Re: [PATCH 15/18] nvmet-tcp: enable TLS handshake upcall

Sagi Grimberg
2023-03-22T12:13:59Z

On 3/21/23 14:43, Hannes Reinecke wrote:
> Add functions to start the TLS handshake upcall.
>
> Signed-off-by: Hannes Reincke <hare@suse.de>
> ---
> drivers/nvme/target/tcp.c | 188 ++++++++++++++++++++++++++++++++++++--
> 1 file changed, 181 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
> index 5c43767c5ecd..6e88e98a2c59 100644
> --- a/drivers/nvme/target/tcp.c
> +++ b/drivers/nvme/target/tcp.c
> @@ -9,8 +9,10 @@
> #include <linux/slab.h>
> #include <linux/err.h>
> #include <linux/nvme-tcp.h>
> +#include <linux/nvme-keyring.h>
> #include <net/sock.h>
> #include <net/tcp.h>
> +#include <net/handshake.h>
> #include <linux/inet.h>
> #include <linux/llist.h>
> #include <crypto/hash.h>
> @@ -40,6 +42,14 @@ module_param(idle_poll_period_usecs, int, 0644);
> MODULE_PARM_DESC(idle_poll_period_usecs,
> "nvmet tcp io_work poll till idle time period in usecs");
>
> +/*
> + * TLS handshake timeout
> + */
> +static int tls_handshake_timeout = 30;

30 ?

> +module_param(tls_handshake_timeout, int, 0644);
> +MODULE_PARM_DESC(tls_handshake_timeout,
> + "nvme TLS handshake timeout in seconds (default 30)");
> +
> #define NVMET_TCP_RECV_BUDGET 8
> #define NVMET_TCP_SEND_BUDGET 8
> #define NVMET_TCP_IO_WORK_BUDGET 64
> @@ -131,6 +141,9 @@ struct nvmet_tcp_queue {
> struct ahash_request *snd_hash;
> struct ahash_request *rcv_hash;
>
> + struct key *tls_psk;
> + struct delayed_work tls_handshake_work;
> +
> unsigned long poll_end;
>
> spinlock_t state_lock;
> @@ -168,6 +181,7 @@ static struct workqueue_struct *nvmet_tcp_wq;
> static const struct nvmet_fabrics_ops nvmet_tcp_ops;
> static void nvmet_tcp_free_cmd(struct nvmet_tcp_cmd *c);
> static void nvmet_tcp_free_cmd_buffers(struct nvmet_tcp_cmd *cmd);
> +static void nvmet_tcp_tls_handshake_timeout_work(struct work_struct *work);
>
> static inline u16 nvmet_tcp_cmd_tag(struct nvmet_tcp_queue *queue,
> struct nvmet_tcp_cmd *cmd)
> @@ -1400,6 +1414,8 @@ static void nvmet_tcp_restore_socket_callbacks(struct nvmet_tcp_queue *queue)
> {
> struct socket *sock = queue->sock;
>
> + if (!sock->sk)
> + return;

Umm, when will the sock not have an sk?

> write_lock_bh(&sock->sk->sk_callback_lock);
> sock->sk->sk_data_ready = queue->data_ready;
> sock->sk->sk_state_change = queue->state_change;
> @@ -1448,7 +1464,8 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
> list_del_init(&queue->queue_list);
> mutex_unlock(&nvmet_tcp_queue_mutex);
>
> - nvmet_tcp_restore_socket_callbacks(queue);
> + if (queue->state != NVMET_TCP_Q_TLS_HANDSHAKE)
> + nvmet_tcp_restore_socket_callbacks(queue);

This is because you only save the callbacks after the handshake
phase is done? Maybe it would be simpler to clear the ops because
the socket is going away anyways...

> cancel_work_sync(&queue->io_work);
> /* stop accepting incoming data */
> queue->rcv_state = NVMET_TCP_RECV_ERR;
> @@ -1469,6 +1486,8 @@ static void nvmet_tcp_release_queue_work(struct work_struct *w)
> nvmet_tcp_free_cmds(queue);
> if (queue->hdr_digest || queue->data_digest)
> nvmet_tcp_free_crypto(queue);
> + if (queue->tls_psk)
> + key_put(queue->tls_psk);
> ida_free(&nvmet_tcp_queue_ida, queue->idx);
> page = virt_to_head_page(queue->pf_cache.va);
> __page_frag_cache_drain(page, queue->pf_cache.pagecnt_bias);
> @@ -1481,11 +1500,15 @@ static void nvmet_tcp_data_ready(struct sock *sk)
>
> trace_sk_data_ready(sk);
>
> - read_lock_bh(&sk->sk_callback_lock);
> - queue = sk->sk_user_data;
> - if (likely(queue))
> - queue_work_on(queue_cpu(queue), nvmet_tcp_wq, &queue->io_work);
> - read_unlock_bh(&sk->sk_callback_lock);
> + rcu_read_lock_bh();
> + queue = rcu_dereference_sk_user_data(sk);
> + if (queue->data_ready)
> + queue->data_ready(sk);
> + if (likely(queue) &&
> + queue->state != NVMET_TCP_Q_TLS_HANDSHAKE)
> + queue_work_on(queue_cpu(queue), nvmet_tcp_wq,
> + &queue->io_work);
> + rcu_read_unlock_bh();

Same comment as the host side. separate rcu stuff from data_ready call.

> }
>
> static void nvmet_tcp_write_space(struct sock *sk)
> @@ -1585,13 +1608,139 @@ static int nvmet_tcp_set_queue_sock(struct nvmet_tcp_queue *queue)
> sock->sk->sk_write_space = nvmet_tcp_write_space;
> if (idle_poll_period_usecs)
> nvmet_tcp_arm_queue_deadline(queue);
> - queue_work_on(queue_cpu(queue), nvmet_tcp_wq, &queue->io_work);
> + queue_work_on(queue_cpu(queue), nvmet_tcp_wq,
> + &queue->io_work);

Why the change?

> }
> write_unlock_bh(&sock->sk->sk_callback_lock);
>
> return ret;
> }
>
> +static void nvmet_tcp_tls_data_ready(struct sock *sk)
> +{
> + struct socket_wq *wq;
> +
> + rcu_read_lock();
> + /* kTLS will change the callback */
> + if (sk->sk_data_ready == nvmet_tcp_tls_data_ready) {
> + wq = rcu_dereference(sk->sk_wq);
> + if (skwq_has_sleeper(wq))
> + wake_up_interruptible_all(&wq->wait);
> + }
> + rcu_read_unlock();
> +}

Can you explain why this is needed? It looks out-of-place.
Who is this waking up? isn't tls already calling the socket
default data_ready that does something similar for userspace?

> +
> +static void nvmet_tcp_tls_handshake_restart(struct nvmet_tcp_queue *queue)
> +{
> + spin_lock(&queue->state_lock);
> + if (queue->state != NVMET_TCP_Q_TLS_HANDSHAKE) {
> + pr_warn("queue %d: TLS handshake already completed\n",
> + queue->idx);
> + spin_unlock(&queue->state_lock);
> + return;
> + }
> + queue->state = NVMET_TCP_Q_CONNECTING;
> + spin_unlock(&queue->state_lock);
> +
> + pr_debug("queue %d: restarting queue after TLS handshake\n",
> + queue->idx);
> + /*
> + * Set callbacks after handshake; TLS implementation
> + * might have changed the socket callbacks.
> + */
> + nvmet_tcp_set_queue_sock(queue);

My understanding is that this is the desired end-state, i.e.
tls connection is ready and now we are expecting nvme traffic?

I think that the function name should be changed, it sounds like
it is restarting the handshake, and it does not appear to do that.

> +}
> +
> +static void nvmet_tcp_save_tls_callbacks(struct nvmet_tcp_queue *queue)
> +{
> + struct sock *sk = queue->sock->sk;
> +
> + write_lock_bh(&sk->sk_callback_lock);
> + rcu_assign_sk_user_data(sk, queue);
> + queue->data_ready = sk->sk_data_ready;
> + sk->sk_data_ready = nvmet_tcp_tls_data_ready;
> + write_unlock_bh(&sk->sk_callback_lock);
> +}
> +
> +static void nvmet_tcp_restore_tls_callbacks(struct nvmet_tcp_queue *queue)
> +{
> + struct sock *sk = queue->sock->sk;
> +
> + if (WARN_ON(!sk))
> + return;
> + write_lock_bh(&sk->sk_callback_lock);
> + /* Only reset the callback if it really is ours */
> + if (sk->sk_data_ready == nvmet_tcp_tls_data_ready)

I still don't understand why our data_ready for tls is needed.
Who are

> + sk->sk_data_ready = queue->data_ready;
> + rcu_assign_sk_user_data(sk, NULL);
> + queue->data_ready = NULL;
> + write_unlock_bh(&sk->sk_callback_lock);
> +}
> +
> +static void nvmet_tcp_tls_handshake_done(void *data, int status,
> + key_serial_t peerid)
> +{
> + struct nvmet_tcp_queue *queue = data;
> +
> + pr_debug("queue %d: TLS handshake done, key %x, status %d\n",
> + queue->idx, peerid, status);
> + if (!status) {
> + spin_lock(&queue->state_lock);
> + queue->tls_psk = key_lookup(peerid);
> + if (IS_ERR(queue->tls_psk)) {
> + pr_warn("queue %d: TLS key %x not found\n",
> + queue->idx, peerid);
> + queue->tls_psk = NULL;
> + }
> + spin_unlock(&queue->state_lock);
> + }
> + cancel_delayed_work_sync(&queue->tls_handshake_work);
> + nvmet_tcp_restore_tls_callbacks(queue);
> + if (status)
> + nvmet_tcp_schedule_release_queue(queue);
> + else
> + nvmet_tcp_tls_handshake_restart(queue);
> +}
> +
> +static void nvmet_tcp_tls_handshake_timeout_work(struct work_struct *w)
> +{
> + struct nvmet_tcp_queue *queue = container_of(to_delayed_work(w),
> + struct nvmet_tcp_queue, tls_handshake_work);
> +
> + pr_debug("queue %d: TLS handshake timeout\n", queue->idx);
> + nvmet_tcp_restore_tls_callbacks(queue);
> + nvmet_tcp_schedule_release_queue(queue);
> +}
> +
> +static int nvmet_tcp_tls_handshake(struct nvmet_tcp_queue *queue)
> +{
> + int ret = -EOPNOTSUPP;
> + struct tls_handshake_args args;
> +
> + if (queue->state != NVMET_TCP_Q_TLS_HANDSHAKE) {
> + pr_warn("cannot start TLS in state %d\n", queue->state);
> + return -EINVAL;
> + }
> +
> + pr_debug("queue %d: TLS ServerHello\n", queue->idx);
> + args.ta_sock = queue->sock;
> + args.ta_done = nvmet_tcp_tls_handshake_done;
> + args.ta_data = queue;
> + args.ta_keyring = nvme_keyring_id();
> + args.ta_timeout_ms = tls_handshake_timeout * 2 * 1024;

why the 2x timeout?

> +
> + ret = tls_server_hello_psk(&args, GFP_KERNEL);
> + if (ret) {
> + pr_err("failed to start TLS, err=%d\n", ret);
> + } else {
> + pr_debug("queue %d wakeup userspace\n", queue->idx);
> + nvmet_tcp_tls_data_ready(queue->sock->sk);
> + queue_delayed_work(nvmet_wq, &queue->tls_handshake_work,
> + tls_handshake_timeout * HZ);
> + }
> + return ret;
> +}
> +
> static void nvmet_tcp_alloc_queue(struct nvmet_tcp_port *port,
> struct socket *newsock)
> {
> @@ -1604,6 +1753,8 @@ static void nvmet_tcp_alloc_queue(struct nvmet_tcp_port *port,
>
> INIT_WORK(&queue->release_work, nvmet_tcp_release_queue_work);
> INIT_WORK(&queue->io_work, nvmet_tcp_io_work);
> + INIT_DELAYED_WORK(&queue->tls_handshake_work,
> + nvmet_tcp_tls_handshake_timeout_work);
> queue->sock = newsock;
> queue->port = port;
> queue->nr_cmds = 0;
> @@ -1646,6 +1797,29 @@ static void nvmet_tcp_alloc_queue(struct nvmet_tcp_port *port,
> list_add_tail(&queue->queue_list, &nvmet_tcp_queue_list);
> mutex_unlock(&nvmet_tcp_queue_mutex);
>
> + if (queue->state == NVMET_TCP_Q_TLS_HANDSHAKE) {
> + nvmet_tcp_save_tls_callbacks(queue);
> + if (!nvmet_tcp_tls_handshake(queue))
> + return;
> + nvmet_tcp_restore_tls_callbacks(queue);
> +
> + /*
> + * If sectype is set to 'tls1.3' TLS is required
> + * so terminate the connection if the TLS handshake
> + * failed.
> + */
> + if (queue->port->nport->disc_addr.tsas.tcp.sectype ==
> + NVMF_TCP_SECTYPE_TLS13) {
> + pr_debug("queue %d sectype tls1.3, terminate connection\n",
> + queue->idx);
> + goto out_destroy_sq;
> + }
> + pr_debug("queue %d fallback to icreq\n", queue->idx);
> + spin_lock(&queue->state_lock);
> + queue->state = NVMET_TCP_Q_CONNECTING;
> + spin_unlock(&queue->state_lock);
> + }
> +
> ret = nvmet_tcp_set_queue_sock(queue);
> if (ret)
> goto out_destroy_sq;

I'm still trying to learn the state machine here, can you share a few
words on it? Also please include it in the next round in the change log.