[PATCH v11 04/18] af_vsock: implement SEQPACKET receive loop

Arseny Krasnov
2021-06-11T11:10:50Z

Add receive loop for SEQPACKET. It looks like receive loop for
STREAM, but there are differences:
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.
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>
---
v10 -> v11:
1) 'msg_ready' input argument removed.
2) On 'vsock_wait_data()' error, error is returned(not 0).
3) Receive loop removed as user is woken up when it is possible
to dequeue whole message.

include/net/af_vsock.h | 4 +++
net/vmw_vsock/af_vsock.c | 55 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index b1c717286993..4d7cf6b2aca2 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h
@@ -135,6 +135,10 @@ struct vsock_transport {
bool (*stream_is_active)(struct vsock_sock *);
bool (*stream_allow)(u32 cid, u32 port);

+ /* SEQ_PACKET. */
+ ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
+ int flags);
+
/* 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 c4f6bfa1e381..87ae26b2e3e1 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1974,6 +1974,56 @@ 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;
+ struct vsock_sock *vsk;
+ ssize_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);
+
+ err = vsock_wait_data(sk, &wait, timeout, NULL, 0);
+ if (err <= 0)
+ goto out;
+
+ record_len = transport->seqpacket_dequeue(vsk, msg, flags);
+
+ if (record_len < 0) {
+ err = -ENOMEM;
+ goto out;
+ }
+
+ if (sk->sk_err) {
+ err = -sk->sk_err;
+ } else if (sk->sk_shutdown & RCV_SHUTDOWN) {
+ err = 0;
+ } else {
+ /* User sets MSG_TRUNC, so return real length of
+ * packet.
+ */
+ if (flags & MSG_TRUNC)
+ err = record_len;
+ else
+ err = len - msg_data_left(msg);
+
+ /* Always set MSG_TRUNC if real length of packet is
+ * bigger than user's buffer.
+ */
+ if (record_len > len)
+ msg->msg_flags |= MSG_TRUNC;
+ }
+
+out:
+ return err;
+}
+
static int
vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
int flags)
@@ -2029,7 +2079,10 @@ 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