[Bluez-users] PAN with ISSC USB-dongle and MTU

[Bluez-users] PAN with ISSC USB-dongle and MTU

[Bernhard Held]

Hi all,

I recently bought 2 mini class-1 bluetooth dongles, and they turned out to
use the ISSC chip.

It was no problem to establish connections with a GPS mouse (rfcomm) and a
Palm T5 (ppp).

But I had big problems with PAN between a desktop and my venerable compaq
armada notebook. I could establish a connection, ping worked. But each time
I tried to transfer some real payload the connection died, and with it some
parts of the bluetooth stack. To restablish the connection most of the time
it's necessary to restart all bluetooth daemons, sometimes even the dongles
must be re-plugged.

I started to play with the ping size. 'ping -s 900' works, 'ping -s 1000'
kills the PAN connection. There was hope! Then I played with MTU (on both
sides): 'ifconfig bnep0 mtu 1000' solves all my problems (default is
1500)!!! With this setting I've a rock solid 75 kByte/s transfer rate over
ftp. A mtu of 1017 still works, 1018 definitely kills the connection. Then
the syslog is flooded with:
> hci_acldata_packet: hci0 ACL packet for unknown connection handle 0
and some stray
> hci_usb_rx_complete: hci0 corrupted packet: type 2 count 423

Small oversteps of MTU 1017 are recoverable, but a MTU 1500 kills my
daemons.

HTH! I'm ready to supply any additional information you need!

Thanks for the great bluez-software!

Bernhard


My config:
SuSE Linux 9.3 with all updates
kernel 2.6.15.1 with 3 tiny patches (not bluetooth related)

# hciconfig -a
hci0:   Type: USB
        BD Address: 00:11:67:18:16:BB ACL MTU: 678:8 SCO MTU: 48:10
        UP RUNNING PSCAN ISCAN
        RX bytes:4845896 acl:47638 sco:0 events:74919 errors:1
        TX bytes:28784762 acl:74470 sco:0 commands:220 errors:0
        Features: 0xbf 0xfe 0x8d 0x78 0x08 0x18 0x00 0x00
        Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
        Link policy: RSWITCH HOLD SNIFF PARK
        Link mode: SLAVE ACCEPT
        Name: 'BlueZ viktoria (0)'
        Class: 0x330104
        Service Classes: Positioning, Networking
        Device Class: Computer, Desktop workstation
        HCI Ver: 1.2 (0x2) HCI Rev: 0x1f4 LMP Ver: 1.2 (0x2) LMP Subver:
0x1f4
        Manufacturer: Integrated System Solution Corp. (57)



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Re: [Bluez-users] PAN with ISSC USB-dongle and MTU

[Paulo Matias]

Really, really thanks!!! I'd the same problem with ISSC and was
fighting with it!
Thanks a lot!!! =3DD
I will test right now your solution!


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Re: [Bluez-users] PAN with ISSC USB-dongle and MTU

[Marcel Holtmann]

Hi Bernhard,

> I recently bought 2 mini class-1 bluetooth dongles, and they turned out to
> use the ISSC chip.
> 
> It was no problem to establish connections with a GPS mouse (rfcomm) and a
> Palm T5 (ppp).

the default L2CAP MTU for RFCOMM connections is 1024 from our side and
most devices cut them down actually. For BNEP we actually try to get a
L2CAP MTU of 1691 for best performance.

> But I had big problems with PAN between a desktop and my venerable compaq
> armada notebook. I could establish a connection, ping worked. But each time
> I tried to transfer some real payload the connection died, and with it some
> parts of the bluetooth stack. To restablish the connection most of the time
> it's necessary to restart all bluetooth daemons, sometimes even the dongles
> must be re-plugged.
> 
> I started to play with the ping size. 'ping -s 900' works, 'ping -s 1000'
> kills the PAN connection. There was hope! Then I played with MTU (on both
> sides): 'ifconfig bnep0 mtu 1000' solves all my problems (default is
> 1500)!!! With this setting I've a rock solid 75 kByte/s transfer rate over
> ftp. A mtu of 1017 still works, 1018 definitely kills the connection. Then
> the syslog is flooded with:
> > hci_acldata_packet: hci0 ACL packet for unknown connection handle 0
> and some stray
> > hci_usb_rx_complete: hci0 corrupted packet: type 2 count 423
> 
> Small oversteps of MTU 1017 are recoverable, but a MTU 1500 kills my
> daemons.

I still hate these chips, because it seems that they are not really
capable of handling big data flows. Even if they are supposed to be and
this should have been verified in the qualification testing. I need to
find the exact chip you have and then do my own testing, but in general
it seems we have no other choice except including some tweaks into the
daemons to deal we bad chips.

Regards

Marcel




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Re: [Bluez-users] PAN with ISSC USB-dongle and MTU

[Paulo Matias]

Yeah, it works! Great! Now I'm running Gentoo Portage in my notebook
via bluetooth NAP at 60kb/s (yeah, my Internet link speed)... =3D)
Someone could put this information at the BlueZ website...

Thanks a lot!
Paulo Matias


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Re: [Bluez-users] PAN with ISSC USB-dongle and MTU

[Marcel Holtmann]

Hi Paulo,

> Yeah, it works! Great! Now I'm running Gentoo Portage in my notebook
> via bluetooth NAP at 60kb/s (yeah, my Internet link speed)... =)
> Someone could put this information at the BlueZ website...

I am curious what happens if you shrink the L2CAP MTU inside the pand.
Maybe this also works. Then it would be easy to add such command line
option and a quirk for ISSC chips.

Regards

Marcel




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