Re: [PATCH v6 2/5] net/handshake: Define handshake_req_keyupdate

On Mon, Dec 1, 2025, at 8:34 PM, [email protected] wrote:
> From: Alistair Francis <[email protected]>
>
> 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 <[email protected]>
> ---
> 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