This patch is for debugging LDAP hangs. If LDAP server loses requests,
this patch will complain about that. Doesn't look like this happens though.

Index: src/auth/db-ldap.c
===================================================================
RCS file: /var/lib/cvs/dovecot/src/auth/db-ldap.c,v
retrieving revision 1.41.2.7
diff -u -r1.41.2.7 db-ldap.c
--- src/auth/db-ldap.c	22 Sep 2006 13:26:44 -0000	1.41.2.7
+++ src/auth/db-ldap.c	15 Oct 2006 17:02:12 -0000
@@ -37,6 +37,9 @@
 #  define LDAP_OPT_SUCCESS LDAP_SUCCESS
 #endif
 
+#define LDAP_REQUEST_TIMEOUT 60
+#define LDAP_TIMEOUT_CHECK_INTERVAL 10
+
 #define DEF(type, name) \
 	{ type, #name, offsetof(struct ldap_settings, name) }
 
@@ -150,6 +153,8 @@
 		}
 	}
 
+	request->sent = ioloop_time;
+
 	msgid = ldap_search(conn->ld, request->base, scope,
 			    request->filter, request->attributes, 0);
 	if (msgid == -1) {
@@ -162,6 +167,29 @@
 	hash_insert(conn->requests, POINTER_CAST(msgid), request);
 }
 
+#ifdef LDAP_REQUEST_TIMEOUT
+static void ldap_requests_check_timeouts(void *context)
+{
+	struct ldap_connection *conn = context;
+	struct hash_iterate_context *iter;
+	void *key, *value;
+
+	iter = hash_iterate_init(conn->requests);
+	while (hash_iterate(iter, &key, &value)) {
+		struct ldap_request *request = value;
+
+		if (ioloop_time - request->sent >= LDAP_REQUEST_TIMEOUT) {
+			i_error("LDAP: Request timed out: base=%s, filter=%s",
+				request->base, request->filter);
+			hash_remove(conn->requests, key);
+			request->callback(conn, request, NULL);
+		}
+	}
+	hash_iterate_deinit(iter);
+	hash_clear(conn->requests, FALSE);
+}
+#endif
+
 static void ldap_conn_retry_requests(struct ldap_connection *conn)
 {
 	struct hash_table *old_requests;
@@ -373,6 +401,10 @@
 
 	net_set_nonblock(fd, TRUE);
 	conn->io = io_add(fd, IO_READ, ldap_input, conn);
+#ifdef LDAP_REQUEST_TIMEOUT
+	conn->to = timeout_add(LDAP_TIMEOUT_CHECK_INTERVAL,
+			       ldap_requests_check_timeouts, conn);
+#endif
 
 	/* in case there are requests waiting, retry them */
         ldap_conn_retry_requests(conn);
@@ -399,6 +431,8 @@
 
 	if (conn->io != NULL)
 		io_remove(&conn->io);
+	if (conn->to != NULL)
+		timeout_remove(&conn->to);
 
 	if (conn->ld != NULL) {
 		ldap_unbind(conn->ld);
Index: src/auth/db-ldap.h
===================================================================
RCS file: /var/lib/cvs/dovecot/src/auth/db-ldap.h,v
retrieving revision 1.20.2.4
diff -u -r1.20.2.4 db-ldap.h
--- src/auth/db-ldap.h	19 Jun 2006 16:10:04 -0000	1.20.2.4
+++ src/auth/db-ldap.h	15 Oct 2006 17:02:12 -0000
@@ -57,6 +57,7 @@
 
 	LDAP *ld;
 	struct io *io;
+	struct timeout *to;
 	struct hash_table *requests;
 
 	char **pass_attr_names, **user_attr_names;
@@ -69,6 +70,8 @@
 	db_search_callback_t *callback;
 	void *context;
 
+	time_t sent;
+
 	const char *base;
 	const char *filter;
 	char **attributes; /* points to pass_attr_names / user_attr_names */