mod_shaper
The mod_shaper module is designed to split overall rates, both
download and upload, for the proftpd daemon among all connected
FTP clients, shaping each session to use only a portion of the overall rate.
mod_shaper shapes both transmitted traffic,
e.g. bits being downloaded via the RETR command, and
received traffic, e.g. bits being uploaded via the
APPE, STOR, and STOU commands.
This module is contained in the mod_shaper.c file for
ProFTPD 1.2.x/1.3.x, and is not compiled by default.
Installation instructions are discussed here.
Detailed documentation on mod_shaper usage can be found
here.
The most current version of mod_shaper can be found at:
http://www.castaglia.org/proftpd/
Please contact TJ Saunders <tj at castaglia.org> with any questions, concerns, or suggestions regarding this module.
The ShaperAll directive is used to configure the overall
mod_shaper settings: the rate for the entire daemon, the
default shares for shaped sessions, and the default priority for shaped
sessions. If specified, the priority cannot be a negative number,
the rates are in KB/s and must be greater than zero, and the
shares must be greater than one. For configuring the priority and
shares for individual sessions, use the ShaperSession directive.
The rate parameter sets both the downrate (i.e. download rate from the server) and the uprate (i.e. the upload rate to the server) at the same time. Use downrate and uprate if you wish to configure different rates for downloads and uploads. Similarly, the shares parameter sets both downshares and upshares.
The default rate is -1.0, which means that in order for
mod_shaper to function properly, a rate, either rate,
downrate or uprate, must be specified.
The default shares setting is 5, the default priority is 10.
Examples:
# Change the overall daemon rate to 100 KB/s ShaperAll rate 100 # Give 20 shares to each session by default, and have an overall rate of 1000 ShaperAll rate 1000 shares 20 # Have a larger number of downshares than upshares ShaperAll rate 1000 downshares 2000 upshares 20 # Configure separate download and upload rates ShaperAll downrate 1000 uprate 500
See also: ShaperSession
The ShaperControlsACLs directive configures access lists of
users or groups who are allowed (or denied) the ability to
use the actions implemented by mod_shaper. The default
behavior is to deny everyone unless an ACL allowing access has been explicitly
configured.
If "allow" is used, then list, a comma-delimited list
of users or groups, can use the given actions; all
others are denied. If "deny" is used, then the list of
users or groups cannot use actions all others are
allowed. Multiple ShaperControlsACLs directives may be used to
configure ACLs for different control actions, and for both users and groups.
The actions provided by mod_shaper are "all",
"info", and "sess".
Examples:
# Allow only user root to alter the overall settings ShaperControlsACLs all allow user root # Allow the ftpadm group to shape current sessions ShaperControlsACLs sess allow group ftpadm # Allow everyone but user bob to see the current shaper stats ShaperControlsACLs info deny user bob
<VirtualHost>, <Global>
The ShaperEngine directive enables or disables the
"shaping" of sessions by mod_shaper. If it is set to
off this module does no shaping of transmitted traffic. Use this
directive to disable the module instead of commenting out all
mod_shaper directives.
The ShaperLog directive is used to a specify a log file for
mod_shaper reporting and debugging. The path parameter
must be the full path to the file to use for logging. Note that this path must
not be to a world-writeable directory and, unless
AllowLogSymlinks is explicitly set to on
(generally a bad idea), the path must not be a symbolic link.
If path is "none", no logging will be done at all.
<VirtualHost>, <Global>, <Anonymous>
The ShaperSession directive is used to set shaping data on a
per-session basis. It is intended to be used within mod_ifsession
conditional configuration blocks. If used, the priority must not
be a negative number. The shares parameters must start with '+' or
'-'; these values adjust the default numbers of shares allotted to a
session, increasing or reducing the sessions's shares. The
ShaperAll directive is used for configuring overall shaping
data.
The shares parameter sets both the downshares (i.e. shares of the download rate) and the upshares (i.e. shares of the upload rate) at the same time. Use downshares and upshares if you wish to configure different shares for downloads and uploads for the session.
Example:
# Reward my friends ShaperSession shares +2 # Punish my enemies ShaperSession shares -4 # Allow for finer control over downloads by allocating more download # shares than upload shares for this session ShaperSession downshares +3 upshares -1 # Let <Directory>-level TransferRate directives take priority ShaperSession priority 3
See also: ShaperAll
The ShaperTable directive configures a path to a file
that mod_shaper uses for storing its shaping data. The given
path must be an absolute path. Note: this directive is
required for mod_shaper to function.
shaper all
The shaper all action is used to change the overall
mod_shaper settings on-the-fly. If specified, the
priority cannot be a negative number, the rates are in KB/s
and must be greater than zero, and the shares must be greater than
one. For changing the priority and shares for individual sessions, use the
shaper sess control action.
The rate parameter sets both the downrate (i.e. download rate from the server) and the uprate (i.e. the upload rate to the server) at the same time. Use downrate and uprate if you wish to configure different rates for downloads and uploads. Similarly, the shares parameter sets both downshares and upshares.
For example, to set the overall rate for the entire daemon to be 2000 KB/s:
ftpdctl shaper all rate 2000To give every session 10 shares, both downshares and upshares, by default:
ftpdctl shaper all shares 10To set the default priority for sessions:
ftpdctl shaper all priority 3Note that multiple parameters can also be used simultaneously:
ftpdctl shaper all rate 2000 shares 10 priority 3
See also: shaper sess
shaper info
The shaper info control action can be used to view information
on currently shaped sessions. This includes the current overall rate, the
default number of shares per session, and the total number of currently
shaped sessions. It also lists the following for each shaped session:
process ID (PID), priority, downshare ("D") and upshare
("U") adjustments, and session downrate and uprate.
Example listing:
# ftpdctl shaper info ftpdctl: Overall Rates: 1000.00 KB/s down, 500.00 KB/s up ftpdctl: Default Shares Per Session: 10 down, 10 up ftpdctl: Default Priority: 2 ftpdctl: Number of Shaped Sessions: 2 ftpdctl: PID Priority DShares DRate (KB/s) UShares URate (KB/s) ftpdctl: ----- -------- -------------- ------------ -------------- ------------ ftpdctl: 21750 2 12/24 (+2) 500.00 7/14 (-3) 250.00 ftpdctl: 21753 2 12/24 (+2) 500.00 7/14 (-3) 250.00The "DShares" and "UShares" columns are formatted as:
sharessession/sharestotal (+|-sharesadjust)The
+2 and -3 in the listing above is due to a
ShaperSession affecting these sessions:
ShaperSession downshares +2 upshares -3
shaper sess
The shaper sess action is used to change session-specific shaping
data on-the-fly. If given, the priority must not be a
negative number. The shares parameters must start with '+' or '-';
these values adjust the default numbers of shares allotted to a session,
increasing or reducing the sessions's shares.
The shares parameter sets both the downshares (i.e. shares of the download rate) and the upshares (i.e. shares of the upload rate) at the same time. Use downshares and upshares if you wish to configure different shares for downloads and uploads for the session.
This example gives user alex an additional 10 shares:
ftpdctl shaper sess user alex shares +10The following sets the priority for host
cache.example.com such
that TransferRate directives in <Anonymous>
sections, <Directory> sections and .ftpacccess
files have precedence (see the usage instructions for
more details on priority):
ftpdctl shaper sess host cache.example.com priority 2One can even change the settings on entire Classes of sessions:
ftpdctl shaper sess class proxy downshares -3 priority 1
See also: shaper all
mod_shaper, copy the mod_shaper.c file
into:
proftpd-dir/contrib/after unpacking the latest proftpd-1.2.x or proftpd-1.3.x source code. Then follow the usual steps for using third-party modules in proftpd, making sure to include the
--enable-ctrls configure option,
which mod_shaper requires:
./configure --enable-ctrls --with-modules=mod_shaper make make install
The ShaperTable is used to hold overall rates, both download
and upload, for the entire daemon, the default number of shares and the
default priority for each session. Then there is a list of shaping data for
each particular session. To determine the portion of the overall rate that a
session gets, mod_shaper calculates the total number of shares,
and divides the overall rate by the total number of shares, resulting in a
rate-per-share value:
ratetotal / sharestotal = rateshareThe rate for a session is then the rate-per-share multiplied by the number of shares for that session:
rateshare * sharessession = ratesessionWhenever a session starts or ends,
mod_shaper recalculates the
total number of shares and each session's rate, thus always adjusting values
for each session so that the total of the session transfer rates never
exceeds the overall mod_shaper rate. This means that
mod_shaper divides the overall rate among all sessions
(unless exempted), not just those sessions that are currently transferring
files. Only if all shaped sessions are transferring data simultaneously will
the overall rates be reached. Note that this calculation is performed
separately for downloads and for uploads; sessions can have different shares
of the download and upload rates.
Also, the transfer rate is calculated at the start of each transfer; the core
proftpd engine does not recalculate the rate during
the data transfer. This means, for example, that if a session gets 100 KB/s
and starts a transfer, then a second session begins and gets 50 KB/s, the first
session's transfer will continue to get 100 KB/s, until that transfer ends.
The next transfer started by the first session would then get 50 KB/s, just
like the second session.
By default, mod_shaper allots 5 shares for every session.
Increasing the default number of shares for a session (using the
ShaperAll configuration directive or the shaper all
control action) does not increase the rate used by every session. If
every session has the same number of shares, then the overall rate is divided
evenly among the sessions; a higher default shares value results in a smaller
rate-per-share value.
What is the benefit of increasing the default shares setting, then? It
allows for finer-grained tuning of shaped sessions, using the
ShaperSession directive and the shaper sess
control actions. An example: given an overall rate of 100 KB/s, a default
shares of 1, and 4 sessions, the rate-per-share will be 25 KB/s
(100 / 4 = 25), and since each session has 1 share, the download rate for
each session is 25 KB/s. Now, what if you want to change these setting
on-the-fly, allow one of the sessions a higher transfer rate, and reduce the
transfer rate for another session? You could add another share to the session
for user dave:
ftpdctl sess user dave shares +1After this, the rate-per-share is 20 KB/s. The session belonging to user
dave now has 2 shares, which means it has a download rate of
40 KB/s; the other sessions now have download rates of 20 KB/s. What about
reducing the rate for one of the other sessions, one belonging to user
anonymous? One might think that:
ftpdctl sess user ftp shares -1would work. It will not. You cannot reduce the number of shares for a given session below 1.
mod_shaper rules do not allow this.
However, if the default shares setting was higher, like 5 or 10, then the
administrator would have enough shares for reducing a session's rate. The
more default shares, the smaller the rate-per-share value, and thus the
finer control, by adding or removing smaller increments, the administrator
has over the shaped sessions.
mod_shaper uses the same mechanism that the standard
proftpd configuration directive, TransferRate, uses
for controlling a session's download rate. Using the same mechanism, though,
means that mod_shaper may interfere with any
TransferRate directives in your proftpd.conf.
Which takes priority, mod_shaper or TransferRate?
This is handled by assigning a priority to each each shaped
session. The priority for TransferRate directives depends on
the configuration context in which the directive appears:
TransferRate Priority
| Context | Priority |
<Global> |
1 |
| server config | 2 |
<VirtualHost> |
2 |
<Anonymous> |
3 |
<Directory> |
4 |
.ftpaccess |
5 |
The default priority assigned to mod_shaper sessions is 10.
This means that mod_shaper takes precedence over
TransferRate. However, if the site administrator needs
<Directory>-level or .ftpaccess-level
TransferRate directives to take priority, then the
ShaperSession directive and shaper sess control
action can be used to assign a priority to shaped sessions that is lower
than that for <Directory> and .ftpaccess.
Configuring mod_shaper
Now that you know how the module works, it's time to see how to construct
a proftpd.conf that enforces the desired shaper policy.
Configuration directives that affect the shaping of sessions have control
action equivalents, i.e. ShaperAll
and shaper all,
ShaperSession and
shaper sess.
This example mod_shaper configuration uses the defaults and
shapes all sessions:
<IfModule mod_shaper.c>
ShaperEngine on
ShaperLog /var/log/ftpd/shaper.log
ShaperTable /var/log/ftpd/shaper.tab
# An overall rate (in KB/s) must be set. This line explicitly
# sets both the download and upload rates to be the same.
ShaperAll downrate 1500 uprate 1500
# Allow all system users to see shaper info
ShaperControlsACLs info allow user *
# Allow FTP admins to alter settings both overall and per-session
ShaperControlsACLs all,sess allow group ftpadm
</IfModule>
To exclude some user from having their sessions shaped by
mod_shaper, use mod_ifsession for a configuration
that adds the following:
<IfModule mod_shaper.c>
<IfUser lucky>
ShaperEngine off
</IfUser>
</IfModule>
which says "If mod_shaper is present, and if the user logging
in is named 'lucky', then disable mod_shaper for this
session." Note that sessions that are not shaped by
mod_shaper cannot be shaped once the user has logged in. Normal
TransferRate directives will still apply to non-shaped sessions.
Similarly, you may wish to have a user that should have a greater portion of the overall download rate available to them:
<IfModule mod_shaper.c>
<IfUser lucky>
ShaperSession downshares +5
</IfUser>
</IfModule>
This gives user lucky an additional 5 shares of the download rate,
on top of the default number of shares for a session. Users can likewise have
their default number of shares reduced, if necessary:
<IfModule mod_shaper.c>
<IfGroup anonftp>
ShaperSession downshares -3
</IfUser>
</IfModule>
The control actions supported by mod_shaper can also be used,
while the daemon and sessions are running, to set the desired shaping values.