Socket type in audio IPC

Hi,

We have a problem with audio IPC, sometimes following printout can be seen in logs when A2DP connection fails:
external/bluetooth/bluez/audio/pcm_bluetooth.c:1609:(audioservice_recv) Too short (1 bytes) IPC packet from bluetoothd

I was not able to catch this issue on my workstation for debugging so far, but it does not seem like ipc.h mismatch between BlueZ and ALSA plugin - we use one BlueZ version for a long time. Perhaps it's because of some unusual fragmentation (not sure how exactly sockets work internally) so my questions is why SOCK_STREAM sockets are used in audio IPC? Doesn't SOCK_SEQPACKET fit better here since we're dealing with messages rather than byte stream? There's no handling of fragmented packets in pcm_bluetooth.c at all so in case recv() returns less bytes than expected this is immediately returned as an error.

BR,
Andrzej

Hi Andrzej,

You're right that SOCK_SEQPACKET would be a better choice. However, changing it would break all existing clients that use SOCK_STREAM. Since we've already introduced the new D-Bus based solution for this which requires updating the clients anyway I don't think it's worth trying to fix this for the old unix socket based solution. FWIW, there are no current plans to keep maintaining pcm_bluetooth.c since most people use pulseaudio or some other solution and since it's quite tricky to make an ALSA userspace plugin use D-Bus properly. Feel free to try to come up with a patch to update pcm_bluetooth.c to use the new Media API though, and it might just live a little bit longer ;)

Johan