[PATCH 00/18] xfrm: Add compat layer

From: Dmitry Safonov
Date: Wed Jul 25 2018 - 22:34:13 EST

Due to some historical mistake, xfrm User ABI differ between native and
compatible applications. The difference is in structures paddings and in
the result in the size of netlink messages.
As it's already visible ABI, it cannot be adjusted by packing structures.

Possibility for compatible application to manage xfrm tunnels was
disabled by: the commmit 19d7df69fdb2 ("xfrm: Refuse to insert 32 bit
userspace socket policies on 64 bit systems") and the commit 74005991b78a
("xfrm: Do not parse 32bits compiled xfrm netlink msg on 64bits host").

By some wonderful reasons and brilliant architecture decisions for
creating userspace, on Arista switches we still use 32-bit userspace
with 64-bit kernel. There is slow movement to full 64-bit build, but
it's not yet here. As the switches need support for ipsec tunnels, the
local kernel has reverted mentioned patches that disable xfrm for
compat apps. On the top of that there is a bunch of disgraceful hacks
in userspace to work around the size check for netlink messages
and all that jazz.

It looks like, we're not the only desirable users of compatible xfrm,
there were a couple of attempts to make it work:

All the discussions end in the conclusion that xfrm should have a full
compatible layer to correctly work with 32-bit applications on 64-bit

In some recent lkml discussion, Linus said that it's worth to fix this
problem and not giving people an excuse to stay on 32-bit kernel:

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.

The first two patches simplify ifdeffery, and while I've already submitted
them a while ago, I'm resending them for completeness:

There is also an exhaustive selftest for ipsec tunnels and to check
that kernel parses correctly the structures those differ in size.
It doesn't depend on any library and compat version can be easy
build with: make CFLAGS=-m32 net/ipsec

Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Cc: Dmitry Safonov <0x7f454c46@xxxxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx

Dmitry Safonov (18):
x86/compat: Adjust in_compat_syscall() to generic code under !COMPAT
compat: Cleanup in_compat_syscall() callers
selftest/net/xfrm: Add test for ipsec tunnel
net/xfrm: Add _packed types for compat users
net/xfrm: Parse userspi_info{,_packed} depending on syscall
netlink: Do not subscribe to non-existent groups
netlink: Pass groups pointer to .bind()
xfrm: Add in-kernel groups for compat notifications
xfrm: Dump usersa_info in compat/native formats
xfrm: Send state notifications in compat format too
xfrm: Add compat support for xfrm_user_expire messages
xfrm: Add compat support for xfrm_userpolicy_info messages
xfrm: Add compat support for xfrm_user_acquire messages
xfrm: Add compat support for xfrm_user_polexpire messages
xfrm: Check compat acquire listeners in xfrm_is_alive()
xfrm: Notify compat listeners about policy flush
xfrm: Notify compat listeners about state flush
xfrm: Enable compat syscalls

arch/x86/include/asm/compat.h | 9 +-
arch/x86/include/asm/ftrace.h | 4 +-
arch/x86/kernel/process_64.c | 4 +-
arch/x86/kernel/sys_x86_64.c | 11 +-
arch/x86/mm/hugetlbpage.c | 4 +-
arch/x86/mm/mmap.c | 2 +-
drivers/firmware/efi/efivars.c | 16 +-
include/linux/compat.h | 4 +-
include/linux/netlink.h | 2 +-
include/net/xfrm.h | 14 -
kernel/audit.c | 2 +-
kernel/time/time.c | 2 +-
net/core/rtnetlink.c | 14 +-
net/core/sock_diag.c | 25 +-
net/netfilter/nfnetlink.c | 24 +-
net/netlink/af_netlink.c | 28 +-
net/netlink/af_netlink.h | 4 +-
net/netlink/genetlink.c | 26 +-
net/xfrm/xfrm_state.c | 5 -
net/xfrm/xfrm_user.c | 690 ++++++++---
tools/testing/selftests/net/.gitignore | 1 +
tools/testing/selftests/net/Makefile | 1 +
tools/testing/selftests/net/ipsec.c | 1987 ++++++++++++++++++++++++++++++++
24 files changed, 2612 insertions(+), 268 deletions(-)
create mode 100644 tools/testing/selftests/net/ipsec.c