Rate limit for ipv6

src/freedombone-utils-mesh

 function global_rate_limit {
     if ! grep -q "tcp_challenge_ack_limit" /etc/sysctl.conf; then
         echo 'net.ipv4.tcp_challenge_ack_limit = 999999999' >> /etc/sysctl.conf
+        echo 'net.ipv6.tcp_challenge_ack_limit = 999999999' >> /etc/sysctl.conf
     else
         sed -i 's|net.ipv4.tcp_challenge_ack_limit.*|net.ipv4.tcp_challenge_ack_limit = 999999999|g' /etc/sysctl.conf
+        sed -i 's|net.ipv6.tcp_challenge_ack_limit.*|net.ipv6.tcp_challenge_ack_limit = 999999999|g' /etc/sysctl.conf
     fi
     sysctl -p -q
 }