[PATCH net-next v3 6/9] tls: Return copied data ahead of a run of empty records

[Chuck Lever <cel@kernel.org>]

Once tls_sw_recvmsg() has copied enough data to meet the receive
low-water mark, the receive loop continues only while another
record is ready. A zero-length application_data record is consumed
without advancing len, so a peer that follows data with a stream of
empty records keeps the reader in the loop. The reader does not get
the data already copied until the stream stops or a signal is
pending. The delay has not been reproduced.

Leave the receive loop at an empty record once the low-water mark
is met. A reader that has copied nothing still reads empty records
for as long as they arrive.

Suggested-by: sashiko-bot <netdev-bot+sashiko@kernel.org>
Link: https://lore.kernel.org/r/179124254665.434549.12245680127262431659@kernel.org
Signed-off-by: Chuck Lever <cel@kernel.org>
---
 net/tls/tls_sw.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/net/tls/tls_sw.c b/net/tls/tls_sw.c
index b7f3edf9828e..fd6f944ffd67 100644
--- a/net/tls/tls_sw.c
+++ b/net/tls/tls_sw.c
@@ -1937,6 +1937,12 @@ int tls_sw_recvmsg(struct sock *sk,
 
 			/* An empty record still marks a boundary. */
 			msg->msg_flags |= MSG_EOR;
+
+			/* Return data already copied instead of holding it
+			 * through a run of empty records.
+			 */
+			if (decrypted + copied >= target)
+				break;
 			continue;
 		}
 

-- 
2.55.0