P4 is a domain-specific language to develop the packet processing of network devices.
These programs can easily hide errors, therefore we give a solution to analyze them
predefined errors in them. This paper shows the idea, which works with the P4 code
as a set of
components and processes them one by one, while calculating their pre- and post-conditions.
This method does not only detect errors between the components and their connections,
it is capable to reveal errors, which are hidden in the middle of a component. The
introduces the method and shows its calculation in an example.