Re: [Bluez-devel] Fwd: hci connect and switch role modifications

[Marcello Cinque <macinque@unina.it>]

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Hi Marcel,

as you asked, i'll send you the modifications separately.

This is the first.
Basically, we added a  mechanism that may use to prevent some errors 
from occurring (error masking mechanism) when performing a 
hci_create_connection. The mechanism is part of the results of our 
research on bluetooth networks. Perhaps the same strategies  can  be  
generalized and applied  on several parts of the code in order to 
improve the overall robustness of the BlueZ stack.
Specifically we added a function to the hci.c file (and related 
hci_lib.h) which name is hci_create_connection_timed.
This function first creates a connection and then checks whether the 
handle is valid (>0) until a given timeout expires. The timeout is 
specified as an additional parameter, in milliseconds. We created this 
function because, while working with bluetooth, we noticed that to get a 
valid handle over a connection may take some time, even after that the 
hci_create_connection function return, due to the asynchronous nature of 
the connection creation process. This could result in a error when 
subsequent calls are performed over the connection with a handle that is 
still not valid (e.g. a bnep create connection call over an already 
created l2cap connection, or a switch role command). This function 
avoids this problem because it returns with no errors only if the 
created connection has a valid handle.
It is worth noting that the function returns a "timer expired (ETIME)" 
error even when the connection is created. This happens when the timeout 
expires but the connection still has a not valid handle. However, the 
handle could become valid after the function exits.

We preferred to provide a new function rather than modifying the 
original ones. This way the user can choose to use the function that 
better suites his requirements.

In order to test and use the new functionalities, we also slightly 
modified the hcitool.c program, so as to add an optional parameter 
"--timeout" to the "cc" command. If the parameter is specified the new 
functions are called, otherwise the original functions are used.

Let me know if this can be of interest, in which case I'll send you also 
the second modification, on the switch role command.

Best regards,
Marcello Cinque
Fabio Cornevilli
Mobilab Research Group - www.mobilab.unina.it



Marcel Holtmann wrote:

>Hi Marcello,
>
>  
>
>>in february I sent you the email in the following, about some proposed 
>>modifications in the HCI connect and switch role APIs. At that time, I also attached 
>>you the unified diff files, which I'm attaching also now.
>>Anyway, I didn't receive any reply. Do you think these modifications are 
>>likely to be integrated in next releases?
>>    
>>
>
>I might have missed that. Sorry, but this can happen from time to time.
>
>If you propose multiple changes then please split them and post them
>separately if possible. This makes it easier for me to review them and
>then integrate them.
>
>Regards
>
>Marcel
>
>
>
>
>_______________________________________________
>Bluez-devel mailing list
>Bluez-devel@lists.sourceforge.net
>https://lists.sourceforge.net/lists/listinfo/bluez-devel
>
>  
>


-- 
Marcello Cinque, PhD Candidate
Dipartimento di Informatica e Sistemistica
Università di Napoli Federico II
Via Claudio, 21 - 80125 Napoli, Italy
Ph:  +39-081-7683874
Fax: +39-081-7683816
Web: wpage.unina.it/macinque
The MobiLab Group - www.mobilab.unina.it 


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