[dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and csum forwarding engine

[Ananyev, Konstantin]

Hi lads,

> -----Original Message-----
> From: Liu, Jijiang
> Sent: Wednesday, January 14, 2015 3:01 AM
> To: Olivier MATZ
> Cc: dev at dpdk.org; Ananyev, Konstantin
> Subject: RE: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and csum forwarding engine
> 
> Hi Olivier,
> 
> > -----Original Message-----
> > From: Olivier MATZ [mailto:olivier.matz at 6wind.com]
> > Sent: Tuesday, January 13, 2015 5:56 PM
> > To: Liu, Jijiang
> > Cc: dev at dpdk.org; Ananyev, Konstantin
> > Subject: Re: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and
> > csum forwarding engine
> >
> > Hi Jijiang,
> >
> > On 01/13/2015 04:04 AM, Liu, Jijiang wrote:
> > > the following two commands are.
> > >
> > > 1. tx_checksum set sw-tunnel-mode on/off
> > >
> > > 2. tx_checksum set hw-tunnel-mode on/off
> > >
> > > For command 1, If the sw-tunnel-mode is set/clear, which will
> > > set/clear a testpmd flag that is used in the process of analyzing
> > > incoming packet., the pseudo-codes are list below,
> > >
> > > If (sw-tunnel-mode)
> > >
> > > 	Csum fwd engine will analyze if incoming packet is a tunneling packet.
> > >                 tunnel = 1;
> > > else
> > >             Csum fwd engine will not analyze if incoming packet is a tunneling
> > packet, and treat all the incoming packets as non-tunneling packets.
> > >             It is used for A.
> >
> > What about "recognize-tunnel" instead of "sw-tunnel-mode"?
> > Or "parse-tunnel"?
> 
> Ok,  "parse-tunnel" or "parse-tunnel-pkt" is better.
> Thanks.
> 
> 
> > To me, using "sw-" or "hw-" prefix is confusing because in any case the checksums
> > can be calculated in software or hardware depending on "tx_checksum set outer-
> > ip hw|sw".
> >
> > Moreover, this command has an impact on receive side, but the name is still
> > "tx_checksum". Maybe this is also confusing.
> Ok,  how about this?
> 
> set  checksum parse-tunnel-pkt on|off  (port-id)
> 
> > > For command 2, If the hw-tunnel-mode is set/clear, which will
> > > set/clear a testpmd flag that is used in the process of how to handle
> > > tunneling packet, the pseudo-codes are list below,
> > >
> > > if (tunnel == 1) { // this is a tunneling packet
> > >              If (hw-tunnel-mode)
> > >                        ol_flags |= PKT_TX_UDP_TUNNEL_PKT;
> > >
> > > 	       Csum fwd engine set PKT_TX_UDP_TUNNEL_PKT offload flag, which
> > means to tell HW treat  the transmit packet as a tunneling packet to do checksum
> > offload.
> > > 	       It is used for B.1
> > >             Else
> > >                        Csum fwd engine doesn't  set PKT_TX_UDP_TUNNEL_PKT offload
> > flag, which means  tell HW to treat the packet as ordinary (non-tunnelled) packet.
> > > 	      It is used for B.2
> > > }
> >
> > What about:
> >    tx_checksum set tunnel-method normal|outer
> > It would select if we use lX_len or outer_lX_len. Is it what you mean?
> 
> tx_checksum set tunnel-method normal|outer
> 
> Let me explain that what differences of  TX checksum mechanism between ixgbe(82599) and i40e(40G NIC) are.
> 
> For 82599, there is only one register that is used for L3 checksum offload. So for tunneling packet, hardware is unable to recognize the
> packet is tunneling packet and  the register cannot be worked for both outer L3 checksum offload and inner L3 checksum offload at the
> same time,  just for outer or inner.
> 
> For i40e(40G NIC),  there are two registers that are user for L3 TX checksum offload, so for tunneling packet, the outer and inner L3
> checksum offload  can be done by hardware at the same time, but a prerequisite is that we must tell
> Hardware the packet is a tunneling packet by setting a register (PKT_TX_UDP_TUNNEL_PKT offload flag is used to indicate to set this
> register.)
> 
> As for other NIC, I think its working mechanism should be same as the i40e if it can recognize tunneling packet.
> 
> So my idea:
> tx_checksum set tunnel-method  tunnel-pkt on|off
> 
> or
> tx_checksum set tunnel-pkt on|off
> 
> What do you think?
> 
> 
> > And this only makes sense when we use hw checksum right?
> yes
> 
> >
> > >> And will it be possible to support future hardware that will be able
> > >> to compute both outer l3, outer l4, l3 and l4 checksums?
> 
> Currently, if outer l4  will be supported in the future, and we can add outer-udp/tcp option into following command.
> Tx_checksum set outer-ip|ip|sctp|udp|tcp.
> 
> 
> > > Yes.
> > > Currently, i40e support outer l3, outer l4, l3 and l4 checksums offload at the
> > same time.
> Sorry, my bad.
> I40e just support outer l3, l3 and l4.
> 
> Fortville can offload the following L3 and L4 integrity checks: IPv4 header(s) checksum for "simple" and tunneled packets, Inner TCP or
> UDP checksum and SCTP CRC integrity. Tunneling UDP headers and GRE header are not offloaded while Fortville leaves their checksum
> field as is. If a checksum is required, software should provide it as well as the inner checksum value(s) that are required for the outer
> checksum.
> 
> >
> > >> I have another idea, please let me know if you find it clearer or not.
> > >> The commands format would be:
> > >>
> > >> tx_checksum <pkt-type> <field1> <action1> <field2> <action2> ...
> > >>
> > >> [...]
> > >>
> > >> What do you think?
> > >
> > > Thanks for your proposal.
> > > It is clear for me.
> > >
> > > But there are two questions for me.
> > >
> > > As I know, in current command line framework, the option in command line is
> > exact match, so you probably have to add duplicated codes when you want to
> > support a new packet types.
> >
> > I don't think it's really a problem. The cmdline library supports string list, so can
> > have the following 3 commands definitions:
> >
> > 1. tx_checksum
> > ip-udp|ip-tcp|ip-sctp|vxlan-ip-udp|vxlan-ip-tcp|vxlan-ip-sctp l3
> > off|sw|hw l4 off|sw|hw
> > 2. tx_checksum ip-other|vxlan-ip-other l3 off|sw|hw 3. tx_checksum vxlan
> > outer-l3 off|sw|hw outer-l4 off|sw|hw
> >
> > Maybe 1 and 2 could be splitted in non-vxlan and vxlan. But only the structure
> > should be redefined to have a different help string, not the callback function.
> 
> 
> Ok, but I think you probably need to add many string in the list :)
> 
> > > Other question:
> > >
> > > Currently, the following testpmd flag is for per port, not for per packet type,
> > when they are set, which will affect whole port, not just for packet type or format,
> > if you  add  <pkt-type> option in cmdline, which means you have to other
> > changes.
> > >
> > > /** Offload IP checksum in csum forward engine */
> > > #define TESTPMD_TX_OFFLOAD_IP_CKSUM          0x0001
> > > /** Offload UDP checksum in csum forward engine */
> > > #define TESTPMD_TX_OFFLOAD_UDP_CKSUM         0x0002
> > > /** Offload TCP checksum in csum forward engine */
> > > #define TESTPMD_TX_OFFLOAD_TCP_CKSUM         0x0004
> > > /** Offload SCTP checksum in csum forward engine */
> > > #define TESTPMD_TX_OFFLOAD_SCTP_CKSUM        0x0008
> > > /** Offload VxLAN checksum in csum forward engine */
> > > #define TESTPMD_TX_OFFLOAD_VXLAN_CKSUM       0x0010
> >
> > We can add a portid in each command.
> 
> Ok, but I think your idea will make the csum fwd engine more complicated.
> 
> > > Of course, it is welcome if you can send this patch set with this idea for
> > community review.
> > Let's first agree on the user API :)
> 
> If you don't have more comments and questions on my current solution, I will send new patch set.
> Or you can send your patch.
> Anyway, our goal is the same.

To be honest, there are so many mails around that subject, so I am already lost :)
Oliver, as I understand you are not happy with the test-pmd commands Frank is proposing.
Both syntax and semantics.
Is that correct?
If so, could you suggest something from your side?
That would allow to configure test-pmd to behave in any of 4 possible ways we discussed previously:
http://dpdk.org/ml/archives/dev/2014-December/009213.html
Thanks
Konstantin

> 
> >
> > Regards,
> > Olivier
> >
> >