From 9918f1633c40c858c3bacbb2c8be4e69d8d8e478 Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Sun, 4 Jan 2026 13:02:01 -0600
Subject: [PATCH] Handle SNMP Counter64 binary values in poller

SNMP Counter64 values (used for interface byte counters) are returned
as 8-byte binary data by SNMPKit and need to be decoded to integers
before database insertion.

Added decode_snmp_value/1 helper that:
- Passes through numeric values unchanged
- Decodes 8-byte binaries as 64-bit unsigned big-endian integers
- Returns nil for unknown formats

Updated both sensor and interface polling to use this decoder,
preventing DBConnection.EncodeError when trying to insert binary
values into integer columns.
---
 lib/towerops/snmp/poller_worker.ex | 60 ++++++++++++++++++++++--------
 1 file changed, 45 insertions(+), 15 deletions(-)

diff --git a/lib/towerops/snmp/poller_worker.ex b/lib/towerops/snmp/poller_worker.ex
index 5a69eb14..4a65e839 100644
--- a/lib/towerops/snmp/poller_worker.ex
+++ b/lib/towerops/snmp/poller_worker.ex
@@ -100,23 +100,34 @@ defmodule Towerops.Snmp.PollerWorker do
   defp poll_sensors(sensors, client_opts, timestamp) do
     Enum.each(sensors, fn sensor ->
       case Client.get(client_opts, sensor.sensor_oid) do
-        {:ok, raw_value} when is_number(raw_value) ->
-          # Calculate actual value using divisor
-          value = raw_value / sensor.sensor_divisor
+        {:ok, raw_value} ->
+          decoded_value = decode_snmp_value(raw_value)
 
-          # Determine status based on value (could be enhanced with thresholds)
-          status = "ok"
+          if is_number(decoded_value) do
+            # Calculate actual value using divisor
+            value = decoded_value / sensor.sensor_divisor
 
-          # Save the reading
-          Snmp.create_sensor_reading(%{
-            sensor_id: sensor.id,
-            value: value,
-            status: status,
-            checked_at: timestamp
-          })
+            # Determine status based on value (could be enhanced with thresholds)
+            status = "ok"
 
-        {:ok, _non_numeric} ->
-          Logger.debug("Non-numeric SNMP value for sensor #{sensor.sensor_descr}")
+            # Save the reading
+            Snmp.create_sensor_reading(%{
+              sensor_id: sensor.id,
+              value: value,
+              status: status,
+              checked_at: timestamp
+            })
+          else
+            Logger.debug("Non-numeric SNMP value for sensor #{sensor.sensor_descr}")
+
+            # Save reading with nil value
+            Snmp.create_sensor_reading(%{
+              sensor_id: sensor.id,
+              value: nil,
+              status: "unknown",
+              checked_at: timestamp
+            })
+          end
 
         {:error, reason} ->
           Logger.warning("Failed to poll sensor #{sensor.sensor_descr}: #{inspect(reason)}")
@@ -160,7 +171,7 @@ defmodule Towerops.Snmp.PollerWorker do
     results =
       Enum.map(oids, fn {key, oid} ->
         case Client.get(client_opts, oid) do
-          {:ok, value} when is_number(value) -> {key, value}
+          {:ok, value} -> {key, decode_snmp_value(value)}
           _ -> {key, nil}
         end
       end)
@@ -168,6 +179,25 @@ defmodule Towerops.Snmp.PollerWorker do
     {:ok, Map.new(results)}
   end
 
+  # Decode SNMP values, handling Counter64 and other binary types
+  defp decode_snmp_value(value) when is_number(value), do: value
+
+  defp decode_snmp_value(value) when is_binary(value) do
+    # Try to decode as Counter64 (8 bytes, big-endian unsigned integer)
+    case byte_size(value) do
+      8 ->
+        <<counter::unsigned-big-integer-size(64)>> = value
+        counter
+
+      _ ->
+        # Unknown binary format, return nil
+        Logger.debug("Unknown SNMP binary value format, size: #{byte_size(value)}")
+        nil
+    end
+  end
+
+  defp decode_snmp_value(_), do: nil
+
   defp build_client_opts(equipment) do
     [
       ip: equipment.ip_address,