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/*++
/* NAME
/* clnt_stream 3
/* SUMMARY
/* client endpoint maintenance
/* SYNOPSIS
/* #include <clnt_stream.h>
/*
/* typedef void (*CLNT_STREAM_HANDSHAKE_FN)(VSTREAM *)
/*
/* CLNT_STREAM *clnt_stream_create(class, service, timeout, ttl,
/* handshake)
/* const char *class;
/* const char *service;
/* int timeout;
/* int ttl;
/* CLNT_STREAM_HANDSHAKE_FN *handshake;
/*
/* VSTREAM *clnt_stream_access(clnt_stream)
/* CLNT_STREAM *clnt_stream;
/*
/* void clnt_stream_recover(clnt_stream)
/* CLNT_STREAM *clnt_stream;
/*
/* void clnt_stream_free(clnt_stream)
/* CLNT_STREAM *clnt_stream;
/* DESCRIPTION
/* This module maintains local IPC client endpoints that automatically
/* disconnect after a being idle for a configurable amount of time,
/* that disconnect after a configurable time to live,
/* and that transparently handle most server-initiated disconnects.
/* Server disconnect is detected by read-selecting the client endpoint.
/* The code assumes that the server has disconnected when the endpoint
/* becomes readable.
/*
/* clnt_stream_create() instantiates a client endpoint.
/*
/* clnt_stream_access() returns an open stream to the service specified
/* to clnt_stream_create(). The stream instance may change between calls.
/* This function returns null when the handshake function returned an
/* error.
/*
/* clnt_stream_recover() recovers from a server-initiated disconnect
/* that happened in the middle of an I/O operation.
/*
/* clnt_stream_free() destroys of the specified client endpoint.
/*
/* Arguments:
/* .IP class
/* The service class, private or public.
/* .IP service
/* The service endpoint name. The name is limited to local IPC
/* over sockets or equivalent.
/* .IP timeout
/* Idle time after which the client disconnects.
/* .IP ttl
/* Upper bound on the time that a connection is allowed to persist.
/* .IP handshake
/* Null pointer, or pointer to function that will be called
/* at the start of a new connection and that returns 0 in case
/* of success.
/* DIAGNOSTICS
/* Warnings: communication failure. Fatal error: mail system is down,
/* out of memory.
/* SEE ALSO
/* mail_proto(3h) low-level mail component glue.
/* LICENSE
/* .ad
/* .fi
/* The Secure Mailer license must be distributed with this software.
/* AUTHOR(S)
/* Wietse Venema
/* IBM T.J. Watson Research
/* P.O. Box 704
/* Yorktown Heights, NY 10598, USA
/*
/* Wietse Venema
/* Google, Inc.
/* 111 8th Avenue
/* New York, NY 10011, USA
/*--*/
/* System library. */
#include <sys_defs.h>
/* Utility library. */
#include <msg.h>
#include <mymalloc.h>
#include <vstream.h>
#include <events.h>
#include <iostuff.h>
/* Global library. */
#include "mail_proto.h"
#include "mail_params.h"
#include "clnt_stream.h"
/* Application-specific. */
/*
* CLNT_STREAM is an opaque structure. None of the access methods can easily
* be implemented as a macro, and access is not performance critical anyway.
*/
struct CLNT_STREAM {
VSTREAM *vstream; /* buffered I/O */
int timeout; /* time before client disconnect */
int ttl; /* time before client disconnect */
CLNT_STREAM_HANDSHAKE_FN handshake;
char *class; /* server class */
char *service; /* server name */
};
static void clnt_stream_close(CLNT_STREAM *);
/* clnt_stream_event - server-initiated disconnect or client-side timeout */
static void clnt_stream_event(int unused_event, void *context)
{
CLNT_STREAM *clnt_stream = (CLNT_STREAM *) context;
/*
* Sanity check. This routine causes the stream to be closed, so it
* cannot be called when the stream is already closed.
*/
if (clnt_stream->vstream == 0)
msg_panic("clnt_stream_event: stream is closed");
clnt_stream_close(clnt_stream);
}
/* clnt_stream_ttl_event - client-side expiration */
static void clnt_stream_ttl_event(int event, void *context)
{
/*
* XXX This function is needed only because event_request_timer() cannot
* distinguish between requests that specify the same call-back routine
* and call-back context. The fix is obvious: specify a request ID along
* with the call-back routine, but there is too much code that would have
* to be changed.
*
* XXX Should we be concerned that an overly aggressive optimizer will
* eliminate this function and replace calls to clnt_stream_ttl_event()
* by direct calls to clnt_stream_event()? It should not, because there
* exists code that takes the address of both functions.
*/
clnt_stream_event(event, context);
}
/* clnt_stream_open - connect to service */
static void clnt_stream_open(CLNT_STREAM *clnt_stream)
{
/*
* Sanity check.
*/
if (clnt_stream->vstream)
msg_panic("clnt_stream_open: stream is open");
/*
* Schedule a read event so that we can clean up when the remote side
* disconnects, and schedule a timer event so that we can cleanup an idle
* connection. Note that both events are handled by the same routine.
*
* Finally, schedule an event to force disconnection even when the
* connection is not idle. This is to prevent one client from clinging on
* to a server forever.
*/
clnt_stream->vstream = mail_connect_wait(clnt_stream->class,
clnt_stream->service);
close_on_exec(vstream_fileno(clnt_stream->vstream), CLOSE_ON_EXEC);
event_enable_read(vstream_fileno(clnt_stream->vstream), clnt_stream_event,
(void *) clnt_stream);
event_request_timer(clnt_stream_event, (void *) clnt_stream,
clnt_stream->timeout);
event_request_timer(clnt_stream_ttl_event, (void *) clnt_stream,
clnt_stream->ttl);
}
/* clnt_stream_close - disconnect from service */
static void clnt_stream_close(CLNT_STREAM *clnt_stream)
{
/*
* Sanity check.
*/
if (clnt_stream->vstream == 0)
msg_panic("clnt_stream_close: stream is closed");
/*
* Be sure to disable read and timer events.
*/
if (msg_verbose)
msg_info("%s stream disconnect", clnt_stream->service);
event_disable_readwrite(vstream_fileno(clnt_stream->vstream));
event_cancel_timer(clnt_stream_event, (void *) clnt_stream);
event_cancel_timer(clnt_stream_ttl_event, (void *) clnt_stream);
(void) vstream_fclose(clnt_stream->vstream);
clnt_stream->vstream = 0;
}
/* clnt_stream_recover - recover from server-initiated disconnect */
void clnt_stream_recover(CLNT_STREAM *clnt_stream)
{
/*
* Clean up. Don't re-connect until the caller needs it.
*/
if (clnt_stream->vstream)
clnt_stream_close(clnt_stream);
}
/* clnt_stream_access - access a client stream */
VSTREAM *clnt_stream_access(CLNT_STREAM *clnt_stream)
{
CLNT_STREAM_HANDSHAKE_FN handshake;
/*
* Open a stream or restart the idle timer.
*
* Important! Do not restart the TTL timer!
*/
if (clnt_stream->vstream == 0) {
clnt_stream_open(clnt_stream);
handshake = clnt_stream->handshake;
} else if (readable(vstream_fileno(clnt_stream->vstream))) {
clnt_stream_close(clnt_stream);
clnt_stream_open(clnt_stream);
handshake = clnt_stream->handshake;
} else {
event_request_timer(clnt_stream_event, (void *) clnt_stream,
clnt_stream->timeout);
handshake = 0;
}
if (handshake != 0 && handshake(clnt_stream->vstream) != 0)
return (0);
return (clnt_stream->vstream);
}
/* clnt_stream_create - create client stream connection */
CLNT_STREAM *clnt_stream_create(const char *class, const char *service,
int timeout, int ttl,
CLNT_STREAM_HANDSHAKE_FN handshake)
{
CLNT_STREAM *clnt_stream;
/*
* Don't open the stream until the caller needs it.
*/
clnt_stream = (CLNT_STREAM *) mymalloc(sizeof(*clnt_stream));
clnt_stream->vstream = 0;
clnt_stream->timeout = timeout;
clnt_stream->ttl = ttl;
clnt_stream->handshake = handshake;
clnt_stream->class = mystrdup(class);
clnt_stream->service = mystrdup(service);
return (clnt_stream);
}
/* clnt_stream_free - destroy client stream instance */
void clnt_stream_free(CLNT_STREAM *clnt_stream)
{
if (clnt_stream->vstream)
clnt_stream_close(clnt_stream);
myfree(clnt_stream->class);
myfree(clnt_stream->service);
myfree((void *) clnt_stream);
}
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