.\"	@(#)bindresvport.3n	2.2 88/08/02 4.0 RPCSRC; from 1.7 88/03/14 SMI
.\"	$NetBSD: bindresvport.3,v 1.14 2017/07/03 21:32:49 wiz Exp $
.\"
.Dd January 27, 2007
.Dt BINDRESVPORT 3
.Os
.Sh NAME
.Nm bindresvport ,
.Nm bindresvport_sa
.Nd bind a socket to a reserved privileged IP port
.Sh LIBRARY
.Lb libc
.Sh SYNOPSIS
.In sys/types.h
.In rpc/rpc.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 reserved 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.
Note that
.Fa sin->sin_family
must be initialized to the address family of the socket, passed by
.Fa sd .
If
.Fa sin->sin_port
is
.Sq 0
then a 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,
a port will be allocated (as above).
However, there is no way for
.Fn bindresvport
to return the allocated port in this case.
.Xr getsockname 2
can be used to determine the assigned port.
.Pp
Only root can bind to a privileged port; this call will fail for any
other users.
.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
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 second argument was supplied,
and address family did not match between arguments.
.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 getsockname 2 ,
.Xr getsockopt 2 ,
.Xr setsockopt 2 ,
.Xr ip 4