.\"	@(#)bindresvport.3n	2.2 88/08/02 4.0 RPCSRC; from 1.7 88/03/14 SMI
.\"	$NetBSD: bindresvport.3,v 1.5 1998/02/05 18:49:05 perry Exp $
.\"
.Dd November 22, 1987
.Dt BINDRESVPORT 3
.Os
.Sh NAME
.Nm bindresvport
.Nd bind a socket to a privileged IP port
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.Fd #include <sys/types.h>
.Fd #include <netinet/in.h>
.Ft int
.Fn bindresvport "int sd" "struct sockaddr_in *sin"
.Sh DESCRIPTION
.Fn bindresvport
is used to bind a socket descriptor to a privileged
.Tn IP
port, that is, a
port number in the range 0-1023.
The routine returns 0 if it is successful,
otherwise -1 is returned and
.Va errno
set to reflect the cause of the error.
.Pp
If
.Fa sin
is a pointer to a
.Ft "struct sockaddr_in"
then the appropriate fields in the structure should be defined.
If
.Fa sin.sin_port
is
.Sq 0
then an anonymous port (in the range 600-1023) will be
chosen, and if
.Xr bind 2
is successful, the
.Fa sin.sin_port
will be updated to contain the allocated port.
.Pp
If
.Fa sin
is the
.Dv NULL
pointer,
an anonymous port will be allocated (as above).
However, there is no way for
.Fn bindresvport
to return the allocated port in this case.
.Pp
Only root can bind to a privileged port; this call will fail for any
other users.
.Sh RETURN VALUES
If the bind is successful, a 0 value is returned.
A return value of -1 indicates an error, which is
further specified in the global
.Va errno .
.Sh ERRORS
.Bl -tag -width Er
.It Bq Er EPFNOSUPPORT
If
.Fa sin
was supplied, and
.Fa sin.sin_family
isn't
.Dv AF_INET .
.El
.Pp
.Fn bindresvport
may also fail and set
.Va errno
for any of the errors specified for the calls
.Xr bind 2 ,
.Xr getsockopt 2 ,
or 
.Xr setsockopt 2 .
.Sh SEE ALSO
.Xr bind 2 ,
.Xr getsockopt 2 ,
.Xr setsockopt 2 ,
.Xr ip 4 .