Exercise for L2 multicast (#288)

exercises/multicast/sig-topo/s1-runtime.json

@@ -0,0 +1,66 @@
+{
+  "target": "bmv2",
+  "p4info": "build/multicast.p4.p4info.txt",
+  "bmv2_json": "build/multicast.json",
+  "table_entries": [
+    {
+      "table": "MyIngress.mac_lookup",
+      "match": {
+        "hdr.ethernet.dstAddr": "08:00:00:00:01:11"
+      },
+      "action_name": "MyIngress.mac_forward",
+      "action_params": {
+        "port": 1
+      }
+    },
+    {
+      "table": "MyIngress.mac_lookup",
+      "match": {
+        "hdr.ethernet.dstAddr": "08:00:00:00:02:22"
+      },
+      "action_name": "MyIngress.mac_forward",
+      "action_params": {
+        "port": 2
+      }
+    },
+    {
+      "table": "MyIngress.mac_lookup",
+      "match": {
+        "hdr.ethernet.dstAddr": "08:00:00:00:03:33"
+      },
+      "action_name": "MyIngress.mac_forward",
+      "action_params": {
+        "port": 3
+      }
+    },
+    {
+      "table": "MyIngress.mac_lookup",
+      "match": {
+        "hdr.ethernet.dstAddr": "08:00:00:00:04:44"
+      },
+      "action_name": "MyIngress.mac_forward",
+      "action_params": {
+        "port": 4
+      }
+    }
+  ],
+  "multicast_group_entries" : [
+    {
+      "multicast_group_id" : 1,
+      "replicas" : [
+        {
+          "egress_port" : 1,
+          "instance" : 1
+        },
+        {
+          "egress_port" : 2,
+          "instance" : 1
+        },
+        {
+          "egress_port" : 3,
+          "instance" : 1
+        }
+      ]
+    }
+  ]
+}

exercises/multicast/sig-topo/topology.json

@@ -0,0 +1,18 @@
+{
+    "hosts": {
+        "h1": {"ip": "10.0.0.1/24", "mac": "08:00:00:00:01:11",
+               "commands":["ip route add 10.0.0.0/24 dev eth0"]},
+        "h2": {"ip": "10.0.0.2/24", "mac": "08:00:00:00:02:22",
+               "commands":["ip route add 10.0.0.0/24 dev eth0"]},
+        "h3": {"ip": "10.0.0.3/24", "mac": "08:00:00:00:03:33",
+               "commands":["ip route add 10.0.0.0/24 dev eth0"]},
+        "h4": {"ip": "10.0.0.4/24", "mac": "08:00:00:00:04:44",
+               "commands":["ip route add 10.0.0.0/24 dev eth0"]}
+    },
+    "switches": {
+        "s1": { "runtime_json" : "sig-topo/s1-runtime.json" }
+    },
+    "links": [
+        ["h1", "s1-p1"], ["h2", "s1-p2"], ["h3", "s1-p3"], ["h4", "s1-p4"]
+    ]
+}