MC7455 doesn't get address with dhcp

sahokas · April 12, 2022, 12:24pm

Hi,

I’m having trouble getting network address for MC7455 module using DHCP client on linux device. We are using MBPL R24 and drivers that come with it. As a work around I query the address with SLQSGetRuntimeSettings and set that address to interface manually. So, network provides address to MC7455 modem, but for some reason DHCP client isn’t able to get it.

We used to have Gobi drivers for MC7455 modems and then there wasn’t any problems with DHCP client. Also, if I now put EM9190 modem to that same system it doesn’t have any issues with DHCP client. DHCP client is able to get the address that network has provided.

So, what could be wrong with MC7455? Linux version is 4.19.168 and MC7455 FW version is
SWI9X30C_02.33.03.00 r8209 CARMD-EV-FRMWR2 2019/08/28 20:59:30

br, Sami

jyijyi · April 12, 2022, 1:08pm

have you tried “sudo udhcpc -i wwan0” ?
Or you are using dhclient?

sahokas · April 12, 2022, 1:14pm

Yes, I’m using udhcpc, but it will never get the address. It will just keep sending discoveries but doesn’t seem to get any offers…

udhcpc: started, v1.30.1
udhcpc: sending discover
udhcpc: sending discover
udhcpc: sending discover
udhcpc: sending discover
udhcpc: sending discover

jyijyi · April 12, 2022, 1:24pm

I remember there is no such issue with my test here:

sahokas · April 12, 2022, 1:44pm

First of all, I don’t have that raw_ip file on my system. I think I had it but now that we are using mbim interface, it isn’t there anymore.

at!usbcomp?
Config Index: 1
Config Type: 1 (Generic)
Interface bitmask: 0000100D (diag,nmea,modem,mbim)

But on the other hand, same goes with EM9190 module. There is no raw_ip file for it either, and it is also configured to use mbim instead of rmnet. But still it works with DHCP client without any problems…

jyijyi · April 12, 2022, 2:41pm

Do you see problem with rmnet?
Or issue only happens on mbim?

sahokas · April 13, 2022, 8:16am

I haven’t been able to verify that. I can’t connect to network, now that modem has been configured to use rmnet. It should be registered, but still it says that no network service.

at!gstatus?
!GSTATUS:
Current Time: 5477 Temperature: 35
Reset Counter: 2 Mode: ONLINE
System mode: LTE PS state: Attached
LTE band: B3 LTE bw: 20 MHz
LTE Rx chan: 1300 LTE Tx chan: 19300
LTE CA state: NOT ASSIGNED
EMM state: Registered Normal Service
RRC state: RRC Idle
IMS reg state: No Srv

PCC RxM RSSI: -71 RSRP (dBm): -100
PCC RxD RSSI: 0 RSRP (dBm): 0
Tx Power: – TAC: 0FAA (4010)
RSRQ (dB): -9.3 Cell ID: 022D1915 (36509973)
SINR (dB): 6.4

OK

AT!SCACT=1,1
+CME ERROR: no network service

jyijyi · April 13, 2022, 8:30am

did you follow the procedure?

sudo qmicli --device=/dev/cdc-wdm0 --wds-noop --client-no-release-cid

sahokas · April 13, 2022, 8:33am

I don’t have that qmicli available right now, so I skipped that one. What does it do exactly? Is it manadatory to be able to connect to network?

sahokas · April 13, 2022, 8:45am

I added qmicli to my system. Lets see if it goes better with it…

sahokas · April 13, 2022, 8:51am

It seems to work if modem is using rmnet:

udhcpc -i wwan0
udhcpc: started, v1.30.1
udhcpc: sending discover
udhcpc: sending select for 100.111.233.24
udhcpc: lease of 100.111.233.24 obtained, lease time 7200

jyijyi · April 13, 2022, 9:58am

then is it ok to use RMNET as use case?

You also can try this script to have DHCP on MBIM interface:

github.com

elementzonline/GSMModem/blob/master/SIM7600/mbim-set-ip/mbim-set-ip

#!/bin/bash
#
# mbim-set-ip script version 1.0
# Modified mbimcli IPv4 IPv6 parsing script based on parts of project https://github.com/grandcentrix/thinkpad-x260-modem-scripts
# Licensed under the Apache License, Version 2.0
# Modified by Jörgen Storvist, Techship http://www.techship.com
#
# Further details in the Techship FAQ sections on using MBIM and setting correct modes in cellular modules:
# https://techship.com/faq/how-to-set-up-a-simple-data-connection-over-the-mbim-interface-using-libmbim-and-driver-cdc-mbim-in-linux/
#
# Installation & Usage: 
#
# Verify that the cellular module is exposing the MBIM interface over the USB interface. 
# Use mbimcli to check status for the cellular connection and enter the PIN code if necessary. 
# Configure mbim-network.conf and place in /etc/ (example file included in the archive, check link bellow for details).
# https://www.freedesktop.org/software/libmbim/man/latest/mbim-network.1.html
# Start the mbim data connection with command:
# mbim-network <MBIM-INTERFACE> start
# Ensure execution of mbim-set-ip script with sufficient system priviledges
# ./mbim-set-ip <MBIM-INTERFACE> <NETWORK-INTERFACE>

This file has been truncated. show original

./mbim-set-ip /dev/cdc-wdm0 wwan0

sahokas · April 13, 2022, 10:25am

Well, that script does basically the same thing as my own link manager as a workaround for this dhcp problem. It queries address from modem and sets it to interface and It’s working fine. But I was just curious about why the dhcp client wouldn’t work in this case. It should on my opinion and it does when using for example EM9190 modem.

I don’t think that rmnet is an option for us. Using that creates a point to point interface and that turned out to be a problem for some third party SW that we are using.

ip link show wwan0
17: wwan0: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UNKNOWN mode DEFAULT group default qlen 1000
link/none

jyijyi · April 13, 2022, 10:29am

ok, maybe you need to use that workaround

sahokas · April 13, 2022, 10:54am

Hmm, yes probably… But I would really like to understand why this doesn’t work. There should be a dhcp server running inside that modem, right? Is there a way to verify if it is running or not?

jyijyi · April 13, 2022, 11:06am

I don’t know, as it works on RMNET, maybe some FW problem on MBIM…

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