bindresvport(3) — Linux manual page


bindresvport(3)         Library Functions Manual         bindresvport(3)

NAME         top

       bindresvport - bind a socket to a privileged IP port

LIBRARY         top

       Standard C library (libc, -lc)

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 is set to indicate 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

              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-

VERSIONS         top

       Present on the BSDs, Solaris, and many other systems.

NOTES         top

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

STANDARDS         top


SEE ALSO         top

       bind(2), getsockname(2)

COLOPHON         top

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