libsocket/inet/bindresvport.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */

/*
 * Portions of this source code were derived from Berkeley 4.3 BSD
 * under license from the Regents of the University of California.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include <sys/types.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netinet/udp.h>
#include <string.h>
#include <unistd.h>

#ifdef SYSV
#define bzero(s, len)   (void) memset((s), 0, (len))
#endif


/*
 * Bind a socket to a privileged IP port
 */
int
bindresvport(int sd, struct sockaddr_in *sin)
{
    struct sockaddr_in myaddr;
    struct sockaddr_in *bindaddr;
    int level, optname;
    int optval, len;
    int ret;

    bindaddr = sin;
    if (bindaddr == (struct sockaddr_in *)0) {
        bindaddr = &myaddr;
        bzero(bindaddr, sizeof (*bindaddr));
        bindaddr->sin_family = AF_INET;
    } else if (bindaddr->sin_family != AF_INET) {
        errno = EPFNOSUPPORT;
        return (-1);
    }

    len = sizeof (optval);
    if (getsockopt(sd, SOL_SOCKET, SO_TYPE, &optval, &len) < 0) {
        return (-1);
    }
    /*
     * Use *_ANONPRIVBIND to ask the kernel to pick a port in the
     * priviledged range for us.
     */
    if (optval == SOCK_STREAM) {
        level = IPPROTO_TCP;
        optname = TCP_ANONPRIVBIND;
    } else if (optval == SOCK_DGRAM) {
        level = IPPROTO_UDP;
        optname = UDP_ANONPRIVBIND;
    } else {
        errno = EPROTONOSUPPORT;
        return (-1);
    }

    optval = 1;
    if (setsockopt(sd, level, optname, &optval, sizeof (optval)) < 0) {
        return (-1);
    }

    bindaddr->sin_port = 0;
    ret = bind(sd, (struct sockaddr *)bindaddr,
        sizeof (struct sockaddr_in));

    /*
     * Always turn off the option when we are done.  Note that by doing
     * this, if the caller has set this option before calling
     * bindresvport(), it will be unset.  But this should never happen...
     */
    optval = 0;
    (void) setsockopt(sd, level, optname, &optval, sizeof (optval));

    if (ret >= 0 && sin != NULL) {
        /*
         * Historical note:
         *
         * Past versions of this bindresvport() code have
         * returned with the reserved port number bound
         * filled in its "sin" parameter (if passed in), perhaps
         * "accidently" because of the structure of historical code.
         *
         * This is not documented but the behavior is
         * explicitly retained here for compatibility to minimize
         * risk to applications, even though it is not clear if this
         * was a design intent.
         */
        len = sizeof (struct sockaddr_in);
        (void) getsockname(sd, (struct sockaddr *)bindaddr, &len);
    }
    return (ret);
}