casa-mp-base

This patch (20060126) makes tcpserver from DJB's ucspi-tcp-0.88 package (see

http://cr.yp.to/ucspi-tcp.html) to modify its behavior if some environment

variables are present.

​

The variables can be preset before starting tcpserver (thus acting as

default for all connections), or, if you use 'tcpserver -x xxx.cdb', they

can be set (or overridden) from xxx.cdb. If none of the variables are set,

tcpserver behaves same as non patched version (except for negligible

performance loss). Any or all variables can be set, as soon as first limit

is reached the connection is dropped. I'd recommend using .cdb files

exclusively though, as you can then modify configuration without killing

tcpserver.

​

The variables are:

​

(1) MAXLOAD 

    maximum 1-minute load average * 100. For example, if you have line

    :allow,MAXLOAD="350" 

    in your rules file from which you created .cdb, the connection will be

    accepted only if load average is below 3.50

​

    See COMPILING instructions above for info on supported systems.

(2) MAXCONNIP

    maximum connections from one IP address. tcpserver's -c flag defines

    maximum number of allowed connections, but it can be abused if

    just one host goes wild and eats all the connections - no other host

    would be able to connect then. If you created your .cdb with:

    :allow,MAXCONNIP="5"

    and run tcpserver -c 50, then each IP address would be able to have at 

    most 5 concurrent connections, while there still could connect 50

    clients total.

    0 is valid value and means 'always reject'

​

(3) MAXCONNC

​

    maximum connections from whole C-class (256 addresses). Extension of

    MAXCONNIP, as sometimes the problematic client has a whole farm of

    client machines with different IP addresses instead of just one IP

    address, and they all try to connect. It might have been more useful to

    be able to specify CIDR block than C-class, but I've decided to KISS.

​

    for example tcpserver -c 200, and .cdb with:

    :allow,MAXCONNC="15"

    will allow at most 15 host from any x.y.z.0/24 address block, while

    still allowing up to 200 total connections.

    0 is valid value and means 'always reject'

​

(4) DIEMSG

    if set and one of the above limits is exceeded, this is the message 

    to be sent to client (CRLF is always added to the text) before terminating

    connection. If unset, the connection simply terminates (after 1 sec delay) 

    if limit is exceeded.

​

    For example:

    DIEMSG="421 example.com Service temporarily not available, closing 

    transmission channel"

​

(5) DIEMSG_MAXLOAD

​

    If set, and a connection is denied because the MAXLOAD limit is exceeded,

    this value will be used instead of DIEMSG.