Topic: How Coova-Chilli Read Config file

As we know, there are many config files under folder /etc/chilli/*/config, and in these files, there are many configurations. such as below:
HS_LANIF=wl0.1            # WAN Interface toward the Internet
HS_NETWORK=     # HotSpot Network (must include HS_UAMLISTEN)
HS_NETMASK=   # HotSpot Network Netmask
HS_UAMLISTEN=   # HotSpot IP Address (on subscriber network)
HS_UAMPORT=3991            # HotSpot UAM Port (on subscriber network)
HS_UAMUIPORT=4991          # HotSpot UAM "UI" Port (on subscriber network, for embedded portal)

I want to add one option in each /etc/chilli/*/config file (Maybe HS_AUTH=1). The problem is I do not know how to read the configuration in source file src/redir.c. Could you help me with this. Thank you very much.