Bluetooth: host: update l2cap stress test

Do these things:
- use the proper macros for reserving the SDU header
- make every L2CAP PDU fragment into 3 ACL packets
- set tx data and verify rx matches the pattern
- measure segment pool usage

Signed-off-by: Jonathan Rico <[email protected]>
(cherry picked from commit 8bc0946)

tests/bluetooth/bsim_bt/bsim_test_l2cap_stress/prj.conf

@@ -18,28 +18,32 @@ CONFIG_BT_GAP_AUTO_UPDATE_CONN_PARAMS=n
 # L2CAP MPS
 # 23+27+27=77 makes exactly three full packets
 CONFIG_BT_L2CAP_TX_MTU=77
-CONFIG_BT_BUF_ACL_TX_SIZE=77
+
+# Use this to send L2CAP PDUs without any fragmentation.
+# In this particular case, we prefer fragmenting to test that code path.
+# CONFIG_BT_BUF_ACL_TX_SIZE=81
+
+# L2CAP PDUs will be fragmented in 3 ACL packets.
+CONFIG_BT_BUF_ACL_TX_SIZE=27
+
 CONFIG_BT_BUF_ACL_TX_COUNT=4
 
 # The minimum value for this is
 # L2AP MPS + L2CAP header (4)
 CONFIG_BT_BUF_ACL_RX_SIZE=81
 
-# TODO: find out why we can't use 16 buffers. It should fit.
-
-CONFIG_BT_L2CAP_TX_BUF_COUNT=30
-# CONFIG_BT_L2CAP_TX_BUF_COUNT=100
-
-CONFIG_BT_BUF_ACL_TX_COUNT=4
+# Governs BT_CONN_TX_MAX, and so must be >= than the max number of
+# peers, since we attempt to send one SDU per peer. The test execution
+# is a bit slowed down by having this at the very minimum, but we want
+# to keep it that way as to stress the stack as much as possible.
+CONFIG_BT_L2CAP_TX_BUF_COUNT=6
 
+CONFIG_BT_CTLR_DATA_LENGTH_MAX=27
 CONFIG_BT_CTLR_RX_BUFFERS=10
-# The ring buffer now has space for three times as much data
-# (default 27, 3*27=81), so that it does not run out of data
-# while waiting for new SDUs to be queued.
-CONFIG_BT_CTLR_DATA_LENGTH_MAX=81
 
 CONFIG_BT_MAX_CONN=10
 
 CONFIG_LOG=y
 CONFIG_ASSERT=y
 CONFIG_BT_DEBUG_LOG=y
+CONFIG_NET_BUF_POOL_USAGE=y

tests/bluetooth/bsim_bt/bsim_test_l2cap_stress/src/main.c

@@ -21,16 +21,21 @@ CREATE_FLAG(flag_l2cap_connected);
 #define INIT_CREDITS 10
 #define SDU_NUM 20
 #define SDU_LEN 1230
+#define NUM_SEGMENTS 10
 
 /* Only one SDU per link will be transmitted at a time */
-/* FIXME: decrease size */
 NET_BUF_POOL_DEFINE(sdu_tx_pool,
- 100, BT_L2CAP_BUF_SIZE(SDU_LEN),
+ CONFIG_BT_MAX_CONN, BT_L2CAP_SDU_BUF_SIZE(SDU_LEN),
+ 8, NULL);
+
+NET_BUF_POOL_DEFINE(segment_pool,
+ /* MTU + 4 l2cap hdr + 4 ACL hdr */
+ NUM_SEGMENTS, BT_L2CAP_BUF_SIZE(CONFIG_BT_L2CAP_TX_MTU),
  8, NULL);
 
 /* Only one SDU per link will be received at a time */
 NET_BUF_POOL_DEFINE(sdu_rx_pool,
- CONFIG_BT_MAX_CONN, BT_L2CAP_BUF_SIZE(SDU_LEN),
+ CONFIG_BT_MAX_CONN, BT_L2CAP_SDU_BUF_SIZE(SDU_LEN),
  8, NULL);
 
 static struct bt_l2cap_le_chan l2cap_channels[L2CAP_CHANS];
@@ -40,6 +45,7 @@ static uint8_t tx_data[SDU_LEN];
 static uint8_t tx_left[L2CAP_CHANS];
 static uint16_t rx_cnt;
 static uint8_t disconnect_counter;
+static uint32_t max_seg_allocated;
 
 int l2cap_chan_send(struct bt_l2cap_chan *chan, uint8_t *data, size_t len)
 {
@@ -52,7 +58,7 @@ int l2cap_chan_send(struct bt_l2cap_chan *chan, uint8_t *data, size_t len)
  return -ENOMEM;
  }
 
- net_buf_reserve(buf, BT_L2CAP_CHAN_SEND_RESERVE);
+ net_buf_reserve(buf, BT_L2CAP_SDU_CHAN_SEND_RESERVE);
  net_buf_add_mem(buf, data, len);
 
  int ret = bt_l2cap_chan_send(chan, buf);
@@ -66,6 +72,19 @@ int l2cap_chan_send(struct bt_l2cap_chan *chan, uint8_t *data, size_t len)
  return ret;
 }
 
+struct net_buf *alloc_seg_cb(struct bt_l2cap_chan *chan)
+{
+ struct net_buf *buf = net_buf_alloc(&segment_pool, K_NO_WAIT);
+
+ if ((NUM_SEGMENTS - segment_pool.avail_count) > max_seg_allocated) {
+ max_seg_allocated++;
+ }
+
+ ASSERT(buf, "Ran out of segment buffers");
+
+ return buf;
+}
+
 struct net_buf *alloc_buf_cb(struct bt_l2cap_chan *chan)
 {
  return net_buf_alloc(&sdu_rx_pool, K_NO_WAIT);
@@ -108,6 +127,9 @@ int recv_cb(struct bt_l2cap_chan *chan, struct net_buf *buf)
  LOG_DBG("len %d", buf->len);
  rx_cnt++;
 
+ /* Verify SDU data matches TX'd data. */
+ ASSERT(memcmp(buf->data, tx_data, buf->len) == 0, "RX data doesn't match TX");
+
  return 0;
 }
 
@@ -137,6 +159,7 @@ static struct bt_l2cap_chan_ops ops = {
  .connected = l2cap_chan_connected_cb,
  .disconnected = l2cap_chan_disconnected_cb,
  .alloc_buf = alloc_buf_cb,
+ .alloc_seg = alloc_seg_cb,
  .recv = recv_cb,
  .sent = sent_cb,
 };
@@ -253,6 +276,11 @@ static void test_peripheral_main(void)
  LOG_DBG("*L2CAP STRESS Peripheral started*");
  int err;
 
+ /* Prepare tx_data */
+ for (size_t i = 0; i < sizeof(tx_data); i++) {
+ tx_data[i] = (uint8_t)i;
+ }
+
  err = bt_enable(NULL);
  if (err) {
  FAIL("Can't enable Bluetooth (err %d)", err);
@@ -358,6 +386,11 @@ static void test_central_main(void)
  LOG_DBG("*L2CAP STRESS Central started*");
  int err;
 
+ /* Prepare tx_data */
+ for (size_t i = 0; i < sizeof(tx_data); i++) {
+ tx_data[i] = (uint8_t)i;
+ }
+
  err = bt_enable(NULL);
  ASSERT(err == 0, "Can't enable Bluetooth (err %d)\n", err);
  LOG_DBG("Central Bluetooth initialized.");
@@ -395,6 +428,8 @@ static void test_central_main(void)
  }
  LOG_DBG("All peripherals disconnected.");
 
+ LOG_DBG("Max segment pool usage: %u bufs", max_seg_allocated);
+
  PASS("L2CAP STRESS Central passed\n");
 }