Create 4 kyu - A Simplistic TCP Finite State Machine (FSM).c

c/4 kyu - A Simplistic TCP Finite State Machine (FSM).c

@@ -0,0 +1,69 @@
+#include <stddef.h>
+
+enum event {
+	APP_PASSIVE_OPEN, APP_ACTIVE_OPEN, APP_SEND, APP_CLOSE,
+  APP_TIMEOUT, RCV_SYN, RCV_ACK, RCV_SYN_ACK, RCV_FIN, RCV_FIN_ACK
+};
+
+enum state {
+	ERROR, CLOSED, LISTEN, SYN_SENT, SYN_RCVD, ESTABLISHED,
+  CLOSE_WAIT, LAST_ACK, FIN_WAIT_1, FIN_WAIT_2, CLOSING, TIME_WAIT,
+};
+
+#define EVENT_COUNT (RCV_FIN_ACK + 1)
+#define STATE_COUNT (TIME_WAIT + 1)
+
+static const enum state table[STATE_COUNT][EVENT_COUNT] = {
+  [CLOSED] = {
+    [APP_PASSIVE_OPEN] = LISTEN,
+    [APP_ACTIVE_OPEN] = SYN_SENT
+  },
+  [LISTEN] = {
+    [RCV_SYN] = SYN_RCVD,
+    [APP_SEND] = SYN_SENT,
+    [APP_CLOSE] = CLOSED
+  },
+  [SYN_RCVD] = {
+    [APP_CLOSE] = FIN_WAIT_1,
+    [RCV_ACK] = ESTABLISHED
+  },
+  [SYN_SENT] = {
+    [RCV_SYN] = SYN_RCVD,
+    [RCV_SYN_ACK] = ESTABLISHED,
+    [APP_CLOSE] = CLOSED
+  },
+  [ESTABLISHED] = {
+    [APP_CLOSE] = FIN_WAIT_1,
+    [RCV_FIN] = CLOSE_WAIT
+  },
+  [FIN_WAIT_1] = {
+    [RCV_FIN] = CLOSING,
+    [RCV_FIN_ACK] = TIME_WAIT,
+    [RCV_ACK] = FIN_WAIT_2
+  },
+  [CLOSING] = {
+    [RCV_ACK] = TIME_WAIT
+  },
+  [FIN_WAIT_2] = {
+    [RCV_FIN] = TIME_WAIT
+  },
+  [TIME_WAIT] = {
+    [APP_TIMEOUT] = CLOSED
+  },
+  [CLOSE_WAIT] = {
+    [APP_CLOSE] = LAST_ACK
+  },
+  [LAST_ACK] = {
+    [RCV_ACK] = CLOSED
+  }
+};
+
+enum state get_TCP_state (size_t n, const enum event events[n])
+{
+  enum state s = CLOSED;
+  for (size_t i = 0; i < n; i++) {
+    s = table[s][events[i]];
+    if (s == ERROR) break;
+  }
+	return s;
+}