From 10cbd8dd483f0fe08d504b6e7094d667d39b310e Mon Sep 17 00:00:00 2001
From: Graham McIntire <graham@mcintire.me>
Date: Sat, 25 Apr 2026 18:05:22 -0500
Subject: [PATCH] fix(remote_ip): log IPv6 in canonical hex via :inet.ntoa

IPv6 segments were being printed in decimal (e.g. 10772:1985:1024:45::1
for 2a14:7c1:400:2d::1), which made request_id logs unreadable.
---
 lib/microwaveprop_web/plugs/remote_ip.ex        |  9 +++++++--
 test/microwaveprop_web/plugs/remote_ip_test.exs | 16 ++++++++++++++++
 2 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/lib/microwaveprop_web/plugs/remote_ip.ex b/lib/microwaveprop_web/plugs/remote_ip.ex
index cdd1ca5a..7b190e57 100644
--- a/lib/microwaveprop_web/plugs/remote_ip.ex
+++ b/lib/microwaveprop_web/plugs/remote_ip.ex
@@ -173,7 +173,12 @@ defmodule MicrowavepropWeb.Plugs.RemoteIp do
       (e <<< 48) + (f <<< 32) + (g <<< 16) + h
   end
 
-  defp format_ip({a, b, c, d}), do: "#{a}.#{b}.#{c}.#{d}"
-  defp format_ip({a, b, c, d, e, f, g, h}), do: "#{a}:#{b}:#{c}:#{d}:#{e}:#{f}:#{g}:#{h}"
+  defp format_ip(ip) when tuple_size(ip) in [4, 8] do
+    case :inet.ntoa(ip) do
+      {:error, _} -> "unknown"
+      charlist -> List.to_string(charlist)
+    end
+  end
+
   defp format_ip(_), do: "unknown"
 end
diff --git a/test/microwaveprop_web/plugs/remote_ip_test.exs b/test/microwaveprop_web/plugs/remote_ip_test.exs
index c6e54227..c72292d0 100644
--- a/test/microwaveprop_web/plugs/remote_ip_test.exs
+++ b/test/microwaveprop_web/plugs/remote_ip_test.exs
@@ -249,6 +249,22 @@ defmodule MicrowavepropWeb.Plugs.RemoteIpTest do
       assert conn.remote_ip == {127, 0, 0, 1}
     end
 
+    test "logs IPv6 peer in canonical hex form, not decimal" do
+      # Regression: a public IPv6 client like 2a14:7c1:400:2d::1 was being
+      # logged as "10772:1985:1024:45:0:0:0:1" because we stringified the
+      # 8-tuple in decimal. Logger metadata should hold the canonical hex.
+      peer = {0x2A14, 0x07C1, 0x0400, 0x002D, 0, 0, 0, 1}
+
+      :get
+      |> conn("/")
+      |> with_peer(peer)
+      |> call_plug()
+
+      assert {:remote_ip, ip_str} = List.keyfind(Logger.metadata(), :remote_ip, 0)
+      assert ip_str =~ "2a14"
+      refute ip_str =~ "10772"
+    end
+
     test "single-host CIDR (/32) trusts only that exact IP" do
       conn =
         :get