function removeExclamationMark(input)
    if input:find('%!$')
    then
        return input(bar:sub(1, -1))
    else
        return input
    end
end

function updatepolicy(input)

    -- target zone where the CNAMEs point to
    myzone = "dhcp.domain.com"

    -- allowed networks to accept updates from
    mynetworks = newNMG()
    mynetworks:addMasks({"1.2.3.4", "127.0.0.1"})

    -- ignore non-authorized networks
    if not mynetworks:match(input:getRemote())
    then
        pdnslog("dynupdate: network check failed from " .. input:getRemote():toString(), pdns.loglevels.Info)
        return false
    end
    pdnslog("dynupdate: incoming request for " .. input:getZoneName():toString(), pdns.loglevels.Info)

    if (input:getQType() == pdns.A and input:getZoneName():toString() == myzone)
    then
        if input:getQName():toString() == hostname .. "." or input:getQName():toString() == hostname .. "." .. input:getZoneName():toString()
        then
            return true
        end
    end

    return false
end