Alex Ward created DISPATCH-2046:
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Summary: Panic in handle due to deleted connector.
Key: DISPATCH-2046
URL: https://issues.apache.org/jira/browse/DISPATCH-2046
Project: Qpid Dispatch
Issue Type: Bug
Components: Routing Engine
Affects Versions: 1.15.0
Reporter: Alex Ward
I am seeing a segv at line 1063 due to ctx->connector being 0 in
server.c:handle().
ugdb-x86_64-7.11-261) p *ctx
$7 = {prev = 0x8023df490, next = 0x802e7a890, name = 0x0, server = 0x80220d0c0,
opened = false, closed = false, closed_locally = false, enqueued = 0, timer =
0x0, pn_conn = 0x8023ec050, pn_sessions = {0x0 <repeats 15 times>}, ssl = 0x0,
listener = 0x0, connector = 0x0, connector_lock = 0x8023e6600, context = 0x0,
user_context = 0x0, link_context = 0x0, connection_id = 12, user_id = 0x0,
free_user_id = false, policy_settings = 0x0, n_sessions = 0, n_senders = 0,
n_receivers = 0, open_container = 0x0, deferred_calls = {head = 0x0, tail =
0x0, scratch = 0x0, size = 0}, deferred_call_lock = 0x8023e65c0, policy_counted
= false, role = 0x801a17660 "route-container", free_link_session_list = {head =
0x0, tail = 0x0, scratch = 0x0, size = 0}, strip_annotations_in = false,
strip_annotations_out = false, wake = 0x8005d6e20 <connection_wake>, rhost =
'\000' <repeats 1024 times>, rhost_port = '\000' <repeats 1056 times>}
As the comment at the start of handle() states, there is only one event being
handled at a time, but it doesn’t look like there is anything to stop someone
clearing ctx->connector between lines 1055 and 1063. The python code seems to
be comin in and deleting the connector while handle is using it
https://github.com/apache/qpid-dispatch/blob/main/src/server.c
989 /* Events involving a connection or listener are serialized by the
proactor so
990 * only one event per connection / listener will be processed at a time.
991 */
992 static bool handle(qd_server_t *qd_server, pn_event_t *e, pn_connection_t
*pn_conn, qd_connection_t *ctx)
993 {
994 if (pn_conn && qdr_is_authentication_service_connection(pn_conn)) {
995 qdr_handle_authentication_service_connection_event(e);
996 return true;
997 }
998
999 switch (pn_event_type(e)) {
…
1051 case PN_TRANSPORT_ERROR:
1052 {
1053 pn_transport_t *transport = pn_event_transport(e);
1054 pn_condition_t* condition = transport ?
pn_transport_condition(transport) : NULL;
1055 if (ctx && ctx->connector) { /* Outgoing connection */
1056 qd_increment_conn_index(ctx);
1057 const qd_server_config_t *config =
&ctx->connector->config;
1058 ctx->connector->state = CXTR_STATE_FAILED;
1059 char conn_msg[300];
1060 if (condition && pn_condition_is_set(condition)) {
1061 qd_format_string(conn_msg, 300, "[C%"PRIu64"]
Connection to %s failed: %s %s", ctx->co nnection_id, config->host_port,
1062 pn_condition_get_name(condition),
pn_condition_get_description(condition));
1063 strcpy(ctx->connector->conn_msg, conn_msg);
1064
1065 qd_log(qd_server->log_source, QD_LOG_INFO, conn_msg);
1066 } else {
Another thread is at line 1063 in qd_connection_manager_delete_connector so it
looks like this thread just cleared ctx->connector that is being used in
handle. What is meant to be preventing this happening?
https://github.com/apache/qpid-dispatch/blob/main/src/connection_manager.c
1055 void qd_connection_manager_delete_connector(qd_dispatch_t *qd, void *impl)
1056 {
1057 qd_connector_t *ct = (qd_connector_t*) impl;
1058 if (ct) {
1059 sys_mutex_lock(ct->lock);
1060 if (ct->ctx) {
1061 ct->ctx->connector = 0;
1062 if(ct->ctx->pn_conn)
1063 qd_connection_invoke_deferred(ct->ctx, deferred_close,
ct->ctx->pn_conn);
1064
1065 }
1066 sys_mutex_unlock(ct->lock);
1067 DEQ_REMOVE(qd->connection_manager->connectors, ct);
1068 qd_connector_decref(ct);
1069 }
1070 }
Does anyone have any suggestions for how to prevent this? Doesn't look like I
could use ct->lock in handle().
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