netdev - Re: [PATCH v3 1/2] net/handshake: Create a NETLINK service for handling handshake requests

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Message-ID: <1a140441-a9d2-2fca-23df-20f1f4ed0079@suse.de>
Date:   Wed, 8 Feb 2023 17:20:47 +0100
From:   Hannes Reinecke <hare@...e.de>
To:     Chuck Lever <chuck.lever@...cle.com>, kuba@...nel.org,
        pabeni@...hat.com, edumazet@...gle.com
Cc:     netdev@...r.kernel.org, hare@...e.com, dhowells@...hat.com,
        bcodding@...hat.com, kolga@...app.com, jmeneghi@...hat.com
Subject: Re: [PATCH v3 1/2] net/handshake: Create a NETLINK service for
 handling handshake requests

On 2/7/23 22:41, Chuck Lever wrote:
> 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 akin to NETLINK_ROUTE 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.
> 
> The notification service uses a multicast group. Each handshake
> protocol (eg, TLSv1.3, PSP, etc) adopts its own group number so that
> the user space daemons for performing the handshakes are completely
> independent of one another. The kernel can then tell via
> netlink_has_listeners() whether a user space daemon is active and
> can handle a handshake request for the desired security layer
> protocol.
> 
> 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. The act of closing the user space
> file descriptor alerts the kernel that the open socket is safe to
> use again. When the user daemon completes a handshake, the kernel is
> responsible for checking that a valid transport layer security
> session has been established.
> 
> Signed-off-by: Chuck Lever <chuck.lever@...cle.com>
> ---
>   include/net/handshake.h            |   37 ++++
>   include/net/net_namespace.h        |    1
>   include/net/sock.h                 |    1
>   include/uapi/linux/handshake.h     |   65 +++++++
>   include/uapi/linux/netlink.h       |    1
>   net/Makefile                       |    1
>   net/handshake/Makefile             |   11 +
>   net/handshake/netlink.c            |  320 ++++++++++++++++++++++++++++++++++++
>   tools/include/uapi/linux/netlink.h |    1
>   9 files changed, 438 insertions(+)
>   create mode 100644 include/net/handshake.h
>   create mode 100644 include/uapi/linux/handshake.h
>   create mode 100644 net/handshake/Makefile
>   create mode 100644 net/handshake/netlink.c
> 
Looks good on first glance; I'll give it a go on my testbed.

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@...e.de                              +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
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