BINDRESVPORT(3)

NAME
bindresvport, bindresvport_sa - bind a socket to a privileged IP port

SYNOPSIS
#include <sys/types.h>
#include <netinet/in.h>
int
bindresvport(int sd, struct sockaddr_in *sin);
int
bindresvport_sa(int sd, struct sockaddr *sa);

DESCRIPTION
The bindresvport() and bindresvport_sa() functions are used to bind a socket descriptor to a privileged IP port, that is, a port number in the range 0-1023. The bindresvport() function operates solely on AF_INET sockets, whereas the bindresvport_sa() function is capable of binding both AF_INET and AF_INET6 sockets.

Only the superuser may bind to a privileged port; these functions will fail for any other user.

sd should be a socket descriptor that was returned by a call to socket(2).

If sin is not the NULL pointer, sin->sin_family must be initialized to the address family of the socket sd. If the value of sin->sin_port is non-zero, bindresvport() will attempt to use the specified port. Otherwise, a free port in the range 600-1023 will be chosen and, if the bind(2) succeeds, sin->sin_port will be updated with the port that was assigned.

If sin is the NULL pointer, a free port in the range 600-1023 will be chosen (as above), but in this case there is no way for bindresvport() to communicate to the caller which port was assigned.

RETURN VALUES
bindresvport() returns 0 if it is successful, otherwise -1 is returned and errno set to reflect the cause of the error.

ERRORS
The bindresvport() function fails if:

[EBADF]
    sd is not a valid descriptor.

[ENOTSOCK]
    sd is not a socket.

[EADDRNOTAVAIL]
    The specified address is not available from the local machine.

[EADDRINUSE]
    The specified address is already in use.

[EINVAL]
    The socket is already bound to an address.

[EINVAL]
    The family of the socket and that requested in sa->sa_family are not equivalent.

[EACCES]
    The requested address is protected, and the current user has inadequate permission to access it.

[EFAULT]
    The name parameter is not in a valid part of the user address space.

[ENOBUFS]
    Insufficient resources were available in the system to perform the operation.

[EPFNOSUPPORT]
    The protocol family has not been configured into the system, no implementation for it exists, or address family did not match between arguments.

SEE ALSO
bind(2), socket(2), rresvport(3), rresvport_af(3)