Re: [PATCH 00/18] xfrm: Add compat layer
Dmitry Safonov <dima(a)arista.com> wrote:
So, here I add a compatible layer to xfrm.
As xfrm uses netlink notifications, kernel should send them in ABI
format that an application will parse. The proposed solution is
to save the ABI of bind() syscall. The realization detail is
to create kernel-hidden, non visible to userspace netlink groups
for compat applications.
Why not use exisiting netlink support?
Just add the 32bit skb to skb64->frag_list and let
netlink find if tasks needs 64 or 32 one.
It only needs this small fix to properly signal the end of a dump:
https://marc.info/?l=linux-netdev&m=126625240303351&w=2
I had started a second attempt to make xfrm compat work,
but its still in early stage.
One link that might still have some value:
https://git.breakpoint.cc/cgit/fw/net-next.git/commit/?h=xfrm_config_comp...
(compat structure definitions with BUILD_BUG_ON checking)
My plan was to make xfrm compat work strictly as shrinker (64->32)
and expander (32->64), i.e. no/little changes to exisiting code and
pass all "expanded" skbs through existing xfrm rcv functions.
Example to illustrate idea:
https://git.breakpoint.cc/cgit/fw/net-next.git/commit/?h=xfrm_config_comp...
... its supposed to take 64bit skb and create a 32bit one from it.
Just for reference; I currently don't plan to work on this again.