load_balancer.xl

import "pkt_headers.xlh";

PacketField ethByte {
	dst = packet.data[5:+1];
}

Constant PKT = 255;

Stage loadBalancer {
	Register global counter, ZERO;

	setFlowKey(tcp.sport, tcp.dport);

	State initial init {
		on(pktRcvd) {
			if(pktRcvd.port == 1, counter > ZERO) {
				counter = counter - 1;
				setField(ethByte.dst, PKT, 0xaa);
				sendPacket(PKT, 2);
				setNextState(server1);
			}

			if(pktRcvd.port == 1, counter == ZERO) {
				counter = counter + 1;
				setField(ethByte.dst, PKT, 0xbb);
				sendPacket(PKT, 3);
				setNextState(server2);
			}
		}
	}

	State server1 {
		setField(ethByte.dst, PKT, 0xaa);
		sendPacket(PKT, 2);
	}

	State server2 {
		setField(ethByte.dst, PKT, 0xbb);
		sendPacket(PKT, 3);
	}

	State any {
		on(pktRcvd) {
			if(pktRcvd.port ==2 ) {
				sendPacket(PKT, 1);
			}
		
			if(pktRcvd.port ==3 ) {
				sendPacket(PKT, 1);
			}
		}
	}
}