usr/src/lib/libsocket/inet/bindresvport.c

   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 }