[PATCH 8/8] SUNRPC: fold xs_sock_process_cmsg() into its only caller

[Chuck Lever <cel@kernel.org>]

xs_sock_process_cmsg() switches on the TLS record type, and every arm
but TLS_RECORD_TYPE_ALERT returns the -EAGAIN its caller passed in.
The DATA arm clears MSG_EOR in the caller's msghdr, but
xs_sock_recvmsg() has already cleared that flag before the call.
Deriving the record type a second time inside the helper also fires
trace_tls_contenttype() twice for every alert.

Move the alert handling into xs_sock_recv_cmsg() and delete the
helper. Every other record type still returns -EAGAIN. The DATA arm's
account of MSG_EOR moves to xs_sock_recvmsg(), where the flag is
cleared.

Signed-off-by: Chuck Lever <cel@kernel.org>
---
 net/sunrpc/xprtsock.c | 85 ++++++++++++++++++---------------------------------
 1 file changed, 30 insertions(+), 55 deletions(-)

diff --git a/net/sunrpc/xprtsock.c b/net/sunrpc/xprtsock.c
index 5527f7f8a185..38dd75a23af7 100644
--- a/net/sunrpc/xprtsock.c
+++ b/net/sunrpc/xprtsock.c
@@ -356,45 +356,6 @@ xs_alloc_sparse_pages(struct xdr_buf *buf, size_t want, gfp_t gfp)
 	return want;
 }
 
-static int
-xs_sock_process_cmsg(struct socket *sock, struct msghdr *msg,
-		     unsigned int *msg_flags, struct cmsghdr *cmsg, int ret)
-{
-	u8 content_type = tls_get_record_type(sock->sk, cmsg);
-	u8 level, description;
-
-	switch (content_type) {
-	case 0:
-		break;
-	case TLS_RECORD_TYPE_DATA:
-		/* TLS sets EOR at the end of each application data
-		 * record, even though there might be more frames
-		 * waiting to be decrypted.
-		 */
-		*msg_flags &= ~MSG_EOR;
-		break;
-	case TLS_RECORD_TYPE_ALERT:
-		tls_alert_recv(sock->sk, msg, &level, &description);
-		/* RFC 8446 Section 6: every alert but a closure alert is
-		 * an error alert, whatever the legacy AlertLevel octet
-		 * says.
-		 */
-		switch (description) {
-		case TLS_ALERT_DESC_CLOSE_NOTIFY:
-		case TLS_ALERT_DESC_USER_CANCELED:
-			ret = -EAGAIN;
-			break;
-		default:
-			ret = -EACCES;
-		}
-		break;
-	default:
-		/* discard this record type */
-		ret = -EAGAIN;
-	}
-	return ret;
-}
-
 static int
 xs_sock_recv_cmsg(struct socket *sock, unsigned int *msg_flags, int flags)
 {
@@ -412,6 +373,7 @@ xs_sock_recv_cmsg(struct socket *sock, unsigned int *msg_flags, int flags)
 		.msg_control = &u,
 		.msg_controllen = sizeof(u),
 	};
+	u8 level, description;
 	int ret;
 
 	iov_iter_kvec(&msg.msg_iter, ITER_DEST, &alert_kvec, 1,
@@ -421,23 +383,32 @@ xs_sock_recv_cmsg(struct socket *sock, unsigned int *msg_flags, int flags)
 	 * kTLS filled in u.cmsg.
 	 */
 	if (ret >= 0 && msg.msg_controllen < sizeof(u)) {
-		if (tls_get_record_type(sock->sk, &u.cmsg) ==
-		    TLS_RECORD_TYPE_ALERT) {
-			/* RFC 8446 Section 5.1 requires a record with an
-			 * Alert type to carry exactly one message. An alert
-			 * is two octets. tls_alert_recv() reads both without
-			 * checking the length. alert_kvec caps the count at
-			 * two, so a longer record fills it as well. kTLS
-			 * sets MSG_EOR only once the record has been
-			 * drained.
-			 */
-			if (ret != sizeof(alert) ||
-			    !(msg.msg_flags & MSG_EOR))
-				return -EACCES;
-			iov_iter_revert(&msg.msg_iter, ret);
+		if (tls_get_record_type(sock->sk, &u.cmsg) !=
+		    TLS_RECORD_TYPE_ALERT)
+			return -EAGAIN;
+		/* RFC 8446 Section 5.1: a record with an Alert type carries
+		 * exactly one message, and an alert is two octets.
+		 * tls_alert_recv() reads both without checking the length.
+		 * alert_kvec caps the count at two, so a longer record
+		 * fills it as well. kTLS sets MSG_EOR only once the
+		 * record has been drained.
+		 */
+		if (ret != sizeof(alert) || !(msg.msg_flags & MSG_EOR))
+			return -EACCES;
+		iov_iter_revert(&msg.msg_iter, ret);
+		tls_alert_recv(sock->sk, &msg, &level, &description);
+		/* RFC 8446 Section 6: every alert but a closure alert is
+		 * an error alert, whatever the legacy AlertLevel octet
+		 * says.
+		 */
+		switch (description) {
+		case TLS_ALERT_DESC_CLOSE_NOTIFY:
+		case TLS_ALERT_DESC_USER_CANCELED:
+			ret = -EAGAIN;
+			break;
+		default:
+			ret = -EACCES;
 		}
-		ret = xs_sock_process_cmsg(sock, &msg, msg_flags, &u.cmsg,
-					   -EAGAIN);
 	}
 	return ret;
 }
@@ -451,6 +422,10 @@ xs_sock_recvmsg(struct socket *sock, struct msghdr *msg, int flags, size_t seek)
 	ret = sock_recvmsg(sock, msg, flags);
 	/* Handle TLS inband control message lazily */
 	if (msg->msg_flags & MSG_CTRUNC) {
+		/* TLS sets EOR at the end of each application data
+		 * record, even though there might be more frames
+		 * waiting to be decrypted.
+		 */
 		msg->msg_flags &= ~(MSG_CTRUNC | MSG_EOR);
 		if (ret == 0 || ret == -EIO)
 			ret = xs_sock_recv_cmsg(sock, &msg->msg_flags, flags);

-- 
2.54.0