Where does Network Manager get the interface address from?

[Chris Green]

On Mon, Oct 11, 2021 at 10:20:02PM +0200, Liam Proven wrote:
> On Mon, 11 Oct 2021 at 22:16, Chris Green <cl at isbd.net> wrote:
> >
> > I have the following configuration file in NetworkManager/system-connections
> [...]
> >     mode=ap
> 
> So it's an access point, IIUIC.
> 
> > When I set my WiFi connection to use this it always give an inet
> > address of 10.42.0.1, where does it get this from?  I can't find
> > anything in /etc that seems to have this address.
> 
> I would guess it's bridging requests to your Ethernet network, so the
> DHCP server on Ethernet is providing the address, and it remembers the
> MAC address that asks for it and always gives that device the same IP
> address?
> 
I don't think so because this is on my home LAN and the DHCP server on
the LAN is dnsmasq running on a Raspberry Pi and the LAN is
192.168.1.0/8, no sign of 10.42.0.0/255 there.

The laptop's ethernet connection is:-

enp0s31f6: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.1.111  netmask 255.255.255.0  broadcast 192.168.1.255
        inet6 fe80::8623:d491:b0d6:e42a  prefixlen 64  scopeid 0x20<link>
        ether c8:5b:76:de:2a:fc  txqueuelen 1000  (Ethernet)
        RX packets 13384  bytes 7166834 (7.1 MB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12478  bytes 1761604 (1.7 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 16  memory 0xec200000-ec220000  

as given to it by the Pi DNS/DHCP server.

The laptop WiFi hotspot is set up as:-

wlp4s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.42.0.1  netmask 255.255.255.0  broadcast 10.42.0.255
        inet6 fe80::65b3:40d0:a7e1:f517  prefixlen 64  scopeid 0x20<link>
        ether 00:28:f8:3d:3b:aa  txqueuelen 1000  (Ethernet)
        RX packets 140282  bytes 115425116 (115.4 MB)
        RX errors 0  dropped 6  overruns 0  frame 0
        TX packets 94423  bytes 16374991 (16.3 MB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

The point of the exercise is to make connections (via redsocks and a
proxy) from WiFi clients to the 'outside world', I had this working a
while ago but intervening system updates have changed things so much
it no longer works and I need to understand it all better to fix it.

-- 
Chris Green