[PATCH 0/3] Enabling IPv6 on Qualcomm MDM9x00 chipsets

[Dan Williams]

On Wed, 2013-11-27 at 12:54 +0100, Bjørn Mork wrote:
> I have tried to get IPv6 going on the Sierra Wireless MC7710 from time
> to time ever since I got it in April 2012. I had some success with a
> Huawei E392 using the same MDM9200 chipset, so I expected IPv6 to just
> work on the MC7710.  But it didn't.  It should be noted that I had
> access to multiple E392 modems at that time, and only some of them
> would connect to an IPv6 APN.  The others showed symptoms similar to
> the MC7710: PDP type IPV6 or IPV4V6 can be configured, but any
> connection attempt would fail.
> 
> Then, in July this year, another frustrated MC7710 user continued the
> old thread I initially started on Sierra's forums, and managed to
> describe the problem a lot better (with a lot less side tracking...):
> http://forum.sierrawireless.com/viewtopic.php?f=117&t=6126&p=30599&hilit=ipv6#p29460
> 
> The discussion following documented the fact that there exists a
> "magic" AT command enabling IPv6 support in the MC7710. This turned
> out to be the problem.  IPv6 support was disabled. Unfortunately
> the actual command is not documented in any publically available
> documentation AFAIK, whether under NDA or not, and is only disclosed
> to Sierra Wireless customers under NDA.  So it cannot be disclosed.
> 
> But NVRAM dumps are not covered by the NDA, and diffing dumps
> before and after running the command shows that there is a single
> bit toggled in NVRAM: the first byte of item #1896 (0x0768) changes
> from 00 to 01.
> 
> Now, I still had an E392 modem with the same problem, and Huawei
> doesn't have a similar AT command AFAIK. Reading NVRAM item #1896
> showed that it was unpopulated, returning an INACTIVE status. But
> writing 01 to it was successful. And it caused IPv6 to magically
> start working!
> 
> So having tested this on two MDM9200 based modems from two different
> vendors, I am pretty sure that this NVRAM item should be set to 01 on
> these devices. The same may also apply to other Qualcomm devices, but
> I've not been able to test it.  The MDM8200 based Huawei E367 modem I
> have will not let me set a IPV6 PDP type, so it will not support IPv6
> in any case.  FWIW, the NVRAM item was unpopulated on this modem as
> well and writing to it doesn't seem to have any ill effects.
> 
> But if you have a Qualcomm based device which appears to support IPv6
> (has the IPV6 PDP type) and an IPv6 enabled SIM, but still cannot make
> it connect, then please try out this utility.

Most of my modems have this NV item inactive; though one (USB551L) has
it enabled, and another (Sierra 313U) has it disabled.

So I decided to test with my Huawei E397Bu-501.

1) run ipv6pref => inactive
2) AT+CGDCONT=1,IPV4V6
3) run ModemManager
4) mmcli -m 0 --simple-connect="apn=epc.tmobile.com,ip-type=IPv4v6"
5) and I *do* get both IPv4 and IPv6 addresses

in other words, I was able to do IPv6 on this device without having set
the IPV6_ENABLED NV item to 1.  Any idea why that is?  Maybe some
versions enable IPv6 unconditionally and don't care about the NV item?

Dan