metrics: Add metrics for rendezvous and introduction request failures.

This introduces a couple of new service side metrics:
* `hs_intro_rejected_intro_req_count`, which counts the number of introduction
  requests rejected by the hidden service
* `hs_rdv_error_count`, which counts the number of rendezvous errors as seen by
  the hidden service (this number includes the number of circuit establishment
  failures, failed retries, end-to-end circuit setup failures)

Closes #40755. This partially addresses #40717.

Signed-off-by: Gabriela Moldovan <gabi@torproject.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/src/feature/hs/hs_metrics.h b/src/feature/hs/hs_metrics.h
index 2e0fa5048d..db02fefcea 100644
--- a/src/feature/hs/hs_metrics.h
+++ b/src/feature/hs/hs_metrics.h
@@ -28,13 +28,17 @@ void hs_metrics_update_by_ident(const hs_metrics_key_t key,
                                 const ed25519_public_key_t *ident_pk,
                                 const uint16_t port, int64_t n);
 void hs_metrics_update_by_service(const hs_metrics_key_t key,
-                                  hs_service_t *service, const uint16_t port,
-                                  int64_t n);
+                                  const hs_service_t *service,
+                                  uint16_t port, int64_t n);
 
 /** New introducion request received. */
 #define hs_metrics_new_introduction(s) \
   hs_metrics_update_by_service(HS_METRICS_NUM_INTRODUCTIONS, (s), 0, 1)
 
+/** Introducion request rejected. */
+#define hs_metrics_reject_intro_req(s) \
+  hs_metrics_update_by_service(HS_METRICS_NUM_REJECTED_INTRO_REQ, (s), 0, 1)
+
 /** Number of bytes written to the application from the service. */
 #define hs_metrics_app_write_bytes(i, port, n) \
   hs_metrics_update_by_ident(HS_METRICS_APP_WRITE_BYTES, (i), (port), (n))
@@ -48,6 +52,10 @@ void hs_metrics_update_by_service(const hs_metrics_key_t key,
 #define hs_metrics_new_established_rdv(s) \
   hs_metrics_update_by_service(HS_METRICS_NUM_ESTABLISHED_RDV, (s), 0, 1)
 
+/** New rendezvous circuit failure. */
+#define hs_metrics_failed_rdv(i) \
+  hs_metrics_update_by_ident(HS_METRICS_NUM_FAILED_RDV, (i), 0, 1)
+
 /** Established rendezvous closed. This is called when the circuit in
  * REND_JOINED state is marked for close. */
 #define hs_metrics_close_established_rdv(i) \