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 5.10 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/.

                                                   2017-09-15                                    BINDRESVPORT(3)