s4:rpc_server: make sure we don't terminate a connection with pending requests (bug #9820)

Sadly we may have nested event loops, which won't work correctly with
broken connections, that's why we have to do this...

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

Autobuild-User(master): Stefan Metzmacher <metze@samba.org>
Autobuild-Date(master): Wed Jul 10 08:47:38 CEST 2013 on sn-devel-104

source4/rpc_server/dcerpc_server.c

@@ -386,6 +386,8 @@ _PUBLIC_ NTSTATUS dcesrv_endpoint_connect(struct dcesrv_context *dce_ctx,
 		return NT_STATUS_NO_MEMORY;
 	}
 
+	p->prev = NULL;
+	p->next = NULL;
 	p->dce_ctx = dce_ctx;
 	p->endpoint = ep;
 	p->contexts = NULL;
@@ -402,7 +404,7 @@ _PUBLIC_ NTSTATUS dcesrv_endpoint_connect(struct dcesrv_context *dce_ctx,
 	p->event_ctx = event_ctx;
 	p->msg_ctx = msg_ctx;
 	p->server_id = server_id;
-	p->processing = false;
+	p->terminate = NULL;
 	p->state_flags = state_flags;
 	ZERO_STRUCT(p->transport);
 
@@ -1143,6 +1145,7 @@ _PUBLIC_ NTSTATUS dcesrv_init_context(TALLOC_CTX *mem_ctx,
 	dce_ctx->lp_ctx = lp_ctx;
 	dce_ctx->assoc_groups_idr = idr_init(dce_ctx);
 	NT_STATUS_HAVE_NO_MEMORY(dce_ctx->assoc_groups_idr);
+	dce_ctx->broken_connections = NULL;
 
 	for (i=0;endpoint_servers[i];i++) {
 		const struct dcesrv_endpoint_server *ep_server;
@@ -1269,12 +1272,45 @@ const struct dcesrv_critical_sizes *dcerpc_module_version(void)
 
 static void dcesrv_terminate_connection(struct dcesrv_connection *dce_conn, const char *reason)
 {
+	struct dcesrv_context *dce_ctx = dce_conn->dce_ctx;
 	struct stream_connection *srv_conn;
 	srv_conn = talloc_get_type(dce_conn->transport.private_data,
 				   struct stream_connection);
 
-	stream_terminate_connection(srv_conn, reason);
+	if (dce_conn->pending_call_list == NULL) {
+		char *full_reason = talloc_asprintf(dce_conn, "dcesrv: %s", reason);
+
+		DLIST_REMOVE(dce_ctx->broken_connections, dce_conn);
+		stream_terminate_connection(srv_conn, full_reason ? full_reason : reason);
+		return;
+	}
+
+	if (dce_conn->terminate != NULL) {
+		return;
+	}
+
+	DEBUG(3,("dcesrv: terminating connection due to '%s' defered due to pending calls\n",
+		 reason));
+	dce_conn->terminate = talloc_strdup(dce_conn, reason);
+	if (dce_conn->terminate == NULL) {
+		dce_conn->terminate = "dcesrv: defered terminating connection - no memory";
+	}
+	DLIST_ADD_END(dce_ctx->broken_connections, dce_conn, NULL);
 }
+
+static void dcesrv_cleanup_broken_connections(struct dcesrv_context *dce_ctx)
+{
+	struct dcesrv_connection *cur, *next;
+
+	next = dce_ctx->broken_connections;
+	while (next != NULL) {
+		cur = next;
+		next = cur->next;
+
+		dcesrv_terminate_connection(cur, cur->terminate);
+	}
+}
+
 /* We need this include to be able to compile on some plateforms
  * (ie. freebsd 7.2) as it seems that <sys/uio.h> is not included
  * correctly.
@@ -1386,6 +1422,8 @@ static void dcesrv_sock_accept(struct stream_connection *srv_conn)
 	struct tevent_req *subreq;
 	struct loadparm_context *lp_ctx = dcesrv_sock->dcesrv_ctx->lp_ctx;
 
+	dcesrv_cleanup_broken_connections(dcesrv_sock->dcesrv_ctx);
+
 	if (!srv_conn->session_info) {
 		status = auth_anonymous_session_info(srv_conn,
 						     lp_ctx,
@@ -1473,10 +1511,23 @@ static void dcesrv_read_fragment_done(struct tevent_req *subreq)
 {
 	struct dcesrv_connection *dce_conn = tevent_req_callback_data(subreq,
 					     struct dcesrv_connection);
+	struct dcesrv_context *dce_ctx = dce_conn->dce_ctx;
 	struct ncacn_packet *pkt;
 	DATA_BLOB buffer;
 	NTSTATUS status;
 
+	if (dce_conn->terminate) {
+		/*
+		 * if the current connection is broken
+		 * we need to clean it up before any other connection
+		 */
+		dcesrv_terminate_connection(dce_conn, dce_conn->terminate);
+		dcesrv_cleanup_broken_connections(dce_ctx);
+		return;
+	}
+
+	dcesrv_cleanup_broken_connections(dce_ctx);
+
 	status = dcerpc_read_ncacn_packet_recv(subreq, dce_conn,
 					       &pkt, &buffer);
 	TALLOC_FREE(subreq);

source4/rpc_server/dcerpc_server.h

@@ -170,6 +170,9 @@ struct dcesrv_connection_context {
 
 /* the state associated with a dcerpc server connection */
 struct dcesrv_connection {
+	/* for the broken_connections DLIST */
+	struct dcesrv_connection *prev, *next;
+
 	/* the top level context for this server */
 	struct dcesrv_context *dce_ctx;
 
@@ -208,7 +211,8 @@ struct dcesrv_connection {
 	/* the transport level session key */
 	DATA_BLOB transport_session_key;
 
-	bool processing;
+	/* is this connection pending termination?  If so, why? */
+	const char *terminate;
 
 	const char *packet_log_dir;
 
@@ -288,6 +292,8 @@ struct dcesrv_context {
 	struct loadparm_context *lp_ctx;
 
 	struct idr_context *assoc_groups_idr;
+
+	struct dcesrv_connection *broken_connections;
 };
 
 /* this structure is used by modules to determine the size of some critical types */