[Bluez-users] Use an ACL link when an SCO link is established

[Bluez-users] Use an ACL link when an SCO link is established

[Michel Leconte]

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Hi all,

my goal is to use an ACL link when an SCO link is established.

I work with two bluetooth development kits from Semtech-Xemics (SE1441). 

They are compliant Bluetooth v1.2. For the following explanations, one kit is noted "A" and the other "B".

1) First, I create an ACL link between "A" and "B" with : hcitool cc BD_ADDR of "B",

2) Once the ACL link is done, "A" execute an "HCI_Setup_Synchronous_Connection" command to "B",

3) At the event of an SCO request connection, "B" respond with an "HCI_Accept_Synchronous_Connection_Request" command.

4) When the SCO link is established, a "Synchronous Connection Complete" HCI event is visible from the hci layer of each kit.

the "hcitool con" gives :

> SCO AA:AA:AA:AA:AA:04 handle 0 state 5 lm SLAVE

> ACL AA:AA:AA:AA:AA:04 handle 0 state 1 lm SLAVE



5) I try to use the ACL link with a l2ping command from B to A

the l2ping command gives :

l2ping AA:AA:AA:AA:AA:04 (BD_ADDR of A)

Ping: AA:AA:AA:AA:AA:04 from AA:AA:AA:AA:AA:05 (data size 44) ...

no response from AA:AA:AA:AA:AA:04: id 0

no response from AA:AA:AA:AA:AA:04: id 1

---------------------------------------------------------------------------------------------------------------------

Question 1 : With this configuration (SCO and ACL links between A and B), why l2ping doesn't work ? 

The ACL link can be used isn't it ?



Question 2 : From the hci dump of each side, I notice that there is a difference between the information

of the command and the OGF and OCF between the parenthesises. See below the hcidump results, the 

 red lines are those which give me a problem. At the "A" side, I send an "HCI_Setup_Asynchronous_Connection" and hcidump indicates an  "HCI_Accept_Synchronous_Connection". I get a similar problem in "B" side an "HCI_Reject_Synchronous_Connection " instead of an " HCI_Accept_Synchronous_Connection ".

When you see the bluetooth spec :

HCI_Setup_Asynchronous_Connection is OGF=0x01 and OCF=0x28 

HCI_Accept_Synchronous_Connection is OGF=0x01 and OCF=0x29 

HCI_Reject_Synchronous_Connection is OGF=0x01 and OCF=0x2A 

 

Do these differences are benign for the bluez stack or they can be the origine

of my problem ??




************************** HCI dump from "A" ***********************************************

HCI sniffer - Bluetooth packet analyzer ver 1.30

device: hci0 snap_len: 1028 filter: 0xffffffff

< HCI Command: Create Connection (0x01|0x0005) plen 13

bdaddr AA:AA:AA:AA:AA:05 ptype 0xcc18 rswitch 0x01 clkoffset 0x0000

Packet type: DM1 DM3 DM5 DH1 DH3 DH5 

> HCI Event: Command Status (0x0f) plen 4

Create Connection (0x01|0x0005) status 0x00 ncmd 1

> HCI Event: Connect Complete (0x03) plen 11

status 0x00 handle 0 bdaddr AA:AA:AA:AA:AA:05 type ACL encrypt 0x00

< HCI Command: Write Link Policy Settings (0x02|0x000d) plen 4

handle 0 policy 0x0f

Link policy: RSWITCH HOLD SNIFF PARK 

> HCI Event: Command Complete (0x0e) plen 6

Write Link Policy Settings (0x02|0x000d) ncmd 1

status 0x00 handle 0

< HCI Command: Accept Synchronous Connection (0x01|0x0028) plen 17

handle 0

40 1F 00 00 40 1F 00 00 FF FF C1 01 00 04 00 

> HCI Event: Max Slots Change (0x1b) plen 3

handle 0 slots 5

> HCI Event: Command Status (0x0f) plen 4

Accept Synchronous Connection (0x01|0x0028) status 0x00 ncmd 1

> HCI Event: Synchronous Connect Complete (0x2c) plen 17

status 0x00 handle 256 bdaddr AA:AA:AA:AA:AA:05 type SCO

Air mode: u-law log

************************** HCI dump from "B" ***********************************************


HCI sniffer - Bluetooth packet analyzer ver 1.30

device: hci0 snap_len: 1028 filter: 0xffffffff

> HCI Event: Connect Request (0x04) plen 10

bdaddr AA:AA:AA:AA:AA:04 class 0x3e0100 type ACL

< HCI Command: Accept Connection Request (0x01|0x0009) plen 7

bdaddr AA:AA:AA:AA:AA:04 role 0x01

Role: Slave

> HCI Event: Command Status (0x0f) plen 4

Accept Connection Request (0x01|0x0009) status 0x00 ncmd 1

> HCI Event: Connect Complete (0x03) plen 11

status 0x00 handle 0 bdaddr AA:AA:AA:AA:AA:04 type ACL encrypt 0x00

< HCI Command: Write Link Policy Settings (0x02|0x000d) plen 4

handle 0 policy 0x0f

Link policy: RSWITCH HOLD SNIFF PARK 

> HCI Event: Command Complete (0x0e) plen 6

Write Link Policy Settings (0x02|0x000d) ncmd 1

status 0x00 handle 0

< HCI Command: Change Connection Packet Type (0x01|0x000f) plen 4

handle 0 ptype 0xcc18

Packet type: DM1 DM3 DM5 DH1 DH3 DH5 

> HCI Event: Command Status (0x0f) plen 4

Change Connection Packet Type (0x01|0x000f) status 0x00 ncmd 1

> HCI Event: Connection Packet Type Changed (0x1d) plen 5

status 0x00 handle 0 ptype 0x0018

Packet type: DM1 DH1 

> HCI Event: Connect Request (0x04) plen 10

bdaddr AA:AA:AA:AA:AA:04 class 0x3e0100 type SCO

< HCI Command: Accept Connection Request (0x01|0x0009) plen 7

bdaddr AA:AA:AA:AA:AA:04 role 0x01

Role: Slave

> HCI Event: Command Status (0x0f) plen 4

Accept Connection Request (0x01|0x0009) status 0x00 ncmd 1

< HCI Command: Reject Synchronous Connection (0x01|0x0029) plen 21

bdaddr AA:AA:AA:AA:AA:04

FF FF FF FF FF FF FF FF FF FF C1 01 FF 04 00 

> HCI Event: Command Status (0x0f) plen 4

Reject Synchronous Connection (0x01|0x0029) status 0x00 ncmd 1

> HCI Event: Synchronous Connect Complete (0x2c) plen 17

status 0x00 handle 256 bdaddr AA:AA:AA:AA:AA:04 type SCO

Air mode: u-law log



Question 3 : The event "Synchronous Connect Complete" gives the handle of the SCO link

in my case the handle value is 256. But when you see upside the hcitool

con result gives a handle 0 ? Is it normal ? 


Question 4 : Here's my software configurations : hcidump 1.30 bluez-libs-2.25 bluez-utils-2.25 linux-debian 2.6.12.2 with an ARM target 



As I have to keep the kernel 2.6.12.2, with wich higher version of bluez-libs, bluez-utils and hcidump can I use to be compliant with my kernel ? 



Thanks to all for any suggestions..

warm regards

Michel

---------------------------------------------------------------------------------------------------------------------

the result of an "hciconfig -a" is :

hci0: Type: UART

BD Address: AA:AA:AA:AA:AA:04 ACL MTU: 339:8 SCO MTU: 180:8

UP RUNNING PSCAN ISCAN

RX bytes:522 acl:0 sco:0 events:61 errors:0

TX bytes:1367 acl:15 sco:0 commands:26 errors:0

Features: 0xff 0xff 0xbd 0xf8 0x1b 0x18 0x00 0x80

Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3

Link policy: RSWITCH HOLD SNIFF PARK

Link mode: SLAVE ACCEPT

Name: 'BlueZ (0)'

Class: 0x3e0100

Service Classes: Networking, Rendering, Capturing

Device Class: Computer, Uncategorized

HCI Ver: 1.2 (0x2) HCI Rev: 0x0 LMP Ver: 1.2 (0x2) LMP Subver: 0xc

Manufacturer: Newlogic (23)

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Re: [Bluez-users] Use an ACL link when an SCO link is established

[Marcel Holtmann]

Hi Michel,

> 
> my goal is to use an ACL link when an SCO link is established.
> 
> I work with two bluetooth development kits from Semtech-Xemics
> (SE1441). 
> 
> They are compliant Bluetooth v1.2. For the following explanations, one
> kit is noted "A" and the other "B".
> 
> 1) First, I create an ACL link between "A" and "B" with : hcitool cc
> BD_ADDR of "B",

first of all, don't do this. The "hcitool cc ..." is for testing only
and doesn't honor the kernel internal reference counting. You will see
side effects and I am not going to help you with it.
> 
> 2) Once the ACL link is done, "A" execute an
> "HCI_Setup_Synchronous_Connection" command to "B",
> 
> 3) At the event of an SCO request connection, "B" respond with an
> "HCI_Accept_Synchronous_Connection_Request" command.
> 
> 4) When the SCO link is established, a "Synchronous Connection
> Complete" HCI event is visible from the hci layer of each kit.
> 
> the "hcitool con" gives :
> 
> > SCO AA:AA:AA:AA:AA:04 handle 0 state 5 lm SLAVE
> 
> > ACL AA:AA:AA:AA:AA:04 handle 0 state 1 lm SLAVE

The eSCO support inside the kernel has never been adapted. You need to
change the kernel to open and accept eSCO connections.
> 
> 5) I try to use the ACL link with a l2ping command from B to A
> 
> the l2ping command gives :
> 
> l2ping AA:AA:AA:AA:AA:04 (BD_ADDR of A)
> 
> Ping: AA:AA:AA:AA:AA:04 from AA:AA:AA:AA:AA:05 (data size 44) ...
> 
> no response from AA:AA:AA:AA:AA:04: id 0
> 
> no response from AA:AA:AA:AA:AA:04: id 1

l2ping will create the ACL link if needed.

> ---------------------------------------------------------------------------------------------------------------------
> 
> Question 1 : With this configuration (SCO and ACL links between A and
> B), why l2ping doesn't work ? 
> 
> The ACL link can be used isn't it ?

Sure. But let the kernel create it. As I said, l2ping will create its
needed ACL link by itself.
> 
> Question 2 : From the hci dump of each side, I notice that there is a
> difference between the information
> 
> of the command and the OGF and OCF between the parenthesises. See
> below the hcidump results, the 
> 
>  red lines are those which give me a problem. At the "A" side, I send
> an "HCI_Setup_Asynchronous_Connection" and hcidump indicates an
> "HCI_Accept_Synchronous_Connection". I get a similar problem in "B"
> side an "HCI_Reject_Synchronous_Connection " instead of an "
> HCI_Accept_Synchronous_Connection ".

This might be an off-by-one bug in hcidump. Check the hcidump source
code and send in a patch for it.
> 
> When you see the bluetooth spec :
> 
> HCI_Setup_Asynchronous_Connection is OGF=0x01 and OCF=0x28 
> 
> HCI_Accept_Synchronous_Connection is OGF=0x01 and OCF=0x29 
> 
> HCI_Reject_Synchronous_Connection is OGF=0x01 and OCF=0x2A 
> 
>  
> 
> Do these differences are benign for the bluez stack or they can be the
> origine
> 
> of my problem ??

The hcidump is stupid and has nothing to do with actual data send to the
chip. This looks like a decoding bug. Or you simply sent the wrong
command. I haven't checked the specification.

> Question 3 : The event "Synchronous Connect Complete" gives the handle
> of the SCO link
> 
> in my case the handle value is 256. But when you see upside the
> hcitool
> 
> con result gives a handle 0 ? Is it normal ? 

Depends on the hardware you use. The handle is 16 bit value and the chip
implementation can at least pick the first 12 bits as it wishes.
> 
> Question 4 : Here's my software configurations : hcidump 1.30
> bluez-libs-2.25 bluez-utils-2.25 linux-debian 2.6.12.2 with an ARM
> target 
> 
>  
> 
> As I have to keep the kernel 2.6.12.2, with wich higher version of
> bluez-libs, bluez-utils and hcidump can I use to be compliant with my
> kernel ? 

The 3.x userspace packages will work with that kernel.

Regards

Marcel




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