Currently, FreeRDP-based server implementations can do connect-time
autodetection.
However, without having any control over it.
In order to be able to override the default connect-time autodetection
handling, introduce three new states for the state machine of the
connection sequence and two new callbacks for the autodetect handling.
These are:
- CONNECTION_STATE_CONNECT_TIME_AUTO_DETECT_BEGIN
- CONNECTION_STATE_CONNECT_TIME_AUTO_DETECT_IN_PROGRESS
- CONNECTION_STATE_CONNECT_TIME_AUTO_DETECT_END
- OnConnectTimeAutoDetectBegin()
- OnConnectTimeAutoDetectProgress()
The END state is pretty simple: When the autodetection is finished and
the autodetect state is FREERDP_AUTODETECT_STATE_COMPLETE, transition
into the next state of the connection sequence.
The BEGIN state is entered, when capability-wise network autodetection
is available.
In this state, the OnConnectTimeAutoDetectBegin callback is called, the
server implementation may initialize any related handling here.
If the server implementation determines, that no further handling is
required, it can end the autodetection phase by returning
FREERDP_AUTODETECT_STATE_COMPLETE.
If not, and an autodetection request is sent, it returns
FREERDP_AUTODETECT_STATE_REQUEST.
The state machine of the connection sequence will then switch into the
IN_PROGRESS state.
In the IN_PROGRESS state, any incoming PDU is handled first, then the
OnConnectTimeAutoDetectProgress callback is called.
Like in the BEGIN state, the return value will determine, whether the
state machine of the connection sequence goes into the END state or goes
into (or rather stays) in the IN_PROGRESS state.
The current state of the autodetect API for the server side does not
include all allowed scenarios where the network autodetection can be
used.
This for example includes the connect-time autodetection, as the
related calls are hidden inside FreeRDP, and not exposed as public API.
In order to avoid duplicate send methods, check the state of the
connection sequence.
If the connection sequence is not yet done, use the connect-time request
types.
Otherwise, use the continuous request types.
The Bandwidth Measure Payload PDU is a little special case, as it is
only allowed to be sent during the connection sequence.
To ensure this, add an assertion in its sending method.
Also fix the handling for the Network Characteristics Sync PDU:
Previously, after parsing the PDU data, the read data was just sent
again to the client, which is wrong.
To fix this issue, introduce a callback for this client-to-server PDU,
so that the actual server implementation can hook up its own handling
for this PDU.
Depending on the situation, the server side may want to discard or use
the retrieved data here.
Moreover, decouple the send-handling for the Network Characteristics
Result PDU from the local autodetect variables.
Currently, these variables are shared between the send and receive
methods.
This leads to access problems, where the server side, wants to use a
different thread to send the autodetect PDU, as the receive handler may
receive an autodetect PDU and overwrite these values with possible
nonsense values.
This is especially the case with RTT response PDUs, as the written
netCharAverageRTT and netCharBaseRTT values are only correct, when only
one RTTRequest happens at a time and no stray RTTResponses are received.
Autodetect packets can be transported either in TCP TPKT packets or be contained
in multi-transport subheaders (transported on UDP). These changes do the appropriate
modifications so that in further developments we can take the transport type in account
when treating / writing these packets.
