which gentoo subsystem is creating a useless route on a wwan interface? and how do I stop it?

Question

I have a Huawei webConnect Jet USB stick that lets me connect to the internet via cellular data connection. After a recent software upgrade the device now creates a useless default route on the wwan interface that interferes with the PPP interface (ppp has been working for the past several years on a couple of laptops).

Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
0.0.0.0         0.0.0.0         0.0.0.0         U     204    0        0 wwp0s20f0u4i1
0.0.0.0         10.64.64.66     0.0.0.0         UG    4005   0        0 ppp2
10.64.64.66     0.0.0.0         255.255.255.255 UH    0      0        0 ppp2
169.254.0.0     0.0.0.0         255.255.0.0     U     204    0        0 wwp0s20f0u4i1

In order to access the internet I have to issue a route del default dev wwp0s20f0u4i1 to get rid of the bogus route and let packets flow through the ppp2 interface correctly.

How do I prevent this useless route from being created? I don't even know which subsystem/software is creating this route.

While it might not be relevant to this issue: This device does require usb_modeswitch to convert it from a storage device into a "serial" modem and make the /dev/ttyUSB[0-2] appear.

Linux herakleion 4.12.12-bob #38 SMP Sat Dec 9 23:32:34 EST 2017 x86_64 Intel(R) Core(TM) i7-7700 CPU @ 3.60GHz GenuineIntel GNU/Linux

https://bugs.gentoo.org/659430

Answer 1

After discussions on the #gentoo IRC channel we eventually figured out that altering /etc/dhcpcd.conf to add

denyinterfaces wwp*

was the solution. OpenRC was probably starting dhcpcd to satisfy some net dependencies in other init scripts. This had not been a problem in the past because there was no wwp* interface until I upgraded my kernel.

That new wwp* interface seems useless to me, but maybe someone who understands it better would know how to configure it to connect to the cellular network. Or maybe it is a mistake and should only be activated for a different piece of hardware that looks similar to mine.