Ifstated

Fast detection of wrong IP

My Vodafone Cable Router often assigns wrong (private) IPs to my upstream interface via DHCP.

Using ifstated we can detect this change and trigger a new DHCP request as long as the wrong IP gets assigned.

cat <<"EOF"> /etc/ifstated.conf
wrong_ip = '( "ifconfig em0 | grep -q 192.168." every 20 )'
state dhcp {
  init {
    run "logger -p daemon.info -t ifstated entering state dhcp"
  }
  if $wrong_ip {
    run "logger -p daemon.info -t ifstated detected wrong ip state dhcp"
    run "sh /etc/netstart em0"
  }
  if ! $wrong_ip {
    run "logger -p daemon.info -t ifstated detected correct ip state dhcp"
  } 
}
EOF

rcctl enable ifstated
rcctl start ifstated