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-rw-r--r--src/global/clnt_stream.c254
1 files changed, 254 insertions, 0 deletions
diff --git a/src/global/clnt_stream.c b/src/global/clnt_stream.c
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+/*++
+/* NAME
+/* clnt_stream 3
+/* SUMMARY
+/* client endpoint maintenance
+/* SYNOPSIS
+/* #include <clnt_stream.h>
+/*
+/* CLNT_STREAM *clnt_stream_create(class, service, timeout, ttl)
+/* const char *class;
+/* const char *service;
+/* int timeout;
+/* int ttl;
+/*
+/* 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.
+/*
+/* 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.
+/* 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
+/*--*/
+
+/* 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 */
+ 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)
+{
+
+ /*
+ * 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);
+ } else if (readable(vstream_fileno(clnt_stream->vstream))) {
+ clnt_stream_close(clnt_stream);
+ clnt_stream_open(clnt_stream);
+ } else {
+ event_request_timer(clnt_stream_event, (void *) clnt_stream,
+ clnt_stream->timeout);
+ }
+ 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 *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->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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