MC7304 takes minutes to get IP address with DHCP

[Dan Williams]

On Tue, 2017-10-24 at 12:42 +0200, Paul Loberg wrote:
> Hi.
> 
> I am testing a computer with a Sierra Wireless MC7304 modem where I
> am
> stuck in debugging why it usually take several minutes to obtain an
> IP
> address via DHCP.
> 
> I'm using libqmi 1.18.0 and a 4.1.35 kernel on Gentoo. To bring up
> the
> connection I do (DEV is /dev/cdc-wdm0)
> 
>  qmicli -d $DEV --wda-set-data-format=802-3
>  qmicli -d $DEV --wds-start-network=apn='internet' --client-no-
> release-cid
>  qmicli -d $DEV --wds-set-autoconnect-settings=enabled,roaming-
> allowed
> 
> After this, "qmicli -d $DEV --wds-get-packet-service-status" will
> show the
> status as "connected" and qmicli -d $DEV --wds-get-current-settings
> does
> show that the connection has been assigned an IP address immediately
> afterwards.
> 
> To configure the interface I rely on dhcpcd which I see report
> "carrier
> acquired" shortly after I bring up the wwan interface with qmicli and
> it
> then start sending DISCOVER requests on the interface. This goes on
> for
> many minutes (sometimes as much as 10 minutes) before a DHCP offer is
> received with the IP that I already observed when doing "qmicli -d
> $DEV
> --wds-get-current-settings".
> 
> What can be causing this? Is it an issue with the mobile broadband
> provider
> or related to my system?
> 
> Would it be safe to parse the output from "qmicli -d $DEV
> --wds-get-current-settings" and configure the wwan interface using
> that
> information? Does any tools exist that does that?

Yes, this is likely what you should do.  Note that new QMI-based
devices often do no support 802.3 mode and some don't support DHCP, but
do support --wds-get-current-settings.  It's not too hard to just parse
that info and run a couple /sbin/ip commands to set up the interface.

Dan