Apache 2: SetEnvIf "IP Range"
Solution 1:
You may use CIDR formatting with Apache 2.4 which allows <If>
:
<If "%{REMOTE_ADDR} -ipmatch 194.8.74.0/23">
SetEnv banned = spammer-ip
</If>
Solution 2:
be aware that variables set through SetEnv are not visible on some operations (see matrix):
http://www.onlinesmartketer.com/2010/05/27/apache-environment-variables-visibility-with-setenv-setenvif-and-rewriterule-directives/
your solution is
SetEnvIfExpr "-R '10.0.0.0/8' || -R '172.16.0.0/12' || -R '192.168.0.0/16'" rfc1918
see https://httpd.apache.org/docs/trunk/mod/mod_setenvif.html#SetEnvIfExpr
Solution 3:
What you've got (SetEnvIfNoCase Remote_Addr "^a.b.c." env_key=env_value) is the best you'll easily do. I've seen this configuration style implemented on a heavily loaded cluster of machines, without any noticeable performance degradation. I agree using regular expressions, when CIDR ranges are more appropriate is annoying. You could write a small program to automatically generate the config from a list of CIDR ranges.
If you're familiar with Perl, you could create a modperl handler, which would allow/deny requests in whichever way you choose. modperl allows your code to run at different points throughout a HTTP request - mod_perl 2.0 HTTP Request Cycle Phases. PerlAuthzHandler would be the appropriate handler to use.
Lockie