IPC(3X) IPC(3X)
NAME
ipccreat, ipcopen, ipclisten, ipcaccept, ipcreject, ipcexec,
ipcpath , ipclogin, ipcrogin - set up connections between
processes or machines
SYNOPSIS
#include <ipc.h>
char *ipcpath(name, network, service)
char *name;
char *network;
char *service;
int ipcopen(name, param)
char *name;
char *param;
int ipccreat(name, param)
char *name;
char *param;
ipcinfo *ipclisten(fd)
int fd;
int ipcaccept(ip)
ipcinfo *ip;
int ipcreject(ip, no, str)
ipcinfo *ip;
int no;
char *str;
int ipcexec(name, param, cmd)
char *name;
char *param;
char *cmd;
int ipclogin(fd)
int fd;
int ipcrogin(fd, opt)
int fd;
char *opt;
extern char *errstr;
DESCRIPTION
These routines establish communication between unrelated
processes, often for networking purposes. They are loaded
by the -lipc option of ld(1).
IPC(3X) IPC(3X)
End points in the network are identified by names of the
form: element[!element]... . The name is translated element
by element relative to the name space selected by the previ-
ous element. The first element is always a name in the
local file system. By convention, all network interfaces
and services mount themselves in For example:
/cs/exec
refers to a local process which has mounted itself (via
ipccreat ) on
/cs/dk!nj/astro/voice
refers to a voice synthesizer attached to Datakit; pro-
cess is the Datakit interface.
/cs/dk!dutoit!exec
is the process that has mounted itself on in machine
`dutoit'.
Ipcpath, forms a network name from its arguments and returns
a pointer to it. It takes three arguments: the destination
name, the default network, and the default service. It
assumes that name is a three part name of the form:
network!host!service. If either network or service is miss-
ing from name, ipcpath supplies them from the default argu-
ments. It then tacks a on the front and returns a pointer
to that. Thus,
ipcpath("dutoit", "dk", "dcon")
returns a pointer to the string `/cs/dk!dutoit!dcon'.
Ipcopen places a call to a named network end point and
returns a file descriptor for the resulting connection.
Param, a whitespace-delimited string of values, specifies
properties which the connection must have. At present four
parameter values are defined:
heavy
light Heavy (usually computer-to-computer) or light
(computer-to-terminal) traffic is expected.
delim The connection must support delimiters; see
stream(4).
hup SIGHUP must be generated at end of file; see
signal(2).
Ipccreat attaches a process to a name space. It returns a
file descriptor representing the attachment. Name and param
mean the same as for ipcopen.
Ipclisten waits for calls (from ipcopen in other processes)
appearing on file descriptor fd (obtained from ipccreat).
IPC(3X) IPC(3X)
When a call arrives, it returns an ipcinfo structure,
defined in
typedef struct {
int reserved[5];
char *name; that being dialed
char *param; parameters used to set up call
char *machine; machine id of caller
char *user; user name of caller
int uid, gid; uid, gid of caller
} ipcinfo;
The call may be accepted by ipcaccept or rejected by
ipcreject. Ipcaccept returns a file descriptor for the con-
nection. Ipcreject takes an integer error number and an
error message string, which will be passed back to the
caller as errno and errstr.
A higher-level routine, ipcexec, executes the command, cmd,
on a named machine. The file descriptor returned by ipcexec
is the standard input, standard output, and standard error
of the command. As in ipcopen, param lists properties
required of the channel.
Once a connection is established using ipcopen it is often
necessary to authenticate yourself to the destination. This
is done using ipclogin and ipcrogin. Ipclogin runs the
client side of the authentication protocol described in
svcmgr(8) for the v9auth action. The supplied fd is the
descriptor returned by ipcopen. Until the authentication is
accepted, ipclogin will prompt the user (using for a login
id and password to be sent over fd.
Ipcrogin runs the client side of the authentication protocol
used by BSD's rlogin and rsh services. Unlike ipclogin, it
will not prompt the user if the authentication fails.
Ipcrogin takes a second argument that is written to fd after
the authentication is accepted.
EXAMPLES
To connect to the voice synthesizer attached to the Datakit:
#include <ipc.h>
main() {
int fd;
fd = ipcopen(ipcpath("voice", "dk", 0), "light");
if(fd<0){
printf("can't connect: %s\n", errstr);
exit(1);
}
...
close(fd);
}
IPC(3X) IPC(3X)
To place a Dataphone call via Datakit; the service name is
derived in an obvious way from the ACU service class; see
dialout(3).
fd = ipcopen(ipcpath("9-1-201-582-0000", "dk", "dial1200"), "light");
To announce as a local service and wait for incoming calls:
#include <ipc.h>
main() {
int fd;
ipcinfo *ip;
fd = ipccreat("/tmp/service", 0);
if(fd<0){
printf("can't announce: %s\n", errstr);
exit(1);
}
while(ip = ipclisten(fd)){
int nfd;
if(i_hate_this_user(ip->machine, ip->user)) {
ipcreject(ip, EACCES, "i hate you");
continue;
}
nfd = ipcaccept(ip);
...
close(nfd);
}
printf("lost the announced connection somehow\n");
exit(1);
}
FILES
the announce point for the Datakit dialer
the announce point for the internet dialer
SEE ALSO
dialout(3), connld(4), dkmgr(8), svcmgr(8), tcpmgr(8)
D. L. Presotto, `Interprocess Communication in the Eighth
Edition UNIX System', this manual, Volume 2
DIAGNOSTICS
Integer return values of -1 and pointer return values of 0
denote error. Errno contains an error code (see intro(2))
and errstr points to an explanatory string.
BUGS
Files created by ipccreat in the local name space are not
removed when the file descriptor returned by ipccreat is
closed.
Information in ipcinfo is no more trustworthy than its ori-
gin. Information, such as user name, sent by foreign
machines may be suspect. On Ethernet or dialup connections
(but not on Datakit) machine names can be forged. Let's not
even think about wire-swappers and wiretappers.