One-way traffic on with the EM7411

Liam liam at commdevices.com
Thu Sep 30 13:05:33 UTC 2021


> Is there any particular reason you're using DHCP, rather than pulling the IP info from the modem via libqmi?

I use DHCP for two reasons:
1. I try to limited the use of all QMI messages as they are a black box and I have seen edge cases where the bus goes unresponsive
2. DHCP allows for more typical Layer 3 behavior that can leverage more accepted, traditional tools. 

> Also, what DHCP client are you using? Lastly, what mode are you running the WWAN interface in, raw-ip or 802.3?
udhcpc as it can handle raw-ip and allows for flexible callback bash scripts to help configuration.

I am running the interface in raw mode:
# cat /sys/class/net/wwan0/qmi/raw_ip
Y

-Liam

-----Original Message-----
From: Dan Williams <dcbw at redhat.com> 
Sent: Wednesday, September 29, 2021 8:49 PM
To: Liam <liam at commdevices.com>; libqmi-devel at lists.freedesktop.org
Subject: Re: One-way traffic on with the EM7411

On Fri, 2021-09-03 at 21:12 +0000, Liam wrote:
> Hi,
>  
> libqmi has performed fantastically with the EM7455. Using the typical 
> ‘qmi-network start’ and then a dhcp client to get an address works 
> pretty seamlessly.
>  
> My problem is that I have been asked to eval the EM7411 and I cannot 
> get DHCP to resolve and traffic is only coming from the interface, not 
> to it. This is the general steps:
> 

Is there any particular reason you're using DHCP, rather than pulling the IP info from the modem via libqmi?

Also, what DHCP client are you using?

Lastly, what mode are you running the WWAN interface in, raw-ip or 802.3?

Dan

>  
>    1. Start qmi-network successfully and confirm the network IP 
> address with --wds-get-current-settings
>    2. Perform DHCP on the ‘wwan0’ interface and fail
>    3. Manually set the wwan0 interface IP to that returned by wds- 
> get-current-settings
>    4. Can see pings comes through the interface, but do not see them 
> or any other traffic coming from it
>  
> ON THE EM7411 DEVICE
> tcpdump: verbose output suppressed, use -v or -vv for full protocol 
> decode listening on wwan0, link-type RAW (Raw IP), capture size 262144 
> bytes
> 09:23:18.783894 IP 10.222.3.169 > 10.222.9.147: ICMP echo request, id 
> 27414, seq 36, length 64
> 09:23:18.784106 IP 10.222.9.147 > 10.222.3.169: ICMP echo reply, id 
> 27414, seq 36, length 64
> 09:23:19.742704 IP 10.222.3.169 > 10.222.9.147: ICMP echo request, id 
> 27414, seq 37, length 64
> 09:23:19.742915 IP 10.222.9.147 > 10.222.3.169: ICMP echo reply, id 
> 27414, seq 37, length 64
>  
> TO THE EM7511 DEVICE
> listening on wwan0, link-type RAW (Raw IP), capture size 262144 bytes
> 21:09:33.866587 IP 10.222.3.169 > 10.222.9.147: ICMP echo request, id 
> 27414, seq 333, length 64
> 21:09:34.870089 IP 10.222.3.169 > 10.222.9.147: ICMP echo request, id 
> 27414, seq 334, length 64
>  
> Anyone have a clue what could be causing this issue? 
>  
> -Liam
>  
>  




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