udp packet payload editing as it arrives at the linux kernel

In order to reduce forwarding traffic, we need to discard certain data items in the udp broadcast payload as it arrives at the linux kernel. I envisage that it's a kernel module hooked up to kernel's NF_IP_PRE_ROUTING hook, examine the packet destined for the broadcast, do the necessary reconstituting of packet to replace the original packet, then issue the ACCEPT to instruct the kernel to pass on to the next stage.