snmp_api.h

/* Portions of this file are subject to the following copyright(s).  See
 * the Net-SNMP's COPYING file for more details and other copyrights
 * that may apply:
 */
/*
 * Portions of this file are copyrighted by:
 * Copyright © 2003 Sun Microsystems, Inc. All rights reserved.
 * Use is subject to license terms specified in the COPYING file
 * distributed with the Net-SNMP package.
 */
#ifndef SNMP_API_H
#define SNMP_API_H

/*
 * @file snmp_api.h - API for access to snmp.
 * 
 * @addtogroup library
 *
 * Caution: when using this library in a multi-threaded application,
 * the values of global variables "snmp_errno" and "snmp_detail"
 * cannot be reliably determined.  Suggest using snmp_error()
 * to obtain the library error codes.
 *
 * @{
 */

#ifndef DONT_SHARE_ERROR_WITH_OTHER_THREADS
#define SET_SNMP_ERROR(x) snmp_errno=(x)
#else
#define SET_SNMP_ERROR(x)
#endif


#ifdef __cplusplus
extern          "C" {
#endif

/***********************************************************
        Copyright 1989 by Carnegie Mellon University

                      All Rights Reserved

Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted,
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in
supporting documentation, and that the name of CMU not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.

CMU DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
CMU BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.
******************************************************************/

struct variable_list;
typedef struct variable_list netsnmp_variable_list;
struct timeval;
struct netsnmp_transport_s;

#define USM_AUTH_KU_LEN     32
#define USM_PRIV_KU_LEN     32

typedef struct snmp_pdu {

    /*
     * Protocol-version independent fields
     */
    long            version;
    int             command;
    long            reqid;  
    long            msgid;
    long            transid;
    long            sessid;
    long            errstat;
    long            errindex;       
    u_long          time;   
    u_long          flags;

    int             securityModel;
    int             securityLevel;  
    int             msgParseModel;

    void           *transport_data;
    int             transport_data_length;

    const oid      *tDomain;
    size_t          tDomainLen;

    netsnmp_variable_list *variables;


    /*
     * SNMPv1 & SNMPv2c fields
     */
    u_char         *community;
    size_t          community_len;  

    /*
     * Trap information
     */
    oid            *enterprise;     
    size_t          enterprise_length;
    long            trap_type;
    long            specific_type;
    unsigned char   agent_addr[4];  

    /*
     *  SNMPv3 fields
     */
    u_char         *contextEngineID;
    size_t          contextEngineIDLen;     
    char           *contextName;
    size_t          contextNameLen;
    u_char         *securityEngineID;
    size_t          securityEngineIDLen;    
    char           *securityName;
    size_t          securityNameLen;        
    
    /*
     * AgentX fields
     *      (also uses SNMPv1 community field)
     */
    int             priority;
    int             range_subid;
    
    void           *securityStateRef;
} netsnmp_pdu;

struct snmp_session;

typedef struct snmp_session netsnmp_session;

typedef int     (*snmp_callback) (int, netsnmp_session *, int,
                                      netsnmp_pdu *, void *);
typedef int     (*netsnmp_callback) (int, netsnmp_session *, int,
                                         netsnmp_pdu *, void *);
struct snmp_session {
    /*
     * Protocol-version independent fields
     */
    long            version;
    int             retries;
    long            timeout;        
    u_long          flags;
    struct snmp_session *subsession;
    struct snmp_session *next;

    char           *peername;
    u_short         remote_port;
    char           *localname;
    u_short         local_port;     
    u_char         *(*authenticator) (u_char *, size_t *, u_char *, size_t);
    netsnmp_callback callback;      
    void           *callback_magic;
    int             s_errno;
    int             s_snmp_errno;   
    long            sessid; 

    /*
     * SNMPv1 & SNMPv2c fields
     */
    u_char         *community;
    size_t          community_len;  
    size_t          rcvMsgMaxSize;
    size_t          sndMsgMaxSize;  

    /*
     * SNMPv3 fields
     */
    u_char          isAuthoritative;
    u_char         *contextEngineID;
    size_t          contextEngineIDLen;     
    u_int           engineBoots;
    u_int           engineTime;
    char           *contextName;
    size_t          contextNameLen;
    u_char         *securityEngineID;
    size_t          securityEngineIDLen;    
    char           *securityName;
    size_t          securityNameLen;

    oid            *securityAuthProto;
    size_t          securityAuthProtoLen;
    u_char          securityAuthKey[USM_AUTH_KU_LEN];       
    size_t          securityAuthKeyLen;
    u_char          *securityAuthLocalKey;       
    size_t          securityAuthLocalKeyLen;       

    oid            *securityPrivProto;
    size_t          securityPrivProtoLen;
    u_char          securityPrivKey[USM_PRIV_KU_LEN];       
    size_t          securityPrivKeyLen;
    u_char          *securityPrivLocalKey;       
    size_t          securityPrivLocalKeyLen;       

    int             securityModel;
    int             securityLevel;  
    char           *paramName;

    void           *securityInfo;

    void           *myvoid;
};

/*
 * A list of all the outstanding requests for a particular session.
 */
#ifdef SNMP_NEED_REQUEST_LIST
typedef struct request_list {
    struct request_list *next_request;
    long            request_id;     /* request id */
    long            message_id;     /* message id */
    netsnmp_callback callback;      /* user callback per request (NULL if unused) */
    void           *cb_data;        /* user callback data per request (NULL if unused) */
    int             retries;        /* Number of retries */
    u_long          timeout;        /* length to wait for timeout */
    struct timeval  time;   /* Time this request was made */
    struct timeval  expire; /* time this request is due to expire */
    struct snmp_session *session;
    netsnmp_pdu    *pdu;    /* The pdu for this request
                             * (saved so it can be retransmitted */
} netsnmp_request_list;
#endif                          /* SNMP_NEED_REQUEST_LIST */

    /*
     * Set fields in session and pdu to the following to get a default or unconfigured value.
     */
#define SNMP_DEFAULT_COMMUNITY_LEN  0   /* to get a default community name */
#define SNMP_DEFAULT_RETRIES        -1
#define SNMP_DEFAULT_TIMEOUT        -1
#define SNMP_DEFAULT_REMPORT        0
#define SNMP_DEFAULT_REQID          -1
#define SNMP_DEFAULT_MSGID          -1
#define SNMP_DEFAULT_ERRSTAT        -1
#define SNMP_DEFAULT_ERRINDEX       -1
#define SNMP_DEFAULT_ADDRESS        0
#define SNMP_DEFAULT_PEERNAME       NULL
#define SNMP_DEFAULT_ENTERPRISE_LENGTH  0
#define SNMP_DEFAULT_TIME           0
#define SNMP_DEFAULT_VERSION        -1
#define SNMP_DEFAULT_SECMODEL       -1
#define SNMP_DEFAULT_CONTEXT        ""
#ifndef NETSNMP_DISABLE_MD5
#define SNMP_DEFAULT_AUTH_PROTO     usmHMACMD5AuthProtocol
#else
#define SNMP_DEFAULT_AUTH_PROTO     usmHMACSHA1AuthProtocol
#endif
#define SNMP_DEFAULT_AUTH_PROTOLEN  USM_LENGTH_OID_TRANSFORM
#ifndef NETSNMP_DISABLE_DES
#define SNMP_DEFAULT_PRIV_PROTO     usmDESPrivProtocol
#else
#define SNMP_DEFAULT_PRIV_PROTO     usmAESPrivProtocol
#endif
#define SNMP_DEFAULT_PRIV_PROTOLEN  USM_LENGTH_OID_TRANSFORM

    NETSNMP_IMPORT const char *snmp_api_errstring(int);
    NETSNMP_IMPORT void     snmp_perror(const char *);
    NETSNMP_IMPORT void     snmp_set_detail(const char *);

#define SNMP_MAX_MSG_SIZE          1472 /* ethernet MTU minus IP/UDP header */
#define SNMP_MAX_MSG_V3_HDRS       (4+3+4+7+7+3+7+16)   /* fudge factor=16 */
#define SNMP_MAX_ENG_SIZE          32
#define SNMP_MAX_SEC_NAME_SIZE     256
#define SNMP_MAX_CONTEXT_SIZE      256
#define SNMP_SEC_PARAM_BUF_SIZE    256

    /*
     * set to one to ignore unauthenticated Reports 
     */
#define SNMPV3_IGNORE_UNAUTH_REPORTS 0

    /*
     * authoritative engine definitions 
     */
#define SNMP_SESS_NONAUTHORITATIVE 0    /* should be 0 to default to this */
#define SNMP_SESS_AUTHORITATIVE    1    /* don't learn engineIDs */
#define SNMP_SESS_UNKNOWNAUTH      2    /* sometimes (like NRs) */

    /*
     * to determine type of Report from varbind_list 
     */
#define REPORT_STATS_LEN 9
#define REPORT_snmpUnknownSecurityModels_NUM 1
#define REPORT_snmpInvalidMsgs_NUM 2
#define REPORT_usmStatsUnsupportedSecLevels_NUM 1
#define REPORT_usmStatsNotInTimeWindows_NUM 2
#define REPORT_usmStatsUnknownUserNames_NUM 3
#define REPORT_usmStatsUnknownEngineIDs_NUM 4
#define REPORT_usmStatsWrongDigests_NUM 5
#define REPORT_usmStatsDecryptionErrors_NUM 6

#define SNMP_DETAIL_SIZE        512

#define SNMP_FLAGS_USER_CREATED    0x200      /* USM user has been created */
#define SNMP_FLAGS_DONT_PROBE      0x100      /* don't probe for an engineID */
#define SNMP_FLAGS_STREAM_SOCKET   0x80
#define SNMP_FLAGS_LISTENING       0x40 /* Server stream sockets only */
#define SNMP_FLAGS_SUBSESSION      0x20
#define SNMP_FLAGS_STRIKE2         0x02
#define SNMP_FLAGS_STRIKE1         0x01

#define CLEAR_SNMP_STRIKE_FLAGS(x) \
        x &= ~(SNMP_FLAGS_STRIKE2|SNMP_FLAGS_STRIKE1)

    /*
     * returns '1' if the session is to be regarded as dead,
     * otherwise set the strike flags appropriately, and return 0
     */
#define SET_SNMP_STRIKE_FLAGS(x) \
        ((   x & SNMP_FLAGS_STRIKE2 ) ? 1 :                             \
         ((( x & SNMP_FLAGS_STRIKE1 ) ? ( x |= SNMP_FLAGS_STRIKE2 ) :   \
                                        ( x |= SNMP_FLAGS_STRIKE1 )),   \
                                        0))

    /*
     * Error return values.
     *
     * SNMPERR_SUCCESS is the non-PDU "success" code.
     *
     * XXX  These should be merged with SNMP_ERR_* defines and confined
     *      to values < 0.  ???
     */
#define SNMPERR_SUCCESS                 (0)     /* XXX  Non-PDU "success" code. */
#define SNMPERR_GENERR                  (-1)
#define SNMPERR_BAD_LOCPORT             (-2)
#define SNMPERR_BAD_ADDRESS             (-3)
#define SNMPERR_BAD_SESSION             (-4)
#define SNMPERR_TOO_LONG                (-5)
#define SNMPERR_NO_SOCKET               (-6)
#define SNMPERR_V2_IN_V1                (-7)
#define SNMPERR_V1_IN_V2                (-8)
#define SNMPERR_BAD_REPEATERS           (-9)
#define SNMPERR_BAD_REPETITIONS         (-10)
#define SNMPERR_BAD_ASN1_BUILD          (-11)
#define SNMPERR_BAD_SENDTO              (-12)
#define SNMPERR_BAD_PARSE               (-13)
#define SNMPERR_BAD_VERSION             (-14)
#define SNMPERR_BAD_SRC_PARTY           (-15)
#define SNMPERR_BAD_DST_PARTY           (-16)
#define SNMPERR_BAD_CONTEXT             (-17)
#define SNMPERR_BAD_COMMUNITY           (-18)
#define SNMPERR_NOAUTH_DESPRIV          (-19)
#define SNMPERR_BAD_ACL                 (-20)
#define SNMPERR_BAD_PARTY               (-21)
#define SNMPERR_ABORT                   (-22)
#define SNMPERR_UNKNOWN_PDU             (-23)
#define SNMPERR_TIMEOUT                 (-24)
#define SNMPERR_BAD_RECVFROM            (-25)
#define SNMPERR_BAD_ENG_ID              (-26)
#define SNMPERR_BAD_SEC_NAME            (-27)
#define SNMPERR_BAD_SEC_LEVEL           (-28)
#define SNMPERR_ASN_PARSE_ERR           (-29)
#define SNMPERR_UNKNOWN_SEC_MODEL       (-30)
#define SNMPERR_INVALID_MSG             (-31)
#define SNMPERR_UNKNOWN_ENG_ID          (-32)
#define SNMPERR_UNKNOWN_USER_NAME       (-33)
#define SNMPERR_UNSUPPORTED_SEC_LEVEL   (-34)
#define SNMPERR_AUTHENTICATION_FAILURE  (-35)
#define SNMPERR_NOT_IN_TIME_WINDOW      (-36)
#define SNMPERR_DECRYPTION_ERR          (-37)
#define SNMPERR_SC_GENERAL_FAILURE      (-38)
#define SNMPERR_SC_NOT_CONFIGURED       (-39)
#define SNMPERR_KT_NOT_AVAILABLE        (-40)
#define SNMPERR_UNKNOWN_REPORT          (-41)
#define SNMPERR_USM_GENERICERROR                (-42)
#define SNMPERR_USM_UNKNOWNSECURITYNAME         (-43)
#define SNMPERR_USM_UNSUPPORTEDSECURITYLEVEL    (-44)
#define SNMPERR_USM_ENCRYPTIONERROR             (-45)
#define SNMPERR_USM_AUTHENTICATIONFAILURE       (-46)
#define SNMPERR_USM_PARSEERROR                  (-47)
#define SNMPERR_USM_UNKNOWNENGINEID             (-48)
#define SNMPERR_USM_NOTINTIMEWINDOW             (-49)
#define SNMPERR_USM_DECRYPTIONERROR             (-50)
#define SNMPERR_NOMIB                   (-51)
#define SNMPERR_RANGE                   (-52)
#define SNMPERR_MAX_SUBID               (-53)
#define SNMPERR_BAD_SUBID               (-54)
#define SNMPERR_LONG_OID                (-55)
#define SNMPERR_BAD_NAME                (-56)
#define SNMPERR_VALUE                   (-57)
#define SNMPERR_UNKNOWN_OBJID           (-58)
#define SNMPERR_NULL_PDU                (-59)
#define SNMPERR_NO_VARS                 (-60)
#define SNMPERR_VAR_TYPE                (-61)
#define SNMPERR_MALLOC                  (-62)
#define SNMPERR_KRB5                    (-63)
#define SNMPERR_PROTOCOL                (-64)
#define SNMPERR_OID_NONINCREASING       (-65)

#define SNMPERR_MAX                     (-65)

#define non_repeaters   errstat
#define max_repetitions errindex

typedef union {
   long           *integer;
   u_char         *string;
   oid            *objid;
   u_char         *bitstring;
   struct counter64 *counter64;
#ifdef NETSNMP_WITH_OPAQUE_SPECIAL_TYPES
   float          *floatVal;
   double         *doubleVal;
   /*
    * t_union *unionVal; 
    */
#endif                          /* NETSNMP_WITH_OPAQUE_SPECIAL_TYPES */
} netsnmp_vardata;


struct variable_list {
   struct variable_list *next_variable;    
   oid            *name;   
   size_t          name_length;    
   u_char          type;   
    netsnmp_vardata val;
   size_t          val_len;
   oid             name_loc[MAX_OID_LEN];  
   u_char          buf[40];
   void           *data;
   void            (*dataFreeHook)(void *);    
   int             index;
};



    /*
     * netsnmp_session *snmp_open(session)
     *      netsnmp_session *session;
     *
     * Sets up the session with the snmp_session information provided
     * by the user.  Then opens and binds the necessary UDP port.
     * A handle to the created session is returned (this is different than
     * the pointer passed to snmp_open()).  On any error, NULL is returned
     * and snmp_errno is set to the appropriate error code.
     */
    netsnmp_session *snmp_open(netsnmp_session *);

    /*
     * int snmp_close(session)
     *     netsnmp_session *session;
     *
     * Close the input session.  Frees all data allocated for the session,
     * dequeues any pending requests, and closes any sockets allocated for
     * the session.  Returns 0 on error, 1 otherwise.
     *
     * snmp_close_sessions() does the same thing for all open sessions
     */
    int             snmp_close(netsnmp_session *);
    int             snmp_close_sessions(void);


    /*
     * int snmp_send(session, pdu)
     *     netsnmp_session *session;
     *     netsnmp_pdu      *pdu;
     *
     * Sends the input pdu on the session after calling snmp_build to create
     * a serialized packet.  If necessary, set some of the pdu data from the
     * session defaults.  Add a request corresponding to this pdu to the list
     * of outstanding requests on this session, then send the pdu.
     * Returns the request id of the generated packet if applicable, otherwise 1.
     * On any error, 0 is returned.
     * The pdu is freed by snmp_send() unless a failure occured.
     */
    int             snmp_send(netsnmp_session *, netsnmp_pdu *);

    /*
     * int snmp_async_send(session, pdu, callback, cb_data)
     *     netsnmp_session *session;
     *     netsnmp_pdu      *pdu;
     *     netsnmp_callback callback;
     *     void   *cb_data;
     *
     * Sends the input pdu on the session after calling snmp_build to create
     * a serialized packet.  If necessary, set some of the pdu data from the
     * session defaults.  Add a request corresponding to this pdu to the list
     * of outstanding requests on this session and store callback and data,
     * then send the pdu.
     * Returns the request id of the generated packet if applicable, otherwise 1.
     * On any error, 0 is returned.
     * The pdu is freed by snmp_send() unless a failure occured.
     */
    int             snmp_async_send(netsnmp_session *, netsnmp_pdu *,
                                    netsnmp_callback, void *);


    /*
     * void snmp_read(fdset)
     *     fd_set  *fdset;
     *
     * Checks to see if any of the fd's set in the fdset belong to
     * snmp.  Each socket with it's fd set has a packet read from it
     * and snmp_parse is called on the packet received.  The resulting pdu
     * is passed to the callback routine for that session.  If the callback
     * routine returns successfully, the pdu and it's request are deleted.
     */
    void            snmp_read(fd_set *);



    /*
     * void
     * snmp_free_pdu(pdu)
     *     netsnmp_pdu *pdu;
     *
     * Frees the pdu and any malloc'd data associated with it.
     */
    void            snmp_free_pdu(netsnmp_pdu *);

    void            snmp_free_var(netsnmp_variable_list *);     /* frees just this one */

    void            snmp_free_varbind(netsnmp_variable_list * var);     /* frees all in list */

    /*
     * int snmp_select_info(numfds, fdset, timeout, block)
     * int *numfds;
     * fd_set   *fdset;
     * struct timeval *timeout;
     * int *block;
     *
     * Returns info about what snmp requires from a select statement.
     * numfds is the number of fds in the list that are significant.
     * All file descriptors opened for SNMP are OR'd into the fdset.
     * If activity occurs on any of these file descriptors, snmp_read
     * should be called with that file descriptor set.
     *
     * The timeout is the latest time that SNMP can wait for a timeout.  The
     * select should be done with the minimum time between timeout and any other
     * timeouts necessary.  This should be checked upon each invocation of select.
     * If a timeout is received, snmp_timeout should be called to check if the
     * timeout was for SNMP.  (snmp_timeout is idempotent)
     *
     * Block is 1 if the select is requested to block indefinitely, rather than
     * time out.  If block is input as 1, the timeout value will be treated as
     * undefined, but it must be available for setting in snmp_select_info.  On
     * return, if block is true, the value of timeout will be undefined.
     *
     * snmp_select_info returns the number of open sockets.  (i.e. The number
     * of sessions open)
     */
    int             snmp_select_info(int *, fd_set *, struct timeval *,
                                     int *);



    /*
     * void snmp_timeout();
     *
     * snmp_timeout should be called whenever the timeout from snmp_select_info
     * expires, but it is idempotent, so snmp_timeout can be polled (probably a
     * cpu expensive proposition).  snmp_timeout checks to see if any of the
     * sessions have an outstanding request that has timed out.  If it finds one
     * (or more), and that pdu has more retries available, a new packet is formed
     * from the pdu and is resent.  If there are no more retries available, the
     * callback for the session is used to alert the user of the timeout.
     */

    void            snmp_timeout(void);


    /*
     * This routine must be supplied by the application:
     *
     * u_char *authenticator(pdu, length, community, community_len)
     * u_char *pdu;         The rest of the PDU to be authenticated
     * int *length;         The length of the PDU (updated by the authenticator)
     * u_char *community;   The community name to authenticate under.
     * int  community_len   The length of the community name.
     *
     * Returns the authenticated pdu, or NULL if authentication failed.
     * If null authentication is used, the authenticator in snmp_session can be
     * set to NULL(0).
     */



    /*
     * This routine must be supplied by the application:
     *
     * int callback(operation, session, reqid, pdu, magic)
     * int operation;
     * netsnmp_session *session;    The session authenticated under.
     * int reqid;                       The request id of this pdu (0 for TRAP)
     * netsnmp_pdu *pdu;        The pdu information.
     * void *magic                      A link to the data for this routine.
     *
     * Returns 1 if request was successful, 0 if it should be kept pending.
     * Any data in the pdu must be copied because it will be freed elsewhere.
     * Operations are defined below:
     */

#define NETSNMP_CALLBACK_OP_RECEIVED_MESSAGE    1
#define NETSNMP_CALLBACK_OP_TIMED_OUT           2
#define NETSNMP_CALLBACK_OP_SEND_FAILED         3
#define NETSNMP_CALLBACK_OP_CONNECT             4
#define NETSNMP_CALLBACK_OP_DISCONNECT          5

    long            snmp_get_next_msgid(void);
    long            snmp_get_next_reqid(void);
    long            snmp_get_next_sessid(void);
    long            snmp_get_next_transid(void);

    int             snmp_oid_compare(const oid *, size_t, const oid *,
                                     size_t);
    int             snmp_oid_ncompare(const oid *, size_t, const oid *,
                                      size_t, size_t);
    int             snmp_oidtree_compare(const oid *, size_t, const oid *,
                                         size_t);
    int             snmp_oidsubtree_compare(const oid *, size_t, const oid *,
                                         size_t);
    int             netsnmp_oid_compare_ll(const oid * in_name1,
                                           size_t len1, const oid * in_name2,
                                           size_t len2, size_t *offpt);
    int             netsnmp_oid_equals(const oid *, size_t, const oid *,
                                       size_t);
    int             netsnmp_oid_tree_equals(const oid *, size_t, const oid *,
                                            size_t);
    int             netsnmp_oid_is_subtree(const oid *, size_t, const oid *,
                                           size_t);
    int             netsnmp_oid_find_prefix(const oid * in_name1, size_t len1,
                                            const oid * in_name2, size_t len2);
    void            init_snmp(const char *);
    u_char         *snmp_pdu_build(netsnmp_pdu *, u_char *, size_t *);
#ifdef NETSNMP_USE_REVERSE_ASNENCODING
    u_char         *snmp_pdu_rbuild(netsnmp_pdu *, u_char *, size_t *);
#endif
    int             snmpv3_parse(netsnmp_pdu *, u_char *, size_t *,
                                 u_char **, netsnmp_session *);
    int             snmpv3_packet_build(netsnmp_session *,
                                        netsnmp_pdu *pdu, u_char * packet,
                                        size_t * out_length,
                                        u_char * pdu_data,
                                        size_t pdu_data_len);
    int             snmpv3_packet_rbuild(netsnmp_session *,
                                         netsnmp_pdu *pdu, u_char * packet,
                                         size_t * out_length,
                                         u_char * pdu_data,
                                         size_t pdu_data_len);
    int             snmpv3_make_report(netsnmp_pdu *pdu, int error);
    int             snmpv3_get_report_type(netsnmp_pdu *pdu);
    int             snmp_pdu_parse(netsnmp_pdu *pdu, u_char * data,
                                   size_t * length);
    u_char         *snmpv3_scopedPDU_parse(netsnmp_pdu *pdu, u_char * cp,
                                           size_t * length);
    void            snmp_store(const char *type);
    void            snmp_shutdown(const char *type);
    netsnmp_variable_list *snmp_pdu_add_variable(netsnmp_pdu *, const oid *,
                                                 size_t, u_char, const u_char *,
                                                 size_t);
    netsnmp_variable_list *snmp_varlist_add_variable(netsnmp_variable_list
                                                     ** varlist,
                                                     const oid * name,
                                                     size_t name_length,
                                                     u_char type,
                                                     const u_char * value,
                                                     size_t len);
    int             snmp_add_var(netsnmp_pdu *, const oid *, size_t, char,
                                 const char *);
    oid            *snmp_duplicate_objid(const oid * objToCopy, size_t);
    u_int           snmp_increment_statistic(int which);
    u_int           snmp_increment_statistic_by(int which, int count);
    u_int           snmp_get_statistic(int which);
    void            snmp_init_statistics(void);
    int             create_user_from_session(netsnmp_session * session);
    int snmp_get_fd_for_session(struct snmp_session *sessp);

    /*
     * New re-allocating reverse encoding functions.  
     */
#ifdef NETSNMP_USE_REVERSE_ASNENCODING

    int        snmpv3_packet_realloc_rbuild(u_char ** pkt, size_t * pkt_len,
                                     size_t * offset,
                                     netsnmp_session * session,
                                     netsnmp_pdu *pdu, u_char * pdu_data,
                                     size_t pdu_data_len);

    int        snmp_pdu_realloc_rbuild(u_char ** pkt, size_t * pkt_len,
                                size_t * offset, netsnmp_pdu *pdu);
#endif



    /*
     * Extended open; fpre_parse has changed.  
     */

    netsnmp_session *snmp_open_ex(netsnmp_session *,
                                  int (*fpre_parse) (netsnmp_session *,
                                                     struct
                                                     netsnmp_transport_s *,
                                                     void *, int),
                                  int (*fparse) (netsnmp_session *,
                                                 netsnmp_pdu *, u_char *,
                                                 size_t),
                                  int (*fpost_parse) (netsnmp_session *,
                                                      netsnmp_pdu *, int),
                                  int (*fbuild) (netsnmp_session *,
                                                 netsnmp_pdu *, u_char *,
                                                 size_t *),
                                  int (*frbuild) (netsnmp_session *,
                                                  netsnmp_pdu *, u_char **,
                                                  size_t *, size_t *),
                                  int (*fcheck) (u_char *, size_t));

    /*
     * provided for backwards compatability.  Don't use these functions.
     * See snmp_debug.h and snmp_debug.c instead.
     */

    void            snmp_set_do_debugging(int);
    int             snmp_get_do_debugging(void);


    /*
     * snmp_error - return error data
     * Inputs :  address of errno, address of snmp_errno, address of string
     * Caller must free the string returned after use.
     */
    void            snmp_error(netsnmp_session *, int *, int *, char **);
    /*
     * single session API.
     *
     * These functions perform similar actions as snmp_XX functions,
     * but operate on a single session only.
     *
     * Synopsis:
     
     void * sessp;
     netsnmp_session session, *ss;
     netsnmp_pdu *pdu, *response;
     
     snmp_sess_init(&session);
     session.retries = ...
     session.remote_port = ...
     sessp = snmp_sess_open(&session);
     ss = snmp_sess_session(sessp);
     if (ss == NULL)
     exit(1);
     ...
     if (ss->community) free(ss->community);
     ss->community = strdup(gateway);
     ss->community_len = strlen(gateway);
     ...
     snmp_sess_synch_response(sessp, pdu, &response);
     ...
     snmp_sess_close(sessp);
     
     * See also:
     * snmp_sess_synch_response, in snmp_client.h.
     
     * Notes:
     *  1. Invoke snmp_sess_session after snmp_sess_open.
     *  2. snmp_sess_session return value is an opaque pointer.
     *  3. Do NOT free memory returned by snmp_sess_session.
     *  4. Replace snmp_send(ss,pdu) with snmp_sess_send(sessp,pdu)
     */

    void            snmp_sess_init(netsnmp_session *);
    void           *snmp_sess_open(netsnmp_session *);
    void           *snmp_sess_pointer(netsnmp_session *);
    netsnmp_session *snmp_sess_session(void *);

    /*
     * Return the netsnmp_transport structure associated with the given opaque
     * pointer.  
     */

    struct netsnmp_transport_s *snmp_sess_transport(void *);
    void            snmp_sess_transport_set(void *,
                                            struct netsnmp_transport_s *);

    /*
     * EXPERIMENTAL API EXTENSIONS ------------------------------------------ 
     * 
     * snmp_sess_add_ex, snmp_sess_add, snmp_add 
     * 
     * Analogous to snmp_open family of functions, but taking an
     * netsnmp_transport pointer as an extra argument.  Unlike snmp_open et
     * al. it doesn't attempt to interpret the in_session->peername as a
     * transport endpoint specifier, but instead uses the supplied transport.
     * JBPN
     * 
     */

    void           *snmp_sess_add_ex(netsnmp_session *,
                                     struct netsnmp_transport_s *,
                                     int (*fpre_parse) (netsnmp_session *,
                                                        struct
                                                        netsnmp_transport_s
                                                        *, void *, int),
                                     int (*fparse) (netsnmp_session *,
                                                    struct snmp_pdu *,
                                                    u_char *, size_t),
                                     int (*fpost_parse) (netsnmp_session *,
                                                         struct snmp_pdu *,
                                                         int),
                                     int (*fbuild) (netsnmp_session *,
                                                    struct snmp_pdu *,
                                                    u_char *, size_t *),
                                     int (*frbuild) (netsnmp_session *,
                                                     struct snmp_pdu *,
                                                     u_char **, size_t *,
                                                     size_t *),
                                     int (*fcheck) (u_char *, size_t),
                                     netsnmp_pdu *(*fcreate_pdu) (struct
                                                                  netsnmp_transport_s
                                                                  *,
                                                                  void *,
                                                                  size_t));

    void           *snmp_sess_add(netsnmp_session *,
                                  struct netsnmp_transport_s *,
                                  int (*fpre_parse) (netsnmp_session *,
                                                     struct
                                                     netsnmp_transport_s *,
                                                     void *, int),
                                  int (*fpost_parse) (netsnmp_session *,
                                                      netsnmp_pdu *, int));

    netsnmp_session *snmp_add(netsnmp_session *,
                              struct netsnmp_transport_s *,
                              int (*fpre_parse) (netsnmp_session *,
                                                 struct netsnmp_transport_s
                                                 *, void *, int),
                              int (*fpost_parse) (netsnmp_session *,
                                                  netsnmp_pdu *, int));
    netsnmp_session *snmp_add_full(netsnmp_session * in_session,
                                   struct netsnmp_transport_s *transport,
                                   int (*fpre_parse) (netsnmp_session *,
                                                      struct
                                                      netsnmp_transport_s
                                                      *, void *, int),
                                   int (*fparse) (netsnmp_session *,
                                                  netsnmp_pdu *, u_char *,
                                                  size_t),
                                   int (*fpost_parse) (netsnmp_session *,
                                                       netsnmp_pdu *, int),
                                   int (*fbuild) (netsnmp_session *,
                                                  netsnmp_pdu *, u_char *,
                                                  size_t *),
                                   int (*frbuild) (netsnmp_session *,
                                                   netsnmp_pdu *,
                                                   u_char **, size_t *,
                                                   size_t *),
                                   int (*fcheck) (u_char *, size_t),
                                   netsnmp_pdu *(*fcreate_pdu) (struct
                                                                netsnmp_transport_s
                                                                *, void *,
                                                                size_t)
        );

    /*
     * use return value from snmp_sess_open as void * parameter 
     */

    int             snmp_sess_send(void *, netsnmp_pdu *);
    int             snmp_sess_async_send(void *, netsnmp_pdu *,
                                         netsnmp_callback, void *);
    int             snmp_sess_select_info(void *, int *, fd_set *,
                                          struct timeval *, int *);
    int             snmp_sess_read(void *, fd_set *);
    void            snmp_sess_timeout(void *);
    int             snmp_sess_close(void *);

    void            snmp_sess_error(void *, int *, int *, char **);
    void            netsnmp_sess_log_error(int priority,
                                           const char *prog_string,
                                           netsnmp_session * ss);
    void            snmp_sess_perror(const char *prog_string,
                                     netsnmp_session * ss);
    const char *    snmp_pdu_type(int type);

    /*
     * end single session API 
     */

    /*
     * generic statistic counters 
     */

    /*
     * snmpv3 statistics 
     */

    /*
     * mpd stats 
     */
#define   STAT_SNMPUNKNOWNSECURITYMODELS     0
#define   STAT_SNMPINVALIDMSGS               1
#define   STAT_SNMPUNKNOWNPDUHANDLERS        2
#define   STAT_MPD_STATS_START               STAT_SNMPUNKNOWNSECURITYMODELS
#define   STAT_MPD_STATS_END                 STAT_SNMPUNKNOWNPDUHANDLERS

    /*
     * usm stats 
     */
#define   STAT_USMSTATSUNSUPPORTEDSECLEVELS  3
#define   STAT_USMSTATSNOTINTIMEWINDOWS      4
#define   STAT_USMSTATSUNKNOWNUSERNAMES      5
#define   STAT_USMSTATSUNKNOWNENGINEIDS      6
#define   STAT_USMSTATSWRONGDIGESTS          7
#define   STAT_USMSTATSDECRYPTIONERRORS      8
#define   STAT_USM_STATS_START               STAT_USMSTATSUNSUPPORTEDSECLEVELS
#define   STAT_USM_STATS_END                 STAT_USMSTATSDECRYPTIONERRORS

    /*
     * snmp counters 
     */
#define  STAT_SNMPINPKTS                     9
#define  STAT_SNMPOUTPKTS                    10
#define  STAT_SNMPINBADVERSIONS              11
#define  STAT_SNMPINBADCOMMUNITYNAMES        12
#define  STAT_SNMPINBADCOMMUNITYUSES         13
#define  STAT_SNMPINASNPARSEERRS             14
    /*
     * #define  STAT_SNMPINBADTYPES              15 
     */
#define  STAT_SNMPINTOOBIGS                  16
#define  STAT_SNMPINNOSUCHNAMES              17
#define  STAT_SNMPINBADVALUES                18
#define  STAT_SNMPINREADONLYS                19
#define  STAT_SNMPINGENERRS                  20
#define  STAT_SNMPINTOTALREQVARS             21
#define  STAT_SNMPINTOTALSETVARS             22
#define  STAT_SNMPINGETREQUESTS              23
#define  STAT_SNMPINGETNEXTS                 24
#define  STAT_SNMPINSETREQUESTS              25
#define  STAT_SNMPINGETRESPONSES             26
#define  STAT_SNMPINTRAPS                    27
#define  STAT_SNMPOUTTOOBIGS                 28
#define  STAT_SNMPOUTNOSUCHNAMES             29
#define  STAT_SNMPOUTBADVALUES               30
    /*
     * #define  STAT_SNMPOUTREADONLYS            31 
     */
#define  STAT_SNMPOUTGENERRS                 32
#define  STAT_SNMPOUTGETREQUESTS             33
#define  STAT_SNMPOUTGETNEXTS                34
#define  STAT_SNMPOUTSETREQUESTS             35
#define  STAT_SNMPOUTGETRESPONSES            36
#define  STAT_SNMPOUTTRAPS                   37
    /*
     * AUTHTRAPENABLE                            38 
     */
#define  STAT_SNMPSILENTDROPS                39
#define  STAT_SNMPPROXYDROPS                 40
#define  STAT_SNMP_STATS_START               STAT_SNMPINPKTS
#define  STAT_SNMP_STATS_END                 STAT_SNMPPROXYDROPS

    /*
     * target mib counters 
     */
#define  STAT_SNMPUNAVAILABLECONTEXTS        41
#define  STAT_SNMPUNKNOWNCONTEXTS            42
#define  STAT_TARGET_STATS_START             STAT_SNMPUNAVAILABLECONTEXTS
#define  STAT_TARGET_STATS_END               STAT_SNMPUNKNOWNCONTEXTS

#define  MAX_STATS                           43

#ifdef __cplusplus
}
#endif
#endif                          /* SNMP_API_H */

---