Monthly Archives: September 2022

CLI, Networking

Prioritize wifi with Network Manager in Arch

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My cable internet has been horrid lately. I wanted to be able to hotspot to my phone while maintaining LAN connections to my servers while the cable company takes its sweet time to fix things. Even though I connected to wifi on my phone, my desktop still prioritized the broken connection and wouldn’t use my phone to get to the internet. I verified this by looking at the routing table and running traceroute

sudo ip route
...
default via 10.137.1.1 dev br0 proto dhcp src 10.10.1.124 metric 425 
default via 172.10.10.1 dev wlp69s0 proto dhcp src 172.10.10.4 metric 600 
...

traceroute google.com --max-hops=1
 1  _gateway (10.10.50.1)  0.409 ms  0.449 ms  0.483 ms

The LAN connection’s default gateway had a lower metric than the mobile hotspot connection (lower takes precedence.) To fix this I ran this networkmanager command (thanks to this post for the inspiration) 

sudo nmcli connection modify "Nicholas’s iPhone" ipv4.route-metric 50

I noticed DNS traffic was also prioritizing my LAN, which I didn’t want. I fixed it with nmcli as well (thanks to this post)

sudo nmcli connection modify "Nicholas’s iPhone" ipv4.dns-priority 1

I then noticed I couldn’t get to certain LAN subnets. I then realized I needed to add some static routes so they don’t try to go over my hotspot connection (which I learned about here)

sudo nmcli connection modify bridge-br0 +ipv4.routes "10.10.50.0/24 10.10.1.1"

Note you may need to refresh your connection once you’ve made changes. You can either disconnect and reconnect to force a refresh, or run this command (as outlined here.) 

sudo nmcli con up bridge-br0 #or whatever your LAN interface name is

Once I refreshed my settings, I was able to get internet via my phone while maintaining all my local network settings.

CLI

Convert music to iPhone ringtones

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I’ve recently crossed into the dark side and gotten my first iPhone. I wanted to set up ringtones for my contacts but discovered that Apple is pretty picky about ringtone file format. After some searching I found the ffmpeg command to run to get the ringtones into a file iPhones are happy with.

The criteria are:

  • aac codec
  • m4r filename
  • 30 seconds or less in duration

I ran into a snag with various things I was trying to convert apparently having more than one stream. I would get the error message 

Could not find tag for codec h264 in stream #0, codec not currently supported in container

I had to use the map command to specify exactly which stream I wanted (just the audio one.) I discovered which stream I wanted by running the ffmpeg -i command on the file to see its available streams. I also discovered that some songs reported incorrect duration. This was fixed with the -write_xing 0 option. Thanks to this gist for the inspiration.

Here is the full command to turn music into an Apple-compatible ringtone. Modify -ss and -to to suit your needs (starting time, to ending time)

ffmpeg -i <input file> -codec:a aac -ss 00:00:59.5 -to 00:01:21.5 -f ipod -map 0:0 -write_xing 0 ringtone.m4r

If taking a ringtone from a video file, I had to specify I wanted stream 1 instead of stream 0:
ffmpeg -i Batman-\ The\ Animated\ Series\ -\ S02E01\ -\ Shadow\ of\ the\ Bat\ \(1\)\ SDTV.avi
-codec:a aac -ss 00:00:20.5 -to 00:00:43.5 -f ipod -write_xing 0 -map 0:1 batman_ringtone.m4r

Once you have the right m4r file, you simply need to plug your iPhone into your computer and fire up iTunes. You can then drag the file into the "Tones" section on the left under "Devices".