bindresvport - bind a socket to a privileged IP port
#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 set to indicate the cause of 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 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.
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.
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
sin->sin_port.
bind(2),
getsockname(2)