tests: bsim: add early disconnect tests for iso and l2cap

Add early_disconnect test cases for iso/cis and l2cap/stress
to test the bluetooth stack handling of disconnects
while transmit is still in progress.

Signed-off-by: Mike J. Chen <mjchen@google.com>

Author: mjchen0

tests/bsim/bluetooth/host/iso/cis/prj.conf

@@ -16,6 +16,7 @@ CONFIG_BT_ISO_TX_MTU=200
 CONFIG_BT_ISO_RX_MTU=200
 
 CONFIG_BT_ISO_LOG_LEVEL_DBG=y
+CONFIG_NET_BUF_POOL_USAGE=y
 
 # Controller Connected ISO configs
 CONFIG_BT_CTLR_CENTRAL_ISO=y

tests/bsim/bluetooth/host/iso/cis/src/cis_central.c

@@ -154,6 +154,11 @@ static void iso_disconnected(struct bt_iso_chan *chan, uint8_t reason)
 
 	err = bt_iso_remove_data_path(chan, BT_HCI_DATAPATH_DIR_HOST_TO_CTLR);
 	TEST_ASSERT(err == 0, "Failed to remove ISO data path: %d", err);
+
+	if (seq_num < 100) {
+		printk("Channel disconnected early, bumping seq_num to 1000 to end test\n");
+		seq_num = 1000;
+	}
 }
 
 static void sdu_sent_cb(struct bt_iso_chan *chan)
@@ -462,9 +467,16 @@ static void test_main(void)
 		k_sleep(K_USEC(interval_us));
 	}
 
-	disconnect_cis();
-	disconnect_acl();
-	terminate_cig();
+	if (seq_num == 100) {
+		disconnect_cis();
+		disconnect_acl();
+		terminate_cig();
+	}
+
+	/* check that all buffers returned to pool */
+	TEST_ASSERT(atomic_get(&tx_pool.avail_count) == ENQUEUE_COUNT,
+		    "tx_pool has non returned buffers, should be %u but is %u",
+		    ENQUEUE_COUNT, atomic_get(&tx_pool.avail_count));
 
 	TEST_PASS("Test passed");
 }

tests/bsim/bluetooth/host/iso/cis/src/cis_peripheral.c

@@ -35,6 +35,9 @@ static const struct bt_data ad[] = {
 };
 static struct bt_iso_chan iso_chan;
 
+static size_t disconnect_after_recv_cnt;
+static size_t iso_recv_cnt;
+
 /** Print data as d_0 d_1 d_2 ... d_(n-2) d_(n-1) d_(n) to show the 3 first and 3 last octets
  *
  * Examples:
@@ -72,14 +75,26 @@ static void iso_print_data(uint8_t *data, size_t data_len)
 	printk("\t %s\n", data_str);
 }
 
+static void disconnect_device(struct bt_conn *conn, void *data)
+{
+	int err = bt_conn_disconnect(conn, BT_HCI_ERR_REMOTE_USER_TERM_CONN);
+
+	TEST_ASSERT(!err, "Failed to initate disconnect (err %d)", err);
+}
+
 static void iso_recv(struct bt_iso_chan *chan, const struct bt_iso_recv_info *info,
 		     struct net_buf *buf)
 {
+	iso_recv_cnt++;
 	if (info->flags & BT_ISO_FLAGS_VALID) {
 		printk("Incoming data channel %p len %u\n", chan, buf->len);
 		iso_print_data(buf->data, buf->len);
 		SET_FLAG(flag_data_received);
 	}
+	if (disconnect_after_recv_cnt && (iso_recv_cnt >= disconnect_after_recv_cnt)) {
+		printk("Disconnecting\n");
+		bt_conn_foreach(BT_CONN_TYPE_LE, disconnect_device, NULL);
+	}
 }
 
 static void iso_connected(struct bt_iso_chan *chan)
@@ -189,12 +204,33 @@ static void test_main(void)
 	}
 }
 
+static void test_main_early_disconnect(void)
+{
+	init();
+
+	disconnect_after_recv_cnt = 10;
+
+	while (true) {
+		adv_connect();
+		bt_testlib_conn_wait_free();
+
+		if (IS_FLAG_SET(flag_data_received)) {
+			TEST_PASS("Test passed");
+		}
+	}
+}
+
 static const struct bst_test_instance test_def[] = {
 	{
 		.test_id = "peripheral",
 		.test_descr = "Peripheral",
 		.test_main_f = test_main,
 	},
+	{
+		.test_id = "peripheral_early_disconnect",
+		.test_descr = "Peripheral that tests early disconnect",
+		.test_main_f = test_main_early_disconnect,
+	},
 	BSTEST_END_MARKER,
 };
 

tests/bsim/bluetooth/host/iso/cis/tests_scripts/cis_early_disconnect.sh

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+# Copyright (c) 2025 Google LLC
+# SPDX-License-Identifier: Apache-2.0
+
+source ${ZEPHYR_BASE}/tests/bsim/sh_common.source
+
+# Tests cleanup within the ble stack for ISO connections when
+# peripheral disconnects early while the central still has
+# buffers queued for sending. Using the base code, which
+# has the central sending 100 ISO packets, the peripheral
+# triggers a disconnect after receiving 10 packets.
+# The central checks that all tx_pool buffers have been
+# returned to the pool after the disconnect.
+simulation_id="iso_cis_early_disconnect"
+verbosity_level=2
+EXECUTE_TIMEOUT=120
+
+cd ${BSIM_OUT_PATH}/bin
+
+Execute ./bs_${BOARD_TS}_tests_bsim_bluetooth_host_iso_cis_prj_conf \
+    -v=${verbosity_level} -s=${simulation_id} -d=0 -testid=central
+
+Execute ./bs_${BOARD_TS}_tests_bsim_bluetooth_host_iso_cis_prj_conf \
+    -v=${verbosity_level} -s=${simulation_id} -d=1 -testid=peripheral_early_disconnect
+
+Execute ./bs_2G4_phy_v1 -v=${verbosity_level} -s=${simulation_id} \
+    -D=2 -sim_length=30e6 $@
+
+wait_for_background_jobs

tests/bsim/bluetooth/host/l2cap/stress/overlay-early-disconnect.conf

@@ -0,0 +1 @@
+CONFIG_BT_L2CAP_SEG_RECV=y