Re: [RFC PATCH v5 04/19] af_vsock: implement SEQPACKET receive loop

Stefano Garzarella
2021-02-22T11:55:32Z

On Thu, Feb 18, 2021 at 08:37:15AM +0300, Arseny Krasnov 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);

I think this should be:
int (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
int flags, bool *msg_ready);

To avoid:
$ ./scripts/checkpatch.pl --strict -g HEAD
CHECK: Alignment should match open parenthesis
#35: FILE: include/net/af_vsock.h:141:
+ 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);
>+

Sorry, I expressed myself wrong.

Here it's fine to avoid the blank line as in the previous version, by
single line I meant the seqpacket_dequeue() call, something like this:

err = transport->seqpacket_dequeue(vsk, msg, flags, &msg_ready);
if (err < 0) {

>+ 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;
>+ }
>+
>+ 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
>