[Jack-Devel] Netjack crashes, alignment broken recently

[Xavier Mendez]

El 11/03/16 a les 12:17, Stéphane Letz ha escrit:
>
> Le 11 mars 2016 à 12:05, Filipe Coelho <falktx at gmail.com> a écrit :
>
>> On 10.03.2016 18:41, Xavier Mendez wrote:
>>> Just compiled the latest jackd2, and when using Netjack both manager and driver crash after sending parameters. I traced back to this change from 02f74a659, which modifies the network parameter struct:
>>>
>>> --- a/common/JackNetTool.h
>>> +++ b/common/JackNetTool.h
>>> @@ -94,9 +94,9 @@ namespace Jack
>>> -        char fName[JACK_CLIENT_NAME_SIZE];
>>> -        char fMasterNetName[JACK_SERVER_NAME_SIZE];
>>> -        char fSlaveNetName[JACK_SERVER_NAME_SIZE];
>>> +        char fName[JACK_CLIENT_NAME_SIZE+1];
>>> +        char fMasterNetName[JACK_SERVER_NAME_SIZE+1];
>>> +        char fSlaveNetName[JACK_SERVER_NAME_SIZE+1];
>>>
>>> That extra byte for the NUL terminator breaks the alignment, and somehow causes some ints to be sent as little-endian:
>>>
>>>     Sample rate : 12288000 frames per second
>>>     Period size : 131072 frames per period
>>>
>>> Reverting the three lines seems to resolve the problem. I don't really see the use for having the NUL terminator go through the network...
>>>
>>> What do you think?
>>
>> I can confirm this is an issue for me.
>> The "-d net" option stopped working some time ago and I've been wondering why, that change seems to be the reason.
>>
>> Reverting it in both client&server makes netmanager work again.
>>
>>
>> Please do a pull request against jack2's github repo.
>> That would be the fastest way to get this fixed upstream.
>>
>
> It would be better to understand why changing the  data structure (which is used both side of the connection… ) caused the crash. Are you sure the code is correctly recompiled everywhere?

Yes, I cloned and compiled 7bdad4966b29 on both ends, and even made sure 
to configure with the same options. The driver end is a Raspberry Pi 
with Raspbian, the manager end is my laptop (x64).

This is the discovery packet I get from the Pi, running "jackd -dnet -n 
raspberrypi -C1 -P1 -i1 -o1":

00000000  70 61 72 61 6d 73 00 00  00 00 00 08 00 00 00 00 
|params..........|
00000010  72 61 73 70 62 65 72 72  79 70 69 00 00 00 00 00 
|raspberrypi.....|
00000020  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00 
|................|
*
00000150  00 00 73 61 6c 61 00 00  00 00 00 00 00 00 00 00 
|..sala..........|
00000160  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00 
|................|
*
00000250  00 00 00 00 00 00 05 dc  00 00 00 00 00 00 00 00 
|................|
00000260  00 00 00 01 00 00 00 01  00 00 00 01 00 00 00 01 
|................|
00000270  00 00 00 00 00 00 00 00  00 00 00 00 00 00 00 00 
|................|
00000280  00 00 00 00 00 00 00 05                           |........|
00000288

As you can see, we have:

fMtu: 00 00 00 05 (correct)
fID: DC 00 00 00
fTransportSync: 00 00 00 00

And then, instead of the expected 00 00 00 01 for fSendAudioChannels, we 
have 00 00 00 00 01, which suggests the compiler has added a byte of 
padding to align the int? I don't know.

> Stéphane
>
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