1 .\" Copyright (c) 1991, 1993
2 .\" The Regents of the University of California. All rights reserved.
4 .\" Redistribution and use in source and binary forms, with or without
5 .\" modification, are permitted provided that the following conditions
7 .\" 1. Redistributions of source code must retain the above copyright
8 .\" notice, this list of conditions and the following disclaimer.
9 .\" 2. Redistributions in binary form must reproduce the above copyright
10 .\" notice, this list of conditions and the following disclaimer in the
11 .\" documentation and/or other materials provided with the distribution.
12 .\" 3. All advertising materials mentioning features or use of this software
13 .\" must display the following acknowledgement:
14 .\" This product includes software developed by the University of
15 .\" California, Berkeley and its contributors.
16 .\" 4. Neither the name of the University nor the names of its contributors
17 .\" may be used to endorse or promote products derived from this software
18 .\" without specific prior written permission.
20 .\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 .\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 .\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 .\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 .\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 .\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 .\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
32 .\" @(#)unix.4 8.1 (Berkeley) 6/9/93
40 .Nd UNIX-domain protocol family
47 protocol family is a collection of protocols
48 that provides local (on-machine) interprocess
49 communication through the normal
60 file system pathnames for addressing.
63 addresses are variable-length file system pathnames of
64 at most 104 characters.
68 .Bd -literal -offset indent
80 causes a socket file to be created in the file system.
83 removed when the socket is closed \(em
85 must be used to remove the file.
93 can be calculated by the macro
99 field must be terminated by a
101 character to be used with
111 protocol family does not support broadcast addressing or any form
114 matching on incoming messages.
115 All addresses are absolute- or relative-pathnames
119 Normal file system access-control mechanisms are also
120 applied when referencing pathnames; e.g., the destination
126 .Sh PASSING FILE DESCRIPTORS
129 sockets support the communication of
131 file descriptors through the use of the
140 Any valid descriptor may be sent in a message.
141 The file descriptor(s) to be passed are described using a
143 that is defined in the include file
145 The type of the message is
147 and the data portion of the messages is an array of integers
148 representing the file descriptors to be passed.
149 The number of descriptors being passed is defined
150 by the length field of the message;
151 the length field is the sum of the size of the header
152 plus the size of the array of file descriptors.
154 The received descriptor is a
156 of the sender's descriptor, as if it were created with a call to
158 Per-process descriptor flags, set with
162 passed to a receiver.
163 Descriptors that are awaiting delivery, or that are
164 purposely not received, are automatically closed by the system
165 when the destination socket is closed.
168 domain sockets support a number of socket options which can be set with
172 .Bl -tag -width ".Dv LOCAL_CONNWAIT"
174 This option may be enabled on
180 This option provides a mechanism for the receiver to
181 receive the credentials of the process as a
188 structure points to a buffer that contains a
190 structure followed by a variable length
192 structure, defined in
197 uid_t sc_uid; /* real user id */
198 uid_t sc_euid; /* effective user id */
199 gid_t sc_gid; /* real group id */
200 gid_t sc_egid; /* effective group id */
201 int sc_ngroups; /* number of supplemental groups */
202 gid_t sc_groups[1]; /* variable length */
208 macro computes the size of the
210 structure for a specified number
214 fields have the following values:
216 cmsg_len = CMSG_LEN(SOCKCREDSIZE(ngroups))
217 cmsg_level = SOL_SOCKET
218 cmsg_type = SCM_CREDS
225 sockets credentials are passed only on the first read from a socket,
226 then system clears the option on socket.
227 .It Dv LOCAL_CONNWAIT
230 sockets, this option causes the
232 function to block until
234 has been called on the listening socket.
235 .It Dv LOCAL_PEERCRED
240 socket returns credentials of the remote side.
241 These will arrive in the form of a filled in
243 structure, defined in
248 u_int cr_version; /* structure layout version */
249 uid_t cr_uid; /* effective user id */
250 short cr_ngroups; /* number of groups */
251 gid_t cr_groups[XU_NGROUPS]; /* groups */
256 fields should be checked against
260 The credentials presented to the server (the
262 caller) are those of the client when it called
264 the credentials presented to the client (the
266 caller) are those of the server when it called
268 This mechanism is reliable; there is no way for either party to influence
269 the credentials presented to its peer except by calling the appropriate
274 under different effective credentials.
276 To reliably obtain peer credentials on a
294 .%T "An Introductory 4.3 BSD Interprocess Communication Tutorial"
299 .%T "An Advanced 4.3 BSD Interprocess Communication Tutorial"