dhcpcd-discuss

Hi Tor

On 21/04/2020 16:14, Tor Rune Skoglund wrote:
> there is a --dhcp option to dhcpcd which seems to be needed when using raw-ip 
> with qmi modems. I have systems who are being moved from 802-3 to raw-ip, since 
> newer modems seem to lack support for 802-3. To keep the setup as generic as 
> possible, we still would like to use dhcpcd without having to define too many 
> details about the actual type of modem on beforehand. Hence, for gms modems 
> using qmi and raw-ip, ideally we would like to just run dhcpcd in the background 
> and it should "just work" when the modem connects, much as when using 802-3 
> (except for a -HUP to dhcpcd).
>
> The *only* way I am able to get dhcpcd to work is by running "dhcpcd --dhcp -z 
> wwp*". That always works.
>
> However, it never works if dhcpcd is already running in the background, no 
> matter if it was started with --dhcp or not, and no matter if the config file's 
> allowinterfaces includes ww*.
>
> So my questions are:
>
> - What does --dhcp actually do in this case? man dhcpcd (at least on my system) 
> does not document the --dhcp option.

dhcpcd.conf(5) does :)

> - What am I doing wrong...? Kindof out of clues now. :)
>
> ip a on wwan, before after the ip address is set:
>
> 5: wwp0s20u5u1i8: <POINTOPOINT,MULTICAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc 
> pfifo_fast state UNKNOWN group default qlen 1000
>      link/none
>      inet 10.214.215.169/30 brd 10.214.215.171 scope global dynamic 
> noprefixroute wwp0s20u5u1i8
>         valid_lft 6868sec preferred_lft 5968sec
>
> These are minimalistic systems using OpenRC and no NetworkManager nor 
> ModemManager. Kernel is 4.9. dhcpcd is 8.1.7 from Gentoo. udhcpc works on the 
> same system.
>
> I presume this is too little info to be able to pinpoint the issue, but any 
> hints are appreciated. Thanks!
>
> BR, Tor Rune Skoglund

So by default, dhcpcd won't work on POINTOPOINT interfaces without some kind of 
config.
putting this at the top of /etc/dhcpcd.conf might fix it for you:
allowinterfaces wwp*

Roy