With very bad timing, it is possible that the teardown script of a
gluon_mesh interface runs when bat0 was just created, but primary0 is not
yet added to it. Although there is no hardif to remove in this case,
bat0 will still be deleted, because there is no hardif in bat0.

Disable the interface removal logic by passing `-M` to `batctl interface`.

There is no setting to explicitly enable mesh interfaces in the config
wizard, so we need to enable mesh interfaces by default when the outdoor
mode is disabled (unless site.conf dictates otherwise).

The simplest way to achieve this is to delete the 5GHz mesh interface
sections when outdoor mode is disabled: 200-wireless would delete and
recreate them a moment later anyways, but by deleting them earlier we
ensure that the disabled status is initialized from site.conf again.

When disabling outdoor mode, 5GHz mesh interfaces should be enabled by
default again (unless disabled in site.conf).

Because is_disabled() was always returning true or false, the
first_non_nil() would never actually check the default setting from
site.conf. This was broken since v2017.1.

Fixes: 6cf03bab ("treewide: replace normal uses of luci.model.uci with simple-uci to reduce LuCI dependencies")

With 11a3b566 ("gluon-web-model: add dependency support for
sections"), a "reset" function was added to all model nodes. This
conflicts with the "reset" field of the Form object, making reset
buttons show labels like "function: 0xbb8d50" and possibly breaking form
processing when packages override the reset field.

The interfaces should always exist and just be disabled when outdoor
mode is enabled. Not creating them at all leads to an issue in the
advanced wifi settings where an additional reload of the page is
necessary after enabling or disabling the ourdoor mode to make the mesh
VIF options appear or disappear.

Instead of relying on the existence of interface sections only (which is
still used for the case of interface types that are not configured at
all in the site config), add a proper dependency.

This fixes section visiblity with enabled outdoor mode after the following
fix, and gives the user immediate feedback (allowing to disable outdoor
mode and enable meshing in a single step).

- Return early
- Rename to has_active_interfaces(), as it returns a boolean

200-wireless will add or remove the mesh network sections of
/etc/config/network. Commit this file, so the modified setting doesn't
get lost on reboot.

Fixes: #2048

Validation errors are mostly handled in the frontend (by displaying
invalid fields with a red background). There was some code left in the
backend for handling different kinds of errors, and returning custom
error messages from validate(), but the resulting value was not used
anywhere.

- Add a dependency array to section template
- Lift dependency handling from AbstractValue to Node
- Split resolve_depends() into a function handling dependencies of a
  node itself (resolve_node_depends()), which now is used for all nodes,
  and the existing recursive descent through the node tree
- When any node's dependencies are not satisfied, all descendents are
  reset recursively, meaning that an option in a section that is hidden
  will always be ignored, as if the option's own dependencies were
  unsatisfied

Fixes: #1349

This is currently unused in our packages.

Fixes dependency tracking for individual <option> elements (currently
unused).

- If luasrcdiet fails for a Lua script, this is a bug that should be
  noticed rather than including the unminified script
- Use .tmp suffix for temporary file rather than .o
- Replace chmod + stat + mv with simpler cp + rm to overwrite file while
  preserving file mode

This allows for multiple mesh legs out of one box. Useful for offloaders
and networks using vlan for separate mesh transport.
Custom mesh interfaces in a VXLAN domain are otherwise firewalled.

This fixes #1479

This adds support for the beacon interval to be set on a per-band base.
This has the potential to reduce the amount of airtime used up for
sending beacon frames.

[Matthias Schiffer: fix up start/stop order and file permissions]

Separate wireless-related helper methods from the util module to a
new wireless module. This keeps them separated, as the amount of
wireless helpers increased in the past, justifying a separate module.

xt_CT was added to kmod-ipt-conntrack a while back. Update our
GLUON_SPECIALIZE_KERNEL rules accordingly.

When building xt_CT into the kernel, one of the symbols IP_NF_RAW and
IP6_NF_RAW must be enabled as well, even though there is no runtime
dependency when building as modules. The kernel grows by less than 1KB
even when both IP_NF_RAW and NETFILTER_XT_TARGET_CT are enabled, making
this change a (very slight) net win in both flash and RAM usage.

Closes #1974

Situation:
==========

$ ls -l /lib/gluon/domains/lindennord.json
lrwxrwxrwx    1 root     root            10 Jan  6 03:42 /lib/gluon/domains/lindennord.json -> dom17.json

Before:
=======

$ gluon-neighbour-info -d ::1 -p 1001 -r nodeinfo -c 1
{
   "node_id": "525400123456",
   "system": {
     "domain_code": "lindennord",
     "site_code": "ffh"
   },
...
}

After:
======

$ gluon-neighbour-info -d ::1 -p 1001 -r nodeinfo -c 1
{
   "node_id": "525400123456",
   "system": {
     "primary_domain_code": "dom17",
     "domain_code": "lindennord",
     "site_code": "ffh"
   },
...
}

Implemented using readlink() and basename() to the selected domain in
/lib/gluon/domains/${DOMAIN}.json.

As a partial fix to #496, do not touch the MAC address of the WAN
interface when using VXLANs (as only the MAC address of the VXLAN
interface matters to batman-adv).

config_ifname was renamed to setup_ifname in Gluon v2015.1.

On PoE-powered devices, we usually want to use WAN for the setup mode.
As all outdoor devices are PoE-powered, we can reuse this function. This
switches the setup mode interface for new installations / after config
reset on a few devices that were missing in this list before.

- Use util.find_phy()
- Stop foreach() as soon as the result is known

The 'preserve' flag can be used to mark a peer so it is not removed or
modified on upgrades. In addition, groups containing preserved peers are
not removed.

Fixes: #557

The netdev() lookup is confusing to use: whenever a interface does not
exist during boot (for example VLAN) or when the address is overridden
from board.json (which is not obvious at all), it will yield either no
address, or a different address than expected.

To avoid this confusion, using board.json-based interface() is
preferable. This converts all uses of netdev() to the corresponding
lan/wan lookups, except for the final fallback for eth0.

In most cases, board.json does not contain any MAC addresses; in this
case, the default MAC address of the underlying interface is to be used.

- Replace misnamed, closure-returning sysfs() to a reusable read() function
- Rename eth() to netdev(), pass full interface name
- Rename board() to interface()
- Split reuable get_netdev_addr() out of netdev()