krb5_init_context() calls cc_context_get_default_ccache_name()

[Alexandra Ellwood]

Hi,

Currently krb5_init_context() calls into CCAPI when it resets the 
ccache name in the context.  It does this by calling 
krb5_cc_set_default_name(context, NULL).

krb5_cc_set_default_name(context, NULL) sets the ccache name in the 
context to its "default" value by calling get_from_os().  On CCAPI 
platforms it calls cc_context_get_default_ccache_name().

The problem is that cc_context_get_default_ccache_name() produces an 
IPC call.  This means that you pay for the overhead of an IPC call just 
for initializing a context.  It also means that the CCAPI server needs 
to be present to answer the request, even though the context may never 
use the ccache.

I would like to change the behavior so that it lazily looks up the 
default ccache.  Basically when you call 
krb5_cc_set_default_name(context, NULL), it will just set the ccache 
name in the context to the NULL string and free the old one.  When you 
call krb5_cc_default_name(context), it will look at the environment 
variable and then call get_from_os().  Basically I just want to defer 
the actual work to when the library needs to look up the ccache name.

Although this changes when the default ccache is looked up, I can't 
think of any practical problems with it based on how callers use 
krb5_contexts.  Can anyone else think of any problems?

I would like this change for krb5-1.4.


--lxs
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Alexandra Ellwood                                           lxs at mit.edu
MIT Information Services & Technology           http://mit.edu/lxs/www/
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