Ethernet interface set to the wrong group

[Apologies to the non-USA readers for the pedantic text.]

Problem
-------

In a machine with 4 Ethernet interfaces, OpenBSD sets to egress the wrong interface.

This is the initial configuration:

```
> cat /etc/hostname.em0
inet 192.168.1.11 255.255.255.0 192.168.1.255
up

> cat /etc/hostname.em1
down

> cat /etc/hostname.ix0
inet 192.168.1.12 255.255.255.0 192.168.1.255
up

> cat /etc/hostname.ix1
down
```

The wire on em0 is hooked to the gateway.
The wire on ix0 is hooked to the LAN switch.

This is the result, in the order given by ifconfig:

```
ix0: flags=2008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LRO> mtu 1500
lladdr ac:1f:6b:6d:1e:f4
index 1 priority 0 llprio 3
groups: egress
media: Ethernet autoselect (10GSFP+Cu full-duplex,rxpause,txpause)
status: active
inet 192.168.1.12 netmask 0xffffff00 broadcast 192.168.1.255

em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
lladdr ac:1f:6b:6d:1d:64
index 3 priority 0 llprio 3
media: Ethernet autoselect (1000baseT full-duplex,rxpause)
status: active
inet 192.168.1.11 netmask 0xffffff00 broadcast 192.168.1.255
```

OpenBSD puts ix0 ahead of em0. I need to know why. Does anybody know?

Steps done to solve the problem
-------------------------------

The aim is to remove ix0 from egress, and add em0 to egress instead.

What do the manuals say?

Interfaces are set up by hostname.if.

hostname.if(5) does not spend a single word on groups.

ifconfig(8) allows adding and removing groups, but is a shell command.

```
> doas ifconfig em0 group egress

> doas ifconfig em0
em0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
lladdr ac:1f:6b:6d:1d:64
index 3 priority 0 llprio 3
groups: egress
media: Ethernet autoselect (1000baseT full-duplex,rxpause)
status: active
inet 192.168.1.11 netmask 0xffffff00 broadcast 192.168.1.255

> doas ifconfig ix0 -group egress

> doas ifconfig ix0
ix0: flags=2008843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST,LRO> mtu 1500
lladdr ac:1f:6b:6d:1e:f4
index 1 priority 0 llprio 3
media: Ethernet autoselect (10GSFP+Cu full-duplex,rxpause,txpause)
status: active
inet 192.168.1.12 netmask 0xffffff00 broadcast 192.168.1.255
```

The command works.

How do I put this into hostname.if?

The temptation is to change the configuration as follows, using ifconfig commands inside hostname.if:

```
> cat /etc/hostname.em0
inet 192.168.1.11 255.255.255.0 192.168.1.255
group egress
up

> cat /etc/hostname.ix0
inet 192.168.1.12 255.255.255.0 192.168.1.255
-group egress
up
```

However, hostname.if does not allow for ifconfig commands.

Out of curiosity, I tried anyway, and as expected the result did not change after reboot.

Oh, look, hostname.if(8) allows to run shell commands...

```
!command
Arbitrary shell commands can be executed using this
directive, as long as they are available in the single-user
environment (for instance, /bin or /sbin). Useful for
doing interface-specific configuration such as setting up
custom routes or default source IP address using route(8)
or establishing tunnels using ifconfig(8). It is worth
noting that "\$if" in a command line will be replaced by
the interface name.
```

Since ifconfig is in /sbin, it is expected to be available in the single-user environment.

This is the resulting configuration:

```
> cat /etc/hostname.em0
inet 192.168.1.11 255.255.255.0 192.168.1.255
up
!ifconfig \$if group egress

> cat /etc/hostname.ix0
inet 192.168.1.12 255.255.255.0 192.168.1.255
up
!ifconfig \$if -group egress
```

After reboot, ix0 is still set to egress, and em0 is still without group, that is hostname.if ignored the specifications.

Can anybody care to explain?