bindresvport(3)                                       Library Functions Manual                                      bindresvport(3)

       bindresvport - bind a socket to a privileged IP port

       Standard C library (libc, -lc)

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

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

       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).)

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

       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  capabil‐
              ity in the user namespace governing its network namespace).

              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.

       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 func‐
       tion MT-Unsafe.

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

       Unlike some bindresvport() implementations, the  glibc  implementation  ignores  any  value  that  the  caller  supplies  in

       bind(2), getsockname(2)

Linux man-pages 6.03                                         2023-02-05                                             bindresvport(3)