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      1 /*
      2  * CDDL HEADER START
      3  *
      4  * The contents of this file are subject to the terms of the
      5  * Common Development and Distribution License, Version 1.0 only
      6  * (the "License").  You may not use this file except in compliance
      7  * with the License.
      8  *
      9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
     10  * or http://www.opensolaris.org/os/licensing.
     11  * See the License for the specific language governing permissions
     12  * and limitations under the License.
     13  *
     14  * When distributing Covered Code, include this CDDL HEADER in each
     15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
     16  * If applicable, add the following below this CDDL HEADER, with the
     17  * fields enclosed by brackets "[]" replaced with your own identifying
     18  * information: Portions Copyright [yyyy] [name of copyright owner]
     19  *
     20  * CDDL HEADER END
     21  */
     22 /*
     23  * Copyright 2004 Sun Microsystems, Inc.  All rights reserved.
     24  * Use is subject to license terms.
     25  */
     26 
     27 /*	Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T	*/
     28 /*	  All Rights Reserved  	*/
     29 
     30 /*
     31  * Portions of this source code were derived from Berkeley 4.3 BSD
     32  * under license from the Regents of the University of California.
     33  */
     34 
     35 #pragma ident	"%Z%%M%	%I%	%E% SMI"
     36 
     37 #include <sys/types.h>
     38 #include <errno.h>
     39 #include <sys/socket.h>
     40 #include <netinet/in.h>
     41 #include <netinet/tcp.h>
     42 #include <netinet/udp.h>
     43 #include <string.h>
     44 #include <unistd.h>
     45 
     46 #ifdef SYSV
     47 #define	bzero(s, len)	(void) memset((s), 0, (len))
     48 #endif
     49 
     50 
     51 /*
     52  * Bind a socket to a privileged IP port
     53  */
     54 int
     55 bindresvport(int sd, struct sockaddr_in *sin)
     56 {
     57 	struct sockaddr_in myaddr;
     58 	struct sockaddr_in *bindaddr;
     59 	int level, optname;
     60 	int optval, len;
     61 	int ret;
     62 
     63 	bindaddr = sin;
     64 	if (bindaddr == (struct sockaddr_in *)0) {
     65 		bindaddr = &myaddr;
     66 		bzero(bindaddr, sizeof (*bindaddr));
     67 		bindaddr->sin_family = AF_INET;
     68 	} else if (bindaddr->sin_family != AF_INET) {
     69 		errno = EPFNOSUPPORT;
     70 		return (-1);
     71 	}
     72 
     73 	len = sizeof (optval);
     74 	if (getsockopt(sd, SOL_SOCKET, SO_TYPE, &optval, &len) < 0) {
     75 		return (-1);
     76 	}
     77 	/*
     78 	 * Use *_ANONPRIVBIND to ask the kernel to pick a port in the
     79 	 * priviledged range for us.
     80 	 */
     81 	if (optval == SOCK_STREAM) {
     82 		level = IPPROTO_TCP;
     83 		optname = TCP_ANONPRIVBIND;
     84 	} else if (optval == SOCK_DGRAM) {
     85 		level = IPPROTO_UDP;
     86 		optname = UDP_ANONPRIVBIND;
     87 	} else {
     88 		errno = EPROTONOSUPPORT;
     89 		return (-1);
     90 	}
     91 
     92 	optval = 1;
     93 	if (setsockopt(sd, level, optname, &optval, sizeof (optval)) < 0) {
     94 		return (-1);
     95 	}
     96 
     97 	bindaddr->sin_port = 0;
     98 	ret = bind(sd, (struct sockaddr *)bindaddr,
     99 	    sizeof (struct sockaddr_in));
    100 
    101 	/*
    102 	 * Always turn off the option when we are done.  Note that by doing
    103 	 * this, if the caller has set this option before calling
    104 	 * bindresvport(), it will be unset.  But this should never happen...
    105 	 */
    106 	optval = 0;
    107 	(void) setsockopt(sd, level, optname, &optval, sizeof (optval));
    108 
    109 	if (ret >= 0 && sin != NULL) {
    110 		/*
    111 		 * Historical note:
    112 		 *
    113 		 * Past versions of this bindresvport() code have
    114 		 * returned with the reserved port number bound
    115 		 * filled in its "sin" parameter (if passed in), perhaps
    116 		 * "accidently" because of the structure of historical code.
    117 		 *
    118 		 * This is not documented but the behavior is
    119 		 * explicitly retained here for compatibility to minimize
    120 		 * risk to applications, even though it is not clear if this
    121 		 * was a design intent.
    122 		 */
    123 		len = sizeof (struct sockaddr_in);
    124 		(void) getsockname(sd, (struct sockaddr *)bindaddr, &len);
    125 	}
    126 	return (ret);
    127 }
    128