inet/bindresvport.c

   1 /*
   2  * Copyright (c) 2010, Oracle America, Inc.
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  *     * Redistributions of source code must retain the above copyright
   9  *       notice, this list of conditions and the following disclaimer.
  10  *     * Redistributions in binary form must reproduce the above
  11  *       copyright notice, this list of conditions and the following
  12  *       disclaimer in the documentation and/or other materials
  13  *       provided with the distribution.
  14  *     * Neither the name of the "Oracle America, Inc." nor the names of its
  15  *       contributors may be used to endorse or promote products derived
  16  *       from this software without specific prior written permission.
  17  *
  18  *   THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  19  *   "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  20  *   LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  21  *   FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  22  *   COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
  23  *   INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  24  *   DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
  25  *   GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  26  *   INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
  27  *   WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  28  *   NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  29  *   OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  30  */
  31
  32 #include <errno.h>
  33 #include <unistd.h>
  34 #include <string.h>
  35 #include <sys/types.h>
  36 #include <sys/socket.h>
  37 #include <netinet/in.h>
  38 #include <libc-lock.h>
  39
  40 /*
  41  * Locks the static variables in this file.
  42  */
  43 __libc_lock_define_initialized (static, lock);
  44
  45 /*
  46  * Bind a socket to a privileged IP port
  47  */
  48 int
  49 bindresvport (int sd, struct sockaddr_in *sin)
  50 {
  51   static short port;
  52   struct sockaddr_in myaddr;
  53   int i;
  54
  55 #define STARTPORT 600
  56 #define LOWPORT 512
  57 #define ENDPORT (IPPORT_RESERVED - 1)
  58 #define NPORTS  (ENDPORT - STARTPORT + 1)
  59   static short startport = STARTPORT;
  60
  61   if (sin == (struct sockaddr_in *) 0)
  62     {
  63       sin = &myaddr;
  64       memset (sin, 0, sizeof (*sin));
  65       sin->sin_family = AF_INET;
  66     }
  67   else if (sin->sin_family != AF_INET)
  68     {
  69       __set_errno (EAFNOSUPPORT);
  70       return -1;
  71     }
  72
  73   if (port == 0)
  74     {
  75       port = (__getpid () % NPORTS) + STARTPORT;
  76     }
  77
  78   /* Initialize to make gcc happy.  */
  79   int res = -1;
  80
  81   int nports = ENDPORT - startport + 1;
  82   int endport = ENDPORT;
  83
  84   __libc_lock_lock (lock);
  85
  86  again:
  87   for (i = 0; i < nports; ++i)
  88     {
  89       sin->sin_port = htons (port++);
  90       if (port > endport)
  91         port = startport;
  92       res = __bind (sd, sin, sizeof (struct sockaddr_in));
  93       if (res >= 0 || errno != EADDRINUSE)
  94         break;
  95     }
  96
  97   if (i == nports && startport != LOWPORT)
  98     {
  99       startport = LOWPORT;
 100       endport = STARTPORT - 1;
 101       nports = STARTPORT - LOWPORT;
 102       port = LOWPORT + port % (STARTPORT - LOWPORT);
 103       goto again;
 104     }
 105
 106   __libc_lock_unlock (lock);
 107
 108   return res;
 109 }
 110 libc_hidden_def (bindresvport)