[networking] add initial reachability signals

Bug: 36240
Change-Id: Ic699b895c2cf6d975c33a959fd582ae9cefcec3d
Reviewed-on: https://fuchsia-review.googlesource.com/c/cobalt-registry/+/392718
Reviewed-by: Mitch Rudominer <rudominer@google.com>
Commit-Queue: Bert Muthalaly <stijlist@google.com>
diff --git a/fuchsia/networking/metrics.yaml b/fuchsia/networking/metrics.yaml
index 105782a..67b5fe2 100644
--- a/fuchsia/networking/metrics.yaml
+++ b/fuchsia/networking/metrics.yaml
@@ -409,3 +409,22 @@
       local_privacy_noise_level: NONE
       window_size:
         - 1
+
+###############################################################################
+# reachability_events
+#
+# When we observe reachability events (at most once a minute), we log them.
+###############################################################################
+- id: 13
+  metric_name: reachability_events
+  metric_type: EVENT_OCCURRED
+  meta_data:
+    max_release_stage: GA
+    expiration_date: "2021/05/21"
+  metric_dimensions:
+    - dimension: reachability_event
+      event_codes:
+        0: unknown
+        1: link_state_down
+        2: link_state_up
+      max_event_code: 32