Basic NETLINK_FIREWALL support. Highlights need for struct alignment

examples/firewall.rb

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+LIBDIR = File.expand_path(File.join(File.dirname(__FILE__), '..', 'lib'))
+$LOAD_PATH.unshift LIBDIR
+
+require 'pp'
+require 'netlink/firewall'
+
+# Example of using Netlink::Firewall to capture all outbound packets
+# to TCP port 7551. Use "telnet 127.0.0.1 7551" to test.
+
+#system("modprobe ip_queue")
+#system("modprobe iptable_filter")
+#system("iptables -I OUTPUT -j QUEUE -p tcp --destination-port 7551")
+nl = Netlink::Firewall::Socket.new
+nl.set_mode(Netlink::IPQ_COPY_PACKET, 128)
+nl.dequeue_packets do |pkt|
+  p pkt
+  Netlink::NF_ACCEPT  # Netlink::NF_DROP
+end