为什么用ADV_DATA做广告会产生无效的参数

问题描述

我正在尝试使用Management API编写一些BlueZ代码，但似乎无法让BlueZ在广告系统上广告任意数据

我有2个测试用C ++进行，另一个使用BlueZ发布的btmgmt工具进行测试

当我运行此命令时，它会以这种方式失败

btmgmt add-adv -d 8C33 1
Add Advertising Failed with status 0x0d (Invalid Parameters)

等效的C ++代码也同样失败

#include <iostream>

extern "C" {
  #include "external/bluetooth/lib/bluetooth.h"
  #include "external/bluetooth/lib/mgmt.h"
  #include "external/bluetooth/lib/hci.h"
  #include "external/bluetooth/lib/hci_lib.h"
  #include "external/bluetooth/src/shared/mgmt.h"
}

static void setup_dv(uint8_t status,uint16_t length,const void *param,void *user_data)
{
  std::cout << "good" << std::endl;
}

struct CPadvertising {
        uint8_t  instance;
        uint32_t flags;
        uint16_t duration;
        uint16_t timeout;
        uint8_t  adv_data_len;
        uint8_t  scan_rsp_len;
        uint8_t  data[4];
} __packed;


int main()
{
  mgmt* sock =  mgmt_new_default();


  CPadvertising* data = new CPadvertising();

  data->instance = 1;
  data->duration = 2;
  data->timeout = 100;
  data->adv_data_len = 4;
  data->scan_rsp_len = 0;
  data->flags = 0;
  data->data[0] = 8;
  data->data[1] = 12;
  data->data[2] = 3;
  data->data[3] = 3;

  mgmt_send(sock,MGMT_OP_ADD_ADVERTISING,index,sizeof(CPadvertising),data,setup_dv,nullptr,nullptr);
  auto  loop = g_main_loop_new(nullptr,FALSE);
  g_main_loop_run(loop);

}

在btmon中有此输出

@ MGMT Command: Add Advertising (0x003e) plen 13                               {0x0003} [hci0] 98.205359
        Instance: 1
        Flags: 0x00000000
        Duration: 2
        Timeout: 100
        Advertising data length: 4
        8 c 3 3                                            .3              
        Scan response length: 0
@ MGMT Event: Command Status (0x0002) plen 3                                   {0x0003} [hci0] 98.205376
      Add Advertising (0x003e)
        Status: Invalid Parameters (0x0d)

请参阅这些文档，我不应该为此获取任何无效参数，但是我可以

https://git.kernel.org/pub/scm/bluetooth/bluez.git/tree/doc/mgmt-api.txt

但是，我知道某些类型的数据确实可以工作

btmgmt add-adv -d 080954657374204C45

甚至以更奇怪的方式工作，在btmon上提示此输出

@ MGMT Command: Add Advertising (0x003e) plen 20                              {0x0002} [hci0] 143.671485
        Instance: 1
        Flags: 0x00000000
        Duration: 0
        Timeout: 0
        Advertising data length: 9
        Name (complete): Test LL <--- What is this
        Scan response length: 0

解决方法

查看btmgmt的来源，这些是可用的选项：

static void add_adv_usage(void)
{
    bt_shell_usage();
    print("Options:\n"
        "\t -u,--uuid <uuid>         Service UUID\n"
        "\t -d,--adv-data <data>     Advertising Data bytes\n"
        "\t -s,--scan-rsp <data>     Scan Response Data bytes\n"
        "\t -t,--timeout <timeout>   Timeout in seconds\n"
        "\t -D,--duration <duration> Duration in seconds\n"
        "\t -P,--phy <phy>           Phy type,Specify 1M/2M/CODED\n"
        "\t -c,--connectable         \"connectable\" flag\n"
        "\t -g,--general-discov      \"general-discoverable\" flag\n"
        "\t -l,--limited-discov      \"limited-discoverable\" flag\n"
        "\t -n,--scan-rsp-local-name \"local-name\" flag\n"
        "\t -a,--scan-rsp-appearance \"appearance\" flag\n"
        "\t -m,--managed-flags       \"managed-flags\" flag\n"
        "\t -p,--tx-power            \"tx-power\" flag\n"
        "e.g.:\n"
        "\tadd-adv -u 180d -u 180f -d 080954657374204C45 1");
}

查看有效的广告，第一个数字是数据的长度，第二个数字是data_type，其余的是local name字符串。所以：

0x08 = Length of datatype is 8
0x09 = Data type is <Complete Local Name>
0x54 = T
0x65 = e
0x73 = s
0x74 = t
0x20 = ' ' 
0x4C = L
0x45 = E

不确定btmon输出中为什么将其显示为Test LL。生病假设这与您记录的运行稍有不同。

查看您的8c33数据； 8c代表长度，而33不是有效的数据类型。

我怀疑您要发送的是制造商数据。假设您没有company identifier，则可以使用0xffff进行测试。

这将是以下命令：

btmgmt add-adv -d 05ffffff8C33 -g 1

哪个在btmon中提供了以下内容

@ MGMT Command: Add Adver.. (0x003e) plen 17  {0x0002} [hci0] 341.378134
        Instance: 1
        Flags: 0x00000002
          Advertise as Discoverable
        Duration: 0
        Timeout: 0
        Advertising data length: 6
        Company: internal use (65535)
          Data: 8c33
        Scan response length: 0

bluetooth c++