol_flags).
> 
> The packet type in 40e is very important for user, using packet type can
> help to speed up packet analysis/identification in their application,
> especially tunneling packet format.
> Now I'm working on implementing packet type definition in rte_ethdev.h
> file and  translation table in i40e, which is almost done. 
> The packet type  definition in in rte_ethdev.h file like below. 
> /*
>  * Ethernet packet type
>  */
> enum rte_eth_ptype {
>         /* undefined packet type, means HW can't recognise it */
>         RTE_PTYPE_UNDEF = 0,
> ...
> 
>         /* IPv4 --> GRE/Teredo/VXLAN --> MAC --> IPv4 */
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv4FRAG_PAY3,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv4_PAY3,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv4_UDP_PAY4,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv4_TCP_PAY4,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv4_SCTP_PAY4,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv4_ICMP_PAY4,
>  
>         /* IPv4 --> GRE/Teredo/VXLAN --> MAC --> IPv6 */
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv6FRAG_PAY3
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv6_PAY3,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv6_UDP_PAY4,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv6_TCP_PAY4,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv6_SCTP_PAY4,
>         RTE_PTYPE_IPv4_GRENAT_MAC_IPv6_ICMP_PAY4,
>  
>         /* IPv4 --> GRE/Teredo/VXLAN --> MAC/VLAN */
>         RTE_PTYPE_IPv4_GRENAT_MACVLAN_PAY3,
> ... 
> }

OK, it seems well abstracted.
I think the last part of these names (PAY3/PAY4) is useless.

When this patch for API and i40e will be ready?
I'd prefer fixing the API instead of removing it.

> Yes, we don't use packet type in many places now, which doesn't mean
> we don't use it  in the future (when supporting another tunneling packet).
> 
> It is ok for me if you want to remove the packet_type filed in mbuf,
> but we will send a separate patch set for introducing packet type in
> the future, which includes 1g/10/40g PMD changes.

When the patches for igb/ixgbe will be ready?

Thanks
-- 
Thomas