Fix: Unwrap SSL socket before closing transport socket.

[maczal]

Unwrap the SSL socket before closing the underlying transport socket instead of just closing SSL socket, to avoid yielding a "The TLS connection was non-properly terminated" warning in gvmd.log on disconnect.

What:

Performing proper disconnect of a TLS connection to skip log warnings from gvmd.

Why:

TLSConnection uses a transport socket and TLS socket wrapped on top of it. When disconnecting, the TLS socket was simply closed. Such behavior caused a log warning on the gvmd side:

md   main:WARNING:2022-05-19 14h13.51 UTC:18703: read_from_client_tls: failed to read from client: The TLS connection was non-properly terminated.

How:

In the change, on disconnect, unwrap() is called first on the TLS socket that closes it and returns the underlying transport socket, then the underlying socket can be closed normally and no warning from the gvmd server is generated.

I tested it using following snippet and observing tail of gvmd.log:

from gvm.connections import TLSConnection
from gvm.transforms import EtreeCheckCommandTransform
from gvm.protocols.gmp import Gmp

conn = TLSConnection(hostname='127.0.0.1', port=9390, timeout=900)
transform=EtreeCheckCommandTransform()

with Gmp(connection=conn, transform=transform) as gmp:
    gmp.get_version()

Checklist:

• Tests (N/A - needs gvmd to be tested)
• CHANGELOG Improved socket handling for TLSConnection.disconnect()
• Documentation N/A