MFC r336587:

tftpd(8): when completing an WRQ, flush the file before acknowleding receipt

tftpd(8) should flush a newly written file to disk before ACKing the final DATA
packet. Otherwise there is a narrow race window when a subsequent read may not
see the file. This is somewhat related to r330710, but the race window is much
smaller. Hopefully this will fix the intermittent tests in Jenkins.

Reported by: Jenkins

MFC r330710:

tftpd: Flush files as soon as they are fully received

On an RRQ, tftpd doesn't exit as soon as it's finished receiving a file.
Instead, it waits five seconds just in case the client didn't receive the
server's last ACK and decides to resend the final DATA packet.
Unfortunately, this created a 5 second delay from when the client thinks
it's done sending the file, and when the file is available for other
processes.

Fix this bug by closing the file as soon as receipt is finished.

PR: 157700
Reported by: Barry Mishler <barry_mishler@yahoo.com>

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

In the old TFTP server, there was an undocumented behavior where
the block counter would rollover to 0 if a file larger
than 65535 blocks was transferred. With the default block size
of 512 octets per block, this is a file size of approximately 32 megabytes.

The new TFTP server code would report an error and stop transferring
the file if a file was larger than 65535 blocks.

This patch restores the old TFTP server's behavior to the new
TFTP server code. If a TFTP client transfers a file larger
than 65535 blocks, and does *not* specify the "rollover" option,
then automatically rollover the block counter to 0 every time
we reach 65535 blocks.

This restores interoperability with the FreeBSD 6 TFTP client.
Without this change, if a FreeBSD 6 TFTP client tried to
retrieve a file larger than 65535 blocks from a FreeBSD 9 TFTP server
, the transfer would fail.
The same file could be retrieved successfully if the same FreeBSD 6
TFTP client was used against a FreeBSD 6 TFTP server.

Approved by: re (kib)
Tested by: Pawan Gupta <pawang at juniper dot net>,
Obtained from: Juniper Networks

Bring in new files from edwin's tftp