Global configuration

init-state state

Set the initial state to state instead of using the first state defined.

Macros

A macro is defined with a command of the form name=value. The macro name can contain letters, digits, and underscores and cannot be a reserved word (for example, state or run). Within unquoted arguments, the string $name is later expanded to value.

Macros are usually used to define tests for state transitions like interface link state or external tests.

Currently an interface can have three different link states:

up

The physical link of the interface is up. For carp(4) interfaces this equals the master state.

down

The physical link of the interface is down. For carp(4) interfaces this equals the backup state.

unknown

The physical link of the interface is unknown. This is because the interface driver does not provide information of the physical link state. For carp(4) interfaces this equals the init state.

In contrast to link state tests, external tests must be run periodically to evaluate their status. The frequency at which an external test is run is set, in seconds, with the every keyword.

For example:

links_up = "em0.link.up && em1.link.up"
net = '( "ping -q -c 1 -w 1 192.168.0.1 > /dev/null" every 10 && \
         "ping -q -c 1 -w 1 192.168.0.2 > /dev/null" every 10 )'

Tests and events

ifstated(8) delegates the process of testing to libevent which associates a value with every test, in this case true or false. Whenever the value of a test associated with the current state changes, an event is triggered and the state's body is processed.

State definitions

ifstated(8) operates on a finite state machine with states and transitions.

Each state consists of an init block and a body. The init block is used to initialise the state and is executed each time the state is entered. The body of a state is only executed when that state is the current state and an event occurs.

The action taken within a certain state is typically made dependent on the evaluation of one or more if statements. Possible actions include executing commands using the run statement, or triggering a state transition with the set-state keyword. It is also possible to write multiple nested if blocks.

For example:

state one {
	init {
		run "logger -t ifstated entering state one"
		run "ifconfig -g carp -carpdemote"
	}

	if ! $net || urndis0.link.up
		set-state two

	if ! $links_up {
		run "ifconfig -g carp carpdemote"

		if urndis0.link.down
			set-state three
	}
}