[systemd-devel] [SPAM] Re: Custom options and passing options via command line.

[Kamil Jońca]

(sent previously from different address)

Lennart Poettering <lennart at poettering.net> writes:

> On Mo, 09.05.22 18:12, Kamil Jońca (kjonca at op.pl) wrote:
>
>> For now I do not know how handle multiple interface where:
>> 1. set routing according to classles routes from dhcp on some
>> interfaces.
>
> We don't do that anyway?

I do not know. When I tried (but it was about year ago) I think it did
not work, but later someone  on list claims that systemd handle proper
DHCP option. 

>
>> 2. set NAT (ie call nftables sctipts) with multitple egress interfaces and bunch
>> of VM-s inside host.
>
> we have native NAT support in .network files? what is missing there?

Will try. When I find some time.

>
>> 3. decide where to resolve names based on domain and existence of ipsec
>> or openvpn tunnel.
>
> Sounds like a job for the resolved domain routing logic, which already
> exists?

Not quite. When I asked previously  I got response, that resolved is
based on interfaces. But ipsec tunnel does not need dedicated interface.

>
> it appears you can use what's already there for these cases. And if
> not, it seems like we could extend things.


> maybe in the end things wouldn't work exactly the same as before, but
> should deliver the same results?

Yes.

>
>> With systemd-networkd I even do not know where to start. And when I try
>> to test somenthig, almost immediately I see that I systemd cannot do
>> something I need.
>
> Start with the documentation? But take a step back, i.e. what is the
> stuff you actually intend to do conceptually, instead of already
> assuming the tech you want to do it with.
>
Let's see.
from SYSTEMD.NETWORK(5)
...
IPMasquerade=   
           Configures IP masquerading for the network interface. If
           enabled, packets forwarded from the network interface will be
           appear as coming from the local host.
....


I still do not know what mean "local host" here. I guess that this will
be interface address.  :) 

I still do not know if this is rather "snat" or rather "masquerade". How
can I decide which to use. And what engine is used here.


I know that networkd cannot handle bridge without ports (quite
convenient when you use it as dummy interface with qemu machines)

[...]
>> I simply want to pass  option during disposinng interface up, and expect
>> this option will be honored. (IE. interface will be default or
>> not.[1])
>
> Afaics RouteMetric= [DHCPv4] section already does all you need. just
> give the iface whose default route you want to take precedence a lower
> metric and you are done.

How? By editing files? And what with other examples?

> Note anyway that networkd assumes it manages an interface in its
> entirety: if you muck with what it sets up it likely will override
> your changes sooner or later, when some event happens... you have a

I do not want interfere with interfaces "per se" I simply want to get
some info from systemd and pass it to dnsmasq (for DNS) or nftables (for
filtering) . That's it.


KJ


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