When a peer is not reading the data we are sending it was for the TLS
DNS code to end up in a situation when it would indefinitely
reschedule send requests, effectively turning the 'uv_loop' into a
busy loop that would consume CPU cycles in endless efforts to send
outgoing data.
The main reason for that was only one send buffer dedicated for sends:
the code would re-queue sends until it is empty - that would never
happen when the remote side is not reading data.
That seems like an omission from the older day of the Network Manager
as it is quiet simple to make the code use multiple buffers for
sends. That ultimately breaks the cycle of futile send request
rescheduling.
As a side effect, this commit also gets rid of one memory copying on a
hot path.
16c1d1eb2e