#!/bin/sh
#----------------------------------------------------------------------------
# /etc/ppp/ip-up200.dns                                          __FLI4LVER__
#
# called whenever an IPv4 PPP connection over default circuit has come up
# and dnsmasq is installed
#
# Creation:     2007-11-293  lanspezi
# Last Update:  $Id$
#----------------------------------------------------------------------------
# back up etc/resolv.dnsmasq to etc/resolv.dnsmasq.bak
# if provider supports sending ip(s) of dns server(s)
#----------------------------------------------------------------------------

. /etc/rc.d/helper-dns_dnsmasq.sh

# $1 = IPv4 network address
# output = 0 if it is a private address according to RFC 1918, 1 otherwise
is_private()
{
    case $1 in
    10.*.*.*)
        return 0
        ;;
    192.168.*.*)
        return 0
        ;;
    172.*.*.*)
        set -- ${1//./ }
        [ $2 -ge 16 -a $2 -lt 32 ] && return 0
        ;;
    esac
    return 1
}

# $1 = IPv4 address of DNS upstream server
# result = 0 if the router is part of the same subnet, 1 otherwise
# output = network the DNS upstream server is part of (if function returns 0)
is_part_of_lan()
{
    local net
    for net in $(get_local_ipv4_subnets)
    do
        local mask=${net#*/}
        local dnsnet=$(netcalc network "$1/$mask")
        if [ "$dnsnet/$mask" = "$net" ]
        then
            echo "$net"
            return 0
        fi
    done
    return 1
}

# $1 = DNS server to add
# expects $resolv_file to contain the file where the DNS server is to be added
# expects $bogus_priv_file to contain the address ranges to be exempted from
#   being forwarded to upstream DNS servers
# creates $bogus_priv_file~ as a backup file if an address range has to be deleted
add_dns_server()
{
    echo "nameserver $1" >> $resolv_file
    echo "using nameserver $1"
    if is_private "$1"
    then
        local lan=$(is_part_of_lan "$1")
        if [ -n "$lan" ]
        then
            # use ~ suffix such that dnsmasq skips this file
            if [ ! -f $bogus_priv_file~ ]
            then
                cp $bogus_priv_file $bogus_priv_file~
            fi
            dns_remove_private_subnet $lan
            echo "  forwarding $(netcalc dnsrev ${lan%/*}) to $1"
        fi
    fi
}

# is a default-route-interface going up?
if [ "$is_default_route" = "yes" ]
then
    # $interface.usepeerdns existing?
    if [ -f /var/run/$interface.usepeerdns ]
    then
        read usepeerdns < /var/run/$interface.usepeerdns
    else
        usepeerdns='no'
    fi

    if [ "$usepeerdns" = "yes" ]
    then
        # pppd sets DNS1 and DNS2
        if [ "$DNS1" -o "$DNS2" ]
        then
            resolv_file=/etc/resolv.dnsmasq
            delegation_file=/etc/dnsmasq.d/dns_delegate.conf
            bogus_priv_file=$dns_private_subnets

            if lock_resource $(basename $resolv_file) ip-up200.dns
            then
                if [ ! -f $resolv_file.bak ]
                then
                    mv $resolv_file $resolv_file.bak
                    echo "# x_USEPEERDNS is set" > $resolv_file
                    chown dns:dns $resolv_file
                fi

                for dns in $DNS1 $DNS2
                do
                    add_dns_server $dns
                done
                if [ -f $bogus_priv_file~ ]
                then
                    dns_update_private_subnets
                fi

                if [ -n "$DNSDOMAIN" ]
                then
                    cp $delegation_file $delegation_file~
                    echo "rebind-domain-ok=/$DNSDOMAIN/" >> $delegation_file
                fi

                if [ -f $delegation_file~ -o -f $bogus_priv_file~ ]
                then
                    killall dnsmasq
                    sleep 1
                    dnsmasq
                else
                    killall -HUP dnsmasq
                fi
                unlock_resource $(basename $resolv_file) ip-up200.dns
            fi
        else
            echo "The DHCPv4 server didn't send any nameserver addresses, DNS forwarders not changed"
        fi
    else
        echo "Using peer DNS servers disabled for $interface"
    fi
fi