WINDOW_UPDATE on ingress traffic

[krizhanovsky]

Motivation

At the moment Tempesta FW announces SETTINGS_INITIAL_WINDOW_SIZE as 2^31-1 (the maximum value) and never updates the window to a client. This may lead to hung connection if a client upload reaches 2GB size.

Scope

#1394 extends TfwStream with the current flow-control window, which also must be tracked on ingress streams and updated (send WINDOW_UPDATE) to a peer, when it reaches 0.

Testing

Just try to upload something like 3GB of data. Probably use some C program for the client to make it faster. Please also update the issue with the resulting transfer speed.

[krizhanovsky]

Fixed in #2009