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The Libspf-alt Application Programming Interface
This file is the start of the documentation on the libspf-alt API. It
is not complete, but it should give you a start. Corrections and/or
suggests are welcome.
Application programs usually include:
spf_win32.h (Win32 only -- must be first)
spf.h
Application programs often include one or more of:
spf_dns_cache.h
spf_dns_resolv.h
spf_dns_windns.h (Win32 only)
spf_dns_null.h
Applications programs may (but usually don't) include:
spf_dns.h
Only programs that are in the library should include spf_internal.h,
spf_dns_internal.h or spf_win32_internal.h.
Details on the actual routines are documented in the above include
files, this document just gives a general overview. The SPF spec
gives a more detailed explanation of the entire SPF system and should
probably be read by anyone using SPF. See:
http://www.ietf.org/internet-drafts/draft-mengwong-spf-00.txt
or doc/draft-mengwong-spf-00.txt
The libspf-alt library creates several opaque "objects", which the
application program receive "ids" to identify them by. These objects
are the configuration object, the SPF record object and the DNS layer
object. These objects can all be mixed and matched. You can evaluate
the same SPF record using different configurations, and/or different
DNS layers.
All of these objects have similar create/reset/dup/destroy functions.
In addition, there are several typedef'ed structures that are used by
libspf-alt. Libspf-alt expects all pointers in these structures to be
malloc'ed.
All of these typedef'ed structures have init/free functions.
The "configuration object"
This object holds the configuration of the environment. It includes
things llke the IP address of the SMTP client, the envelope-from email
address, default explanation text, whitelists, etc. There are a bunch
of functions that can change the configureation (SPF_set_*()) and
others that can read the configuration (SPF_get_*())
The "SPF record object"
This object contains the SPF record in byte-compiled form.
The "DNS object"
This object contains information about how DNS lookups should be
done.
Objects are created with the SPF_create_<object-name>() function or by
duplicating an existing object using the SPF_dup_<object-name>() function.
Every object created must be destroyed with the
SPF_destroy_<object-name>() function.
Objects can be reset to their initial condition by calling then
SPF_reset_<object-name>() function.
The results from the SPF byte-compiler are returned in a SPF_c_results_t
variable. The application is responsible for freeing the memory
associated with this structure by calling SPF_free_c_results().
The output from an SPF evaluation are returned in a SPF_output_t
variable. The application is responsible for freeing memory
associated with this structure by calling SPF_free_output().
There is a very simple example program available called spf_example.c
in the bin directory. The spfquery.c and spftest.c programs provide a
little more sophisitcated usage of libspf-alt.
-wayne
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