Why NM seems to behave differently in initrd from in real root?

[Coiby Xu <coxu redhat com>]

Hi NM developers,

This is Coiby from the Red Hat Kernel Debug team who is responsible for 
Fedora/RHEL's kexec-tools. Currently, kexec-tools parses ifcfg-* or 
.nmconnection to build up dracut cmdline parameter like ip= to set 
up kdump initrd network which is tedious and error-prone. Recently, I'm 
implementing a different approach which is to set up kdump initrd network 
by copying connection profiles from real root to initrd directly. However, 
one unexpected thing is NM seems to behave differently in initrd from in 
real root and the same connection profiles copied from the real root lead 
to different result in kdump initrd. So is there a general reason why NM 
behaves differently in initrd and real root? Is it a better approach that 
kexec-tools sets up kdump initrd network by copying connection profiles 
from real root to kdump initrd? It will be appreciated if NM developers 
could provide answers or comments on these questions since you are experts 
on this type of problems.

For the details of how NM behaves differently in kdump initrd, I've 
reported some of the inconsistent behaviours as bugs [1] [2]. 
connection.wait-device-timeout=6000 and connection.autoconnect=false
could be used to bypass [1] and [2] respectively so the same connections 
could be brought up in initrd. A third issue for which I haven't found a 
workaround is the case of bridging network over VLAN network over teaming 
network where I create a teaming network interface which is used as the 
parent interface of a VLAN interface which is in turn a slave interface 
of network bridge. The problem is the network bridge sometimes gets the 
IP address belonging the VLAN subnet but sometimes not. Btw, the third
issue is found on a physical machine and can't be reproduced on a VM.

I've tested the modified kexec-tools [3] by setting up different networks 
including the aforementioned bridging network over VLAN network over 
teaming network. Other tests including bridging network over physical 
interface/bonding network/teaming network/VLAN network, VLAN network 
over physical interface/bonding network/teaming work and etc. All tests
have passed for VM. And except for the bridging network over VLAN network 
over teaming network, the tests have also passed for one physical machine. 
But I'm not sure if they are sufficient considering there is 
machine-specific issue like znet network device. Any suggestion is
welcome.

Thanks!


[1] https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/803
[2] https://bugzilla.redhat.com/show_bug.cgi?id=2007563
[3] https://src.fedoraproject.org/fork/coiby/rpms/kexec-tools/commits/direct_nm


--
Best regards,
Coiby