[gessler]

You need ifstated or relayd, here is my ifstated.conf (I use 3 different pf.conf, 1 Dual Wan conf, and 1 gw1 conf and 1 gw2 conf):

net1 = '"ping -q -c1 -w1 10.1.1.1 >/dev/null" every 5'
net2 = '"ping -q -c1 -w1 10.222.222.222 >/dev/null" every 5'

init-state one

state one {
    init {
        run "route delete default 10.1.1.1"
        run "route delete default 10.222.222.222"
        run "route add -mpath default 10.1.1.1"
        run "route add -mpath default 10.222.222.222"
    }
    if ! $net1 {
    if $net2
       set-state two
    }
    if ! $net2 {
    if $net1
       set-state three
    }
}

state two {
    init {
        run "route delete default 10.1.1.1"
        run "route delete default 10.222.222.222"
        run "route add -mpath default 10.222.222.222"
        run "pfctl -f /etc/pf.conf.gw2"
    }
    if $net1 {
    if $net2
       set-state four
    }
    if ! $net2 {
    if $net1
       set-state three
    }
}

state three {
    init {
        run "route delete default 10.1.1.1"
        run "route delete default 10.222.222.222"
        run "route add -mpath default 10.1.1.1"
        run "pfctl -f /etc/pf.conf.gw1"
    }
    if $net1 {
    if $net2
       set-state four
    }
    if ! $net1 {
    if $net2
       set-state two
    }
}

state four {
    init {
        run "route delete default 10.1.1.1"
        run "route delete default 10.222.222.222"
        run "route add -mpath default 10.1.1.1"
        run "route add -mpath default 10.222.222.222"
        run "pfctl -f /etc/pf.conf"
    }
    if ! $net1 {
    if $net2
       set-state two
    }
    if ! $net2 {
    if $net1
       set-state three
    }
}