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Message-Id: <962da16d-b16c-461f-bb35-75c58d89fe3a@app.fastmail.com>
Date: Tue, 02 Dec 2025 08:49:12 -0500
From: "Chuck Lever" <cel@...nel.org>
To: alistair23@...il.com, "Chuck Lever" <chuck.lever@...cle.com>,
hare@...nel.org, kernel-tls-handshake@...ts.linux.dev,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-doc@...r.kernel.org, linux-nvme@...ts.infradead.org,
linux-nfs@...r.kernel.org
Cc: kbusch@...nel.org, axboe@...nel.dk, hch@....de, sagi@...mberg.me,
kch@...dia.com, hare@...e.de, "Alistair Francis" <alistair.francis@....com>
Subject: Re: [PATCH v6 2/5] net/handshake: Define handshake_req_keyupdate
On Mon, Dec 1, 2025, at 8:34 PM, alistair23@...il.com wrote:
> From: Alistair Francis <alistair.francis@....com>
>
> Add a new handshake_req_keyupdate() function which is similar to the
> existing handshake_req_submit().
>
> The new handshake_req_keyupdate() does not add the request to the hash
> table (unlike handshake_req_submit()) but instead uses the existing
> request from the initial handshake.
>
> During the initial handshake handshake_req_submit() will add the request
> to the hash table. The request will not be removed from the hash table
> unless the socket is closed (reference count hits zero).
>
> After the initial handshake handshake_req_keyupdate() can be used to re-use
> the existing request in the hash table to trigger a KeyUpdate with
> userspace.
>
> Signed-off-by: Alistair Francis <alistair.francis@....com>
> ---
> v6:
> - New patch
>
> net/handshake/handshake.h | 2 +
> net/handshake/request.c | 95 +++++++++++++++++++++++++++++++++++++++
> 2 files changed, 97 insertions(+)
>
> diff --git a/net/handshake/handshake.h b/net/handshake/handshake.h
> index a48163765a7a..04feacd1e21d 100644
> --- a/net/handshake/handshake.h
> +++ b/net/handshake/handshake.h
> @@ -84,6 +84,8 @@ void handshake_req_hash_destroy(void);
> void *handshake_req_private(struct handshake_req *req);
> struct handshake_req *handshake_req_hash_lookup(struct sock *sk);
> struct handshake_req *handshake_req_next(struct handshake_net *hn, int
> class);
> +int handshake_req_keyupdate(struct socket *sock, struct handshake_req
> *req,
> + gfp_t flags);
> int handshake_req_submit(struct socket *sock, struct handshake_req
> *req,
> gfp_t flags);
> void handshake_complete(struct handshake_req *req, unsigned int status,
> diff --git a/net/handshake/request.c b/net/handshake/request.c
> index 274d2c89b6b2..916caab88fe0 100644
> --- a/net/handshake/request.c
> +++ b/net/handshake/request.c
> @@ -196,6 +196,101 @@ struct handshake_req *handshake_req_next(struct
> handshake_net *hn, int class)
> }
> EXPORT_SYMBOL_IF_KUNIT(handshake_req_next);
>
> +/**
> + * handshake_req_keyupdate - Submit a KeyUpdate request
> + * @sock: open socket on which to perform the handshake
> + * @req: handshake arguments, this must already be allocated and exist
> + * in the hash table, which happens as part of handshake_req_submit()
> + * @flags: memory allocation flags
> + *
> + * Return values:
> + * %0: Request queued
> + * %-EINVAL: Invalid argument
> + * %-EBUSY: A handshake is already under way for this socket
Or, an initial handshake hasn't been done yet. Perhaps that
deserves its own errno value...
Thanks for considering this idea!
> + * %-ESRCH: No handshake agent is available
> + * %-EAGAIN: Too many pending handshake requests
> + * %-ENOMEM: Failed to allocate memory
> + * %-EMSGSIZE: Failed to construct notification message
> + * %-EOPNOTSUPP: Handshake module not initialized
> + *
> + * A zero return value from handshake_req_submit() means that
> + * exactly one subsequent completion callback is guaranteed.
> + *
> + * A negative return value from handshake_req_submit() means that
> + * no completion callback will be done and that @req has been
> + * destroyed.
> + */
> +int handshake_req_keyupdate(struct socket *sock, struct handshake_req *req,
> + gfp_t flags)
> +{
> + struct handshake_net *hn;
> + struct net *net;
> + struct handshake_req *req_lookup;
> + int ret;
> +
> + if (!sock || !req || !sock->file) {
> + kfree(req);
> + return -EINVAL;
> + }
> +
> + req->hr_sk = sock->sk;
> + if (!req->hr_sk) {
> + kfree(req);
> + return -EINVAL;
> + }
> + req->hr_odestruct = req->hr_sk->sk_destruct;
> + req->hr_sk->sk_destruct = handshake_sk_destruct;
> +
> + ret = -EOPNOTSUPP;
> + net = sock_net(req->hr_sk);
> + hn = handshake_pernet(net);
> + if (!hn)
> + goto out_err;
> +
> + ret = -EAGAIN;
> + if (READ_ONCE(hn->hn_pending) >= hn->hn_pending_max)
> + goto out_err;
> +
> + spin_lock(&hn->hn_lock);
> + ret = -EOPNOTSUPP;
> + if (test_bit(HANDSHAKE_F_NET_DRAINING, &hn->hn_flags))
> + goto out_unlock;
> + ret = -EBUSY;
> +
> + req_lookup = handshake_req_hash_lookup(sock->sk);
> + if (!req_lookup)
> + goto out_unlock;
> +
> + if (req_lookup != req)
> + goto out_unlock;
> + if (!__add_pending_locked(hn, req))
> + goto out_unlock;
> + spin_unlock(&hn->hn_lock);
> +
> + test_and_clear_bit(HANDSHAKE_F_REQ_COMPLETED, &req->hr_flags);
> +
> + ret = handshake_genl_notify(net, req->hr_proto, flags);
> + if (ret) {
> + trace_handshake_notify_err(net, req, req->hr_sk, ret);
> + if (remove_pending(hn, req))
> + goto out_err;
> + }
> +
> + /* Prevent socket release while a handshake request is pending */
> + sock_hold(req->hr_sk);
> +
> + trace_handshake_submit(net, req, req->hr_sk);
> + return 0;
> +
> +out_unlock:
> + spin_unlock(&hn->hn_lock);
> +out_err:
> + trace_handshake_submit_err(net, req, req->hr_sk, ret);
> + handshake_req_destroy(req);
> + return ret;
> +}
> +EXPORT_SYMBOL(handshake_req_keyupdate);
> +
> /**
> * handshake_req_submit - Submit a handshake request
> * @sock: open socket on which to perform the handshake
> --
> 2.51.1
--
Chuck Lever
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