packetforge: add packetforge for generic flow to extras

Add a new tool packetforge to extras. This tool is to support generic flow.
Packetforge is a library to translate naming or json profile format flow
pattern to the required input of generic flow, i.e. spec and mask. Using
python script flow_create.py, it can add and enable a new flow rule for
an interface via flow VAPI, and can delete an existed flow rule as well.
Command examples are shown below. Json profile examples can be found in
./parsegraph/samples.

Naming format input:
python flow_create.py --add -p "mac()/ipv4(src=1.1.1.1,dst=2.2.2.2)/udp()"
-a "redirect-to-queue 3" -i 1
python flow_create.py --del -i 1 -I 0

Json profile format input:
python flow_create.py -f "./flow_rule_examples/mac_ipv4.json" -i 1

With this command, flow rule can be added or deleted, and the flow
entry can be listed with "show flow entry" command in VPP CLI.

Packetforge is based on a parsegraph. The parsegraph can be built by
users. A Spec can be found in ./parsegraph as guidance. More details
about packetforge are in README file.

Type: feature

Signed-off-by: Ting Xu <ting.xu@intel.com>
Change-Id: Ia9f539741c5dca27ff236f2bcc493c5dd48c0df1
diff --git a/extras/packetforge/parsegraph/nodes/l2tpv2data.json b/extras/packetforge/parsegraph/nodes/l2tpv2data.json
new file mode 100644
index 0000000..d9e8b00
--- /dev/null
+++ b/extras/packetforge/parsegraph/nodes/l2tpv2data.json
@@ -0,0 +1,79 @@
+{
+    "type" : "node",
+    "name" : "l2tpv2data",
+    "layout" : [
+        {
+            "name" : "t",
+            "size" : "1",
+            "default" : "0",
+            "readonly" : "true"
+        },
+        {
+            "name" : "l",
+            "size" : "1"
+        },
+        {
+            "name" : "reserved",
+            "size" : "2"
+        },
+        {
+            "name" : "s",
+            "size" : "1"
+        },
+        {
+            "name" : "reserved",
+            "size" : "1"
+        },
+        {
+            "name" : "o",
+            "size" : "1"
+        },
+        {
+            "name" : "p",
+            "size" : "1"
+        },
+        {
+            "name" : "reserved",
+            "size" : "4"
+        },
+        {
+            "name" : "version",
+            "size" : "4",
+            "default" : "2",
+            "readonly" : "true"
+        },
+        {
+            "name" : "length",
+            "size" : "16",
+            "optional" : "l=1"
+        },
+        {
+            "name" : "tunnelid",
+            "size" : "16"
+        },
+        {
+            "name" : "sessionid",
+            "size" : "16"
+        },
+        {
+            "name" : "ns",
+            "size" : "16",
+            "optional" : "s=1"
+        },
+        {
+            "name" : "nr",
+            "size" : "16",
+            "optional" : "s=1"
+        },
+        {
+            "name" : "offsetsize",
+            "size" : "16",
+            "optional" : "o=1"
+        },
+        {
+            "name" : "offsetpad",
+            "size" : "offsetsize<<3",
+            "optional" : "o=1"
+        }
+    ]
+}