Re: [PATCH v2 0/4] net: Checksum offload changes - Part IV

Don't do skb_checksum more than once per packet

Was wondering in which cases does the stack perform the checksum more
than once? __skb_checksum_complete_head() already sets the ip_summed
to CHECKSUM_UNNECESSARY, so future checksum calculations are avoided.
What am I missing?

Thanks
Sharat

On Wed, Jun 11, 2014 at 4:46 PM, David Miller [off-list ref] wrote:

From: Tom Herbert <redacted>
Date: Tue, 10 Jun 2014 18:54:03 -0700 (PDT)

quoted

I am working on overhauling RX checksum offload. Goals of this effort
are:

- Specify what exactly it means when driver returns CHECKSUM_UNNECESSARY
- Preserve CHECKSUM_COMPLETE through encapsulation layers
- Don't do skb_checksum more than once per packet
- Unify GRO and non-GRO csum verification as much as possible
- Unify the checksum functions (checksum_init)
- Simply code

What is in this fourth patch set:

- Preserve CHECKSUM_COMPLETE instead of changing it to
  CHECKSUM_UNNECESSARY. This allows correct reuse in validating multiple
  csums in a packet.
- When SW needs to compute the packet checksum, save it as
  CHECKSUM_COMPLETE. Also mark that checksum was compute by SW.
- Add skb_gro_postpull_rcsum to udp and vxlan to make GRO work with
  CHECKSUM_COMPLETE.

v2: Removed patch setting skb_encapsulation when validating checksum
    in tcp_gro_receive

Please review carefully and test if possible, mucking with basic
checksum functions is always a little precarious :-)

Series applied, thanks Tom.
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