Fix assert when client aborts during backfill (#6809)

Co-authored-by: Susan Hinrichs <shinrich@verizonmedia.com>

Author: shinrich

proxy/http/Http1ClientSession.cc

@@ -264,6 +264,8 @@ Http1ClientSession::do_io_close(int alerrno)
     _reader->consume(_reader->read_avail());
   } else {
     read_state = HCS_CLOSED;
+    SET_HANDLER(&Http1ClientSession::state_wait_for_sm_shutdown);
+    ka_vio = _vc->do_io_read(this, INT64_MAX, read_buffer);
     HttpSsnDebug("[%" PRId64 "] session closed", con_id);
     HTTP_SUM_DYN_STAT(http_transactions_per_client_con, transact_count);
     HTTP_DECREMENT_DYN_STAT(http_current_client_connections_stat);
@@ -274,6 +276,16 @@ Http1ClientSession::do_io_close(int alerrno)
   }
 }
 
+int
+Http1ClientSession::state_wait_for_sm_shutdown(int event, void *data)
+{
+  STATE_ENTER(&Http1ClientSession::state_wait_for_sm_shutdown, event, data);
+  ink_assert(read_state == HCS_CLOSED);
+
+  // Just eat IO events until the state machine has finished
+  return 0;
+}
+
 int
 Http1ClientSession::state_wait_for_close(int event, void *data)
 {

proxy/http/Http1ClientSession.h

@@ -87,6 +87,7 @@ class Http1ClientSession : public ProxySession
   int state_keep_alive(int event, void *data);
   int state_slave_keep_alive(int event, void *data);
   int state_wait_for_close(int event, void *data);
+  int state_wait_for_sm_shutdown(int event, void *data);
 
   enum C_Read_State {
     HCS_INIT,
@@ -96,11 +97,10 @@ class Http1ClientSession : public ProxySession
     HCS_CLOSED,
   };
 
-  NetVConnection *client_vc = nullptr;
-  int magic                 = HTTP_SS_MAGIC_DEAD;
-  int transact_count        = 0;
-  bool half_close           = false;
-  bool conn_decrease        = false;
+  int magic          = HTTP_SS_MAGIC_DEAD;
+  int transact_count = 0;
+  bool half_close    = false;
+  bool conn_decrease = false;
 
   MIOBuffer *read_buffer  = nullptr;
   IOBufferReader *_reader = nullptr;

proxy/http/HttpSM.cc

@@ -3271,6 +3271,11 @@ HttpSM::tunnel_handler_ua(int event, HttpTunnelConsumer *c)
         server_session->get_netvc()->set_active_timeout(HRTIME_SECONDS(t_state.txn_conf->background_fill_active_timeout));
       }
 
+      // Even with the background fill, the client side should go down
+      c->write_vio = nullptr;
+      c->vc->do_io_close(EHTTP_ERROR);
+      c->alive = false;
+
     } else {
       // No background fill
       p = c->producer;