Implement fetching files from XMLRPC or static directory

[affenull2345]

Linked Items

Fixes #6

Description

Implement the functionality behind the TFTP server by requesting a file from Cobbler via XMLRPC. If Cobbler cannot return a file at the requested path, cobbler-tftp will fall back to serving files from a local static directory.

This is much slower than a normal TFTP server: on my laptop, it can handle about 25 requests per second but is too slow for 30.

TODO

• [X] Implement the get_tftp_file endpoint in Cobbler: https://github.com/cobbler/cobbler/pull/3549
• [x] Use the configured username and password when accessing the Cobbler API
• [X] Ensure that the fallback does not access any files outside the static directory (e.g. via .. in the path)

Category

This is related to a:

• [ ] Bugfix
• [X] Feature
• [ ] Packaging
• [ ] Docs
• [ ] Code Quality
• [ ] Refactoring
• [ ] Miscellaneous

Tests

• [ ] Unit-Tests were created
• [ ] System-Tests were created
• [ ] Code is already covered by Unit-Tests
• [ ] Code is already covered by System-Tests
• [ ] No tests required

[SchoolGuy]

Since I wasn't able to merge the parent PR we cannot merge this for now. We will leave this as is until the parent PR is ready.