On 10 October 2016 at 17:50, Bill Fischofer <bill.fischo...@linaro.org>
wrote:

> This patch adds support for packet references and splices following
> discussions at LAS16 on this subject.
>
> I've changed things around from Petri's original proposal by splitting this
> into two separate APIs: odp_packet_splice() and odp_packet_ref(), where the
> latter is just a splice of a zero-length header on to a base packet. The
> various odp packet manipulation APIs have also been enhanced to behave
> sensibly when presented with a spliced packet as input. Reference counts
> are
> used to enable odp_packet_free() to not free a packet until all splices
> based
> on it are also freed.
>
Seems OK.


>
> Also added are two new APIs for working with spliced packets as these seem
> necessary for completeness:
>
> - odp_packet_is_a_splice() tells whether an input packet is a splice, and
> if
> so how many spliced packets it contains
>
> - odp_packet_is_spliced() tells whether any splices have been created on
> this
> packet, and if so how many.
>
Is there any conceptual difference between the base packet and any splices?

Can you add a splice to a splice?


>
> Note that there is no odp_packet_unsplice() API. To remove a splice from a
> base packet currently requres that the splice be freed via an
> odp_packet_free() call. We should discuss and decide if such an API is
> warranted for symmetry.
>
As long as odp_packet_free() respects any additional references (to
segments)
caused by splicing, I don't think we need any free splice call. How would
it be
different from odp_packet_free()?

What happens when you truncate the tail? E.g. of the base packet?
Does this affect the splices? (I prefer not).

To use this splice API for fragmentation, you want to be able to add
splices with new
L2/IP headers at suitable places (at each MTU point) and then truncate the
base packet
so that only the just added splice refers the the data beyond the new end
of the base
packet.

It would be useful to use the API for reassembly. Splice fragment N onto
fragment N+1
(after the IP header of frag N+1) and free fragment N+1. Repeat for all
fragments from
last to first. The splice for the first fragment will then refer to the
complete reassembled
datagram.

It seems like these use cases should be supported by this API if the
specification is
written with this in mind.

I will check the later patches as well. We have a bunch of use cases define
here:
https://docs.google.com/document/d/1r4olxr39fHvgFACQp_1RL_mh9736no3TFaVM7_XkUtM/edit



>
> Changes for v4:
> - Add negative tests to validation test suite
> - Fix implementation bugs relating to negative tests
>
> Changes for v3:
> - Bug fixes (detected by the validation tests)
> - Addition of validation tests for these new APIs
> - Diagrams and User Guide documentation for these new APIs
>
> Changes for v2:
> - Bug fixes
> - Enhance ODP packet segment APIs to behave properly with spliced packets
>
> Bill Fischofer (5):
>   api: packet: add support for packet splices and references
>   linux-generic: packet: implement splice/reference apis
>   validation: packet: add packet splice/reference tests
>   doc: images: add images for packet splice/reference documentation
>   doc: userguide: add user documentation for packet splice/reference
>     APIs
>
>  doc/images/doublesplice.svg                        |  67 ++++++
>  doc/images/pktref.svg                              |  49 +++++
>  doc/images/splice.svg                              |  64 ++++++
>  doc/users-guide/users-guide-packet.adoc            | 118 ++++++++++
>  include/odp/api/spec/packet.h                      | 103 +++++++++
>  .../linux-generic/include/odp_packet_internal.h    |  54 ++++-
>  platform/linux-generic/odp_packet.c                | 241
> ++++++++++++++++++---
>  test/common_plat/validation/api/packet/packet.c    | 176 +++++++++++++++
>  test/common_plat/validation/api/packet/packet.h    |   1 +
>  9 files changed, 836 insertions(+), 37 deletions(-)
>  create mode 100644 doc/images/doublesplice.svg
>  create mode 100644 doc/images/pktref.svg
>  create mode 100644 doc/images/splice.svg
>
> --
> 2.7.4
>
>

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