LBER_SOCKBUF

Section: C Library Functions (3)
Updated: 2018/12/19
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NAME

ber_sockbuf_alloc, ber_sockbuf_free, ber_sockbuf_ctrl, ber_sockbuf_add_io, ber_sockbuf_remove_io, Sockbuf_IO - OpenLDAP LBER I/O infrastructure

LIBRARY

OpenLDAP LBER (liblber, -llber)

SYNOPSIS

#include <lber.h>

Sockbuf *ber_sockbuf_alloc( void );

void ber_sockbuf_free(Sockbuf *sb);

int ber_sockbuf_ctrl(Sockbuf *sb, int opt, void *arg);

int ber_sockbuf_add_io(Sockbuf *sb, Sockbuf_IO *sbio, int layer, void *arg);

int ber_sockbuf_remove_io(Sockbuf *sb, Sockbuf_IO *sbio, int layer);

typedef struct sockbuf_io_desc {
int sbiod_level;
Sockbuf *sbiod_sb;
Sockbuf_IO *sbiod_io;
void *sbiod_pvt;
struct sockbuf_io_desc *sbiod_next;
} Sockbuf_IO_Desc;

typedef struct sockbuf_io {
int (*sbi_setup)(Sockbuf_IO_Desc *sbiod, void *arg);
int (*sbi_remove)(Sockbuf_IO_Desc *sbiod);
int (*sbi_ctrl)(Sockbuf_IO_Desc *sbiod, int opt, void *arg);
ber_slen_t (*sbi_read)(Sockbuf_IO_Desc *sbiod, void *buf, ber_len_t len);
ber_slen_t (*sbi_write)(Sockbuf_IO_Desc *sbiod, void *buf, ber_len_t len);
int (*sbi_close)(Sockbuf_IO_Desc *sbiod);
} Sockbuf_IO;

DESCRIPTION

These routines are used to manage the low level I/O operations performed by the Lightweight BER library. They are called implicitly by the other libraries and usually do not need to be called directly from applications. The I/O framework is modularized and new transport layers can be supported by appropriately defining a Sockbuf_IO structure and installing it onto an existing Sockbuf. Sockbuf structures are allocated and freed by ber_sockbuf_alloc() and ber_sockbuf_free(), respectively. The ber_sockbuf_ctrl() function is used to get and set options related to a Sockbuf or to a specific I/O layer of the Sockbuf. The ber_sockbuf_add_io() and ber_sockbuf_remove_io() functions are used to add and remove specific I/O layers on a Sockbuf.

Options for ber_sockbuf_ctrl() include:

LBER_SB_OPT_HAS_IO: Takes a Sockbuf_IO * argument and returns 1 if the given handler is installed on the Sockbuf, otherwise returns 0.
LBER_SB_OPT_GET_FD: Retrieves the file descriptor associated to the Sockbuf; arg must be a ber_socket_t *. The return value will be 1 if a valid descriptor was present, -1 otherwise.
LBER_SB_OPT_SET_FD: Sets the file descriptor of the Sockbuf to the descriptor pointed to by arg; arg must be a ber_socket_t *. The return value will always be 1.
LBER_SB_OPT_SET_NONBLOCK: Toggles the non-blocking state of the file descriptor associated to the Sockbuf. arg should be NULL to disable and non-NULL to enable the non-blocking state. The return value will be 1 for success, -1 otherwise.
LBER_SB_OPT_DRAIN: Flush (read and discard) all available input on the Sockbuf. The return value will be 1.
LBER_SB_OPT_NEEDS_READ: Returns non-zero if input is waiting to be read.
LBER_SB_OPT_NEEDS_WRITE: Returns non-zero if the Sockbuf is ready to be written.
LBER_SB_OPT_GET_MAX_INCOMING: Returns the maximum allowed size of an incoming message; arg must be a ber_len_t *. The return value will be 1.
LBER_SB_OPT_SET_MAX_INCOMING: Sets the maximum allowed size of an incoming message; arg must be a ber_len_t *. The return value will be 1.

Options not in this list will be passed down to each Sockbuf_IO handler in turn until one of them processes it. If the option is not handled ber_sockbuf_ctrl() will return 0.

Multiple Sockbuf_IO handlers can be stacked in multiple layers to provide various functionality. Currently defined layers include

LBER_SBIOD_LEVEL_PROVIDER: the lowest layer, talking directly to a network
LBER_SBIOD_LEVEL_TRANSPORT: an intermediate layer
LBER_SBIOD_LEVEL_APPLICATION: a higher layer

Currently defined Sockbuf_IO handlers in liblber include

ber_sockbuf_io_tcp: The default stream-oriented provider
ber_sockbuf_io_fd: A stream-oriented provider for local IPC sockets
ber_sockbuf_io_dgram: A datagram-oriented provider. This handler is only present if the liblber library was built with LDAP_CONNECTIONLESS defined.
ber_sockbuf_io_readahead: A buffering layer, usually used with a datagram provider to hide the datagram semantics from upper layers.
ber_sockbuf_io_debug: A generic handler that outputs hex dumps of all traffic. This handler may be inserted multiple times at arbitrary layers to show the flow of data between other handlers.

Additional handlers may be present in libldap if support for them was enabled:

ldap_pvt_sockbuf_io_sasl: An application layer handler for SASL encoding/decoding.
sb_tls_sbio: A transport layer handler for SSL/TLS encoding/decoding. Note that this handler is private to the library and is not exposed in the API.

The provided handlers are all instantiated implicitly by libldap, and applications generally will not need to directly manipulate them.

ACKNOWLEDGEMENTS

OpenLDAP Software is developed and maintained by The OpenLDAP Project <http://www.openldap.org/>. OpenLDAP Software is derived from the University of Michigan LDAP 3.3 Release.