Unexpected behavior of L2CAP LE Credit Based Flow Control Mode

[xiaobye-ctf]

Describe the bug In the function l2cap_cbm_run_channel, assuming that the GATT server and client establish a connection based on L2CAP LE Credit Based Flow Control Mode. If the GATT server receive LE_CREDIT_BASED_CONNECTION_REQUEST, then its channel->local_mps should also be initialized. https://github.com/bluekitchen/btstack/blob/272986f17af35a67815ab20897f6c91e710322a4/src/l2cap.c#L2057

Otherwise, the GATT server will always fail to receive L2CAP packets from the GATT client since channel->local_mps is 0 in the code below. https://github.com/bluekitchen/btstack/blob/272986f17af35a67815ab20897f6c91e710322a4/src/l2cap.c#L5218-L5223

To Reproduce Steps to reproduce the behavior:

1. Run example le_credit_based_flow_control_mode_server and le_credit_based_flow_control_mode_client .

Expected behavior The output below is expected output of le_credit_based_flow_control_mode_client

BTstack booting up..
Local version information:
- HCI Version    0x0d
- HCI Revision   0000
- LMP Version    0x0d
- LMP Subversion 0xffff
- Manufacturer   0x5f1
Nordic Semiconductor nRF5 chipset.
BTstack up and running on 00:00:00:00:00:00.
Start scanning!
Stop scan. Connect to device with addr C0:00:00:00:00:00.
Connection Interval: 30.00 ms
Connection Latency: 4
Connect to performance test service.
L2CAP: CBM Channel successfully opened: C0:00:00:00:00:00, handle 0x0000, psm 0x25, local cid 0x41, remote cid 0x41
Test packet size: 1000
: 24000 bytes -> 7.973 kB/s
: 22000 bytes -> 7.161 kB/s
: 22000 bytes -> 7.159 kB/s

But this is what I got.

BTstack booting up..
Local version information:
- HCI Version    0x0d
- HCI Revision   0000
- LMP Version    0x0d
- LMP Subversion 0xffff
- Manufacturer   0x5f1
Nordic Semiconductor nRF5 chipset.
BTstack up and running on 00:00:00:00:00:00.
Start scanning!
Stop scan. Connect to device with addr C0:00:00:00:00:00.
Connection Interval: 30.00 ms
Connection Latency: 4
Connect to performance test service.
L2CAP: CBM Channel successfully opened: C0:00:00:00:00:00, handle 0x0000, psm 0x25, local cid 0x41, remote cid 0x41
Test packet size: 1000
L2CAP: Channel closed 0x41
Disconnected C0:00:00:00:00:00

Environment: (please complete the following information):

• Current BTstack branch: develop