[Buildroot] [PATCH v2] set simple network setup via the system configuration submenu

[Jeremy Rosen <jeremy.rosen@openwide.fr>]

Andr?, all

----- Mail original -----
> 2014/10/22 Jeremy Rosen <jeremy.rosen@openwide.fr>:
> > 
> > 
> > Hey, thanks for the review, Bash and Makefile are the two
> > programming
> > languages I was never able to really master
> > 
> > ----- Mail original -----
> >> Hi,
> >>
> >> 2014-10-20 16:14 GMT+02:00 J?r?my Rosen
> >> <jeremy.rosen@openwide.fr>:
> >>> This patch allows the setup of simple /etc/network/interfaces via
> >>> the
> >>> configuration menus instead of using an overlay
> >>>
> >>> * supports manual ipv4 configuration
> >>> * supports dhcp configuration
> >>>
> >>> Signed-off-by: J?r?my Rosen <jeremy.rosen@openwide.fr>
> >>>
> >>> ---
> >>>
> >>> This patch is here to avoid having to do an overlay for the most
> >>> common
> >>> cases (ipv4 with fixed IP or DHCP)
> >>>
> >>> It can be made more complex (second network if, support ipv6)
> >>> depending on
> >>> what people want/need, but I want to keep it simple. The point is
> >>> to avoid
> >>> having to tweak overlays to change stuff that everybody needs to
> >>> change for
> >>> prototyping
> >>>
> >>> When networkd is enabled, this option will be deactivated.
> >>> Networkd
> >>> support
> >>> is tricky to get right on first approximation. It can be added
> >>> later if it
> >>> is deemed usefull
> >>
> >> I'm willing to add networkd support once your work has been merged
> >> ;)
> >>
> > 
> > I've already been working on it, it's indeed quite easy but there
> > is
> > a tricky question that needs resolving, so I didn't include it in
> > this
> > patch. Basically I have a problem with dealing with default values
> > with
> > static IP settings
> > 
> > * The script need to fail if no value is provided for address
> > * The script needs to build correctly with default values
> > (autobuilder)
> > * There is no "correct" default values to use
> > * We should not let an unconfigured Adress on the network.
> > 
> > Right now, ADDRESS defaults to 0.0.0.0 which is interpreted by
> > net-utils
> > as "incorrect address, don't configure the interface" (so it ends
> > up
> > enabled but with no IP address) I'm happy with that, it's ok with
> > my
> > requirement
> > 
> > But I could not find an equivalent setting for networkd.
> 
> In the .network file, omit the "[Address]" section / "Address=" line.
> The interface gets upped, but no ip address gets assigned.
> I've attached some ".network" file examples below.
> 

Awesome, i'll look into it.

> > 0.0.0.0 is
> > interpreted as "automatically find an IP address" and I couldn't
> > find
> > any documentation on how it does that (does it check the network
> > for
> > collision ? It seems to use the netmask to choose the base address
> > and
> > it makes sure there is no conflict with other interfaces on the
> > same
> > machine, but that's all I could find)
> > 
> 
> That's all it does: ensure that each automatic address is unique on a
> single
> system, i.e. doesn't clash with any configured addr or any addr that
> has
> already been assigned.
> 
> It might be useful for virtual ethernet setups (veth and whatnot),
> but IMO
> that's out of scope for simple network setup, so my suggestion would
> be to
> handle "0.0.0.0" as <not configured> => no "Address=" in the .network
> file.
> It also makes BR2_SIMPLE_NETWORK_IPV4_IPV4_ADDRESS semantically
> equivalent
> for both output formats.
> 

yes, that's how i'll do it.

> Alternatives, all with the disadvantage of adding unnecessary
> complexity:
> * introduce a dummy value, e.g. "-"
> * add another choice to the "Configuration type" prompt,
>   BR2_SIMPLE_NETWORK_IPV4_NONE (or similar)
> 

There is already a "none" case where eht0 is not configured at all.
This is only to be able to build with the autobuilder. The autobuilder
might randomly select a static configuration and the build should not
fail in that case. That configuration (setting to manual but leaving
an address of 0.0.0.0) makes no sense from a user point of view.

A user that doesn't want eth0 would select the "do not configure the
interface" option that wouldn't generate any config file

> 
> > So right now I'm open to suggestions on that particular problem,
> > generating
> > the actual .network file shouldn't be very hard (I temptatively
> > call it
> > busybox.networks rather than <name>.network to be sure to overwrite
> > it
> > on the next iteration of the script)
> > 
> 
> Not sure if it's a binding convention, but these files are usually
> prefixed
> with a number 01..99, e.g. "50-buildroot.network".
> 

it seems so. I now generate 80-buildroot.network (80 is used by all
the .network files I have found lying around)

> > 
> >> Just for reference, my notes on what needs to be done:
> >> * no loopback setup, systemd does it on its own
> > 
> > yes, I found that out, it's simple to deal with since loopback is
> > not a config
> > option for net-utils anymore
> > 
> >> * creation of a ".network" file - .ini file (equivalent to
> >> /etc/network/interfaces), requires conversion of the netmask to
> >> cidr
> >> format (255.255.255.0 => 24 a.s.o.)
> > 
> > I found how to do that in shell script somewher on stackoverflow,
> > so
> > not a problem
> > 
> >> * -optionally- disable "predictable" network interface renaming
> >> ("eth0"=>"enp2s0") [0] so that one can actually rely on eth0's
> >> existence
> >>
> > 
> > that's a good idea, but predicatable interface names seems to
> > already
> > be disabled on buildroot builds. I wasn't able to find out why and
> > I
> > didn't dig since I was dropping networkd support at that point. It
> > seems that there is something weird there...
> > 
> 
> It's not disabled, but under certain circumstances it's not "active",
> for example
> if the kernel-provided name is deemed to be stable, e.g. qemu/kvm
> with virtio netdev.
> You can provoke it by plugging in an usb wlan adapter, which appears
> as "wlp0s20u10"/...
> in 'ip link'/'ifconfig'.
> On x86 consumer-grade hardware, the wired interfaces get always
> renamed, too.
> 
> There are several ways to disable it, but the best solution -for me-
> is
> "ln -s /dev/null $(TARGET_DIR)/etc/systemd/network/99-default.link",
> which still allows
> custom interface renaming in /etc/systemd/network/ while disabling
> the default policy.
> 

I'll have a look at that. On the raspberry pi (my testing hw) it is
named eth0 so testing this is tricky. I probably can't go further than
"I test that the link is correctly set, not that networkd reacts 
correctly"


At this point I have too many changes to v3 to wait much longer, so
I'll integrate networkd and resubmit today

Regards

Jeremy

> ---
> .network file examples:
> 
> # "0.0.0.0"
> [Match]
> Name=eth0
> 
> [Network]
> Description=buildroot-configured interface
> (EOF)
> 
> # any other manual ip addr
> [Match]
> Name=eth0
> 
> [Network]
> Description=buildroot-configured interface
> 
> [Address]
> Address=192.168.1.2/24
> Broadcast=192.168.1.255 ## if configured
> 
> [Route]
> Gateway=192.168.1.1 ## if configured
> (EOF)
> 
> # dhcp
> [Match]
> Name=eth0
> 
> [Network]
> Description=buildroot-configured interface
> DHCP=v4
> (EOF)
> 
> Notes:
> * the "Gateway=" line can also be moved to the "[Network]" section
>   (+ drop the "[Route]" section)
> 
> * "Address=" should have its own section because of "Broadcast="
> 
> --
> Andr?
> 
>