bind(2) - NetBSD Manual Pages

BIND(2)                   NetBSD Programmer's Manual                   BIND(2)


NAME

     bind - bind a name to a socket


LIBRARY

     Standard C Library (libc, -lc)


SYNOPSIS

     #include <sys/types.h>
     #include <sys/socket.h>

     int
     bind(int s, const struct sockaddr *name, socklen_t namelen);


DESCRIPTION

     bind() assigns a name to an unnamed socket.  When a socket is created
     with socket(2) it exists in a name space (address family) but has no name
     assigned.  bind() requests that name be assigned to the socket.


NOTES

     Binding a name in the UNIX domain creates a socket in the file system
     that must be deleted by the caller when it is no longer needed (using
     unlink(2)).

     The rules used in name binding vary between communication domains.  Con-
     sult the manual entries in section 4 for detailed information.


RETURN VALUES

     If the bind is successful, a 0 value is returned.  A return value of -1
     indicates an error, which is further specified in the global errno.


ERRORS

     The bind() call will fail if:

     [EBADF]       s is not a valid descriptor.

     [ENOTSOCK]    s is not a socket.

     [EADDRNOTAVAIL]
                   The specified address is not available from the local ma-
                   chine.

     [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
                   name->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 ad-
                   dress space.

     The following errors are specific to binding names in the UNIX domain.

     [ENOTDIR]     A component of the path prefix is not a directory.

     [ENAMETOOLONG]
                   A component of a pathname exceeded {NAME_MAX} characters,
                   or an entire path name exceeded {PATH_MAX} characters.

     [ENOENT]      A prefix component of the path name does not exist.

     [ELOOP]       Too many symbolic links were encountered in translating the
                   pathname.

     [EIO]         An I/O error occurred while making the directory entry or
                   allocating the inode.

     [EROFS]       The name would reside on a read-only file system.

     [EISDIR]      An empty pathname was specified.


SEE ALSO

     connect(2), listen(2), socket(2), getsockname(2)


HISTORY

     The bind() function call appeared in 4.2BSD.


SECURITY CONSIDERATIONS

     bind() was changed in NetBSD 1.4 to prevent the binding of a socket to
     the same port as an existing socket when all of the following is true:
           +   either of the existing or new addresses is INADDR_ANY,
           +   the uid of the new socket is not root, and the uids of the cre-
               ators of the sockets are different,
           +   the address is not a multicast address, and
           +   both sockets are not bound to INADDR_ANY with SO_REUSEPORT set.

     This prevents an attack where a user could bind to a port with the host's
     IP address (after setting SO_REUSEADDR) and `steal' packets destined for
     a server that bound to the same port with INADDR_ANY.

NetBSD 1.5                      March 23, 1999                               2