use of dynamic "Environment" variables in native SP configuration

[David Mansfield]

Hi All:

I'm hoping to have a single apache SP with two different IdP.  I'd like 
to distinguish them by passing the entityId of the desired IdP as 
described in NativeSPContentSettings.  As I understand it it could be 
done by ShibRequestSetting an apache config, or using RequestMapper.

However, the determining factor for selecting the IdP is the source ip 
address (internal network users vs external network users).  I can use 
apache mod_rewrite to set an ENV variable based on the source IP address 
but I cannot see how to use this variable in ShibRequestSetting. And the 
RequestMapper does not allow differentiation based on source address.

Does the ShibRequestSetting interpolate env variables, or is there an 
"internal" way to set the session creation parameters?

Alternatively, maybe mod_rewrite could be used on the 
/Shibboleth.sso/Login URL?

Any/all ideas appreciated.

Thanks,
David Mansfield
Cobite, INC.