On 10/25/22 09:25, Aleksander Morgado wrote:
Hey Peter!
Hey Alek!
No, the DHCP server is running in the modem, to ease the configuration
process on the host side. Qualcomm modems have it for sure, there are
several other manufacturers that don't.
There is no DHCP protocol used in between the modem and the network,
IP assignment is done via 3GPP protocols.
Ah thanks, that clarifies some unrelated matters for me.
Anyway, it's certainly true that DHCP
is not always provided. But also, with a static IP assignment as it is done
in OpenWrt, there's no mechanism if the IP changes - this can happen due to
expiry of the IP, changing stations (i.e, a moving devicde) or other upstream
network churn. In such cases, you continue to be connected to the network, but
lose IP connectivity unless you have another mechanism to watch for such
changes.
If I'm not mistaken, a network-initiated disconnection is reported in
such cases (which openwrt git master branch supports), and the modem
just needs to re-establish the bearer with a reconnection. If this is
not always the case, we should definitely trigger a disconnection of
the modem ourselves upon detecting the IP reconfiguration. I'll ask
around to see what modems usually do in this regard.
When was this introduced? I guess it's not in any release yet. What I do
know for sure is that there isn't any/good handling in older setups, we
added explicit monitoring to check the assigned IP and then reconfigure
the interface.
The further problem is that there isn't a good way to test this other
than just waiting - sometimes after 12 hours or so it might get triggered
or not at all, or it has to be moved location - i.e, a different cell tower.
If there was a way to trigger this situation upstream, that'd be great.
