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ISNS(3) Library Functions Manual ISNS(3)
NAME
isns - iSNS protocol support library
LIBRARY
Internet Storage Name Service Library (libisns, -lisns)
SYNOPSIS
#include <isns.h>
int
isns_init(ISNS_HANDLE *h, int is_server);
void
isns_stop(ISNS_HANDLE h);
int
isns_add_servercon(ISNS_HANDLE h, int fd, struct addrinfo *ai);
int
isns_init_reg_refresh(ISNS_HANDLE h, const char *node, int interval);
ISNS_TRANS
isns_new_trans(ISNS_HANDLE h, uint16_t func_id, uint16_t pdu_flags);
int
isns_add_tlv(ISNS_TRANS t, uint32_t tag, int data_len,
const void *data_p);
int
isns_add_string(ISNS_TRANS t, uint32_t tag, const char *s);
int
isns_send_trans(ISNS_TRANS t, const struct timespec *timeout_p,
uint32_t *status_p);
int
isns_get_tlv(ISNS_TRANS t, int which_tlv, uint32_t *tag_p,
int data_len_p, void **data_pp);
void
isns_free_trans(ISNS_TRANS t);
DESCRIPTION
The isns library exports an API that simplifies Internet Storage Name
Service (iSNS) client implementations. The API defines a transactional
model in support of:
⊕ generating iSNS messages composed of iSNS attributes expressed
in Tag-Length-Value (TLV) data format
⊕ submitting iSNS Protocol (iSNSP) messages
⊕ optionally waiting for iSNSP responses
isns does not currently support receipt of iSNS Heartbeat messages, State
Change Notification (SCN) messages, or Entity Status Inquiry (ESI)
messages.
INITIALIZATION
An iSNS client that uses isns must call isns_init() to initialize the
iSNS environment. This call will create a thread to handle client-server
communication, and as such should only be called when thread creation is
appropriate (such as after a daemonized program forks).
The value passed as is_server is used to set iSNSP message format Flags
"Sender is the iSNS client" (bit position 16) and "Sender is the iSNS
server" (bit position 17). For now the value 0 (zero) should be passed
for is_server. The value returned in h should be considered opaque by
the caller. This value is passed unchanged to isns_add_servercon(),
isns_init_reg_refresh(), isns_stop(), and isns_new_trans().
isns_stop() should be called when the iSNS environment is no longer
needed. This call will kill any threads created by isns_init().
CONFIGURATION
Following initialization, isns_add_servercon() should be used to make the
iSNS environment aware of the iSNS server to which iSNSP queries and
requests are to be sent. This routine should not be called by a program
acting as an iSNS server.
A connected TCP socket descriptor is passed as parameter fd. Parameter
ai is the address of the remote TCP endpoint. It is included so that
reconnection may be attempted by isns in the event that the TCP
connection is broken.
Certain iSNS servers will limit registration lifetimes, and will refresh
registrations after any request from a given iSNS entity. The
isns_init_reg_refresh() function offers a way for isns to refresh
registrations on behalf of the iSNS client.
Parameter node is the "iSCSI Name" attribute used for the periodic
queries. It should be the name of an iSCSI node within the registered
iSNS entity. The desired refresh interval, in seconds, is passed in
parameter interval.
TRANSACTIONS
isns_new_trans() creates new iSNS transactions.
Parameter func_id is used as the iSNSP message id. Parameter pdu_flags
is used to set iSNSP message format Flags and is exposed to allow callers
to set flag "Replace flag" (bit position 19). This provides callers with
a way to specify whether a Device Attribute Registration Request is
intended to update or replace an existing registration. This is
currently the only use defined for parameter pdu_flags.
Once a new transaction has been created, callers can specify iSNS
attributes used for registration and query requests. TLV data may be
added using either isns_add_tlv() or isns_add_string().
Parameter tag is the iSNS Tag corresponding to the attribute being added.
Parameter data_len is the length of the attribute value. Parameter
data_p references the attribute value. The caller does not need to
handle iSNS attribute 4-byte alignment requirements. This is handled by
the iSNS environment on behalf of the caller. isns_add_string() may be
used if the attribute value is a NUL terminated C string.
Once a transaction has been populated with any required TLV data,
isns_send_trans() can be used to submit an iSNSP registration or query
message.
Callers that submit iSNSP query messages may need to wait for returned
data. isns_send_trans() supports bounded waits. Successful waits, those
that do not time out, return the iSNSP response status code received in
the iSNSP response message. If a wait does time out, the value of
status_p is undefined. Callers that do not need to wait for returned
data can simply pass NULL for parameter timeout_p. Callers should set
parameter status_p to NULL if not waiting.
isns_get_tlv() is used to retrieve TLV data returned in a transaction.
The first call to isns_get_tlv() should pass the value ISNS_TLV_FIRST for
parameter which_tlv. Each subsequent TLV can be retrieved by passing in
ISNS_TLV_NEXT in place of ISNS_TLV_FIRST.
When a caller is done with a transaction, having submitted either a
registration or a query message and retrieved any returned TLV data,
isns_free_trans() should be used to release resources used by the
transaction.
RETURN VALUES
isns_init(), isns_add_servercon(), isns_init_reg_refresh(),
isns_add_tlv(), isns_add_string(), and isns_send_trans() return 0 on
success, or -1 on failure. isns_new_trans() returns 0 on success, or
ISNS_INVALID_TRANS on failure. isns_get_tlv() returns 0 on success, or
ENOENT if there are no TLVs to retrieve.
HISTORY
isns first appeared in NetBSD 6.0. The isns implementation was
contributed to the NetBSD Foundation by Wasabi Systems, Inc.
NetBSD 10.99 October 1, 2009 NetBSD 10.99