NAME

in.ftpd, ftpdfix - the FTP server, with downloads that arrive whole

SYNOPSIS

/usr/sbin/in.ftpd

DESCRIPTION

The ftpdfix package replaces /usr/sbin/in.ftpd, the system's FTP server, which inetd(1M) starts for each connection, with the stock program changed in one place: how it closes the data connection of a download (RETR, LIST, NLST). Everything else, commands, options and messages, is as ftpd(1M) describes.

The stock server closed the data connection as soon as it had written the file, and the system's TCP then threw away whatever the client had not yet acknowledged: the end of a download could be missing, while the server still answered 226 Transfer complete. In passive mode this happened often. In active mode the stock server lingered in the close instead, for up to 60 seconds, a path of the system's TCP that is not safe when the client sends after the close.

This server shuts down its own side of the data connection (the client then sees the end of the file after the last byte), waits until the client has read everything and closed its side, and only then closes the connection. The wait is bounded: a client that never closes its side is let go after at most 60 seconds, and the connection is then closed as before. Nothing lingers in the close, in either mode.

A client that reads a download to its end and then closes the data connection, as every FTP client does, sees no difference but whole files.

FILES

/opt/amix/doc/ftpdfix/README.md

the bytes changed and why

SEE ALSO

ftpd(1M), inetd(1M), ftp(1)