Intel Threading Building Blocks

Synchronization with the pipeline item and concurrent hash maps

You synchronize packet information between stages using the Threading Building Blocks pipeline template. Each filter returns a packet_trace instance that is passed to the next stage.

The pipeline template is given a packet trace structure that consists of:

	typedef struct {
	    nic_t packetNic;     // the NIC packet into and out of router
	    ip_t packetDestIp;   // destination IP into and out of router
	    ip_t packetSrcIp;    // source IP into and out of router
	    port_t packetDestPort; // destinationPort paired w/destination IP
	    port_t packetSrcPort;  // source Port paired w/source IP
	    protocol_t packetProtocol;// packet protocol type
	    port_t packetPayloadApp;  // any of the packet worth simulating
	} packet_trace;

A packet will be transformed, filter by filter, from what would come into the router into what would go out of the router. For example, for an outbound packet, the NAT would change the packetSrcIp to be the IP of the router outgoing_ip. That is how every device in the Ethernet will see the local network. And it will change the packetSrcPort to the router port mapped in its mapped_ports_table.

The other synchronized structures are the data tables in the local network router. The network_table is used to map the IP to the NIC in packet forwarding. It is implemented using a concurrent hash map (Chapter 5).

	typedef tbb::concurrent_hash_map<ip_t, nic_t, ip_addr_comparator>
	                                                           network_table;

The key data structure for mapping a router port is the ...