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bindresvport(3)


NAME

   bindresvport - bind a socket to a privileged IP port

SYNOPSIS

   #include <sys/types.h>
   #include <netinet/in.h>

   int bindresvport(int sockfd, struct sockaddr_in *sin);

DESCRIPTION

   bindresvport()  is  used  to  bind  the  socket referred to by the file
   descriptor sockfd to a privileged anonymous IP port, that  is,  a  port
   number arbitrarily selected from the range 512 to 1023.

   If  the  bind(2)  performed by bindresvport() is successful, and sin is
   not  NULL,  then  sin->sin_port  returns  the  port   number   actually
   allocated.

   sin  can  be NULL, in which case sin->sin_family is implicitly taken to
   be AF_INET.  However, in this case, bindresvport() has no way to return
   the  port  number  actually  allocated.  (This information can later be
   obtained using getsockname(2).)

RETURN VALUE

   bindresvport() returns 0 on success; otherwise -1 is returned and errno
   set to indicate the cause of the error.

ERRORS

   bindresvport()  can  fail  for  any of the same reasons as bind(2).  In
   addition, the following errors may occur:

   EACCES The calling process was not privileged (on  Linux:  the  calling
          process  did not have the CAP_NET_BIND_SERVICE capability in the
          user namespace governing its network namespace).

   EADDRINUSE
          All privileged ports are in use.

   EAFNOSUPPORT (EPFNOSUPPORT in glibc 2.7 and earlier)
          sin is not NULL and sin->sin_family is not AF_INET.

ATTRIBUTES

   For  an  explanation  of  the  terms  used   in   this   section,   see
   attributes(7).

   
   Interface       Attribute      Value                   
   
   bindresvport()  Thread safety  glibc >= 2.17: MT-Safe  
                                  glibc < 2.17: MT-Unsafe 
   
   The  bindresvport()  function  uses  a  static  variable  that  was not
   protected by a lock before  glibc  2.17,  rendering  the  function  MT-
   Unsafe.

CONFORMING TO

   Not in POSIX.1.  Present on the BSDs, Solaris, and many other systems.

NOTES

   Unlike  some  bindresvport()  implementations, the glibc implementation
   ignores any value that the caller supplies in sin->sin_port.

SEE ALSO

   bind(2), getsockname(2)

COLOPHON

   This page is part of release 4.09 of the Linux  man-pages  project.   A
   description  of  the project, information about reporting bugs, and the
   latest    version    of    this    page,    can     be     found     at
   https://www.kernel.org/doc/man-pages/.

                              2016-10-08                   BINDRESVPORT(3)



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