Change the output of nm_platform_error_to_string() to print the numeric value.
Also, accept a string buffer instead of using an alloca() allocated buffer.

There is still a macro to provide the previous functionality, but it
was ill-suited to call from inside a loop.

The default value for miimon, when missing in the setting, is 0 if
arp_interval is != 0, and 100 otherwise. So, when generating a
connection, let's ignore miimon=0 (which means that miimon is
disabled) and accept any other value. Adding miimon=100 does not cause
any harm to the connection assumption.

While at it, slightly improve the code: ignore_if_zero() is not useful
for 'updelay','downdelay','arp_interval' because zero is their default
value, so introduce a new function that checks if the value is the
default (and specially handles 'miimon').

Reported-by: Taketo Kabe <rkabe@vega.pgw.jp>

https://bugzilla.redhat.com/show_bug.cgi?id=1463077

Previously, master device types like bridge, bond, and team
would overwrite is_available() and check_connection_available()
and always return TRUE.

The device already expresses via nm_device_is_master() that it
is of a master kind. Refactor the code, so, instead of having these
device types overwrite is_available() and check_connection_available(),
let the parents implementation react on nm_device_is_master().

There is no change in behavior at all. Instead, the knowledge how to
treat a master device moves from the device implementation to the
parent class.

Don't crash if the bond mode can't be read from sysfs - for example
when the interface disappears. The generated connection will be bogus,
but at that point it doesn't matter because the in-memory connection
will be destroyed.

Fixes: 056a973a4fdb68abe8bc7bfc5f31250345d71f21

https://bugzilla.redhat.com/show_bug.cgi?id=1459580

Upstream commit [1] changed in the kernel the default value of
tlb_dynamic_lb bond from 1 to 0 when the mode is not tlb. This is not
wrong, as the option value doesn't really matter for other modes, but
it breaks the connection matching because we read back a 0 value when
we expect a default of 1.

Fix this in a generic way by ignoring altogether options that are not
relevant for the current bond mode, because they are removed from the
connection during normalization.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=8b426dc54cf4056984bab7dfa48c92ee79a46434

https://bugzilla.redhat.com/show_bug.cgi?id=1457909

We don't need this flexibility of having a full fledged GObject
property for is-master. The property value only depends on the
device's class.

Reduce the use of NM_PLATFORM_GET / nm_platform_get() to get
the platform singleton instance.

For one, this is a step towards supporting namespaces, where we need
to use different NMNetns/NMPlatform instances depending on in which
namespace the device lives.

Also, we should reduce our use of singletons. They are difficult to
coordinate on shutdown. Instead there should be a clear order of
dependencies, expressed by owning a reference to those singelton
instances. We already own a reference to the platform singelton,
so use it and avoid NM_PLATFORM_GET.

(cherry picked from commit 94d9ee129d85ff926a10de78fedcc6b57cdcdb19)

src/devices/nm-device-bond.c: In function 'check_changed_options':
src/devices/nm-device-bond.c:529:4: error: 'name' may be used uninitialized in this function [-Werror=maybe-uninitialized]
    g_set_error (error,
    ^
src/devices/nm-device-bond.c:505:14: note: 'name' was declared here
  const char *name, *value_a, *value_b;
              ^
src/devices/nm-device-bond.c:528:8: error: 'value_a' may be used uninitialized in this function [-Werror=maybe-uninitialized]
   if (!nm_streq0 (value_a, value_b)) {
        ^
src/devices/nm-device-bond.c:505:21: note: 'value_a' was declared here
  const char *name, *value_a, *value_b;
                     ^

(cherry picked from commit f66de1dd0f44178fa6d0a3940a61e323559dcce6)

Only a couple of bond options (active_slave, primary) are supported at
for now.

The kernel doesn't accept an interface to be set as active_slave until
the interface is enslaved to the bond. Delay the initialization of the
property.