metrics: Add stats for num circ reaching max cell outq

Part of #40708

Signed-off-by: David Goulet <dgoulet@torproject.org>

src/core/or/relay.c

@@ -128,6 +128,7 @@ uint64_t stats_n_relay_cells_delivered = 0;
 /** Stats: how many circuits have we closed due to the cell queue limit being
  * reached (see append_cell_to_circuit_queue()) */
 uint64_t stats_n_circ_max_cell_reached = 0;
+uint64_t stats_n_circ_max_cell_outq_reached = 0;
 
 /**
  * Update channel usage state based on the type of relay cell and
@@ -3252,6 +3253,7 @@ append_cell_to_circuit_queue(circuit_t *circ, channel_t *chan,
     /* This DoS defense only applies at the Guard as in the p_chan is likely
      * a client IP attacking the network. */
     if (exitward && CIRCUIT_IS_ORCIRC(circ)) {
+      stats_n_circ_max_cell_outq_reached++;
       dos_note_circ_max_outq(CONST_TO_OR_CIRCUIT(circ)->p_chan);
     }
 

src/core/or/relay.h

@@ -15,6 +15,7 @@
 extern uint64_t stats_n_relay_cells_relayed;
 extern uint64_t stats_n_relay_cells_delivered;
 extern uint64_t stats_n_circ_max_cell_reached;
+extern uint64_t stats_n_circ_max_cell_outq_reached;
 
 const char *relay_command_to_string(uint8_t command);
 

src/feature/relay/relay_metrics.c

@@ -314,6 +314,12 @@ fill_dos_values(void)
           metrics_format_label("type", "circuit_killed_max_cell"));
   metrics_store_entry_update(sentry, stats_n_circ_max_cell_reached);
 
+  sentry = metrics_store_add(the_store, rentry->type, rentry->name,
+                             rentry->help);
+  metrics_store_entry_add_label(sentry,
+          metrics_format_label("type", "circuit_killed_max_cell_outq"));
+  metrics_store_entry_update(sentry, stats_n_circ_max_cell_outq_reached);
+
   sentry = metrics_store_add(the_store, rentry->type, rentry->name,
                              rentry->help);
   metrics_store_entry_add_label(sentry,