Test that we send multiple datagrams in one go if appropriate

If we have enough data for more than one datagram then we should send more
than one datagram

test/quicapitest.c

@@ -933,6 +933,64 @@ static int test_back_pressure(void)
     return testresult;
 }
 
+
+static int conn_close_ctr = 0;
+
+static void conn_close_cb(int write_p, int version, int content_type,
+                          const void *buf, size_t msglen, SSL *ssl, void *arg)
+{
+    PACKET pkt;
+    uint64_t frame_type;
+
+    if (!write_p)
+        return;
+
+    if (content_type != SSL3_RT_QUIC_FRAME_FULL
+            && content_type != SSL3_RT_QUIC_FRAME_HEADER)
+        return;
+
+    if (!PACKET_buf_init(&pkt, buf, msglen))
+        return;
+
+    if (!ossl_quic_wire_peek_frame_header(&pkt, &frame_type, NULL))
+        return;
+
+    if (frame_type == OSSL_QUIC_FRAME_TYPE_CONN_CLOSE_TRANSPORT)
+        conn_close_ctr++;
+}
+
+/* Test that we only get one CONNECTION_CLOSE when we only expect one */
+static int test_conn_close(void)
+{
+    SSL_CTX *cctx = SSL_CTX_new_ex(libctx, NULL, OSSL_QUIC_client_method());
+    SSL *clientquic = NULL;
+    QUIC_TSERVER *qtserv = NULL;
+    int testresult = 0;
+
+    if (!TEST_ptr(cctx)
+            || !TEST_true(qtest_create_quic_objects(libctx, cctx, NULL, cert,
+                                                    privkey, 0, &qtserv,
+                                                    &clientquic, NULL))
+            || !TEST_true(qtest_create_quic_connection(qtserv, clientquic)))
+        goto err;
+
+    conn_close_ctr = 0;
+    SSL_set_msg_callback(clientquic, conn_close_cb);
+    SSL_shutdown(clientquic);
+    SSL_handle_events(clientquic);
+    if (!TEST_int_eq(conn_close_ctr, 1))
+        goto err;
+
+    testresult = 1;
+ err:
+    SSL_free(clientquic);
+    ossl_quic_tserver_free(qtserv);
+    SSL_CTX_free(cctx);
+
+    return testresult;
+}
+
+
 OPT_TEST_DECLARE_USAGE("provider config certsdir datadir\n")
 
 int setup_tests(void)
@@ -1001,6 +1059,7 @@ int setup_tests(void)
     ADD_ALL_TESTS(test_quic_set_fd, 3);
     ADD_TEST(test_bio_ssl);
     ADD_TEST(test_back_pressure);
+    ADD_TEST(test_conn_close);
     return 1;
  err:
     cleanup_tests();