Hi Alex,
> I already thought many times to introduce something like that. Here is a draft
> for introducing the generic 6lowpan private data into each lowpan interface.
> For the beginning I introduced the enum "lltype" which contains the LL type of
> a lowpan interface.
>
> Use cases for such feature (LL types):
>
> - If we do in upper layers (6LoWPAN/IPv6) a evaluation of dev->type then
> the value is on all lowpan interfaces "APRHRD_6LOWPAN". If we checked on
> "dev->type" and it's ARPHRD_6LOWPAN we can safe use lowpan_priv to get
> 6LoWPAN generic private data. With this data we can check the LL type which
> can be currently BTLE or IEEE802154. This could be useful to make different
> handling in iphc compress/decompress and evaluating LL private data of skb
> control block "skb->cb".
>
> Example (802.15.4 has different address handling functionality):
>
> switch (lowpan_priv(dev)->lltype) {
> case LOWPAN_LLTYPE_BTLE:
> /* do EUI64 btle handling */
> break;
> case LOWPAN_LLTYPE_IEEE802154:
> /* do complicated short/extended address handling */
> /* we can surely call skb->cb to some other private data from LL
> which was set before iphc compress/decompress function call */
> break;
> }
>
> The handling is currently for 802.15.4 is in generic 6lowpan code currently
> not quite. This should be handled by private data. At the moment btle use
> the same handling like for 802.15.4 extended address. Nevertheless is we can
> cleanup some handling then in generic iphc functionality.
>
> This also possible in layers like IPv6, just doing a check on APRHRD_6LOWPAN
> before calling lowpan_priv(dev)->lltype, then we are sure that the private
> data of the interface is a 6LoWPAN interface and we can cast it to lowpan_priv.
> Then we can do 6LoWPAN generic stuff OR 6lowpan specific LL stuff.
>
> - In Lukasz Duda RFC for introducing stateful address compression, I saw
> some behaviour which such functionality is also useful. Currently we don't
> have a allocated space for a 6LoWPAN generic space which is assigned to a
> lowpan interface. When LL layers (BTLE, IEEE802154) calls iphc
> compress/decompress Lukasz had no change to access some room which is needed
> for storing the context information into a table. The workaround for this
> feature was to add allocate a static data room for the table and doing a
> lookup/match of netdev name. Which a generic 6lowpan private data room per each
> lowpan interface we can put this table according to the netdev private room,
> which means in short: no lookup is needed anymore, just dereferencing lowpan_priv.
>
> In upper layer like IPv6 Lukasz could use that to get the stateful context
> table information as an example for doing 6LoWPAN generic stuff in upper
> layers.
>
>
> Note about the implementation for LL 6LoWPAN private pointer:
>
> I stole some mechanism from wireless for that. See [0], the vif struct is part
> of sdata which is also part of private data of a wireless interface (mac80211).
> I hope I can just adapt this behaviour.
>
> - Alex
>
> Cc: Jonathan Corbet <corbet@xxxxxxx>
> Cc: linux-doc@xxxxxxxxxxxxxxx
>
> [0] http://lxr.free-electrons.com/source/include/net/mac80211.h#L1366
>
> changes since PATCH (was RFC before):
> - rename ll_type,ll_foo to lltype, llfoo
> - add documentation for generic 6lowpan interfaces API
> - add net/6lowpan/core.c for core functionality, like setup or cleanup
> lowpan netdev interfaces, which is necessary e.g. heap allocation/free
> - add LOWPAN_PRIV_SIZE for provide API functionality to calculate
> private data
> - rebase to current bluetooth-next/master
> - add documentation in cc for the Documentation branch
>
> changes since v2:
> - rename L2/l2 to LL/ll. I think the usually word in ietf for L2 is
> LL which means "link layer". Also ipv6 stack use ll for variables like
> lladdr -> link layer address.
> - rebase to current bluetooth-next/master
> - remove some brackets in function lowpan_priv.
>
> Alexander Aring (4):
> Bluetooth: 6lowpan: change netdev_priv to lowpan_dev
> 6lowpan: add generic 6lowpan netdev private data
> 6lowpan: move module_init into core functionality
> documentation: networking: add 6lowpan documentation
>
> Documentation/networking/6lowpan.txt | 51 ++++++++++++++++++++++++++++++++++++
> MAINTAINERS | 1 +
> include/net/6lowpan.h | 23 ++++++++++++++++
> net/6lowpan/Makefile | 2 +-
> net/6lowpan/core.c | 40 ++++++++++++++++++++++++++++
> net/6lowpan/iphc.c | 19 --------------
> net/bluetooth/6lowpan.c | 11 +++++---
> net/ieee802154/6lowpan/6lowpan_i.h | 3 ++-
> net/ieee802154/6lowpan/core.c | 4 ++-
> 9 files changed, 128 insertions(+), 26 deletions(-)
> create mode 100644 Documentation/networking/6lowpan.txt
> create mode 100644 net/6lowpan/core.c
I went ahead and applied all 4 patches to bluetooth-next tree. That way they get exposure.
Regards
Marcel
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