- NetBSD Manual Pages
BIND(2) NetBSD System Calls Manual BIND(2)
Powered by man-cgi (2021-06-01).
Maintained for NetBSD
by Kimmo Suominen.
Based on man-cgi by Panagiotis Christias.
bind -- bind a name to a socket
Standard C Library (libc, -lc)
bind(int s, const struct sockaddr *name, socklen_t namelen);
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. namelen
indicates the amount of space pointed to by name, in bytes.
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
The rules used in name binding vary between communication domains. Con-
sult the manual entries in section 4 for detailed information.
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.
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
[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
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 charac-
ters, or an entire path name exceeded PATH_MAX charac-
[ENOENT] A prefix component of the path name does not exist.
[ELOOP] Too many symbolic links were encountered in translat-
ing 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.
connect(2), getsockname(2), listen(2), socket(2)
The bind() function call appeared in 4.2BSD.
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.
bind() was changed in NetBSD 4.0 to honor the user's umask when binding
sockets in the local domain. This was done to match the behavior of
other operating systems, including FreeBSD, OpenBSD, and Linux, and to
improve compatibility with some third-party software. Please note that
this behavior is not portable. If you must bind a local socket in a por-
table and secure way, you need to make a directory with tight permissions
and then create the socket inside it.
NetBSD 5.0 August 30, 2005 NetBSD 5.0