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.Dd Sep 28, 2017
.Dt T_BIND 3NSL
.Os
.Sh NAME
.Nm t_bind
.Nd bind an address to a tansport endpoint
.Sh SYNOPSIS
.Lb libnsl
.In xti.h
.Ft int
.Fo t_bind
.Fa "int fd"
.Fa "const struct t_bind *req"
.Fa "stuct t_bind *ret"
.Fc
.Sh DESCRIPTION
This routine is part of the
.Sy XTI
interfaces that evolved from the
.Sy TLI
interfaces.
.Sy XTI
represents the future evolution of these
interfaces.
However,
.Sy TLI
interfaces are supported for compatibility.
When using a
.Sy TLI
routine that has the same name as an
.Sy XTI
routine, the
.In tiuser.h
header file must be used.
Refer to the
.Sx "TLI COMPATIBILITY"
section for a description of differences between the two interfaces.
.Pp
This function associates a protocol address with the transport endpoint
specified by
.Fa fd
and activates that transport endpoint.
In connection mode, the transport provider may begin enqueuing incoming
connect indications, or servicing a connection request on the transport
endpoint.
In connectionless-mode, the transport user may send or receive data units
through the transport endpoint.
.Pp
The
.Fa req
and
.Fa ret
arguments point to a
.Vt t_bind
structure containing the following members:
.Pp
.Bl -item -offset indent -compact
.It
struct netbuf addr;
.It
unsigned qlen;
.El
.Pp
The
.Sy addr
field of the
.Vt t_bind
structure specifies a protocol address, and the
.Sy qlen
field is used to indicate the maximum number of outstanding connection
indications.
.Pp
The parameter
.Fa req
is used to request that an address, represented by the
.Vt netbuf
structure, be bound to the given transport endpoint.
The parameter
.Sy len
specifies the number of bytes in the address, and
.Sy buf
points to the address buffer.
For
.Xr tcp 4P
and
.Xr udp 4P
transports,
.Sy buf
points to a
.Xr sockaddr 3SOCKET
buffer \(em either
.Vt "struct sockaddr_in"
or
.Vt "struct sockaddr_in6"
(depending on if IPv4 or IPv6 is being used).
The parameter
.Sy maxlen
has no meaning for the
.Fa req
argument.
.Pp
On return,
.Fa ret
contains an encoding for the address that the transport provider actually
bound to the transport endpoint; if an address was specified in
.Fa req ,
this will be an encoding of the same address.
In
.Fa ret ,
the user specifies
.Sy maxlen ,
which is the maximum size of the address buffer, and
.Sy buf
which points to the buffer where the address is to be placed.
On return,
.Sy len
specifies the number of bytes in the bound address, and
.Sy buf
points to the bound address.
If
.Sy maxlen
equals zero, no address is returned.
If
.Sy maxlen
is greater than zero and less than the length of the address,
.Fn t_bind
fails with
.Va t_errno
set to
.Er TBUFOVFLW .
.Pp
If the requested address is not available,
.Fn t_bind
will return  -1 with
.Va t_errno
set as appropriate.
If no address is specified in
.Fa req
(the
.Sy len
field of
.Sy addr
in
.Fa req
is zero or
.Fa req
is
.Sy NULL ) ,
the transport provider will assign an appropriate address to be
bound, and will return that address in the
.Sy addr
field of
.Fa ret .
If the transport provider could not allocate an address,
.Fn t_bind
will fail
with
.Va t_errno
set to
.Er TNOADDR .
.Pp
The parameter
.Fa req
may be a null pointer if the user does not wish to
specify an address to be bound.
Here, the value of
.Sy qlen
is assumed to be zero, and the transport provider will assign an address to
the transport endpoint.
Similarly,
.Fa ret
may be a null pointer if the user does not care
what address was bound by the provider and is not interested in the negotiated
value of
.Sy qlen .
It is valid to set
.Fa req
and
.Fa ret
to the null pointer for the same call, in which case the provider chooses the
address to bind to the transport endpoint and does not return that information
to the user.
.Pp
The
.Sy qlen
field has meaning only when initializing a connection-mode
service.
It specifies the number of outstanding connection indications that the
transport provider should support for the given transport endpoint.
An outstanding connection indication is one that has been passed to the
transport user by the transport provider but which has not been accepted or
rejected.
A value of
.Sy qlen
greater than zero is only meaningful when issued by a
passive transport user that expects other users to call it.
The value of
.Sy qlen
will be negotiated by the transport provider and may be changed if
the transport provider cannot support the specified number of outstanding
connection indications.
However, this value of
.Sy qlen
will never be negotiated from a requested value greater than zero to zero.
This is a requirement on transport providers; see
.Sx WARNINGS
below.
On return, the
.Sy qlen
field in
.Fa ret
will contain the negotiated value.
.Pp
If
.Fa fd
refers to a connection-mode service, this function allows more than
one transport endpoint to be bound to the same protocol address.
It is not
possible to bind more than one protocol address to the same transport endpoint.
However, the transport provider must also support this capability.
If a user binds more than one transport endpoint to the same protocol address,
only one endpoint can be used to listen for connection indications associated
with that protocol address.
In other words, only one
.Fn t_bind
for a given protocol address may specify a value of
.Sy qlen
greater than zero.
In this way, the
transport provider can identify which transport endpoint should be notified of
an incoming connection indication.
If a user attempts to bind a protocol address to a second transport endpoint
with a value of
.Sy qlen
greater than zero,
.Fn t_bind
will return  -1 and set
.Va t_errno
to
.Er TADDRBUSY .
When a user accepts a connection on the transport endpoint that is being used
as the listening endpoint, the bound protocol address will be found to be busy
for the duration of the connection, until a
.Xr t_unbind 3NSL
or
.Xr t_close 3NSL
call has been issued.
No other transport endpoints may be bound for listening on that same protocol
address while that initial listening endpoint is active (in the data transfer
phase or in the
.Sy T_IDLE
state).
This will prevent more than one transport endpoint bound to the same
protocol address from accepting connection indications.
.Pp
If
.Fa fd
refers to connectionless mode service, this function allows for
more than one transport endpoint to be associated with a protocol address,
where the underlying transport provider supports this capability (often in
conjunction with value of a protocol-specific option).
If a user attempts to bind a second transport endpoint to an already bound
protocol address when such capability is not supported for a transport provider,
.Fn t_bind
will
return  -1 and set
.Va t_errno
to
.Er TADDRBUSY .
.Sh RETURN VALUES
Upon successful completion, a value of 0 is returned.
Otherwise, a value of
-1 is returned and
.Va t_errno
is set to indicate an error.
.Sh VALID STATES
.Sy T_UNBND
.Sh ERRORS
On failure,
.Va t_errno
is set to one of the following:
.Bl -tag -width Er
.It Er TACCES
The user does not have permission to use the specified address.
.It Er TADDRBUSY
The requested address is in use.
.It Er TBADADDR
The specified protocol address was in an incorrect format or contained illegal
information.
.It Er TBADF
The specified file descriptor does not refer to a transport endpoint.
.It Er TBUFOVFLW
The number of bytes allowed for an incoming argument
.Pa Sy maxlen
is greater than 0 but not sufficient to store the value of that argument.
The provider's state will change to
.Sy T_IDLE
and the information to be returned in
.Fa ret
will be discarded.
.It Er TOUTSTATE
The communications endpoint referenced by
.Fa fd
is not in one of the states in which a call to this function is valid.
.It Er TNOADDR
The transport provider could not allocate an address.
.It Er TPROTO
This error indicates that a communication problem has been detected between XTI
and the transport provider for which there is no other suitable XTI error
.Pq Va t_errno .
.It Er TSYSERR
A system error has occurred during execution of this function.
.El
.Sh TLI COMPATIBILITY
The
.Sy XTI
and
.Sy TLI
interface definitions have common names but use different header files.
This, and other semantic differences between the two interfaces are described
in the subsections below.
.Ss "Interface Header"
The
.Sy XTI
interfaces use the header file,
.In xti.h .
.Sy TLI
interfaces should
.Em not
use this header.
They should use the header:
.In tiuser.h
.Ss "Address Bound"
The user can compare the addresses in
.Fa req
and
.Fa ret
to determine whether the transport provider bound the transport endpoint to a
different address than that requested.
.Ss "Error Description Values"
The
.Va t_errno
values
.Er TPROTO
and
.Er TADDRBUSY
can be set by the
.Sy XTI
interface but cannot be set by the
.Sy TLI
interface.
.Pp
A
.Va t_errno
value that this routine can return under different circumstances than its
.Sy XTI
counterpart is
.Er TBUFOVFLW .
It can be returned even when the
.Sy maxlen
field of the corresponding buffer has been set to zero.
.Sh MT-LEVEL
Safe
.Sh SEE ALSO
.Xr t_accept 3NSL ,
.Xr t_alloc 3NSL ,
.Xr t_close 3NSL ,
.Xr t_connect 3NSL ,
.Xr t_unbind 3NSL ,
.Xr sockaddr 3SOCKET ,
.Xr attributes 7
.Sh WARNINGS
The requirement that the value of
.Sy qlen
never be negotiated from a requested value greater than zero to zero implies
that transport providers, rather than the XTI implementation itself, accept
this restriction.
.Pp
An implementation need not allow an application explicitly to bind more than
one communications endpoint to a single protocol address, while permitting more
than one connection to be accepted to the same protocol address.
That means that although an attempt to bind a communications endpoint to some
address with
.Sy qlen=0
might be rejected with
.Er TADDRBUSY ,
the user may nevertheless
use this (unbound) endpoint as a responding endpoint in a call to
.Xr t_accept 3NSL .
To become independent of such implementation differences,
the user should supply unbound responding endpoints to
.Xr t_accept 3NSL .
.Pp
The local address bound to an endpoint may change as result of a
.Xr t_accept 3NSL
or
.Xr t_connect 3NSL
call.
Such changes are not necessarily reversed when the connection is released.