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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).

       ┌───────────────┬───────────────┬─────────────────────────┐
       │InterfaceAttributeValue                   │
       ├───────────────┼───────────────┼─────────────────────────┤
       │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 5.01 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)