[ovsp4rt] Implement GetTxAccVsiPort()

[ffoulkes]

• Extracted code from ConfigFdbEntry() and ConfigSrcPortEntry() to a new GetTxAccVsiPort() function. This reduces the complexity of the calling functions, which don't need to know how the port is obtained, and it removes duplicate code.

See later comments in the PR for AI analysis of this refactoring.

This PR is ES2K-specific. GetTxiAccVsiPort is only called by ES2K functions.

Note

The purpose of this PR is to refactor. I propose to make the mutability changes noted in the comments in a second PR, and any other changes in subsequent PRs.

[ffoulkes]

Here is ChatGPT's assessment of the first refactoring:

Let's compare the original and refactored code and identify key differences to determine if they are functionally equivalent:

Key Changes:

1. Refactoring of TxAccVsi Port Logic:

   • Original Code: The logic to obtain the src_port was handled directly within DoConfigFdbEntry. It involves calling GetTxAccVsiTableEntry, processing the ReadResponse, and extracting the src_port.
   • Refactored Code: This logic has been extracted into a new function, GetTxAccVsiPort, which encapsulates the same functionality. The refactored DoConfigFdbEntry then calls this function and updates learn_info.src_port accordingly.

2. GetTxAccVsiPort:

   In the refactored version, the code that fetches the src_port from the TxAccVsiTableEntry and processes the response has been moved to a separate function (GetTxAccVsiPort). This makes the DoConfigFdbEntry function cleaner and easier to follow. The GetTxAccVsiPort function itself returns the processed src_port, which is then used in the DoConfigFdbEntry function.

3. host_sp Handling:

   In the original code, the host_sp variable is calculated inline within the DoConfigFdbEntry function.
   In the refactored code, host_sp is calculated in the GetTxAccVsiPort function and then returned to DoConfigFdbEntry.

4. Error Handling:

   Both versions handle errors similarly, but the error handling is encapsulated in the GetTxAccVsiPort function in the refactored version. It checks if the result is an error (!status.ok()) before continuing.

Functional Equivalence:

• The core logic of connecting to the client, fetching P4Info, checking tunnel entries, and configuring the FDB entries remains unchanged in both versions.
• The refactoring does not alter the behavior of the system. It simply moves the logic of obtaining the src_port into a separate function (GetTxAccVsiPort), which is then invoked in DoConfigFdbEntry. This refactor improves the modularity and readability of the code without changing its overall functionality.
• The handling of the learn_info.src_port and the update logic is preserved in the refactored code, so the flow of the program remains the same.

Conclusion:

The original and refactored code are functionally equivalent. The refactoring only reorganizes the code to improve clarity and modularity, without altering the core behavior.

[ffoulkes]

Its conclusions on the second refactoring were as follows:

Functional Equivalence:

• Core Logic: The core logic remains the same as in the original code. The refactored version still follows the same steps—connect to the client, fetch P4Info, get the src_port, and configure the entry. The main difference is that fetching and processing the src_port has been abstracted into the helper function GetTxAccVsiPort.
• Error Handling: The error handling around the src_port retrieval and the flow of control in case of failure are consistent with the original version.

Conclusion:

The refactored code is functionally equivalent to the original code. The change primarily improves the structure of the function by extracting the logic for obtaining and processing the src_port into the GetTxAccVsiPort function. This refactor makes the DoConfigSrcPortEntry function cleaner and more maintainable, while maintaining the same behavior as the original code.

[ffoulkes]

If we replace break with return host_sp, we can (1) define and initialize host_sp within the if statement, and (2) change line 2153 to return 0.

I also propose to rename the loop index from param_bytes to i. The long name is misleading and adds unnecessary complexity.