Implement LogFormat variable for data transfer average speed

[graxlop]

Hello,

I would like to request an additional variable for mod_log that would show the average transfer speed.

Maybe a format like KB/s, MB/s, etc.

Thanks

[Castaglia]

Average over what unit of time? For the overall transfer? If for the entire transfer, that can easily be computed, by a log post-processor, from the total number of bytes (%b) and the transfer time (%T). I'm not sure what value would really be added in having ProFTPD do this...

[graxlop]

Yes, for the entire transfer. I find it useful for debugging purposes and it seems like most other FTP server software out there supports this functionality, so I'm sure others would appreciate it as well.

[Castaglia]

What other FTP servers have you seen do this, and how? I admit I don't often see just what other features other FTP servers have...

[graxlop]

Pure-FTPd and vsftpd both have this functionality in their logs by default. A quick look at the vsftpd source code shows that they do it like you've described above, taking the transfer size and transfer time.

Here's an example of what vsftpd default transfer log looks like:

Fri Jul 14 06:26:14 2017 [pid 30373] [Username] OK DOWNLOAD: Client "5.5.5.5", "/Folder/Test.file", 537563631 bytes, 6118.22Kbyte/sec

[Castaglia]

Seems like a reasonable request. This will not be added to the fixed xferlog(5) format, but I think we can log a message (at INFO level) on completion of a file transfer, and supply a LogFormat variable for it as well for ExtendedLog cases.

This will be (roughly) equivalent to "%{file-size}/%{transfer-millisecs}", adjusted to use units of KB/s rather than B/ms.

[Castaglia]

For my reference, pure-ftpd uses "KB/sec" (see here), whereas vsftpd uses "Kbyte/sec" (see here). I think ProFTPD uses "KB" elsewhere, so I'll use "KB/s".

[Castaglia]

Implemented in master now. Thanks!