Hi Qinglai,
>> Besides, as you mentioned, the ixgbe driver doesn't leverage the hardware
>> receive checksum offloading at all.
On the Rx side, ixgbe driver support the Rx checksum validation via hardware
offload. There is a simple example @ DPDK\app\test-pmd\csumonly.c to check
IPv4/L4 checksum error~
/* Update the L3/L4 checksum error packet count */
rx_bad_ip_csum += (uint16_t) ((pkt_ol_flags &
PKT_RX_IP_CKSUM_BAD) != 0);
rx_bad_l4_csum += (uint16_t) ((pkt_ol_flags &
PKT_RX_L4_CKSUM_BAD) != 0);
-----Original Message-----
From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of jigsaw
Sent: Saturday, October 05, 2013 3:11 AM
To: Venkatesan, Venky
Cc: dev at dpdk.org
Subject: Re: [dpdk-dev] [PATCH] Request for comments on ixgbe TSO support
Hi Stephen,
Thanks for showing a bigger picture.
GSO is quite big implementation, that I think it won't be easily ported to
DPDK. The mbuf needs to be equipped with many fields from skb to be able to
deal with GSO.
Do you have the plan to port GSO to DPDK, or you would like to keep GSO in
scope of virtio?
Regarding checksum flags, actually I was also thinking of extending ol_flags
but then I gave it up coz I was worried about the size of mbuf.
My current patch has to push some work to user, due to the fact that mbuf
delivers too few info (such as L2 and L3 protocol details).
Besides, as you mentioned, the ixgbe driver doesn't leverage the hardware
receive checksum offloading at all. And if this is to be supported, the
checksum flag need further extension.
(On the other hand, TSO doesn't care about receive checksum offloading).
Again, do you have plans to extend cksum flags so that virio feels more
comfortable with DPDK?
Hi Venky,
I can either make the commit now as is, or wait till the cksum flags extension
is in place. If Stephen (or somebody else) has the plan for better support for
cksum offloading or GSO, it is perhaps better to implement TSO on top of that.
BTW, I have another small question. Current TSO patch offloads the TCP/IP
pseudo cksum work to user. Do you think DPDK could provide some utility
functions for TCP/IPv4/IPv6 pseudo cksum calculation and updating?
thx &
rgds,
-Qinglai
On Fri, Oct 4, 2013 at 9:38 PM, Venkatesan, Venky <venky.venkatesan at
intel.com> wrote:
> Stephen,
>
> Agree on the checksum flag definition. I'm presuming that we should do this
> on the L3 and L4 checksums separately (that ol_flags field is another one
> that needs extension in the mbuf).
>
> Regards,
> -Venky
>
>
> -----Original Message-----
> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Stephen Hemminger
> Sent: Friday, October 04, 2013 11:23 AM
> To: jigsaw
> Cc: dev at dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] Request for comments on ixgbe TSO
> support
>
> On Fri, 4 Oct 2013 20:54:31 +0300
> jigsaw <jigsaw at gmail.com> wrote:
>
>> Hi Stephen,
>>
>>
>> >>This will work for local generated packets but overlapping existing field
>> >>won't work well for forwarding.
>> So adding a new mss field in mbuf could be the way out? or I
>> misunderstand something.
>>
>> >> What we want to be able to do is to take offload (jumbo) packets
>> >> in with from virtio
>> Sorry I don't understand why TSO is connected to virtio. Could you
>> give more details here?
>> Are you suggesting this TSO patch overlaps your work, or it should be
>> based on your work?
>
> I am working on a better virtio driver. Already have lots more features
> working, and doing better offload support is planned.
>
> TSO is a subset of the more generic segment offload (GSO) on Linux.
> With virtio is possible to receive GSO packets as well as send them.
> This feature is negotiated between guest and host.
>
> The idea is that between guests they can exchange jumbo (64K) packets even
> with a smaller MTU. This helps in many ways. One example is only a single
> route lookup is needed.
>
> Another issue is that the current DPDK model of offload flags for checksum is
> problematic.
> It matches what is available in Intel hardware and is not easily
> generalizable to other devices.
>
> Current DPDK flag is checksum bad. I would like to change it to
> checksum known good. Then drivers which dont' do checksum would leave
> it 0, but if receive checksum is known good set it to 1. Basically 1
> means known good, and
> 0 means unknown (or bad). Higher level software can then do sw checksum if
> necessary.
