iptables-restore <<-_eof;
-A INPUT
    -p tcp
    -m tcp
        --dport 80
        --tcp-flags FIN,SYN,RST,ACK SYN
    -m connlimit
        --connlimit-above 20
        --connlimit-mask 24
    -j REJECT
        --reject-with tcp-reset
_eof

This is how I want to write iptables rules, but does not work, since iptables-restore
does not allow \n

would it be possible to do something hacky like:

-A INPUT $(..?
   -p tcp
   ...
)

and make it look like a oneliner for iptables-restore..?