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Date:   Sat, 18 Mar 2023 12:18:12 -0400
From:   Chuck Lever <>
Subject: [PATCH v7 0/2] Another crack at a handshake upcall mechanism


Here is v7 of a series to add generic support for transport layer
security handshake on behalf of kernel socket consumers (user space
consumers use a security library directly, of course). A summary of
the purpose of these patches is archived here:

v7 again has considerable churn, for two reasons:

- I incorporated more C code generated from the YAML spec, and
- I moved net/tls/tls_handshake.c to net/handshake/

Other significant changes are listed below.

The full patch set to support SunRPC with TLSv1.3 is available in
the topic-rpc-with-tls-upcall branch here, based on net-next/main:

This patch set includes support for in-transit confidentiality and
peer authentication for both the Linux NFS client and server.

A user space handshake agent for TLSv1.3 to go along with the kernel
patches is available in the "netlink-v7" branch here:


Major changes since v6:
- YAML spec and generated artifacts are now under dual license
- Addressed Jakub's v6 review comments
- Implemented a memory-sensitive limit on the number of pending
  handshake requests
- Implemented upcall support for multiple peer identities

Major changes since v5:
- Added a "timeout" attribute to the handshake netlink protocol
- Removed the GnuTLS-specific "priorities" attribute
- Added support for keyrings to restrict access to keys
- Simplified the kernel consumer TLS handshake API
- The handshake netlink protocol can handle multiple peer IDs or
  certificates in the ACCEPT and DONE operations, though the
  implementation does not yet support it.

Major changes since v4:
- Rebased onto net-next/main
- Replaced req reference counting with ->sk_destruct
- CMD_ACCEPT now does the equivalent of a dup(2) rather than an
- CMD_DONE no longer closes the user space socket endpoint
- handshake_req_cancel is now tested and working
- Added a YAML specification for the netlink upcall protocol, and
  simplified the protocol to fit the YAML schema
- Added an initial set of tracepoints

Changes since v3:
- Converted all netlink code to use Generic Netlink
- Reworked handshake request lifetime logic throughout
- Global pending list is now per-net
- On completion, return the remote's identity to the consumer

Changes since v2:
- Replaced listen(2) / poll(2) with a multicast notification service
- Replaced accept(2) with a netlink operation that can return an
  open fd and handshake parameters
- Replaced close(2) with a netlink operation that can take arguments

Changes since RFC:
- Generic upcall support split away from kTLS
- Added support for TLS ServerHello
- Documentation has been temporarily removed while API churns


Chuck Lever (2):
      net/handshake: Create a NETLINK service for handling handshake requests
      net/tls: Add kernel APIs for requesting a TLSv1.3 handshake

 Documentation/netlink/specs/handshake.yaml | 124 ++++++
 Documentation/networking/index.rst         |   1 +
 Documentation/networking/tls-handshake.rst | 217 +++++++++++
 MAINTAINERS                                |  10 +
 include/net/handshake.h                    |  43 +++
 include/trace/events/handshake.h           | 159 ++++++++
 include/uapi/linux/handshake.h             |  72 ++++
 net/Kconfig                                |   5 +
 net/Makefile                               |   1 +
 net/handshake/Makefile                     |  11 +
 net/handshake/genl.c                       |  58 +++
 net/handshake/genl.h                       |  24 ++
 net/handshake/handshake.h                  |  82 ++++
 net/handshake/netlink.c                    | 316 ++++++++++++++++
 net/handshake/request.c                    | 307 +++++++++++++++
 net/handshake/tlshd.c                      | 417 +++++++++++++++++++++
 net/handshake/trace.c                      |  20 +
 17 files changed, 1867 insertions(+)
 create mode 100644 Documentation/netlink/specs/handshake.yaml
 create mode 100644 Documentation/networking/tls-handshake.rst
 create mode 100644 include/net/handshake.h
 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/tlshd.c
 create mode 100644 net/handshake/trace.c

Chuck Lever

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