[RFC PATCH v8 04/19] af_vsock: implement SEQPACKET receive loop

Arseny Krasnov
2021-04-13T12:44:51Z

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>
---
v7 -> v8:
- Length of message is now not returned by callback, it returns only
length of data read by each call.
- Previous case, when EAGAIN is return and dequeue loop restarted now
removed(in this simplified version we consider that message could not
be corrupted).
- MSG_TRUNC in input flags is now handled by callback.

include/net/af_vsock.h | 4 +++
net/vmw_vsock/af_vsock.c | 66 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 69 insertions(+), 1 deletion(-)

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index b1c717286993..5175f5a52ce1 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, 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 c4f6bfa1e381..d9fb4f9a3063 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c
@@ -1974,6 +1974,67 @@ 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;
+ bool msg_ready;
+ 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);
+ msg_ready = false;
+ record_len = 0;
+
+ while (1) {
+ ssize_t tmp_record_len;
+
+ if (vsock_wait_data(sk, &wait, timeout, NULL, 0) <= 0) {
+ /* In case of any loop break(timeout, signal
+ * interrupt or shutdown), we report user that
+ * nothing was copied.
+ */
+ err = 0;
+ break;
+ }
+
+ tmp_record_len = transport->seqpacket_dequeue(vsk, msg, flags, &msg_ready);
+
+ if (tmp_record_len < 0) {
+ err = -ENOMEM;
+ break;
+ }
+
+ record_len += tmp_record_len;
+
+ if (msg_ready)
+ break;
+ }
+
+ if (sk->sk_err)
+ err = -sk->sk_err;
+ else if (sk->sk_shutdown & RCV_SHUTDOWN)
+ err = 0;
+
+ if (msg_ready && err == 0) {
+ err = record_len;
+
+ /* 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)
@@ -2029,7 +2090,10 @@ 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