Load newline ipv4 subnet list into nftables set. ip blacklist blackhole denylist filter

loadblacklist.sh

 nft add set netdev filter blackhole {type ipv4_addr\; counter\; auto-merge\; flags interval\; elements={$(grep -oP '^ *(?:[0-9]{1,3}\.){3}[0-9]{1,3}/{0,1}[0-9]{0,2}' blacklist.txt | tr '\n' ',' | sed 's/,*$//')}\;}
 
 # (don't forget to add a drop rule checking the @blackhole rule)