Add calc from p4/tutorials as examples/calc.app

examples/calc.app/README.md

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+# Implementing a P4 Calculator
+
+## Introduction
+
+The objective of this tutorial is to implement a basic calculator
+using a custom protocol header written in P4. The header will contain
+an operation to perform and two operands. When a switch receives a
+calculator packet header, it will execute the operation on the
+operands, and return the result to the sender.
+
+## Step 1: Run the (incomplete) starter code
+
+The directory with this README also contains a skeleton P4 program,
+`calc.p4`, which initially drops all packets.  Your job will be to
+extend it to properly implement the calculator logic.
+
+As a first step, compile the incomplete `calc.p4` and bring up a
+switch in Mininet to test its behavior.
+
+1. In your shell, run:
+   ```bash
+   p4app run examples/calc.app
+   ```
+   This will:
+   * start a p4app container
+
+   * compile `calc.p4`, and
+
+   * start a Mininet instance with one switches (`s1`) connected to
+     one host (`h1`).
+
+2. We've written a small Python-based driver program that will allow
+you to test your calculator. You can run the driver program directly
+from the Mininet command prompt:
+
+```
+mininet> h1 python calc.py 
+> 
+```
+
+3. The driver program will provide a new prompt, at which you can type
+basic expressions. The test harness will parse your expression, and
+prepare a packet with the corresponding operator and operands. It will
+then send a packet to the switch for evaluation. When the switch
+returns the result of the computation, the test program will print the
+result. However, because the calculator program is not implemented,
+you should see an error message.
+
+```
+> 1+1
+Didn't receive response
+>
+```
+
+## Step 2: Implement Calculator
+
+To implement the calculator, you will need to define a custom
+calculator header, and implement the switch logic to parse header,
+perform the requested operation, write the result in the header, and
+return the packet to the sender.
+
+We will use the following header format:
+
+             0                1                  2              3
+      +----------------+----------------+----------------+---------------+
+      |      P         |       4        |     Version    |     Op        |
+      +----------------+----------------+----------------+---------------+
+      |                              Operand A                           |
+      +----------------+----------------+----------------+---------------+
+      |                              Operand B                           |
+      +----------------+----------------+----------------+---------------+
+      |                              Result                              |
+      +----------------+----------------+----------------+---------------+
+
+
+-  P is an ASCII Letter 'P' (0x50)
+-  4 is an ASCII Letter '4' (0x34)
+-  Version is currently 0.1 (0x01)
+-  Op is an operation to Perform:
+ -   '+' (0x2b) Result = OperandA + OperandB
+ -   '-' (0x2d) Result = OperandA - OperandB
+ -   '&' (0x26) Result = OperandA & OperandB
+ -   '|' (0x7c) Result = OperandA | OperandB
+ -   '^' (0x5e) Result = OperandA ^ OperandB
+
+
+We will assume that the calculator header is carried over Ethernet,
+and we will use the Ethernet type 0x1234 to indicate the presence of
+the header.
+
+Given what you have learned so far, your task is to implement the P4
+calculator program. There is no control plane logic, so you need only
+worry about the data plane implementation.
+
+A working calculator implementation will parse the custom headers,
+execute the mathematical operation, write the result in the result
+field, and return the packet to the sender.
+
+## Step 3: Run your solution
+
+Follow the instructions from Step 1.  This time, you should see the
+correct result:
+
+```
+> 1+1
+2
+>
+```

examples/calc.app/calc.p4

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+/* -*- P4_16 -*- */
+
+/*
+ * P4 Calculator
+ *
+ * This program implements a simple protocol. It can be carried over Ethernet
+ * (Ethertype 0x1234).
+ *
+ * The Protocol header looks like this:
+ *
+ *        0                1                  2              3
+ * +----------------+----------------+----------------+---------------+
+ * |      P         |       4        |     Version    |     Op        |
+ * +----------------+----------------+----------------+---------------+
+ * |                              Operand A                           |
+ * +----------------+----------------+----------------+---------------+
+ * |                              Operand B                           |
+ * +----------------+----------------+----------------+---------------+
+ * |                              Result                              |
+ * +----------------+----------------+----------------+---------------+
+ *
+ * P is an ASCII Letter 'P' (0x50)
+ * 4 is an ASCII Letter '4' (0x34)
+ * Version is currently 0.1 (0x01)
+ * Op is an operation to Perform:
+ *   '+' (0x2b) Result = OperandA + OperandB
+ *   '-' (0x2d) Result = OperandA - OperandB
+ *   '&' (0x26) Result = OperandA & OperandB
+ *   '|' (0x7c) Result = OperandA | OperandB
+ *   '^' (0x5e) Result = OperandA ^ OperandB
+ *
+ * The device receives a packet, performs the requested operation, fills in the 
+ * result and sends the packet back out of the same port it came in on, while 
+ * swapping the source and destination addresses.
+ *
+ * If an unknown operation is specified or the header is not valid, the packet
+ * is dropped 
+ */
+
+#include <core.p4>
+#include <v1model.p4>
+
+/*
+ * Define the headers the program will recognize
+ */
+
+/*
+ * Standard Ethernet header 
+ */
+header ethernet_t {
+    bit<48> dstAddr;
+    bit<48> srcAddr;
+    bit<16> etherType;
+}
+
+/*
+ * This is a custom protocol header for the calculator. We'll use 
+ * etherType 0x1234 for it (see parser)
+ */
+const bit<16> P4CALC_ETYPE = 0x1234;
+const bit<8>  P4CALC_P     = 0x50;   // 'P'
+const bit<8>  P4CALC_4     = 0x34;   // '4'
+const bit<8>  P4CALC_VER   = 0x01;   // v0.1
+const bit<8>  P4CALC_PLUS  = 0x2b;   // '+'
+const bit<8>  P4CALC_MINUS = 0x2d;   // '-'
+const bit<8>  P4CALC_AND   = 0x26;   // '&'
+const bit<8>  P4CALC_OR    = 0x7c;   // '|'
+const bit<8>  P4CALC_CARET = 0x5e;   // '^'
+
+header p4calc_t {
+    bit<8>  op;
+/* TODO
+ * fill p4calc_t header with P, four, ver, op, operand_a, operand_b, and res
+   entries based on above protocol header definition.
+ */
+}
+
+/*
+ * All headers, used in the program needs to be assembled into a single struct.
+ * We only need to declare the type, but there is no need to instantiate it,
+ * because it is done "by the architecture", i.e. outside of P4 functions
+ */
+struct headers {
+    ethernet_t   ethernet;
+    p4calc_t     p4calc;
+}
+
+/*
+ * All metadata, globally used in the program, also  needs to be assembled 
+ * into a single struct. As in the case of the headers, we only need to 
+ * declare the type, but there is no need to instantiate it,
+ * because it is done "by the architecture", i.e. outside of P4 functions
+ */
+
+struct metadata {
+    /* In our case it is empty */
+}
+
+/*************************************************************************
+ ***********************  P A R S E R  ***********************************
+ *************************************************************************/
+parser MyParser(packet_in packet,
+                out headers hdr,
+                inout metadata meta,
+                inout standard_metadata_t standard_metadata) {    
+    state start {
+        packet.extract(hdr.ethernet);
+        transition select(hdr.ethernet.etherType) {
+            P4CALC_ETYPE : check_p4calc;
+            default      : accept;
+        }
+    }
+
+    state check_p4calc {
+        /* TODO: just uncomment the following parse block */
+        /* 
+        transition select(packet.lookahead<p4calc_t>().p,
+        packet.lookahead<p4calc_t>().four,
+        packet.lookahead<p4calc_t>().ver) {
+            (P4CALC_P, P4CALC_4, P4CALC_VER) : parse_p4calc;
+            default                          : accept;
+        }
+        */
+    }
+
+    state parse_p4calc {
+        packet.extract(hdr.p4calc);
+        transition accept;
+    }
+}
+
+/*************************************************************************
+ ************   C H E C K S U M    V E R I F I C A T I O N   *************
+ *************************************************************************/
+control MyVerifyChecksum(inout headers hdr,
+                         inout metadata meta) {
+    apply { }
+}
+
+/*************************************************************************
+ **************  I N G R E S S   P R O C E S S I N G   *******************
+ *************************************************************************/
+control MyIngress(inout headers hdr,
+                  inout metadata meta,
+                  inout standard_metadata_t standard_metadata) {
+    action send_back(bit<32> result) {
+        /* TODO
+         * - put the result back in hdr.p4calc.res
+         * - swap MAC addresses in hdr.ethernet.dstAddr and
+         *   hdr.ethernet.srcAddr using a temp variable
+         * - Send the packet back to the port it came from
+             by saving standard_metadata.ingress_port into
+             standard_metadata.egress_spec
+         */ 
+    }
+
+    action operation_add() {
+        /* TODO call send_back with operand_a + operand_b */
+    }
+
+    action operation_sub() {
+        /* TODO call send_back with operand_a - operand_b */
+    }
+
+    action operation_and() {
+        /* TODO call send_back with operand_a & operand_b */
+    }
+
+    action operation_or() {
+        /* TODO call send_back with operand_a | operand_b */
+    }
+
+    action operation_xor() {
+        /* TODO call send_back with operand_a ^ operand_b */
+    }
+
+    action operation_drop() {
+        mark_to_drop(standard_metadata);
+    }
+
+    table calculate {
+        key = {
+            hdr.p4calc.op        : exact;
+        }
+        actions = {
+            operation_add;
+            operation_sub;
+            operation_and;
+            operation_or;
+            operation_xor;
+            operation_drop;
+        }
+        const default_action = operation_drop();
+        const entries = {
+            P4CALC_PLUS : operation_add();
+            P4CALC_MINUS: operation_sub();
+            P4CALC_AND  : operation_and();
+            P4CALC_OR   : operation_or();
+            P4CALC_CARET: operation_xor();
+        }
+    }
+
+    apply {
+        if (hdr.p4calc.isValid()) {
+            calculate.apply();
+        } else {
+            operation_drop();
+        }
+    }
+}
+
+/*************************************************************************
+ ****************  E G R E S S   P R O C E S S I N G   *******************
+ *************************************************************************/
+control MyEgress(inout headers hdr,
+                 inout metadata meta,
+                 inout standard_metadata_t standard_metadata) {
+    apply { }
+}
+
+/*************************************************************************
+ *************   C H E C K S U M    C O M P U T A T I O N   **************
+ *************************************************************************/
+
+control MyComputeChecksum(inout headers hdr, inout metadata meta) {
+    apply { }
+}
+
+/*************************************************************************
+ ***********************  D E P A R S E R  *******************************
+ *************************************************************************/
+control MyDeparser(packet_out packet, in headers hdr) {
+    apply {
+        packet.emit(hdr.ethernet);
+        packet.emit(hdr.p4calc);
+    }
+}
+
+/*************************************************************************
+ ***********************  S W I T T C H **********************************
+ *************************************************************************/
+
+V1Switch(
+MyParser(),
+MyVerifyChecksum(),
+MyIngress(),
+MyEgress(),
+MyComputeChecksum(),
+MyDeparser()
+) main;