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.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
The
.Fn bindresvport
and
.Fn bindresvport_sa
functions are used to bind a socket descriptor to a privileged
.Tn IP
port, that is, a port number in the range 0-1023.
The
.Fn bindresvport
function operates solely on
.Dv AF_INET
sockets, whereas the
.Fn bindresvport_sa
function is capable of binding both
.Dv AF_INET
and
.Dv AF_INET6
sockets.
.Pp
Only the superuser may bind to a privileged port;
these functions will fail for any other user.
.Pp
.Fa sd
should be a socket descriptor that was returned by a call to
.Xr socket 2 .
.Pp
If
.Va sin
is not the NULL pointer,
.Va sin->sin_family
must be initialized to the address family of the socket
.Va sd .
If the value of
.Va sin->sin_port
is non-zero,
.Fn bindresvport
will attempt to use the specified port.
Otherwise, a free port in the range 600-1023 will be chosen and,
if the
.Xr bind 2
succeeds,
.Va sin->sin_port
will be updated with the port that was assigned.
.Pp
If
.Va sin
is the NULL pointer, a free port in the range 600-1023 will be chosen
(as above), but in this case there is no way for
.Fn bindresvport
to communicate to the caller which port was assigned.
.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