1 files changed, 278 insertions, 0 deletions

diff --git a/src/global/clnt_stream.c b/src/global/clnt_stream.c
new file mode 100644
index 0000000..ca3ce4f
--- /dev/null
+++ b/src/global/clnt_stream.c
@@ -0,0 +1,278 @@
+/*++
+/* 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);
+}