NAME
bind —
bind a name to a socket
LIBRARY
Standard C Library (libc, -lc)
SYNOPSIS
#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.
namelen indicates the amount of space
pointed to by
name, in bytes.
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. Consult 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:
-
-
- [
EACCES
]
- The requested address is protected, and the current user
has inadequate permission to access it.
-
-
- [
EADDRINUSE
]
- The specified address is already in use.
-
-
- [
EADDRNOTAVAIL
]
- The specified address is not available from the local
machine.
-
-
- [
EAFNOSUPPORT
]
- Addresses in the specified address family cannot be used
with this socket.
-
-
- [
EBADF
]
- s is not a valid descriptor.
-
-
- [
EFAULT
]
- The name parameter is not in a valid
part of the user address space.
-
-
- [
EINVAL
]
- The socket is already bound to an address; or the family of
the socket and that requested in name->sa_family
are not equivalent.
-
-
- [
ENOTSOCK
]
- s is not a socket.
The following errors are specific to binding names in the
UNIX domain.
-
-
- [
EIO
]
- An I/O error occurred while making the directory entry or
allocating the inode.
-
-
- [
EISDIR
]
- An empty pathname was specified.
-
-
- [
ELOOP
]
- Too many symbolic links were encountered in translating the
pathname.
-
-
- [
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.
-
-
- [
ENOTDIR
]
- A component of the path prefix is not a directory.
-
-
- [
EROFS
]
- The name would reside on a read-only file system.
SEE ALSO
connect(2),
getsockname(2),
listen(2),
socket(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 creators 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 portable and secure way, you need to make a directory with tight
permissions and then create the socket inside it.