Check how wrapping is done in P4

p4src/actions_delta_checksum.p4

@@ -52,7 +52,7 @@ action v6sum() {
     tmp = (tmp >> 16) + (tmp & 0xffff);
 //    tmp = tmp + (tmp >> 16);
     tmp = ~tmp;
-//    meta.v6sum = (bit<16>) ((((tmp>>8) & 0xff)|tmp<<8) & 0xffff) ;
+
     meta.v6sum = (bit<16>) tmp;
 }
 

p4src/wraptest.p4

@@ -0,0 +1,50 @@
+/* -*- P4_16 -*- */
+#include <core.p4>
+#include <v1model.p4>
+
+#include "headers.p4"
+#include "parsers.p4"
+
+control MyIngress(inout headers hdr,
+    inout metadata meta,
+    inout standard_metadata_t standard_metadata) {
+
+	/********************** APPLYING TABLES ***********************************/
+    apply {
+        if(hdr.tcp.isValid()) {
+            /* test wrap around */
+            hdr.tcp.checksum = 0xffff;
+            hdr.tcp.checksum = checksum + 2;
+        }
+        standard_metadata.egress_spec = 1;
+    }
+}
+
+control MyEgress(inout headers hdr,
+                 inout metadata meta,
+                 inout standard_metadata_t standard_metadata) {
+	apply {
+	}
+}
+
+control MyVerifyChecksum(inout headers hdr, inout metadata meta) {
+    apply {}
+}
+
+
+control MyComputeChecksum(inout headers  hdr, inout metadata meta) {
+    apply {}
+}
+
+/*************************************************************************
+***********************  S W I T C H  *******************************
+*************************************************************************/
+
+V1Switch(
+    MyParser(),
+    MyVerifyChecksum(),
+    MyIngress(),
+    MyEgress(),
+    MyComputeChecksum(),
+    MyDeparser()
+) main;