[dpdk-dev] [PATCH v3 08/13] testpmd: rework csum forward engine
jijiang.liu at intel.com
Thu Nov 27 09:34:05 CET 2014
> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Thursday, November 27, 2014 12:35 AM
> To: Olivier MATZ; dev at dpdk.org
> Cc: Walukiewicz, Miroslaw; Liu, Jijiang; Liu, Yong; jigsaw at gmail.com; Richardson,
> Subject: RE: [PATCH v3 08/13] testpmd: rework csum forward engine
> Hi Oliver,
> > -----Original Message-----
> > From: Olivier MATZ [mailto:olivier.matz at 6wind.com]
> > Sent: Wednesday, November 26, 2014 2:55 PM
> > To: Ananyev, Konstantin; dev at dpdk.org
> > Cc: Walukiewicz, Miroslaw; Liu, Jijiang; Liu, Yong; jigsaw at gmail.com;
> > Richardson, Bruce
> > Subject: Re: [PATCH v3 08/13] testpmd: rework csum forward engine
> > Hi Konstantin,
> > On 11/26/2014 01:25 PM, Ananyev, Konstantin wrote:
> > >> By the way (this is probably off-topic), but I'm wondering if the
> > >> TX flags should have the same values than the RX flags:
> > >>
> > >> #define PKT_TX_IPV4 PKT_RX_IPV4_HDR
> > >> #define PKT_TX_IPV6 PKT_RX_IPV6_HDR
> > >
> > > Thought about that too.
> > > From one side, it is a bit out of our concept: separate RX and TX falgs.
> > > From other side, it allows us to save 2 bits in the ol_flags.
> > > Don't have any strong opinion here.
> > > What do you think?
> > I have no strong opinion too, but I have a preference for 2 different
> > bit values for these flags:
> > - as you say, it's matches the concept (RX and TX flags are separated)
> > - 64 bits is a lot, we have some time before there is no more available
> > bit... and I hope we it will never occur because it would become
> > complex for an application to handle them all
> > - it will avoid to send a packet with a bad info:
> > - we receive a Ether/IP6/IP4/L4/data packet
> > - the driver sets PKT_RX_IPV6_HDR
> > - the stack decapsulates IP6
> > - the stack sends the packet, it has the PKT_TX_IPV6 flag but it's an
> > IPv4 packet
> Ah yes, you right, if we keep them the same, then upper layer always has to clear
> PKT_RX_IPV4_HDR | PKT_RX_IPV6_HDR before setting TX offload flags and
> passing packet to the PMD for TX.
> And if the upper layer wouldn't do that - it might cause a problem.
> With your example above - if at last step the stack sets PKT_TX_IP_CKSUM for
> the packet, then PMD will receive an mbuf with (PKT_TX_IPV6 |
> PKT_TX_IP_CKSUM) set.
> Though from PKT_TX_IP_CKSUM/ PKT_TX_IPV6/ PKT_TX_IPV4 only one can be
> set, as they are mutually exclusive.
> So i40e PMD will get confused and might not be able to arm TX descriptor
> So yes, we need to make them a proper TX flags.
I have changed definitions of the two flags in the patch of rework VXLAN TX checksum.
> Thanks for spotting it.
> > This is not a real problem as the flag will not be used by the
> > driver/hardware (it's only mandatory for hw cksum / tso), but
> > it can be confusing.
> > Regards,
> > Olivier
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