|
|
|
An rpc server can be started from inetd. The only differences from the usual code are that svcudp_create should be called as:
since inet passes a socket file as descriptor 0, and svc_register should be called as:
with the final flag as 0, since the program will already have been registered by inetd. If you want to exit from the server process and return control to inet, you must explicitly exit since svc_run never returns.
Upon execution,
inetd
reads its configuration information from a configuration
file which, by default, is
/etc/inetd.conf.
There must be an entry for each field in the configuration
file, with entries for each field separated by a tab or
a space. Comments are denoted by a ``#'' at the beginning
of a line. The fields of the configuration file are as follows:
service name
socket type
protocol
wait/nowait
user
server program
server program arguments
For rpc services:
service name/version
socket type
protocol
wait/nowait
user
server program
server program arguments
The service name entry is the name of a valid service in the file /etc/services/. For ``internal'' services (discussed below), the service name must be the official name of the service (that is, the first entry in /etc/services).
For RPC services the entry is the name of a valid service in the file /etc/rpc with version = 1-x. An example might be ``mountd/1-2''
The socket type should be one of ``stream'', ``dgram'', ``raw'', ``rdm'', or ``seqpacket'', depending on whether the socket is a stream, datagram, raw, reliably delivered message, or sequenced packet socket.
The protocol must be a valid protocol as given in /etc/protocols. Examples might be ``tcp'' or ``udp''.
For RPC services the protocol is of the form rcp/protocol. Examples might be ``rpc/tcp'' or ``rpc/udp''.
The wait/nowait entry is applicable to datagram (and rpc) sockets only (other sockets should have a ``nowait'' entry in this space). If a datagram server connects to its peer, freeing the socket so inetd can received further messages on the socket, it is said to be a ``multi-threaded'' server, and should use the ``nowait'' entry. For datagram servers which process all incoming datagrams on a socket and eventually time out, the server is said to be ``single-threaded'' and should use a ``wait'' entry. ``Comsat'' (``biff'') and ``talk'' are both examples of the latter type of datagram server. Tftpd is an exception; it is a datagram server that establishes pseudo-connections. It must be listed as ``wait'' in order to avoid a race; the server reads the first packet, creates a new socket, and then forks and exits to allow inetd to check for new service requests to spawn new servers.
The user entry should contain the user name of the user as whom the server should run. This allows for servers to be given less permission than root.
The server program entry should contain the pathname of the program which is to be executed by inetd when a request is found on its socket. If inetd provides this service internally, this entry should be ``internal''.
The arguments to the server program should be just as they normally are, starting with argv[0], which is the name of the program. If the service is provided internally, the word ``internal'' should take the place of this entry.
Inetd provides several ``trivial'' services internally by use of routines within itself. These services are ``echo'', ``discard'', ``chargen'' (character generator), ``daytime'' (human readable time), and ``time'' (machine readable time, in the form of the number of seconds since midnight, January 1, 1900). All of these services are tcp based. For details of these services, consult the appropriate RFC from the Network Information Center.
Inetd rereads its configuration file when it receives a hangup signal, SIGHUP. Services may be added, deleted or modified when the configuration file is reread.
|
|
|
Created by unroff & hp-tools. © somebody (See intro for details). All Rights Reserved. Last modified 11/5/97