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.\" $OpenBSD: bindresvport.3,v 1.17 2000/01/26 08:40:15 deraadt Exp $
.\"
.Dd August 9, 1997
.Dt BINDRESVPORT 3
.Os
.Sh NAME
.Nm bindresvport ,
.Nm bindresvport_sa
.Nd bind a socket to a privileged IP port
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <netinet/in.h>
.Ft int
.Fn bindresvport "int sd" "struct sockaddr_in *sin"
.Ft int
.Fn bindresvport_sa "int sd" "struct sockaddr *sa"
.Sh DESCRIPTION
.Fn bindresvport
and
.Fn bindresvport_sa
are used to bind a socket descriptor to a privileged
.Tn IP
port, that is, a port number in the range 0-1023.
.Fa sd
is a socket descriptor that was returned by a call to
.Xr socket 2 .
.Pp
Only root can bind to a privileged port; this call will fail for any
other users.
.Pp
When
.Va sin
is not null,
.Va sin->sin_family
must be initialized to the address family of the socket, passed by
.Va sd .
If the value of
.Va sin->sin_port
is non-zero,
.Fn bindresvport
attempts to use the specified port. If that fails, it
chooses another privileged port number automatically.
.Pp
It is legal to pass null pointer to
.Va sin .
In this case, the caller cannot get the port number
.Fn bindresvport
has picked.
.Pp
Function prototype of
.Fn bindresvport
is biased to
.Dv AF_INET
socket.
.Fn bindresvport_sa
acts exactly the same, with more neutral function prototype.
Note that both functions behave exactly the same, and
both support
.Dv AF_INET6
sockets as well as
.Dv AF_INET
sockets.
.Sh RETURN VALUES
.Fn bindresvport
returns 0 if it is successful, otherwise \-1 is returned and
.Va errno
set to reflect the cause of the error.
.Sh ERRORS
The
.Fn bindresvport
function fails if:
.Bl -tag -width Er
.It Bq Er EBADF
.Fa sd
is not a valid descriptor.
.It Bq Er ENOTSOCK
.Fa sd
is not a socket.
.It Bq Er EADDRNOTAVAIL
The specified address is not available from the local machine.
.It Bq Er EADDRINUSE
The specified address is already in use.
.It Bq Er EINVAL
The socket is already bound to an address.
.It Bq Er EINVAL
The family of the socket and that requested in
.Va sa->sa_family
are not equivalent.
.It Bq Er EACCES
The requested address is protected, and the current user
has inadequate permission to access it.
.It Bq Er EFAULT
The
.Fa name
parameter is not in a valid part of the user
address space.
.It Bq Er ENOBUFS
Insufficient resources were available in the system
to perform the operation.
.It Bq Er EPFNOSUPPORT
The protocol family has not been configured into the
system, no implementation for it exists,
or address family did not match between arguments.
.El
.Sh SEE ALSO
.Xr bind 2 ,
.Xr socket 2 ,
.Xr rresvport 3 ,
.Xr rresvport_af 3
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