Provide a simpler example ifstated.conf.

The existing example was written over a decade ago, when carp(4) was
not supporting carpdemote and did not track it's interfaces link state itself.
OK jmc@, rob@

src/etc/examples/ifstated.conf

@@ -1,72 +1,52 @@
-# $OpenBSD: ifstated.conf,v 1.1 2014/07/11 16:36:35 deraadt Exp $
-# This is a sample config for a pair of firewalls with two interfaces
+# $OpenBSD: ifstated.conf,v 1.2 2018/01/20 23:07:58 mpf Exp $
+# This is a sample config for a pair of firewalls with three physical interfaces
 #
-# carp0 and carp1 have ip addresses on 192.168.3.0/24 and 192.168.6.0/24
-# respectively.
-
-# net.inet.carp.preempt must be enabled (set to 1) for this to work correctly.
-
-# Uncomment one of the following lines to force primary/backup status.
-# init-state primary
-# init-state backup
-
-carp_up = "carp0.link.up && carp1.link.up"
-carp_down = "!carp0.link.up && !carp1.link.up"
-carp_sync = "carp0.link.up && carp1.link.up || \
-    !carp0.link.up && !carp1.link.up"
-
-# The "net" addresses are other addresses which can be used to determine
-# whether we have connectivity. Make sure the hosts are always up, or
-# test multiple ip's, 'or'-ing the tests.
-net = '( "ping -q -c 1 -w 1 192.168.6.8 > /dev/null" every 10 && \
-    "ping -q -c 1 -w 1 192.168.3.8 > /dev/null" every 10)'
-
-# The peer addresses below are the real ip addresses of the OTHER firewall
-peer = '( "ping -q -c 1 -w 1 192.168.6.7 > /dev/null" every 10 && \
-    "ping -q -c 1 -w 1 192.168.3.7 > /dev/null" every 10)'
-
-state auto {
-	if $carp_up
-		set-state primary
-	if $carp_down
-		set-state backup
-}
-
-state primary {
-	init {
-		run "ifconfig carp0 advskew 10"
-		run "ifconfig carp1 advskew 10"
+# The two firefall interfaces are made redundant on each side using 
+# carp0 and carp1.
+#
+# A third interface em2 connects each firewall to the DMZ where it can
+# reach a syslog server with the IP 192.168.1.10
+# 
+# This config does two things:
+#  1. Monitor the reachability of the syslog server and demote
+#     the carp interface group to provoke a failover if the syslog server
+#     is not reachable. We do that by using ping(1) and checking
+#     the link state of em2.
+#  2. Log carp failovers
+
+
+dmz_if_up = 'em2.link.up'
+dmz_if_down = 'em2.link.down'
+
+syslog_ok = '"ping -q -c 1 -w 1 192.168.1.10 >/dev/null 2>&1" every 10'
+
+# ifstated starts up with the first defined state
+state neutral {
+	if $dmz_if_down {
+		run "logger -st ifstated 'interface to syslog server em2 is down'"
+		set-state demoted
 	}
-	if ! $net
+	if ! $syslog_ok {
+		run "logger -st ifstated 'could not reach syslog server'"
 		set-state demoted
+	}
 }
 
 state demoted {
 	init {
-		run "ifconfig carp0 advskew 254"
-		run "ifconfig carp1 advskew 254"
+		run "ifconfig -g carp carpdemote" 
 	}
-	if $net
-		set-state primary
-}
-
-state promoted {
-	init {
-		run "ifconfig carp0 advskew 0"
-		run "ifconfig carp1 advskew 0"
+	if $dmz_if_up && $syslog_ok {
+		run "logger -st ifstated 'syslog server is ok again'"
+		# remove our carp demotion
+		run "ifconfig -g carp -carpdemote" 
+		set-state neutral
 	}
-	if $peer || ! $net
-		set-state backup
 }
 
-state backup {
-	init {
-		run "ifconfig carp0 advskew 100"
-		run "ifconfig carp1 advskew 100"
-	}
-	# The "sleep 5" below is a hack to dampen the $carp_sync when we come
-	# out of promoted state. Thinking about the correct fix...
-	if ! $carp_sync && $net && "sleep 5" every 10
-		if ! $carp_sync && $net
-			set-state promoted
-}
+# commands in the global scope are always run
+if carp0.link.up
+	run "logger -st ifstated 'carp0 is master'"
+if carp0.link.down
+	run "logger -st ifstated 'carp0 is backup'"
+