Issues if cellular network doesn't hand out DNS?

1

Hi,

I have a WP7702 and are trying to send data over NB-IoT. Using a Vodafone SIM I succeeded in sending data over TCP and UDP. Using a T-Mobile SIM the same application won’t send any data to my server. Legato throws a lot of errors related to DNS and WiFi (my application doesn’t use WiFi or functions for DNS), and eventually crashes. I have the impression that the T-Mobile SIM doesn’t hand out IP addresses of DNS servers and that this is causing the Data Connection Service to crash. Is Legato indeed depending on the cellular network to hand out DNS, even if no DNS query is needed? Is there a way around this, or will there be in the future?

The errors that keep on apearing:
Jan 6 05:22:08 | wifiService[685] | | WIFICLIENT_DISCONNECT
Jan 6 05:22:08 | wifiService[685] | | Failed to connect to non-global ctrl_ifname: wlan0 error: No such file or directory
Jan 6 05:22:08 | wifiService[685]/daemon T=main | pa_wifi_client_ti.c pa_wifiClient_Disconnect() 1056 | WiFi Client Command Failed: (24832)wlan0 WIFICLIENT_DISCONNECT
Jan 6 05:22:08 | dcsDaemon[14814]/dcsDaemon T=main | dcsServer.c TryStopWifiSession() 1505 | Impossible to disconnect wifi client
Jan 6 05:22:08 | dcsDaemon[14814]/le_pa_dcs T=main | pa_dcs_linux.c pa_dcs_SetDefaultGateway() 568 | Default gateway or interface is empty
Jan 6 05:22:08 | dcsDaemon[14814]/dcsDaemon T=main | dcsServer.c LoadSelectedTechProfile() 955 | No value set for ‘SSID’!
Jan 6 05:22:08 | dcsDaemon[14814]/dcsDaemon T=main | dcsServer.c TryStartWifiSession() 1323 | Impossible to use Wifi profile, result -1 (LE_NOT_FOUND)
Jan 6 05:22:08 | wifiService[685]/daemon T=main | le_wifiClient.c le_wifiClient_Disconnect() 1282 | Disconnect
Jan 6 05:22:08 | modemDaemon[679]/le_pa T=main | pa_mrc_qmi.c pa_mrc_GetNetworkRegState() 1945 | called
Jan 6 05:22:08 | wifiService[685] | | WIFICLIENT_DISCONNECT
Jan 6 05:22:08 | wifiService[685] | | Failed to connect to non-global ctrl_ifname: wlan0 error: No such file or directory
Jan 6 05:22:08 | wifiService[685]/daemon T=main | pa_wifi_client_ti.c pa_wifiClient_Disconnect() 1056 | WiFi Client Command Failed: (24832)wlan0 WIFICLIENT_DISCONNECT
Jan 6 05:22:08 | dcsDaemon[14814]/dcsDaemon T=main | dcsServer.c TryStopWifiSession() 1505 | Impossible to disconnect wifi client
Jan 6 05:22:08 | dcsDaemon[14814]/le_pa_dcs T=main | pa_dcs_linux.c pa_dcs_SetDefaultGateway() 568 | Default gateway or interface is empty
Jan 6 05:22:08 | dcsDaemon[14814]/le_pa_dcs T=main | pa_dcs_linux.c pa_dcs_SetDefaultGateway() 568 | Default gateway or interface is empty
Jan 6 05:22:08 | modemDaemon[679]/le_pa T=main | pa_mrc_qmi.c pa_mrc_GetNetworkRegState() 1945 | called

Best regards,

Isabel.

2

Hi Isabel,

The log seems more related to WiFi failure, to make sure it is T-Mobile DNS issue, would you please try

app stop wifiService
app restart dataConnectionService

Then run the original app (to establish data connection and send data) to see does similar log raised.

Or to remove wifiService completely as you are not using it.

app remove wifiService

By the way, are you using the T-Mobile package below?
https://source.sierrawireless.com/resources/airprime/software/wp77xx/wp77xx-firmware-latest-release/

Thx

3

There was a recent change that might address the issue:
https://github.com/legatoproject/legato-af/commit/04fc4e3e47411b39397683cfdee3dc0642f6302d#diff-fc07efa2fab12f9c5826c0129984648d

The issue, in that case, was that dcsDaemon was tearing down the cellular connection if DNS was not provided by the network, despite a valid Gateway being provided. The fix is in Legato 18.02.0, which isn’t formally part of a WP77xx release yet.

It matches your description, but I’m not familiar enough with the problem to be sure it matches your logs. Hope it helps.

1 Like
4

This issue seems to affect legato 19.11.6 again, whereas it did not affect 19.0.2.

The offending commit could be Convert le_data code and logic to use le_dcs to interface with data c… · legatoproject/legato-af@d3122bd · GitHub

When using an APN that does not hand out DNS, the following legato log appears:

“Releasing data channel upon failure to retry setting DNS configuration; error -6”