On 3/18/23 17:18, Chuck Lever wrote:

From: Chuck Lever <redacted>

When a kernel consumer needs a transport layer security session, it
first needs a handshake to negotiate and establish a session. This
negotiation can be done in user space via one of the several
existing library implementations, or it can be done in the kernel.

No in-kernel handshake implementations yet exist. In their absence,
we add a netlink service that can:

a. Notify a user space daemon that a handshake is needed.

b. Once notified, the daemon calls the kernel back via this
    netlink service to get the handshake parameters, including an
    open socket on which to establish the session.

c. Once the handshake is complete, the daemon reports the
    session status and other information via a second netlink
    operation. This operation marks that it is safe for the
    kernel to use the open socket and the security session
    established there.

The notification service uses a multicast group. Each handshake
mechanism (eg, tlshd) adopts its own group number so that the
handshake services are completely independent of one another. The
kernel can then tell via netlink_has_listeners() whether a handshake
service is active and prepared to handle a handshake request.

A new netlink operation, ACCEPT, acts like accept(2) in that it
instantiates a file descriptor in the user space daemon's fd table.
If this operation is successful, the reply carries the fd number,
which can be treated as an open and ready file descriptor.

While user space is performing the handshake, the kernel keeps its
muddy paws off the open socket. A second new netlink operation,
DONE, indicates that the user space daemon is finished with the
socket and it is safe for the kernel to use again. The operation
also indicates whether a session was established successfully.

Signed-off-by: Chuck Lever <redacted>
---
  Documentation/netlink/specs/handshake.yaml |  122 +++++++++++
  MAINTAINERS                                |    8 +
  include/trace/events/handshake.h           |  159 ++++++++++++++
  include/uapi/linux/handshake.h             |   70 ++++++
  net/Kconfig                                |    5
  net/Makefile                               |    1
  net/handshake/Makefile                     |   11 +
  net/handshake/genl.c                       |   57 +++++
  net/handshake/genl.h                       |   23 ++
  net/handshake/handshake.h                  |   82 +++++++
  net/handshake/netlink.c                    |  316 ++++++++++++++++++++++++++++
  net/handshake/request.c                    |  307 +++++++++++++++++++++++++++
  net/handshake/trace.c                      |   20 ++
  13 files changed, 1181 insertions(+)
  create mode 100644 Documentation/netlink/specs/handshake.yaml
  create mode 100644 include/trace/events/handshake.h
  create mode 100644 include/uapi/linux/handshake.h
  create mode 100644 net/handshake/Makefile
  create mode 100644 net/handshake/genl.c
  create mode 100644 net/handshake/genl.h
  create mode 100644 net/handshake/handshake.h
  create mode 100644 net/handshake/netlink.c
  create mode 100644 net/handshake/request.c
  create mode 100644 net/handshake/trace.c

Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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