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From: Jorgen Hansen <jhansen@vmware.com>
To: Arseny Krasnov <arseny.krasnov@kaspersky.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>,
	Stefano Garzarella <sgarzare@redhat.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>,
	Norbert Slusarek <nslusarek@gmx.net>,
	Andra Paraschiv <andraprs@amazon.com>,
	Colin Ian King <colin.king@canonical.com>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stsp2@yandex.ru" <stsp2@yandex.ru>,
	"oxffffaa@gmail.com" <oxffffaa@gmail.com>
Subject: Re: [RFC PATCH v5 04/19] af_vsock: implement SEQPACKET receive loop
Date: Thu, 25 Feb 2021 16:27:10 +0000	[thread overview]
Message-ID: <125822F8-C6D5-4892-BD32-A7189578B3DE@vmware.com> (raw)
In-Reply-To: <20210218053719.1067237-1-arseny.krasnov@kaspersky.com>

On 18 Feb 2021, at 06:37, Arseny Krasnov <arseny.krasnov@kaspersky.com> wrote:
> 
> This adds receive loop for SEQPACKET. It looks like receive loop for
> STREAM, but there is a little bit difference:
> 1) It doesn't call notify callbacks.
> 2) It doesn't care about 'SO_SNDLOWAT' and 'SO_RCVLOWAT' values, because
>   there is no sense for these values in SEQPACKET case.
> 3) It waits until whole record is received or error is found during
>   receiving.
> 4) It processes and sets 'MSG_TRUNC' flag.
> 
> So to avoid extra conditions for two types of socket inside one loop, two
> independent functions were created.
> 
> Signed-off-by: Arseny Krasnov <arseny.krasnov@kaspersky.com>
> ---
> include/net/af_vsock.h   |  5 +++
> net/vmw_vsock/af_vsock.c | 97 +++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 101 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index b1c717286993..01563338cc03 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -135,6 +135,11 @@ struct vsock_transport {
> 	bool (*stream_is_active)(struct vsock_sock *);
> 	bool (*stream_allow)(u32 cid, u32 port);
> 
> +	/* SEQ_PACKET. */
> +	size_t (*seqpacket_seq_get_len)(struct vsock_sock *vsk);
> +	int (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
> +				     int flags, bool *msg_ready);
> +
> 	/* Notification. */
> 	int (*notify_poll_in)(struct vsock_sock *, size_t, bool *);
> 	int (*notify_poll_out)(struct vsock_sock *, size_t, bool *);
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index d277dc1cdbdf..b754927a556a 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -1972,6 +1972,98 @@ static int __vsock_stream_recvmsg(struct sock *sk, struct msghdr *msg,
> 	return err;
> }
> 
> +static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
> +				     size_t len, int flags)
> +{
> +	const struct vsock_transport *transport;
> +	const struct iovec *orig_iov;
> +	unsigned long orig_nr_segs;
> +	bool msg_ready;
> +	struct vsock_sock *vsk;
> +	size_t record_len;
> +	long timeout;
> +	int err = 0;
> +	DEFINE_WAIT(wait);
> +
> +	vsk = vsock_sk(sk);
> +	transport = vsk->transport;
> +
> +	timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
> +	orig_nr_segs = msg->msg_iter.nr_segs;
> +	orig_iov = msg->msg_iter.iov;
> +	msg_ready = false;
> +	record_len = 0;
> +
> +	while (1) {
> +		err = vsock_wait_data(sk, &wait, timeout, NULL, 0);
> +
> +		if (err <= 0) {
> +			/* In case of any loop break(timeout, signal
> +			 * interrupt or shutdown), we report user that
> +			 * nothing was copied.
> +			 */
> +			err = 0;
> +			break;
> +		}
> +
> +		if (record_len == 0) {
> +			record_len =
> +				transport->seqpacket_seq_get_len(vsk);
> +
> +			if (record_len == 0)
> +				continue;
> +		}
> +
> +		err = transport->seqpacket_dequeue(vsk, msg,
> +					flags, &msg_ready);
> +
> +		if (err < 0) {
> +			if (err == -EAGAIN) {
> +				iov_iter_init(&msg->msg_iter, READ,
> +					      orig_iov, orig_nr_segs,
> +					      len);
> +				/* Clear 'MSG_EOR' here, because dequeue
> +				 * callback above set it again if it was
> +				 * set by sender. This 'MSG_EOR' is from
> +				 * dropped record.
> +				 */
> +				msg->msg_flags &= ~MSG_EOR;
> +				record_len = 0;
> +				continue;
> +			}

So a question for my understanding of the flow here. SOCK_SEQPACKET is reliable, so
what does it mean to drop the record? Is the transport supposed to roll back to the
beginning of the current record? If the incoming data in the transport doesn’t follow
the protocol, and packets need to be dropped, shouldn’t the socket be reset or similar?
Maybe there is potential for simplifying the flow if that is the case.

> +
> +			err = -ENOMEM;
> +			break;
> +		}
> +
> +		if (msg_ready)
> +			break;
> +	}
> +
> +	if (sk->sk_err)
> +		err = -sk->sk_err;
> +	else if (sk->sk_shutdown & RCV_SHUTDOWN)
> +		err = 0;
> +
> +	if (msg_ready) {
> +		/* User sets MSG_TRUNC, so return real length of
> +		 * packet.
> +		 */
> +		if (flags & MSG_TRUNC)
> +			err = record_len;
> +		else
> +			err = len - msg->msg_iter.count;
> +
> +		/* Always set MSG_TRUNC if real length of packet is
> +		 * bigger than user's buffer.
> +		 */
> +		if (record_len > len)
> +			msg->msg_flags |= MSG_TRUNC;
> +	}
> +
> +	return err;
> +}
> +
> static int
> vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 			  int flags)
> @@ -2027,7 +2119,10 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> 		goto out;
> 	}
> 
> -	err = __vsock_stream_recvmsg(sk, msg, len, flags);
> +	if (sk->sk_type == SOCK_STREAM)
> +		err = __vsock_stream_recvmsg(sk, msg, len, flags);
> +	else
> +		err = __vsock_seqpacket_recvmsg(sk, msg, len, flags);
> 
> out:
> 	release_sock(sk);
> -- 
> 2.25.1
> 


  parent reply	other threads:[~2021-02-25 16:28 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-18  5:33 [RFC PATCH v5 00/19] virtio/vsock: introduce SOCK_SEQPACKET support Arseny Krasnov
2021-02-18  5:36 ` [RFC PATCH v5 01/19] af_vsock: update functions for connectible socket Arseny Krasnov
2021-02-22 10:50   ` Stefano Garzarella
2021-02-22 10:58     ` Arseny Krasnov
2021-02-22 11:09       ` Stefano Garzarella
2021-02-18  5:36 ` [RFC PATCH v5 02/19] af_vsock: separate wait data loop Arseny Krasnov
2021-02-22 11:29   ` Stefano Garzarella
2021-02-25 14:24   ` Jorgen Hansen
2021-02-25 17:01     ` Arseny Krasnov
2021-02-18  5:36 ` [RFC PATCH v5 03/19] af_vsock: separate receive " Arseny Krasnov
2021-02-22 11:43   ` Stefano Garzarella
2021-02-18  5:37 ` [RFC PATCH v5 04/19] af_vsock: implement SEQPACKET receive loop Arseny Krasnov
2021-02-22 11:53   ` Stefano Garzarella
2021-02-25 16:27   ` Jorgen Hansen [this message]
2021-02-25 17:00     ` Arseny Krasnov
2021-02-18  5:37 ` [RFC PATCH v5 05/19] af_vsock: separate wait space loop Arseny Krasnov
2021-02-22 12:06   ` Stefano Garzarella
2021-02-18  5:38 ` [RFC PATCH v5 06/19] af_vsock: implement send logic for SEQPACKET Arseny Krasnov
2021-02-18  5:38 ` [RFC PATCH v5 07/19] af_vsock: rest of SEQPACKET support Arseny Krasnov
2021-02-22 14:12   ` Stefano Garzarella
2021-02-18  5:38 ` [RFC PATCH v5 08/19] af_vsock: update comments for stream sockets Arseny Krasnov
2021-02-22 14:18   ` Stefano Garzarella
2021-02-18  5:39 ` [RFC PATCH v5 09/19] virtio/vsock: set packet's type in send Arseny Krasnov
2021-02-23 13:42   ` Stefano Garzarella
2021-02-18  5:39 ` [RFC PATCH v5 10/19] virtio/vsock: simplify credit update function API Arseny Krasnov
2021-02-23 13:49   ` Stefano Garzarella
2021-02-18  5:39 ` [RFC PATCH v5 11/19] virtio/vsock: dequeue callback for SOCK_SEQPACKET Arseny Krasnov
2021-02-23 14:15   ` Stefano Garzarella
2021-02-23 14:17   ` Michael S. Tsirkin
2021-02-24  5:07     ` Arseny Krasnov
2021-02-24  6:41       ` Michael S. Tsirkin
2021-02-24  8:31         ` Stefano Garzarella
2021-02-27  8:58         ` Arseny Krasnov
2021-02-18  5:39 ` [RFC PATCH v5 12/19] virtio/vsock: fetch length for SEQPACKET record Arseny Krasnov
2021-02-18  5:40 ` [RFC PATCH v5 13/19] virtio/vsock: add SEQPACKET receive logic Arseny Krasnov
2021-02-18  5:40 ` [RFC PATCH v5 14/19] virtio/vsock: rest of SOCK_SEQPACKET support Arseny Krasnov
2021-02-18  5:40 ` [RFC PATCH v5 15/19] virtio/vsock: setup SEQPACKET ops for transport Arseny Krasnov
2021-02-18  5:41 ` [RFC PATCH v5 16/19] vhost/vsock: " Arseny Krasnov
2021-02-18  5:41 ` [RFC PATCH v5 17/19] vsock/loopback: " Arseny Krasnov
2021-02-18  5:42 ` [RFC PATCH v5 18/19] vsock_test: add SOCK_SEQPACKET tests Arseny Krasnov
2021-02-18  5:42 ` [RFC PATCH v5 19/19] virtio/vsock: update trace event for SEQPACKET Arseny Krasnov
2021-03-02 22:25   ` Steven Rostedt
2021-03-03 10:42     ` Arseny Krasnov
2021-02-22 14:23 ` [RFC PATCH v5 00/19] virtio/vsock: introduce SOCK_SEQPACKET support Stefano Garzarella
2021-02-23 14:50   ` Stefano Garzarella
2021-02-24  4:29     ` Arseny Krasnov
2021-02-24  8:23       ` Stefano Garzarella
2021-02-24  8:28         ` Arseny Krasnov
2021-02-24  8:35           ` Stefano Garzarella
2021-02-24  8:36             ` Arseny Krasnov

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