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BINDRESVPORT(3) Linux Programmer's Manual 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  allo-
     cated.

     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  pro-
     tected 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.