My question is: what does it really do? For instance, if I set it to true, what does it do to packages (datagrams?) that I want to write to the TUN device? As far as I noticed it does not mean that all packets to be written to the TUN device will be discarded rather than processed in another manner. Does it mean this?
So I can only track what it does only this far:
public Builder setBlocking(boolean blocking) {
mConfig.blocking = blocking;
return this;
}
And that
public class Builder {
private final VpnConfig mConfig = new VpnConfig();
//other stuff here ...
}
I also read the official description, but it is still unclear to me. Googling it will only lead to search results related to "how to bypass VPN blocking".
It does refer to blocking I/O and has nothing to do with blocking traffic or how packets are treated. Instead it changes how your program interacts with the file descriptor.
In blocking mode, operations like read()/write() will block until some data has been transferred (or an error occurred) whereas in non-blocking mode the operations may return immediately (with EAGAIN or EWOULDBLOCK) if the file descriptor is currently not ready and the operation would block.