(1) Coding style changes.
(2) If the server does not acknowledge any blocksize option,
revert to the default blocksize of 512 bytes.
(3) Send ACK if the first packet happens to be the last packet.
(4) Do not accept blocksize greater than what was requested.
(5) Drop any unwanted OACK received if a tftp transfer is already
in progress.
(6) Terminate incomplete transfers with a special no-error ERROR packet.
Otherwise we rely on the tftp server to time out, which it does
eventually, after re-sending the last packet several times and spamming
the system log about it every time. This idea is borrowed from the
PXE client, which does exactly that.
Submitted by: Alexander Kabaev <kan@FreeBSD.org>
Reviewed and Tested by: Santhanakrishnan Balraj <sbalraj at juniper dot net>
23a5bce73f