.\" .\" Copyright (c) 2004-2005 .\" Hartmut Brandt. .\" All rights reserved. .\" Copyright (c) 2001-2003 .\" Fraunhofer Institute for Open Communication Systems (FhG Fokus). .\" All rights reserved. .\" .\" Author: Harti Brandt .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in the .\" documentation and/or other materials provided with the distribution. .\" .\" THIS SOFTWARE IS PROVIDED BY AUTHOR AND CONTRIBUTORS ``AS IS'' AND .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE .\" ARE DISCLAIMED. IN NO EVENT SHALL AUTHOR OR CONTRIBUTORS BE LIABLE .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF .\" SUCH DAMAGE. .\" .\" $Begemot: bsnmp/snmpd/snmpmod.3,v 1.14 2005/10/04 13:30:35 brandt_h Exp $ .\" .Dd December 19, 2010 .Dt SNMPMOD 3 .Os .Sh NAME .Nm INSERT_OBJECT_OID_LINK_INDEX , .Nm INSERT_OBJECT_INT_LINK_INDEX , .Nm FIND_OBJECT_OID_LINK_INDEX , .Nm NEXT_OBJECT_OID_LINK_INDEX , .Nm FIND_OBJECT_INT_LINK_INDEX , .Nm NEXT_OBJECT_INT_LINK_INDEX , .Nm INSERT_OBJECT_OID_LINK , .Nm INSERT_OBJECT_INT_LINK , .Nm FIND_OBJECT_OID_LINK , .Nm NEXT_OBJECT_OID_LINK , .Nm FIND_OBJECT_INT_LINK , .Nm NEXT_OBJECT_INT_LINK , .Nm INSERT_OBJECT_OID , .Nm INSERT_OBJECT_INT , .Nm FIND_OBJECT_OID , .Nm FIND_OBJECT_INT , .Nm NEXT_OBJECT_OID , .Nm NEXT_OBJECT_INT , .Nm this_tick , .Nm start_tick , .Nm get_ticks , .Nm systemg , .Nm comm_define , .Nm community , .Nm oid_zeroDotZero , .Nm oid_usmUnknownEngineIDs , .Nm oid_usmNotInTimeWindows , .Nm reqid_allocate , .Nm reqid_next , .Nm reqid_base , .Nm reqid_istype , .Nm reqid_type , .Nm timer_start , .Nm timer_start_repeat , .Nm timer_stop , .Nm fd_select , .Nm fd_deselect , .Nm fd_suspend , .Nm fd_resume , .Nm or_register , .Nm or_unregister , .Nm buf_alloc , .Nm buf_size , .Nm snmp_input_start , .Nm snmp_input_finish , .Nm snmp_output , .Nm snmp_send_port , .Nm snmp_send_trap , .Nm snmp_pdu_auth_access .Nm string_save , .Nm string_commit , .Nm string_rollback , .Nm string_get , .Nm string_get_max , .Nm string_free , .Nm ip_save , .Nm ip_rollback , .Nm ip_commit , .Nm ip_get , .Nm oid_save , .Nm oid_rollback , .Nm oid_commit , .Nm oid_get , .Nm index_decode , .Nm index_compare , .Nm index_compare_off , .Nm index_append , .Nm index_append_off , .Nm snmpd_usmstats , .Nm bsnmpd_get_usm_stats , .Nm bsnmpd_reset_usm_stats , .Nm usm_first_user , .Nm usm_next_user , .Nm usm_find_user , .Nm usm_new_user , .Nm usm_delete_user , .Nm usm_flush_users , .Nm usm_user , .Nm snmpd_target_stat , .Nm bsnmpd_get_target_stats , .Nm target_first_address , .Nm target_next_address , .Nm target_new_address , .Nm target_activate_address , .Nm target_delete_address , .Nm target_first_param , .Nm target_next_param , .Nm target_new_param , .Nm target_delete_param , .Nm target_first_notify , .Nm target_next_notify , .Nm target_new_notify , .Nm target_delete_notify , .Nm target_flush_all , .Nm target_address , .Nm target_param , .Nm target_notify .Nd "SNMP daemon loadable module interface" .Sh LIBRARY Begemot SNMP library .Pq libbsnmp, -lbsnmp .Sh SYNOPSIS .In bsnmp/snmpmod.h .Fn INSERT_OBJECT_OID_LINK_INDEX "PTR" "LIST" "LINK" "INDEX" .Fn INSERT_OBJECT_INT_LINK_INDEX "PTR" "LIST" "LINK" "INDEX" .Fn FIND_OBJECT_OID_LINK_INDEX "LIST" "OID" "SUB" "LINK" "INDEX" .Fn FIND_OBJECT_INT_LINK_INDEX "LIST" "OID" "SUB" "LINK" "INDEX" .Fn NEXT_OBJECT_OID_LINK_INDEX "LIST" "OID" "SUB" "LINK" "INDEX" .Fn NEXT_OBJECT_INT_LINK_INDEX "LIST" "OID" "SUB" "LINK" "INDEX" .Fn INSERT_OBJECT_OID_LINK "PTR" "LIST" "LINK" .Fn INSERT_OBJECT_INT_LINK "PTR" "LIST" "LINK" .Fn FIND_OBJECT_OID_LINK "LIST" "OID" "SUB" "LINK" .Fn FIND_OBJECT_INT_LINK "LIST" "OID" "SUB" "LINK" .Fn NEXT_OBJECT_OID_LINK "LIST" "OID" "SUB" "LINK" .Fn NEXT_OBJECT_INT_LINK "LIST" "OID" "SUB" "LINK" .Fn INSERT_OBJECT_OID "PTR" "LIST" .Fn INSERT_OBJECT_INT "PTR" "LIST" .Fn FIND_OBJECT_OID "LIST" "OID" "SUB" .Fn FIND_OBJECT_INT "LIST" "OID" "SUB" .Fn NEXT_OBJECT_OID "LIST" "OID" "SUB" .Fn NEXT_OBJECT_INT "LIST" "OID" "SUB" .Vt extern uint64_t this_tick ; .Vt extern uint64_t start_tick ; .Ft uint64_t .Fn get_ticks "void" .Vt extern struct systemg systemg ; .Ft u_int .Fn comm_define "u_int priv" "const char *descr" "struct lmodule *mod" "const char *str" .Ft const char * .Fn comm_string "u_int comm" .Vt extern u_int community ; .Vt extern const struct asn_oid oid_zeroDotZero ; .Ft u_int .Fn reqid_allocate "int size" "struct lmodule *mod" .Ft int32_t .Fn reqid_next "u_int type" .Ft int32_t .Fn reqid_base "u_int type" .Ft int .Fn reqid_istype "int32_t reqid" "u_int type" .Ft u_int .Fn reqid_type "int32_t reqid" .Ft void * .Fn timer_start "u_int ticks" "void (*func)(void *)" "void *uarg" "struct lmodule *mod" .Ft void * .Fn timer_start_repeat "u_int ticks" "u_int repeat_ticks" "void (*func)(void *)" "void *uarg" "struct lmodule *mod" .Ft void .Fn timer_stop "void *timer_id" .Ft void * .Fn fd_select "int fd" "void (*func)(int, void *)" "void *uarg" "struct lmodule *mod" .Ft void .Fn fd_deselect "void *fd_id" .Ft void .Fn fd_suspend "void *fd_id" .Ft int .Fn fd_resume "void *fd_id" .Ft u_int .Fn or_register "const struct asn_oid *oid" "const char *descr" "struct lmodule *mod" .Ft void .Fn or_unregister "u_int or_id" .Ft void * .Fn buf_alloc "int tx" .Ft size_t .Fn buf_size "int tx" .Ft enum snmpd_input_err .Fo snmp_input_start .Fa "const u_char *buf" "size_t len" "const char *source" .Fa "struct snmp_pdu *pdu" "int32_t *ip" "size_t *pdulen" .Fc .Ft enum snmpd_input_err .Fo snmp_input_finish .Fa "struct snmp_pdu *pdu" "const u_char *rcvbuf" .Fa "size_t rcvlen" "u_char *sndbuf" "size_t *sndlen" "const char *source" .Fa "enum snmpd_input_err ierr" "int32_t ip" "void *data" .Fc .Ft void .Fo snmp_output .Fa "struct snmp_pdu *pdu" "u_char *sndbuf" "size_t *sndlen" .Fa "const char *dest" .Fc .Ft void .Fo snmp_send_port .Fa "void *trans" "const struct asn_oid *port" .Fa "struct snmp_pdu *pdu" "const struct sockaddr *addr" "socklen_t addrlen" .Fc .Ft void .Fn snmp_send_trap "const struct asn_oid *oid" "..." .Ft enum snmp_code .Fn snmp_pdu_auth_access "struct snmp_pdu *pdu" "int32_t *ip" .Ft int .Fn string_save "struct snmp_value *val" "struct snmp_context *ctx" "ssize_t req_size" "u_char **strp" .Ft void .Fn string_commit "struct snmp_context *ctx" .Ft void .Fn string_rollback "struct snmp_context *ctx" "u_char **strp" .Ft int .Fn string_get "struct snmp_value *val" "const u_char *str" "ssize_t len" .Ft int .Fn string_get_max "struct snmp_value *val" "const u_char *str" "ssize_t len" "size_t maxlen" .Ft void .Fn string_free "struct snmp_context *ctx" .Ft int .Fn ip_save "struct snmp_value *val" "struct snmp_context *ctx" "u_char *ipa" .Ft void .Fn ip_rollback "struct snmp_context *ctx" "u_char *ipa" .Ft void .Fn ip_commit "struct snmp_context *ctx" .Ft int .Fn ip_get "struct snmp_value *val" "u_char *ipa" .Ft int .Fn oid_save "struct snmp_value *val" "struct snmp_context *ctx" "struct asn_oid *oid" .Ft void .Fn oid_rollback "struct snmp_context *ctx" "struct asn_oid *oid" .Ft void .Fn oid_commit "struct snmp_context *ctx" .Ft int .Fn oid_get "struct snmp_value *val" "const struct asn_oid *oid" .Ft int .Fn index_decode "const struct asn_oid *oid" "u_int sub" "u_int code" "..." .Ft int .Fn index_compare "const struct asn_oid *oid1" "u_int sub" "const struct asn_oid *oid2" .Ft int .Fn index_compare_off "const struct asn_oid *oid1" "u_int sub" "const struct asn_oid *oid2" "u_int off" .Ft void .Fn index_append "struct asn_oid *dst" "u_int sub" "const struct asn_oid *src" .Ft void .Fn index_append_off "struct asn_oid *dst" "u_int sub" "const struct asn_oid *src" "u_int off" .Vt extern struct snmpd_usmstat snmpd_usmstats ; .Ft struct snmpd_usmstat * .Fn bsnmpd_get_usm_stats "void" .Ft void .Fn bsnmpd_reset_usm_stats "void" .Ft struct usm_user * .Fn usm_first_user "void" .Ft struct usm_user * .Fn usm_next_user "struct usm_user *uuser" .Ft struct usm_user * .Fn usm_find_user "uint8_t *engine" "uint32_t elen" "char *uname" .Ft struct usm_user * .Fn usm_new_user "uint8_t *engine" "uint32_t elen" "char *uname" .Ft void .Fn usm_delete_user "struct usm_user *" .Ft void .Fn usm_flush_users "void" .Vt extern struct usm_user *usm_user; .Ft struct snmpd_target_stats * .Fn bsnmpd_get_target_stats "void" .Ft struct target_address * .Fn target_first_address "void" .Ft struct target_address * .Fn target_next_address "struct target_address *" .Ft struct target_address * .Fn target_new_address "char *" .Ft int .Fn target_activate_address "struct target_address *" .Ft int .Fn target_delete_address "struct target_address *" .Ft struct target_param * .Fn target_first_param "void" .Ft struct target_param * .Fn target_next_param "struct target_param *" .Ft struct target_param * .Fn target_new_param "char *" .Ft int .Fn target_delete_param "struct target_param *" .Ft struct target_notify * .Fn target_first_notify "void" .Ft struct target_notify * .Fn target_next_notify "struct target_notify *" .Ft struct target_notify * .Fn target_new_notify "char *" .Ft int .Fn target_delete_notify "struct target_notify *" .Ft void .Fn target_flush_all "void" .Vt extern const struct asn_oid oid_usmUnknownEngineIDs; .Vt extern const struct asn_oid oid_usmNotInTimeWindows; .Sh DESCRIPTION The .Xr bsnmpd 1 SNMP daemon implements a minimal MIB which consists of the system group, part of the SNMP MIB, a private configuration MIB, a trap destination table, a UDP port table, a community table, a module table, a statistics group and a debugging group. All other MIBs are support through loadable modules. This allows .Xr bsnmpd 1 to use for task, that are not the classical SNMP task. .Ss MODULE LOADING AND UNLOADING Modules are loaded by writing to the module table. This table is indexed by a string, that identifies the module to the daemon. This identifier is used to select the correct configuration section from the configuration files and to identify resources allocated to this module. A row in the module table is created by writing a string of non-zero length to the .Va begemotSnmpdModulePath column. This string must be the complete path to the file containing the module. A module can be unloaded by writing a zero length string to the path column of an existing row. .Pp Modules may depend on each other an hence must be loaded in the correct order. The dependencies are listed in the corresponding manual pages. .Pp Upon loading a module the SNMP daemon expects the module file to a export a global symbol .Va config . This symbol should be a variable of type .Vt struct snmp_module : .Bd -literal -offset indent typedef enum snmpd_proxy_err (*proxy_err_f)(struct snmp_pdu *, void *, const struct asn_oid *, const struct sockaddr *, socklen_t, enum snmpd_input_err, int32_t); struct snmp_module { const char *comment; int (*init)(struct lmodule *, int argc, char *argv[]); int (*fini)(void); void (*idle)(void); void (*dump)(void); void (*config)(void); void (*start)(void); proxy_err_f proxy; const struct snmp_node *tree; u_int tree_size; void (*loading)(const struct lmodule *, int); }; .Ed .Pp This structure must be statically initialized and its fields have the following functions: .Bl -tag -width ".It Va tree_size" .It Va comment This is a string that will be visible in the module table. It should give some hint about the function of this module. .It Va init This function is called upon loading the module. The module pointer should be stored by the module because it is needed in other calls and the argument vector will contain the arguments to this module from the daemons command line. This function should return 0 if everything is ok or an UNIX error code (see .Xr errno 3 ) . Once the function returns 0, the .Va fini function is called when the module is unloaded. .It Va fini The module is unloaded. This gives the module a chance to free resources that are not automatically freed. Be sure to free all memory, because daemons tend to run very long. This function pointer may be .Li NULL if it is not needed. .It Va idle If this function pointer is not .Li NULL , the function pointed to by it is called whenever the daemon is going to wait for an event. Try to avoid using this feature. .It Va dump Whenever the daemon receives a .Li SIGUSR1 it dumps it internal state via .Xr syslog 3 . If the .Va dump field is not .Li NULL it is called by the daemon to dump the state of the module. .It Va config Whenever the daemon receives a .Li SIGHUP signal it re-reads its configuration file. If the .Va config field is not .Li NULL it is called after reading the configuration file to give the module a chance to adapt to the new configuration. .It Va start If not .Li NULL this function is called after successful loading and initializing the module to start its actual operation. .It Va proxy If the daemon receives a PDU and that PDU has a community string whose community was registered by this module and .Va proxy is not .Li NULL than this function is called to handle the PDU. .It Va tree This is a pointer to the node array for the MIB tree implemented by this module. .It Va tree_size This is the number of nodes in .Va tree . .It Va loading If this pointer is not .Li NULL it is called whenever another module was loaded or unloaded. It gets a pointer to that module and a flag that is 0 for unloading and 1 for loading. .El .Pp When everything is ok, the daemon merges the module's MIB tree into its current global tree, calls the modules .Fn init function. If this function returns an error, the modules MIB tree is removed from the global one and the module is unloaded. If initialization is successful, the modules .Fn start function is called. After it returns the .Fn loaded functions of all modules (including the loaded one) are called. .Pp When the module is unloaded, its MIB tree is removed from the global one, the communities, request id ranges, running timers and selected file descriptors are released, the .Fn fini function is called, the module file is unloaded and the .Fn loaded functions of all other modules are called. .Ss IMPLEMENTING TABLES There are a number of macros designed to help implementing SNMP tables. A problem while implementing a table is the support for the GETNEXT operator. The GETNEXT operation has to find out whether, given an arbitrary OID, the lessest table row, that has an OID higher than the given OID. The easiest way to do this is to keep the table as an ordered list of structures each one of which contains an OID that is the index of the table row. This allows easy removal, insertion and search. .Pp The helper macros assume, that the table is organized as a TAILQ (see .Xr queue 3 and each structure contains a .Vt struct asn_oid that is used as index. For simple tables with only a integer or unsigned index, an alternate form of the macros is available, that presume the existence of an integer or unsigned field as index field. .Pp The macros have name of the form .Bd -literal -offset indent {INSERT,FIND,NEXT}_OBJECT_{OID,INT}[_LINK[_INDEX]] .Ed .Pp The .Fn INSERT_* macros are used in the SET operation to insert a new table row into the table. The .Fn FIND_* macros are used in the GET operation to find a specific row in the table. The .Fn NEXT_* macros are used in the GETNEXT operation to find the next row in the table. The last two macros return a pointer to the row structure if a row is found, .Li NULL otherwise. The macros .Fn *_OBJECT_OID_* assume the existence of a .Vt struct asn_oid that is used as index, the macros .Fn *_OBJECT_INT_* assume the existence of an unsigned integer field that is used as index. .Pp The macros .Fn *_INDEX allow the explicit naming of the index field in the parameter .Fa INDEX , whereas the other macros assume that this field is named .Va index . The macros .Fn *_LINK_* allow the explicit naming of the link field of the tail queues, the others assume that the link field is named .Va link . Explicitly naming the link field may be necessary if the same structures are held in two or more different tables. .Pp The arguments to the macros are as follows: .Bl -tag -width "INDEX" .It Fa PTR A pointer to the new structure to be inserted into the table. .It Fa LIST A pointer to the tail queue head. .It Fa LINK The name of the link field in the row structure. .It Fa INDEX The name of the index field in the row structure. .It Fa OID Must point to the .Va var field of the .Fa value argument to the node operation callback. This is the OID to search for. .It Fa SUB This is the index of the start of the table index in the OID pointed to by .Fa OID . This is usually the same as the .Fa sub argument to the node operation callback. .El .Ss DAEMON TIMESTAMPS The variable .Va this_tick contains the tick (there are 100 SNMP ticks in a second) when the current PDU processing was started. The variable .Va start_tick contains the tick when the daemon was started. The function .Fn get_ticks returns the current tick. The number of ticks since the daemon was started is .Bd -literal -offset indent get_ticks() - start_tick .Ed .Ss THE SYSTEM GROUP The scalar fields of the system group are held in the global variable .Va systemg : .Bd -literal -offset indent struct systemg { u_char *descr; struct asn_oid object_id; u_char *contact; u_char *name; u_char *location; uint32_t services; uint32_t or_last_change; }; .Ed .Ss COMMUNITIES The SNMP daemon implements a community table. On recipte of a request message the community string in that message is compared to each of the community strings in that table, if a match is found, the global variable .Va community is set to the community identifier for that community. Community identifiers are unsigned integers. For the three standard communities there are three constants defined: .Bd -literal -offset indent #define COMM_INITIALIZE 0 #define COMM_READ 1 #define COMM_WRITE 2 .Ed .Pp .Va community is set to .Li COMM_INITIALIZE while the assignments in the configuration file are processed. To .Li COMM_READ or .Li COMM_WRITE when the community strings for the read-write or read-only community are found in the incoming PDU. .Pp Modules can define additional communities. This may be necessary to provide transport proxying (a PDU received on one communication link is proxied to another link) or to implement non-UDP access points to SNMP. A new community is defined with the function .Fn comm_define . It takes the following parameters: .Bl -tag -width ".It Fa descr" .It Fa priv This is an integer identifying the community to the module. Each module has its own namespace with regard to this parameter. The community table is indexed with the module name and this identifier. .It Fa descr This is a string providing a human readable description of the community. It is visible in the community table. .It Fa mod This is the module defining the community. .It Fa str This is the initial community string. .El .Pp The function returns a globally unique community identifier. If a SNMPv1 or SNMPv2 PDU is received who's community string matches, this identifier is set into the global .Va community . .Pp The function .Fn comm_string returns the current community string for the given community. .Pp All communities defined by a module are automatically released when the module is unloaded. .Ss THE USER-BASED SECURITY GROUP The scalar statistics of the USM group are held in the global variable .Va snmpd_usmstats : .Bd -literal -offset indent struct snmpd_usmstat { uint32_t unsupported_seclevels; uint32_t not_in_time_windows; uint32_t unknown_users; uint32_t unknown_engine_ids; uint32_t wrong_digests; uint32_t decrypt_errors; }; .Ed .Fn bsnmpd_get_usm_stats returns a pointer to the global structure containing the statistics. .Fn bsnmpd_reset_usm_stats clears the statistics of the USM group. .Pp A global list of configured USM users is maintained by the daemon. .Bd -literal -offset indent struct usm_user { struct snmp_user suser; uint8_t user_engine_id[SNMP_ENGINE_ID_SIZ]; uint32_t user_engine_len; char user_public[SNMP_ADM_STR32_SIZ]; uint32_t user_public_len; int32_t status; int32_t type; SLIST_ENTRY(usm_user) up; }; .Ed This structure represents an USM user. The daemon only responds to SNMPv3 PDUs with user credentials matching an USM user entry in its global list. If a SNMPv3 PDU is received, whose security model is USM, the global .Va usm_user is set to point at the user entry that matches the credentials contained in the PDU. However, the daemon does not create or remove USM users, it gives an interface to external loadable module(s) to manage the list. .Fn usm_new_user adds an user entry in the list, and .Fn usm_delete_user deletes an existing entry from the list. .Fn usm_flush_users is used to remove all configured USM users. .Fn usm_first_user will return the first user in the list, or .Li NULL if the list is empty. .Fn usm_next_user will return the next user of a given entry if one exists, or .Li NULL . The list is sorted according to the USM user name and Engine ID. .Fn usm_find_user returns the USM user entry matching the given .Fa engine and .Fa uname or .Li NULL if an user with the specified name and engine id is not present in the list. .Ss THE MANAGEMENT TARGET GROUP The Management Target group holds target address information used when sending SNMPv3 notifications. .Pp The scalar statistics of the Management Target group are held in the global variable .Va snmpd_target_stats : .Bd -literal -offset indent struct snmpd_target_stats { uint32_t unavail_contexts; uint32_t unknown_contexts; }; .Ed .Fn bsnmpd_get_target_stats returns a pointer to the global structure containing the statistics. .Pp Three global lists of configured management target addresses, parameters and notifications respectively are maintained by the daemon. .Bd -literal -offset indent struct target_address { char name[SNMP_ADM_STR32_SIZ]; uint8_t address[SNMP_UDP_ADDR_SIZ]; int32_t timeout; int32_t retry; char taglist[SNMP_TAG_SIZ]; char paramname[SNMP_ADM_STR32_SIZ]; int32_t type; int32_t socket; int32_t status; SLIST_ENTRY(target_address) ta; }; .Ed This structure represents a SNMPv3 Management Target address. Each time a SNMP TRAP is send the daemon will send the Trap to all active Management Target addresses in its global list. .Bd -literal -offset indent struct target_param { char name[SNMP_ADM_STR32_SIZ]; int32_t mpmodel; int32_t sec_model; char secname[SNMP_ADM_STR32_SIZ]; enum snmp_usm_level sec_level; int32_t type; int32_t status; SLIST_ENTRY(target_param) tp; }; .Ed This structure represents the information used to generate SNMP messages to the associated SNMPv3 Management Target addresses. .Bd -literal -offset indent struct target_notify { char name[SNMP_ADM_STR32_SIZ]; char taglist[SNMP_TAG_SIZ]; int32_t notify_type; int32_t type; int32_t status; SLIST_ENTRY(target_notify) tn; }; .Ed This structure represents Notification Tag entries - SNMP notifications are sent to the Target address for each entry in the Management Target Address list that has a tag matching the specified tag in this structure. .Pp The daemon does not create or remove entries in the Management Target group lists, it gives an interface to external loadable module(s) to manage the lists. .Fn target_new_address adds a target address entry, and .Fn target_delete_address deletes an existing entry from the target address list. .Fn target_activate_address creates a socket associated with the target address entry so that SNMP notifications may actually be send to that target address. .Fn target_first_address will return a pointer to the first target address entry in the list, while .Fn target_next_address will return a pointer to the next target address of a given entry if one exists. .Fn target_new_param adds a target parameters' entry, and .Fn target_delete_param deletes an existing entry from the target parameters list. .Fn target_first_param will return a pointer to the first target parameters' entry in the list, while .Fn target_next_param will return a pointer to the next target parameters of a given entry if one exists. .Fn target_new_notify adds a notification target entry, and .Fn target_delete_notify deletes an existing entry from the notification target list. .Fn target_first_notify will return a pointer to the first notification target entry in the list, while .Fn target_next_notify will return a pointer to the next notification target of a given entry if one exists. .Fn target_flush_all is used to remove all configured data from the three global Management Target Group lists. .Ss WELL KNOWN OIDS The global variable .Va oid_zeroDotZero contains the OID 0.0. The global variables .Va oid_usmUnknownEngineIDs .Va oid_usmNotInTimeWindows contains the OIDs 1.3.6.1.6.3.15.1.1.4.0 and 1.3.6.1.6.3.15.1.1.2.0 used in the SNMPv3 USM Engine Discovery. .Ss REQUEST ID RANGES For modules that implement SNMP client functions besides SNMP agent functions it may be necessary to identify SNMP requests by their identifier to allow easier routing of responses to the correct sub-system. Request id ranges provide a way to acquire globally non-overlapping sub-ranges of the entire 31-bit id range. .Pp A request id range is allocated with .Fn reqid_allocate . The arguments are: the size of the range and the module allocating the range. For example, the call .Bd -literal -offset indent id = reqid_allocate(1000, module); .Ed .Pp allocates a range of 1000 request ids. The function returns the request id range identifier or 0 if there is not enough identifier space. The function .Fn reqid_base returns the lowest request id in the given range. .Pp Request id are allocated starting at the lowest one linear throughout the range. If the client application may have a lot of outstanding request the range must be large enough so that an id is not reused until it is really expired. .Fn reqid_next returns the sequentially next id in the range. .Pp The function .Fn reqid_istype checks whether the request id .Fa reqid is within the range identified by .Fa type . The function .Fn reqid_type returns the range identifier for the given .Fa reqid or 0 if the request id is in none of the ranges. .Ss TIMERS The SNMP daemon supports an arbitrary number of timers with SNMP tick granularity. The function .Fn timer_start arranges for the callback .Fa func to be called with the argument .Fa uarg after .Fa ticks SNMP ticks have expired. .Fa mod is the module that starts the timer. These timers are one-shot, they are not restarted. Repeatable timers are started with .Fn timer_start_repeat which takes an additional argument .Fa repeat_ticks . The argument .Fa ticks gives the number of ticks until the first execution of the callback, while .Fa repeat_ticks is the number of ticks between invocations of the callback. Note, that currently the number of initial ticks silently may be set identical to the number of ticks between callback invocations. The function returns a timer identifier that can be used to stop the timer via .Fn timer_stop . If a module is unloaded all timers started by the module that have not expired yet are stopped. .Ss FILE DESCRIPTOR SUPPORT A module may need to get input from socket file descriptors without blocking the daemon (for example to implement alternative SNMP transports). .Pp The function .Fn fd_select causes the callback function .Fa func to be called with the file descriptor .Fa fd and the user argument .Fa uarg whenever the file descriptor .Fa fd can be read or has a close condition. If the file descriptor is not in non-blocking mode, it is set to non-blocking mode. If the callback is not needed anymore, .Fn fd_deselect may be called with the value returned from .Fn fd_select . All file descriptors selected by a module are automatically deselected when the module is unloaded. .Pp To temporarily suspend the file descriptor registration .Fn fd_suspend can be called. This also causes the file descriptor to be switched back to blocking mode if it was blocking prior the call to .Fn fd_select . This is necessary to do synchronous input on a selected socket. The effect of .Fn fd_suspend can be undone with .Fn fd_resume . .Ss OBJECT RESOURCES The system group contains an object resource table. A module may create an entry in this table by calling .Fn or_register with the .Fa oid to be registered, a textual description in .Fa str and a pointer to the module .Fa mod . The registration can be removed with .Fn or_unregister . All registrations of a module are automatically removed if the module is unloaded. .Ss TRANSMIT AND RECEIVE BUFFERS A buffer is allocated via .Fn buf_alloc . The argument must be 1 for transmit and 0 for receive buffers. The function may return .Li NULL if there is no memory available. The current buffersize can be obtained with .Fn buf_size . .Sh PROCESSING PDUS For modules that need to do their own PDU processing (for example for proxying) the following functions are available: .Pp Function .Fn snmp_input_start decodes the PDU, searches the community, and sets the global .Va this_tick . It returns one of the following error codes: .Bl -tag -width ".It Er SNMPD_INPUT_VALBADLEN" .It Er SNMPD_INPUT_OK Everything ok, continue with processing. .It Er SNMPD_INPUT_FAILED The PDU could not be decoded, has a wrong version or an unknown community string. .It Er SNMPD_INPUT_VALBADLEN A SET PDU had a value field in a binding with a wrong length field in an ASN.1 header. .It Er SNMPD_INPUT_VALRANGE A SET PDU had a value field in a binding with a value that is out of range for the given ASN.1 type. .It Er SNMPD_INPUT_VALBADENC A SET PDU had a value field in a binding with wrong ASN.1 encoding. .It Er SNMPD_INPUT_TRUNC The buffer appears to contain a valid begin of a PDU, but is too short. For streaming transports this means that the caller must save what he already has and trying to obtain more input and reissue this input to the function. For datagram transports this means that part of the datagram was lost and the input should be ignored. .El .Pp The function .Fn snmp_input_finish does the other half of processing: if .Fn snmp_input_start did not return OK, tries to construct an error response. If the start was OK, it calls the correct function from .Xr bsnmpagent 3 to execute the request and depending on the outcome constructs a response or error response PDU or ignores the request PDU. It returns either .Er SNMPD_INPUT_OK or .Er SNMPD_INPUT_FAILED . In the first case a response PDU was constructed and should be sent. .Pp The function .Fn snmp_output takes a PDU and encodes it. .Pp The function .Fn snmp_send_port takes a PDU, encodes it and sends it through the given port (identified by the transport and the index in the port table) to the given address. .Pp The function .Fn snmp_send_trap sends a trap to all trap destinations. The arguments are the .Fa oid identifying the trap and a NULL-terminated list of .Vt struct snmp_value pointers that are to be inserted into the trap binding list. .Fn snmp_pdu_auth_access verifies whether access to the object IDs contained in the .Fa pdu should be granted or denied, according to the configured View-Based Access rules. .Fa ip contains the index of the first varbinding to which access was denied, or 0 if access to all varbindings in the PDU is granted. .Ss SIMPLE ACTION SUPPORT For simple scalar variables that need no dependencies a number of support functions is available to handle the set, commit, rollback and get. .Pp The following functions are used for OCTET STRING scalars, either NUL terminated or not: .Bl -tag -width "XXXXXXXXX" .It Fn string_save should be called for SNMP_OP_SET. .Fa value and .Fa ctx are the resp\&.\& arguments to the node callback. .Fa valp is a pointer to the pointer that holds the current value and .Fa req_size should be -1 if any size of the string is acceptable or a number larger or equal zero if the string must have a specific size. The function saves the old value in the scratch area (note, that any initial value must have been allocated by .Xr malloc 3 ) , allocates a new string, copies over the new value, NUL-terminates it and sets the new current value. .It Fn string_commit simply frees the saved old value in the scratch area. .It Fn string_rollback frees the new value, and puts back the old one. .It Fn string_get is used for GET or GETNEXT. The function .It Fn string_get_max can be used instead of .Fn string_get to ensure that the returned string has a certain maximum length. If .Fa len is -1, the length is computed via .Xr strlen 3 from the current string value. If the current value is NULL, a OCTET STRING of zero length is returned. .It Fn string_free must be called if either rollback or commit fails to free the saved old value. .El .Pp The following functions are used to process scalars of type IP-address: .Bl -tag -width "XXXXXXXXX" .It Fn ip_save Saves the current value in the scratch area and sets the new value from .Fa valp . .It Fn ip_commit Does nothing. .It Fn ip_rollback Restores the old IP address from the scratch area. .It Fn ip_get Retrieves the IP current address. .El .Pp The following functions handle OID-typed variables: .Bl -tag -width "XXXXXXXXX" .It Fn oid_save Saves the current value in the scratch area by allocating a .Vt struct asn_oid with .Xr malloc 3 and sets the new value from .Fa oid . .It Fn oid_commit Frees the old value in the scratch area. .It Fn oid_rollback Restores the old OID from the scratch area and frees the old OID. .It Fn oid_get Retrieves the OID .El .Ss TABLE INDEX HANDLING The following functions help in handling table indexes: .Bl -tag -width "XXXXXXXXX" .It Fn index_decode Decodes the index part of the OID. The parameter .Fa oid must be a pointer to the .Va var field of the .Fa value argument of the node callback. The .Fa sub argument must be the index of the start of the index in the OID (this is the .Fa sub argument to the node callback). .Fa code is the index expression (parameter .Fa idx to the node callback). These parameters are followed by parameters depending on the syntax of the index elements as follows: .Bl -tag -width ".It Li OCTET STRING" .It Li INTEGER .Vt int32_t * expected as argument. .It Li COUNTER64 .Vt uint64_t * expected as argument. Note, that this syntax is illegal for indexes. .It Li OCTET STRING A .Vt u_char ** and a .Vt size_t * expected as arguments. A buffer is allocated to hold the decoded string. .It Li OID A .Vt struct asn_oid * is expected as argument. .It Li IP ADDRESS A .Vt u_int8_t * expected as argument that points to a buffer of at least four byte. .It Li COUNTER, GAUGE, TIMETICKS A .Vt u_int32_t expected. .It Li NULL No argument expected. .El .It Fn index_compare compares the current variable with an OID. .Fa oid1 and .Fa sub come from the node callback arguments .Fa value->var and .Fa sub resp. .Fa oid2 is the OID to compare to. The function returns -1, 0, +1 when the variable is lesser, equal, higher to the given OID. .Fa oid2 must contain only the index part of the table column. .It Fn index_compare_off is equivalent to .Fn index_compare except that it takes an additional parameter .Fa off that causes it to ignore the first .Fa off components of both indexes. .It Fn index_append appends OID .Fa src beginning at position .Fa sub to .Fa dst . .It Fn index_append_off appends OID .Fa src beginning at position .Fa off to .Fa dst beginning at position .Fa sub + .Fa off . .El .Sh SEE ALSO .Xr gensnmptree 1 , .Xr bsnmpd 1 , .Xr bsnmpagent 3 , .Xr bsnmpclient 3 , .Xr bsnmplib 3 .Sh STANDARDS This implementation conforms to the applicable IETF RFCs and ITU-T recommendations. .Sh AUTHORS .An Hartmut Brandt Aq harti@FreeBSD.org