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

[Liu, Jijiang]

Hi,

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Wednesday, January 7, 2015 8:07 PM
> To: Liu, Jijiang; 'Olivier MATZ'
> Cc: dev at dpdk.org
> Subject: RE: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and
> csum forwarding engine
> 
> 
> 
> > -----Original Message-----
> > From: Liu, Jijiang
> > Sent: Wednesday, January 07, 2015 11:39 AM
> > To: Ananyev, Konstantin; 'Olivier MATZ'
> > Cc: dev at dpdk.org
> > Subject: RE: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and
> > csum forwarding engine
> >
> > Hi Konstantin,
> >
> > > -----Original Message-----
> > > From: Ananyev, Konstantin
> > > Sent: Wednesday, January 7, 2015 5:59 PM
> > > To: Liu, Jijiang; 'Olivier MATZ'
> > > Cc: dev at dpdk.org
> > > Subject: RE: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum command
> > > and csum forwarding engine
> > >
> > > Hi Frank,
> > >
> > > > -----Original Message-----
> > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Liu, Jijiang
> > > > Sent: Wednesday, January 07, 2015 2:04 AM
> > > > To: 'Olivier MATZ'
> > > > Cc: dev at dpdk.org
> > > > 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: Saturday, December 13, 2014 12:33 AM
> > > > > To: Liu, Jijiang
> > > > > Cc: dev at dpdk.org
> > > > > Subject: Re: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum
> > > > > command and csum forwarding engine
> > > > >
> > > > > Hello,
> > > > >
> > > > > On 12/12/2014 04:48 AM, Liu, Jijiang wrote:
> > > > > > The 'hw/sw' option  is used to set/clear the flag of enabling
> > > > > > TX tunneling packet
> > > > > checksum hardware offload in testpmd application.
> > > > >
> > > > > This is not clear at all.
> > > > > In your command, there is (hw|sw|none).
> > > > > Are you talking about inner or outer?
> > > > > Is this command useful for any kind of packet?
> > > > > How does it combine with "tx_checksum set outer-ip (hw|sw)"?
> > > > >
> > > >
> > > > I rethink these TX checksum commands in this patch set and agree
> > > > with you that we should make some changes for having clear meaning for
> them.
> > > >
> > > > There are  3 commands in patch set as follows, 1. tx_checksum set
> > > > tunnel (hw|sw|none) (port-id)
> > > >
> > > > Now I also think the command 1 may confuse user, they probably
> > > > don't understand  why we need 'hw' or 'sw' option and when  to use
> > > > the two option, so I will replace the command with 'tx_checksum
> > > > set hw-tunnel-mode
> > > (on|off) (port-id)' command.
> > >
> > > I am a bit confused here, could you explain what would be a
> > > behaviour for 'on' and 'off'?
> > > Konstantin
> >
> > I have explained the behaviour for 'on' and'off' below,
> >
> > The command 'tx_checksum set hw-tunnel-mode (on|off)  (port-id)' is
> > used to set/clear  TESTPMD_TX_OFFLOAD_TUNNEL_CKSUM flag.
> >
> > Actually, the PKT_TX_UDP_TUNNEL_PKT offload flag will be set if the
> > testpmd flag is set, which means to tell HW treat  that transmit
> > packet as a tunneling packet to do checksum offload  When 'on' is set, which is
> able to meet Method B.1 and method C.
> >
> > When 'off' is set, the TESTPMD_TX_OFFLOAD_TUNNEL_CKSUM is not needed
> > to set, so the PKT_TX_UDP_TUNNEL_PKT offload flag is not needed to
> > set,  then HW treat  that transmit packet as a non-tunneling packet. It is able to
> meet Method B.2.
> >
> > Is the explanation not clear?
> 
> Ok, and how I can set method A (testpmd treat all packets as non-tunnelling and
> never look beyond outer L4 header) then?
> Konstantin


> > > > As to case A, I think it is not mandatory to cover it in csum fwd
> > > > engine for tunneling packet.

If you think the case A is essential, and it must be covered in  csum fwd, then we can add a command:

tx_checksum set sw-tunnel-mode (on|off)  (port-id)

if the 'off' is set ,  csum fwd engine don't check  if that packet is a tunneling packet and treat all packets as non-tunneling and never look beyond outer L4 header.

if the 'on' is set,  csum fwd engine will check if that packet is a tunneling packet.

And we are able to test all of cases in  http://dpdk.org/ml/archives/dev/2014-December/009213.html

Test case A:

tx_checksum set sw-tunnel-mode off
tx_checksum set hw-tunnel-mode off
tx_checksum set  ip   hw

test case B.1:

tx_checksum set sw-tunnel-mode on
tx_checksum set hw-tunnel-mode on
tx_checksum set  ip   hw
tx_checksum set  tcp   hw

test case B.2:

tx_checksum set sw-tunnel-mode on
tx_checksum set hw-tunnel-mode off
tx_checksum set  ip   hw

test case C:

tx_checksum set sw-tunnel-mode on
tx_checksum set hw-tunnel-mode on
tx_checksum set  outer-ip   hw
tx_checksum set  ip   hw
tx_checksum set  tcp   hw


 In addition, the reason of discarding ' tx_checksum set  tunnel (hw|sw|none) (port-id)' command is that  user probably confuse the following case.
 tx_checksum set  tunnel sw
tx_checksum set  ip   hw

In fact, we are still using hardware TX checksum offload in this case,  but the command " tx_checksum set  tunnel sw"  seems tell user that software compute the checksum.

> >
> > >
> > > >
> > > > 2. tx_checksum set outer-ip (hw|sw) (port-id) 3. tx_checksum set
> > > > (ip|udp|tcp|sctp) (hw|sw) (port-id)
> > > >
> > > > The command 2 will be merged into command 3, the new command is '
> > > > tx_checksum set  (outer-ip|ip|udp|tcp|sctp) (hw|sw) (port- id)'.
> > > >
> > > > These most of the cases in
> > > > http://dpdk.org/ml/archives/dev/2014-December/009213.html will be
> > > > covered by using the two commands
> > > >
> > > > The command 'tx_checksum set hw-tunnel-mode (on|off)  (port-id)'
> > > > is used to set/clear  TESTPMD_TX_OFFLOAD_TUNNEL_CKSUM flag.
> > > > Actually, the PKT_TX_UDP_TUNNEL_PKT offload flag will be set if
> > > > the testpmd flag is set, which tell driver/HW treat  that transmit
> > > > packet as a
> > > tunneling packet.
> > > >
> > > > When 'on' is set, which is able to meet Method B.1 and method C.
> > > >
> > > > When 'off' is set, the TESTPMD_TX_OFFLOAD_TUNNEL_CKSUM is not
> > > > needed to set, so the PKT_TX_UDP_TUNNEL_PKT offload flag is not
> > > > needed to set,  then
> > > HW treat  that transmit packet as a non-tunneling packet. It is able
> > > to meet Method B.2.
> > > >
> > > > As to case A, I think it is not mandatory to cover it in csum fwd
> > > > engine for
> > > tunneling packet.
> > > >
> > > > Is the above description clear for you?
> > > >
> > > > > Regards,
> > > > > Olivier