I like your solution to prevent the kernel from interfering with your packets.
An alternative method I've used in the past is to add an iptables rule to silently drop the incoming packets. libpcap sees the packets before they are dropped, so you'll still be able to react to them, but the kernel will ignore them (and therefore won't attempt to RST them).
An alternative method I've used in the past is to add an iptables rule to silently drop the incoming packets. libpcap sees the packets before they are dropped, so you'll still be able to react to them, but the kernel will ignore them (and therefore won't attempt to RST them).