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Support for Bluetooth LE L2CAP Connection-oriented channels through AF_BLUETOOTH/BTPROTO_L2CAP socket #129288

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themadinventor opened this issue Jan 25, 2025 · 2 comments
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Support for Bluetooth LE L2CAP Connection-oriented channels through AF_BLUETOOTH/BTPROTO_L2CAP socket #129288

themadinventor opened this issue Jan 25, 2025 · 2 comments
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extension-modules C modules in the Modules dir type-feature A feature request or enhancement

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@themadinventor
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themadinventor commented Jan 25, 2025 •
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Feature or enhancement

Proposal:

As has been discussed previously (69242, 70145), "new" fields have been added in sockaddr_l2, but are still not supported in CPython's socket implementation.

  • The lack of l2_bdaddr_type prevents opening L2CAP connection-oriented channels to Bluetooth LE devices.
  • Likewise, the missing l2_cid prevents raw access to e.g ATT.

My suggestion is to add support for a third and fourth optional element in the address tuple for l2_cid and l2_bdaddr_type respectively.

  • Only one of psm and cid can be non-zero. This is enforced by the kernel.
  • l2_bdaddr_type can take the value of BDADDR_LE_PUBLIC or BDADDR_LE_RANDOM. BDADDR_BREDR is implied if the element is missing, preserving compatibility with existing code.

I.e for LE CoC connection to PSM 0x80

sock = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP)
sock.connect((bdaddr, 0x80, 0, BDADDR_LE_RANDOM))

For a raw LE ATT connection:

CID_ATT = 0x04
sock = socket(AF_BLUETOOTH, SOCK_SEQPACKET, BTPROTO_L2CAP)
s.bind((BDADDR_ANY, 0, CID_ATT, BDADDR_LE_RANDOM))
s.connect((bdaddr, 0, CID_ATT, BDADDR_LE_RANDOM))

while keeping the existing format for classic BR/EDR L2CAP.

sock.connect((bdaddr, 0x80))

I have a working implementation of this locally (tested on Linux 6.11) and will file a PR for review as soon as I've got this issue number assigned.

This is my first attempt at contributing to CPython, so I apologize in advance for any mistakes in the process.

Edit 2025-01-26: Added CID field to proposal. PR to be updated.

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

#69242
#70145

Linked PRs
@themadinventor themadinventor added the type-feature A feature request or enhancement label Jan 25, 2025
themadinventor added a commit to themadinventor/cpython that referenced this issue Jan 25, 2025
@themadinventor
pythongh-129288: Add optional bdaddr_type in BTPROTO_L2CAP socket add…
702f477 
…ress tuple

To be able to connect L2CAP sockets to Bluetooth LE devices, the l2_bdaddr_type must be set to BDADDR_LE_PUBLIC or BDADDR_LE_RANDOM.
This change adds support for providing the l2_bdaddr_type as an optional, traliing element in the address tuple passed to connect()
@bedevere-app bedevere-app bot mentioned this issue Jan 25, 2025
Merged
themadinventor added a commit to themadinventor/cpython that referenced this issue Jan 25, 2025
@themadinventor
pythongh-129288: Expose socket.BDADDR_BREDR, socket.BDADDR_LE_PUBLIC,…
d45523c 
… socket.BDADDR_RANDOM only if defined for target

Add check that BDADDR_BREDR is defined as Windows build may set USE_BLUETOOTH but not BDADDR_*
themadinventor added a commit to themadinventor/cpython that referenced this issue Jan 26, 2025
@themadinventor
pythongh-129288: Add optional CID field in BTPROTO_L2CAP socket addre…
e9b2a54 
…ss tuple

This change adds support for the CID field in the socket address tuple. This allows e.g raw LE ATT connections.
themadinventor added a commit to themadinventor/cpython that referenced this issue Jan 26, 2025
@themadinventor
pythongh-129288: Fix NEWS blurb formatting
4c123f6
@picnixz picnixz added the extension-modules C modules in the Modules dir label Jan 27, 2025
themadinventor added a commit to themadinventor/cpython that referenced this issue Jan 27, 2025
@themadinventor
Merge branch 'main' into pythongh-129288
4259dca
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 23, 2025
@themadinventor
pythongh-129288: Update docs for socket to include new BTPROTO_L2CAP …
d771afb 
…address fields

Update documentation to mention the new cid and bdaddr_type fields for BTPROTO_L2CAP connections.
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 23, 2025
@themadinventor
Merge branch 'main' into pythongh-129288
508ef7d
@themadinventor
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Kindly reminding about this PR, which I hope is uncontroversial and quick to review :)

(The docs says it's ok to ping after one month of no feedback, to make sure it's not forgotten [1].)

[1] https://devguide.python.org/getting-started/pull-request-lifecycle/#reviewing

themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 25, 2025
@themadinventor
pythongh-129288: Improve docs for socket on BTPROTO_L2CAP, BDADDR_BRE…
60abd6e 
…DR et al
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 25, 2025
@themadinventor
pythongh-129288: Move BDADDR_BREDR et al macros to use BTPROTO_L2CAP …
2c537ba 
…guard
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 25, 2025
@themadinventor
pythongh-129288: Update comment re discarding cid for BR/EDR L2CAP so…
b25005e 
…cket
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 25, 2025
@themadinventor
Merge pull request #1 from encukou/pythongh-129288
05de5ee 
BTPROTO_L2CAP extenstion: Expand the docs & provide link targets for the constants
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 25, 2025
@themadinventor
pythongh-129288: Add tests for BTPROTO_L2CAP socket
8532c5b
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 26, 2025
@themadinventor
pythongh-129288: Add HAVE_SOCKET_BLUETOOTH_L2CAP to socket tests
1af3e88
themadinventor added a commit to themadinventor/cpython that referenced this issue Feb 26, 2025
@themadinventor
pythongh-129288 Revert skip criteria for testCreateL2capSocket
5a1eaa3
encukou pushed a commit that referenced this issue Feb 27, 2025
@themadinventor
gh-129288: Add optional l2_cid and l2_bdaddr_type in BTPROTO_L2CAP so…
45a24f5 
…cket address tuple (#129293)

Add two optional, traling elements in the AF_BLUETOOTH socket address tuple:

- l2_cid, to allow e.g raw LE ATT connections
- l2_bdaddr_type. To be able to connect L2CAP sockets to Bluetooth LE devices,
  the l2_bdaddr_type must be set to BDADDR_LE_PUBLIC or BDADDR_LE_RANDOM.
@encukou
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encukou commented Feb 27, 2025

Thank you for the addition!

@encukou encukou closed this as completed Feb 27, 2025
@encukou encukou mentioned this issue Feb 27, 2025
Closed
seehwan pushed a commit to seehwan/cpython that referenced this issue Apr 16, 2025
@themadinventor @seehwan80
pythongh-129288: Add optional l2_cid and l2_bdaddr_type in BTPROTO_L2…
d29bc64 
…CAP socket address tuple (python#129293)

Add two optional, traling elements in the AF_BLUETOOTH socket address tuple:

- l2_cid, to allow e.g raw LE ATT connections
- l2_bdaddr_type. To be able to connect L2CAP sockets to Bluetooth LE devices,
  the l2_bdaddr_type must be set to BDADDR_LE_PUBLIC or BDADDR_LE_RANDOM.
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