libdspam(3) Core message processing and classification library for DSPAM


#include <libdspam.h>

DSPAM_CTX *dspam_init(const char *username, const char *group,
const char *home, int operating_mode, u_int32_t flags);

DSPAM_CTX *dspam_create(const char *username, const char *group,
const char *home, int operating_mode, u_int32_t flags);

int dspam_addattribute(DSPAM_CTX *CTX, const char *key,
const char *value);

int dspam_clearattributes(DSPAM_CTX *CTX);

int dspam_attach(DSPAM_CTX *CTX, void *dbh);

int dspam_process(DSPAM_CTX *CTX, const char *message);

int dspam_getsource(DSPAM_CTX *CTX, char *buf, size_t size);

int dspam_detach(DSPAM_CTX *CTX);

int dspam_destroy(DSPAM_CTX *CTX);


libdspam provides core message processing and classification functionality.

The dspam_init() function creates and initializes a new classification context and attaches the context to whatever backend storage facility was configured. The user and group arguments provided are used to read and write information stored for the user and group specified. The home argument is used to configure libdspam's storage around the base directory specified. The mode specifies the operating mode to initialize the classification context with and may be one of:

 DSM_PROCESS   Classify and learn the supplied message using whatever training mode is specified
 DSM_CLASSIFY  Classify the supplied message only; do not learn or update any counters.
 DSM_TOOLS     No processing, attach to storage only

The flags provided further tune the classification context for a specific function. Multiple flags may be OR'd together.

 DSF_UNLEARN   Unlearn the message
 DSF_BIAS      Assign processor bias to unknown tokens
 DSF_SIGNATURE A binary signature is requested/provided
 DSF_NOISE     Apply Bayesian Noise Reduction logic
 DSF_WHITELIST Use automatic whitelisting logic
 DSF_MERGED    Merge group metadata with user's in memory

Upon successful completion, dspam_init() will return a pointer to a new classification context structure containing a copy of the configuration passed into dspam_init(), a connected storage driver handle, and a set of preliminary user control data read from storage.

The dspam_create() function performs in exactly the same manner as the dspam_init() function, but does not attach to storage. Instead, the caller must also call dspam_attach() after setting any storage- specific attributes using dspam_addattribute(). This is useful for cases where the implementor would prefer to configure storage internally rather than having libdspam read a configuration from a file.

The dspam_addattribute() function is called to set attributes within the classification context. Some storage drivers support the use of passing specific attributes such as server connect information. The driver-independent attributes supported by DSPAM include:

 IgnoreHeader   Specify a specific header to ignore 
 LocalMX        Specify a local mail exchanger to assist in 
                correct results from dspam_getsource().

Only driver-dependent attributes need be set prior to a call to dspam_attach(). Driver-independent attributes may be set both before and after storage has been attached.

The dspam_attach() function attaches the storage interface to the classification context and alternatively established an initial connection with storage if dbh is NULL. Some storage drivers support only a NULL value for dbh, while others (such as mysql_drv, pgsql_drv, and sqlite_drv) allow an open database handle to be attached. This function should only be called after an initial call to dspam_create() and should never be called if using dspam_init(), as storage is automatically attached by a call to dspam_init().

The dspam_process() function performs analysis of the message passed into it and will return zero on successful completion. If successful, CTX->result will be set to one of three classification results:

 DSR_ISSPAM        Message was classified as spam
 DSR_ISINNOCENT    Message was classified as nonspam
 DSR_ISWHITELISTED Recipient was automatically whitelisted

Should the call fail, one of the following errors will be returned:

 EINVAL    An invalid call or invalid parameter used.
 EUNKNOWN  Unexpected error, such as malloc() failure
 EFILE     Error opening or writing to a file or file handle
 ELOCK     Locking failure
 EFAILURE  The operation itself has failed

The dspam_getsource() function extracts the source sender from the message passed in during a call to dspam_process() and writes not more than size bytes to buf.

The dspam_detach() function can be called when a detachment from storage is desired, but the context is still needed. The storage driver is closed, leaving the classification context in place. Once the context is no longer needed, another call to dspam_destroy() should be made. If you are closing storage and destroying the context at the same time, it is not necessary to call this function. Instead you may call dspam_destroy() directly.

The dspam_clearattributes() function is called to clear any attributes previously set using dspam_addattribute() within the classification context. It is necessary to call this function prior to replacing any attributes already written.

The dspam_destroy() function should be called when the context is no longer needed. If a connection was established to storage internally, the connection is closed and all data is flushed and written. If a handle was attached, the handle will remain open.


Copyright © 2002-2011 DSPAM Project
All rights reserved.

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