lib/tls: may need to send in receive loop

The engine can signal us that it needs to send some data (especially
connection aborts), and we should be responsive to that request rather
than spinning to timeout (or forever, perhaps) for an event that's not
coming.

Author: nwf

lib/tls/tls.cc

@@ -295,6 +295,23 @@ namespace
 				  {
 					  return -ENOTCONN;
 				  }
+
+				  if ((state & BR_SSL_SENDREC) == BR_SSL_SENDREC)
+				  {
+					  // If we need to send records, send them first.
+					  auto [sent, unfinished] = send_records(t, connection);
+					  if (sent == -ECOMPARTMENTFAIL)
+					  {
+						  // The TCP/IP stack crashed; tell the
+						  // caller that the link is dead.
+						  return -ENOTCONN;
+					  }
+					  if (sent <= 0)
+					  {
+						  return sent;
+					  }
+				  }
+
 				  if ((state & BR_SSL_RECVAPP) == BR_SSL_RECVAPP)
 				  {
 					  // If there are data ready to receive, return