/etc/wide-dhcpv6/dhcp6c-script is in wide-dhcpv6-client 20080615-16.
This file is owned by root:root, with mode 0o755.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 | #!/bin/sh
# dhcp6c-script for Debian/Ubuntu. Jérémie Corbier, April, 2006.
# resolvconf support by Mattias Guns, May 2006.
RESOLVCONF="/sbin/resolvconf"
[ -f /etc/default/wide-dhcpv6-client ] && . /etc/default/wide-dhcpv6-client
if [ -n "$new_domain_name" -o -n "$new_domain_name_servers" ]; then
    old_resolv_conf=/etc/resolv.conf
    new_resolv_conf=/etc/resolv.conf.dhcp6c-new
    rm -f $new_resolv_conf
    if [ -n "$new_domain_name" ]; then
        echo search $new_domain_name >> $new_resolv_conf
    fi
    if [ -n "$new_domain_name_servers" ]; then
        for nameserver in $new_domain_name_servers; do
            # No need to add an already existing nameserver
            res=$(grep "nameserver $nameserver" $old_resolv_conf)
            if [ -z "$res" ]; then
                echo nameserver $nameserver >> $new_resolv_conf
            fi
        done
    fi
    # Use resolvconf if available
    if [ -h "$old_resolv_conf" -a -x "$RESOLVCONF" ]; then
        for IFACE in $INTERFACES; do
            cat $new_resolv_conf | $RESOLVCONF -a $IFACE
        done
    else
        # To preserve IPv4 informations...
        cat $old_resolv_conf >> $new_resolv_conf
        chown --reference=$old_resolv_conf $new_resolv_conf
        chmod --reference=$old_resolv_conf $new_resolv_conf
        mv -f $new_resolv_conf $old_resolv_conf
    fi
fi
exit 0
 |