Fix lime-config fail when there is no lower iface

[pony1k]

On a mercusys mr70x, lime-config does not work. It throws the following error:

network.scandevices.owrt_network_interface_parser found ifname wan
ls: /sys/class/net/wan/lower*: No such file or directory
/usr/lib/lua/lime/network.lua:223: attempt to index field '?' (a nil value)
stack traceback:
        /usr/lib/lua/lime/config.lua:221: in function </usr/lib/lua/lime/config.lua:221>
        [C]: in function 'foreach'
        /usr/lib/lua/lime/network.lua:339: in function 'scandevices'
        /usr/lib/lua/lime/network.lua:373: in function </usr/lib/lua/lime/network.lua:364>
        [C]: in function 'xpcall'
        /usr/lib/lua/lime/config.lua:221: in function 'main'
        /usr/bin/lime-config:55: in main chunk
        [C]: ?

It seems that an interface that is called "wan" does not always have link to a lower interface in /sys/class/net. This is how I would like to fix it. I've tested it already on a mercusys mr70x and it is working fine.

[codecov-commenter]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (0c8a915) 79.56% compared to head (38e3e7f) 79.53%.

❗ Current head 38e3e7f differs from pull request most recent head d5befee. Consider uploading reports for the commit d5befee to get more accurate results

Files	Patch %	Lines
...ges/lime-system/files/usr/lib/lua/lime/network.lua	83.33%	2 Missing ⚠️

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##           master    #1080      +/-   ##
==========================================
- Coverage   79.56%   79.53%   -0.04%     
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  Lines        4561     4564       +3     
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- Misses        932      934       +2     

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[ilario]

Uh... Unexpected. Do you have idea if this is a new thing of OpenWrt 23?
Anyway, the code looks good to me.
After this change, does the WAN work?

[pony1k]

I believe this is because wan is not a switch port, but connected directly to the CPU. See here for mr70x:
https://github.com/openwrt/openwrt/blob/6497cdba09d6faa04a4f74465ed95ae21e2ff1ff/target/linux/ramips/dts/mt7621_mercusys_mr70x-v1.dts#L134-L171
While for the archer-c6 as an example:
https://github.com/openwrt/openwrt/blob/6497cdba09d6faa04a4f74465ed95ae21e2ff1ff/target/linux/ramips/dts/mt7621_tplink_archer-x6-v3.dtsi#L182-L218

The wan port works. I checked.

[ilario]

Anyway it is something new... I didn't see such messages when using OpenWrt 19.07 (cannot remember if I used also OpenWrt 22) on YouHua WR1200JS that has a very similar DTS... Mah...

[G10h4ck]

Looks good to me too, thanks @pony1k

[ilario]

Sorry for not testing before.
In your case, @pony1k, did this work for activating the dhcp for the wan entry in the /etc/config/network file?
I tried with a YouHua WR1200JS and the dhcp is indicated in /etc/config/lime-autogen but not in /etc/config/network.

So I think we should run devices[dev] = {} even if lower_if does not exist:

devices[dev] = {}
if lower_if then                                                               
  devices[lower_if] = { nobridge = true }                                
  utils.log( "network.scandevices.dev_parser found WAN port %s " ..      
  "and marking %s as nobridge", dev, lower_if )               
else                                                                           
  utils.log( "network.scandevices.dev_parser found WAN port %s", dev)    
end

[pony1k]

You're right. If I had tried activating dhcp for the wan entry, it would probably have failed.

What you are proposing looks good.