bindresvport(3) — Linux manual page


BINDRESVPORT(3)           Linux Programmer's Manual          BINDRESVPORT(3)

NAME         top

       bindresvport - bind a socket to a privileged IP port

SYNOPSIS         top

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

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

DESCRIPTION         top

       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

       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         top

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

ERRORS         top

       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).

              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         top

       For an explanation of the terms used in this section, see

       │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-

CONFORMING TO         top

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

NOTES         top

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

SEE ALSO         top

       bind(2), getsockname(2)

COLOPHON         top

       This page is part of release 5.08 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

                                 2017-09-15                  BINDRESVPORT(3)