From de002f99037a5017c4d6d43dca289994dce94832 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Sat, 17 Jan 2026 11:36:37 -0600
Subject: [PATCH] Cap storage/memory usage sensors at 100% to handle device
 firmware bugs

Fixes an issue where storage usage was reporting values over 200,000% due to
incorrect SNMP values from the device. This can occur when:
- Device firmware has bugs in hrStorageUsed/hrStorageSize reporting
- SNMP allocation units differ between OIDs
- Values are read during device reconfiguration

Changes:
- PollerWorker: Cap percentage sensors at 100%, log warning with raw values
- Mikrotik profile: Cap storage usage at 100% during discovery
- NetSnmp profile: Cap memory usage at 100% during discovery

The raw percentage is logged before capping to help diagnose device issues.
All percentage sensors now have consistent validation across polling and discovery.
---
 lib/towerops/snmp/poller_worker.ex     | 20 +++++++++++++++++++-
 lib/towerops/snmp/profiles/mikrotik.ex | 19 +++++++++++++++++--
 lib/towerops/snmp/profiles/net_snmp.ex | 15 ++++++++++++++-
 3 files changed, 50 insertions(+), 4 deletions(-)

diff --git a/lib/towerops/snmp/poller_worker.ex b/lib/towerops/snmp/poller_worker.ex
index 3438efc0..265b448b 100644
--- a/lib/towerops/snmp/poller_worker.ex
+++ b/lib/towerops/snmp/poller_worker.ex
@@ -278,7 +278,25 @@ defmodule Towerops.Snmp.PollerWorker do
          size when is_number(size) <- decode_snmp_value(size_raw),
          true <- size > 0 do
       percentage = used / size * 100
-      {:ok, percentage}
+
+      # Validate percentage and warn if it exceeds 100%
+      # This can happen if the device reports incorrect SNMP values or if
+      # hrStorageAllocationUnits differs between used/size OIDs
+      capped_percentage =
+        if percentage > 100 do
+          Logger.warning(
+            "Percentage sensor #{sensor.sensor_descr} (#{sensor.sensor_type}) " <>
+              "exceeded 100%: #{Float.round(percentage, 2)}% " <>
+              "(used=#{used} from #{used_oid}, size=#{size} from #{size_oid}). " <>
+              "Capping at 100%. This may indicate a device firmware bug."
+          )
+
+          100.0
+        else
+          percentage
+        end
+
+      {:ok, capped_percentage}
     else
       {:error, reason} -> {:error, reason}
       false -> {:error, :division_by_zero}
diff --git a/lib/towerops/snmp/profiles/mikrotik.ex b/lib/towerops/snmp/profiles/mikrotik.ex
index 413b8e8b..7cb5f299 100644
--- a/lib/towerops/snmp/profiles/mikrotik.ex
+++ b/lib/towerops/snmp/profiles/mikrotik.ex
@@ -282,6 +282,21 @@ defmodule Towerops.Snmp.Profiles.Mikrotik do
       percent = used / size * 100
       type = determine_storage_type(descr)
 
+      # Cap percentage at 100% and log warning if exceeded
+      # This can happen if the device reports incorrect SNMP values
+      capped_percent =
+        if percent > 100 do
+          Logger.warning(
+            "Storage sensor #{descr} exceeded 100%: #{Float.round(percent, 2)}% " <>
+              "(used=#{used} from #{used_oid}, size=#{size} from #{size_oid}). " <>
+              "Capping at 100%. This may indicate a device firmware bug."
+          )
+
+          100.0
+        else
+          percent
+        end
+
       %{
         sensor_type: "#{type}_usage",
         sensor_index: index,
@@ -289,8 +304,8 @@ defmodule Towerops.Snmp.Profiles.Mikrotik do
         sensor_descr: descr,
         sensor_unit: "%",
         sensor_divisor: 1,
-        last_value: percent,
-        status: storage_status(type, percent),
+        last_value: capped_percent,
+        status: storage_status(type, capped_percent),
         metadata: %{
           size_oid: size_oid,
           calculation: "percentage"
diff --git a/lib/towerops/snmp/profiles/net_snmp.ex b/lib/towerops/snmp/profiles/net_snmp.ex
index 1b1930ae..3babe497 100644
--- a/lib/towerops/snmp/profiles/net_snmp.ex
+++ b/lib/towerops/snmp/profiles/net_snmp.ex
@@ -208,7 +208,20 @@ defmodule Towerops.Snmp.Profiles.NetSnmp do
 
         used_percent =
           if total_kb && total_kb > 0 && used_kb do
-            used_kb / total_kb * 100
+            percent = used_kb / total_kb * 100
+
+            # Cap percentage at 100% and log warning if exceeded
+            if percent > 100 do
+              Logger.warning(
+                "Memory usage exceeded 100%: #{Float.round(percent, 2)}% " <>
+                  "(used=#{used_kb} KB, total=#{total_kb} KB). " <>
+                  "Capping at 100%. This may indicate a device firmware bug."
+              )
+
+              100.0
+            else
+              percent
+            end
           end
 
         [