13 and later
When a host connects to the listening sendmail server, that server forks a child copy of
itself to handle the new connection. Before forking, the server increments the connection
count associated with the IP address of the connecting client. When the forked child
finishes and exits, the server decrements that count.
Beginning withV8.13 sendmail, th e${client_connections} macro holds that count as its
value, making it available for use in rule sets.
WithV8.13, if you declare FEATURE(conncontrol) (?§17.8.13 on page 619), a rule set called
ConnControl will be added to your configuration file that looks up the current IP address in
the access database. The source text file for the access database may contain that address
with a literal ClientConn: prefix, as, for example:
ClientConn:123.45.67.89 12
Note that the literal prefix is followed by the IP address to be looked up, then tabs or
spaces,* and lastly by the limit to impose on the maximum number of connections for that
IP address.
* Unless the -t command-line argument is used with makemap to change the separator.
This is the Title of the Book, eMatter Edition
Copyright ?© 2007 O??™Reilly & Associates, Inc. All rights reserved.
812 | Chapter 21: The D (Define a Macro) Configuration Command
If the number of connections (as stored in this ${client_connections} macro) exceeds the
limit imposed inside the access database, the new connection is rejected with the following
error:
433 4.
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