在Linux上直接控制HCI设备(绕过蓝牙驱动程序) [英] Direct Control of HCI Device (Bypass Bluetooth Drivers) on Linux

问题描述

我需要直接控制HCI设备，而不会干扰Linux驱动程序/内核.例如，当创建与外围设备的LE连接时，驱动程序会独立发送"LE Con​​nection Update"命令，这是我要避免的.

I need to control an HCI device directly without the Linux drivers/kernel interfering. For example, when creating an LE connection to a peripheral, the driver is independently sending an "LE Connection Update" command which I would like to avoid.

尽管有两种方法可以解决此问题:

I though of two approaches to resolve this:

1. 配置蓝牙驱动程序以某种方式禁用对HCI设备的干扰(类似于hciattach上的-r标志)，然后使用常规的AF_BLUEOOTH套接字控制HCI设备.
2. 禁用此特定的HCI设备，但保留父char设备并直接连接到它.

到目前为止，我还没有成功找到一种方法来实现这些方法.

So far I did not succeed in finding a way of how to implement any of these approaches.

我还应该提到，我仍需要系统使用其他的HCI设备来正常"使用，因此完全禁用蓝牙驱动程序不是一种选择.

I should also mention that I still need a different HCI device to be "normally" used by the system so disabling the bluetooth drivers completely is not an option.

推荐答案

我能够实现选项#1.

挖掘Linux内核代码中的蓝牙驱动程序，我找到了用于将HCI套接字与hci_channel=1绑定的选项. HCI_USER_CHANNEL的枚举是1，它导致驱动程序不向HCI设备添加自己的命令.

Digging in the Linux kernel code for bluetooth drivers, I found an option for binding an HCI socket with hci_channel=1. 1 is the enum for HCI_USER_CHANNEL which causes the driver not to add its own commands to the HCI device.

要在C语言中实现此目标:

struct sockaddr_hci {
    sa_family_t     hci_family;
    unsigned short  hci_dev;
    unsigned short  hci_channel;
};

struct sockaddr_hci a;

memset(&a, 0, sizeof(a));
a.hci_family = AF_BLUETOOTH;
a.hci_dev = 0; //0 for hci0
a.hci_channel = 1; //1 for HCI_CHANNEL_USER

bind(sock, (struct sockaddr *) &a, sizeof(a));

要在Python中实现此目的:

Python的套接字模块不支持此选项. Scapy中实现了针对Python中缺少支持的解决方法: https://github.com/secdev/scapy/blob/d2f2b0c7b46b607fcdf79860f8f866446bb625fb/scapy/layers/bluetooth.py#L808

Python's socket module does not support this option. A workaround for the missing support in Python was implemented in Scapy: https://github.com/secdev/scapy/blob/d2f2b0c7b46b607fcdf79860f8f866446bb625fb/scapy/layers/bluetooth.py#L808

C ++示例: https://github.com/sandeepmistry/node-bluetooth-hci-socket/blob/560a956c3e1421e31366115444ca9027d45b0e71/src/BluetoothHciSocket.cpp#L184

如果您对Linux内核的相关部分感兴趣:

If you are interested in the relevant part of the Linux kernel: https://github.com/torvalds/linux/blob/86292b33d4b79ee03e2f43ea0381ef85f077c760/net/bluetooth/hci_sock.c#L1693

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