Re: ANN: NetworkManager 1.0.0 released!

On Sun, Dec 21, 2014 at 12:15 PM, Tore Anderson <tore fud no> wrote:
This release brings [...] WWAN IPv6 support

Before you rush off to upload 1.0.0 to the various distros, I'd like to
remind you of This
is going to break WWAN connections for quite a few people, and they
will need manual configuration to recover.

The problem is that NetworkManager 1.0.0 will, when everything is left
at its defaults, attempt to use the dual-stack IPV4V6 PDP context type
if ModemManager reports that the modem supports it. This is a sane
thing to do by default, I think. However - even if the modem supports
it, the network operator might not. If so, the network attachment will
fail. Since NM doesn't retry with IP[v4] and/or IPV6, this failure is
final and the user is left without network connectivity. In order to
force IPv4-only connections, the user must manually disable IPv6 (and
vice versa).

This will happens for standard WWAN connections where the user goes
through the «Set up a Mobile Broadband Connection» wizard, changing as
little as possible - including any connections created in this way in
previous NM versions. That means that for users who upgrade to NM
1.0.0, previously working connection profiles will break.

Are you suggesting that by default NM should try with IPv4 or IPv6 PDP
context types if both are enabled and IPV4V6 fails?
In QMI modems it is ModemManager the one connecting separately IPv4
and IPv6 WDS sessions when IPv4v6 is requested.

This issue is aggravated by the fact that ModemManager will advertise
IPV4V6 support for all MBIM modems (even if the modem doesn't support
it, which I believe is the case for the vast majority of 3G modems),
That makes NM always try IPV4V6, but if the modem doesn't support it,
MM will immediately fail with the error "NoDeviceSupport". So if the
user has a MBIM modem that doesn't support IPV4V6, NM 1.0.0 will break
regardless of what the network provider supports.

Unfortunately I don't know of any command that we could use to query
the MBIM modem of supported IP types.

If MBIM modems do not always handle IPv4v6 PDP context types, and if
there is no MBIM command to ask for that, should we instead default to
not showing IPv4v6 as supported?


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