adde flowlet_switching exercise

SIGCOMM_2015/flowlet_switching/p4src/includes/headers.p4

@@ -0,0 +1,56 @@
+/*
+Copyright 2013-present Barefoot Networks, Inc. 
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+header_type ethernet_t {
+    fields {
+        dstAddr : 48;
+        srcAddr : 48;
+        etherType : 16;
+    }
+}
+
+header_type ipv4_t {
+    fields {
+        version : 4;
+        ihl : 4;
+        diffserv : 8;
+        totalLen : 16;
+        identification : 16;
+        flags : 3;
+        fragOffset : 13;
+        ttl : 8;
+        protocol : 8;
+        hdrChecksum : 16;
+        srcAddr : 32;
+        dstAddr: 32;
+    }
+}
+
+header_type tcp_t {
+    fields {
+        srcPort : 16;
+        dstPort : 16;
+        seqNo : 32;
+        ackNo : 32;
+        dataOffset : 4;
+        res : 3;
+        ecn : 3;
+        ctrl : 6;
+        window : 16;
+        checksum : 16;
+        urgentPtr : 16;
+    }
+}