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From: Jon Hoffman <Jon.Hoffman@myfuelmaster.com>
To: "linux-bluetooth@vger.kernel.org" <linux-bluetooth@vger.kernel.org>
Date: Tue, 9 Feb 2016 13:17:56 -0500
Subject: Bluetooth PAN Connection - NAP and GN
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Hello,
I am hoping that someone on this list can tell me what I am doing wrong or at least point me in the right direction.

As part of a number of proof-of-concepts, I am trying to setup a PAN between two devices.  For this particular proof-of-concepts I am trying to setup a Bluetooth Legacy connection.  I have successfully setup this connection using the NAP scenario however we are not looking to route anything outside of connection.  Since we do not want to route (security also says we need to disable routing) we would prefer to use either a GN (Group Ad-Hoc Network) or a PANU-PANU connection however I have been unable to get this to work.   

My slave device (where the server is being setup at) is running the Linux kernel 4.4 (also tried it on a 4.1.13 kernel) with Bluez 5.35 (tried it with 5.23 on the 4.1.13 kernel).  I have tried three master devices (device making the connection) and have the same issue with all three.  They are:
  -Linux kernel 4.1.13 with bluez 5.23 using blueman as the UI
  -Windows 10
  -iOS 9.2.1

I have run hcidump to see what is going on during the pairing/connection of the NAP connection and also the GN connection to see what is different.  Below are sniplets of what I am seeing.  For the NAP connection I am seeing this:

information about the NAP from the hcidump
           record #6
              aid 0x0000 (SrvRecHndl)
                 uint 0x10007
              aid 0x0001 (SrvClassIDList)
                 < uuid-16 0x1116 (NAP) >
              aid 0x0004 (ProtocolDescList)
                 < < uuid-16 0x0100 (L2CAP) uint 0xf > <
                 uuid-16 0x000f (BNEP) uint 0x100 < uint 0x800 uint 0x806 > > >
              aid 0x0005 (BrwGrpList)
                 < uuid-16 0x1002 (PubBrwsGrp) >
              aid 0x0006 (LangBaseAttrIDList)
                 < uint 0x656e uint 0x6a uint 0x100 >
              aid 0x0009 (BTProfileDescList)
                 < < uuid-16 0x1116 (NAP) uint 0x100 > >
              aid 0x0100 (SrvName)
                 str "Network service"
              aid 0x0101 (SrvDesc)
                 str "Network service"
              aid 0x030a (SecurityDescription)
                 uint 0x1
              aid 0x030b (NetAccessType)
                 uint 0xfffe
              aid 0x030c (MaxNetAccessRate)
                 uint 0x0  

Then for the actual connection attempt I see this:

> ACL data: handle 11 flags 0x02 dlen 12
    L2CAP(s): Connect req: psm 15 scid 0x0041
< ACL data: handle 11 flags 0x00 dlen 16
    L2CAP(s): Connect rsp: dcid 0x0041 scid 0x0041 result 1 status 2
      Connection pending - Authorization pending
< ACL data: handle 11 flags 0x00 dlen 16
    L2CAP(s): Connect rsp: dcid 0x0041 scid 0x0041 result 0 status 0
      Connection successful

And after this my connection is established and all is well.  For the GN network this is what I am seeing beginning with the information about the GN.

           record #6
              aid 0x0000 (SrvRecHndl)
                 uint 0x10007
              aid 0x0001 (SrvClassIDList)
                 < uuid-16 0x1117 (GN) >
              aid 0x0004 (ProtocolDescList)
                 < < uuid-16 0x0100 (L2CAP) uint 0xf > <
                 uuid-16 0x000f (BNEP) uint 0x100 < uint 0x800 uint 0x806 > > >
              aid 0x0005 (BrwGrpList)
                 < uuid-16 0x1002 (PubBrwsGrp) >
              aid 0x0006 (LangBaseAttrIDList)
                 < uint 0x656e uint 0x6a uint 0x100 >
              aid 0x0009 (BTProfileDescList)
                 < < uuid-16 0x1117 (GN) uint 0x100 > >
              aid 0x0100 (SrvName)
                 str "Network service"
              aid 0x0101 (SrvDesc)
                 str "Network service"
              aid 0x030a (SecurityDescription)
                 uint 0x1

and when the connection is made I see this: 

> ACL data: handle 11 flags 0x02 dlen 12
    L2CAP(s): Connect req: psm 15 scid 0x0041
< ACL data: handle 11 flags 0x00 dlen 16
    L2CAP(s): Connect rsp: dcid 0x0041 scid 0x0041 result 1 status 2
      Connection pending - Authorization pending
< ACL data: handle 11 flags 0x00 dlen 16
    L2CAP(s): Connect rsp: dcid 0x0041 scid 0x0041 result 3 status 0
      Connection refused - security block

Since the issue is obviously a security block I have tried to figure out how to disable the security.  I have ran hciconfig with the noauth and noencrypt options but those do not seem to help.  I have also use bluetoothctl to trust the devices which worked to get the NAP working.  I have done a lot of reading but I have been unable to find much on the GN or PANU options.  Here is what I do to setup the server:

        echo "Setting up routing"
        /etc/init.d/radvd restart

        echo "setting up bridge"
        brctl addbr pan0
        brctl setfd pan0 0
        brctl stp pan0 off

        echo "setting pan0 local IP address"
        ifconfig pan0 192.168.3.2 
        ifconfig pan0 inet6 add fd00::5ef3:70ff:xxxx:xxxx/64
        ip link set pan0 up

        echo "starting bt-network server"
        #bt-network -d -s nap pan0 
        bt-network -d -s gn pan0 
        sleep 1

        #echo "starting dhcp server"
        /etc/init.d/dnsmasq restart 
        sleep 1

        echo " "

I enable the bt-network line for the particular connection I am trying to setup.
I know I am probably just missing something pretty easy but I have been chasing this for a few days now and I cannot seem to find what I am missing.  Any suggestions or ideas of where to look would be appreciated.
Thanks,

?Jon