NAME

       bindresvport - bind a socket to a privileged IP port

LIBRARY

       Standard C library (libc, -lc)

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 is set to indicate 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.

VERSIONS

       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.

STANDARDS

       BSD.

SEE ALSO

       bind(2), getsockname(2)

Linux man-pages 6.9.1                              2024-05-02                                    bindresvport(3)