[dpdk-dev] [PATCH v6 1/9] librte_mbuf:the rte_mbuf structure changes
helin.zhang at intel.com
Wed Nov 12 15:31:50 CET 2014
> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com]
> Sent: Wednesday, November 12, 2014 9:26 PM
> To: Liu, Jijiang
> Cc: Zhang, Helin; dev at dpdk.org; Richardson, Bruce
> Subject: Re: [dpdk-dev] [PATCH v6 1/9] librte_mbuf:the rte_mbuf structure
> Hi guys,
> We still have some problems with the mbuf changes introduced for VXLAN.
> I want to raise the packet type issue here.
> 2014-10-23 02:23, Zhang, Helin:
> > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Thomas Monjalon
> > > 2014-10-21 14:14, Liu, Jijiang:
> > > > From: Thomas Monjalon [mailto:thomas.monjalon at 6wind.com]
> > > > > 2014-10-21 16:46, Jijiang Liu:
> > > > > > - uint16_t reserved2; /**< Unused field. Required for padding */
> > > > > > +
> > > > > > + /**
> > > > > > + * Packet type, which is used to indicate ordinary L2 packet
> format and
> > > > > > + * also tunneled packet format such as IP in IP, IP in GRE, MAC in
> > > > > > + * and MAC in UDP.
> > > > > > + */
> > > > > > + 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
> > 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:
> > > > 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:
> Regarding adding a packet_type in mbuf, we ever had a lot of discussions as
> 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
Though I haven't investigate this too much, my opinion is that we should
use packet_type in the future, and rework igb/ixgbe PMD to remove all
packet types in ol_flags and use packet_type instead.
Then example app can use the packet type directly. And all igb, ixgbe and
i40e packet_type are consistent. Sure we might need to define all packet
types in rte_ethdev.h or similar header files.
> 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).
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