[Click Modular Router] Protocol implementation tutorial - part 4 DummyRequest

Now that we can print and classify our dummy protocol packets it’s time to generate some, namely dummy requests packets. To create a dummy request packet you need to pass along a string to DummyRequest as a UDP packet containing the string and a dummy request packet will be generated. The way to inject a “request string” might seem odd but it’s a very simple thing to implement. Note that injecting a string could be done using click handlers (I will explain later what those are).

In the following we assume that the incoming packet have the data() pointer at the start of the request string. Thus to create a dummy request packet from the incoming packet containing the string you must:

1. Create a dummy protocol structure
2. Fill the structure (with appropriate T, Data and an arbitrary Len)
3. Create the packet and copy the structure to it

Note that you may also create the packet, cast the data() pointer to your structure and fill the pointer. I prefer to do it in the 3 steps above for clarity.

The element class definition is pretty standard with the addition of a function described above and the headroom for the dummy request packet:

The implementation is pretty easy, you just need to be careful about the length of the incoming string. I chose to pad smaller (smaller than DUMMYPROTO_DATA_LEN defined in the DummyProto.hh) strings with ‘\0’, longer strings are truncated.