Allow fetching over IPv6

Mint/Finch disable IPv6 by default preventing us from
fetching anything from IPv6-only hosts without this.

CHANGELOG.md

@@ -4,6 +4,15 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## Unreleased
+
+## Added
+
+## Changed
+
+## Fixed
+- Issue preventing fetching anything from IPv6-only instances
+
 ## 2024.02
 
 ## Added

lib/pleroma/application.ex

@@ -288,6 +288,7 @@ defmodule Pleroma.Application do
       |> Config.get([])
       |> Pleroma.HTTP.AdapterHelper.add_pool_size(pool_size)
       |> Pleroma.HTTP.AdapterHelper.maybe_add_proxy_pool(proxy)
+      |> Pleroma.HTTP.AdapterHelper.ensure_ipv6()
       |> Keyword.put(:name, MyFinch)
 
     [{Finch, config}]

lib/pleroma/http/adapter_helper.ex

@@ -65,6 +65,15 @@ defmodule Pleroma.HTTP.AdapterHelper do
     |> put_in([:pools, :default, :size], pool_size)
   end
 
+  def ensure_ipv6(opts) do
+    # Default transport opts already enable IPv6, so just ensure they're loaded
+    opts
+    |> maybe_add_pools()
+    |> maybe_add_default_pool()
+    |> maybe_add_conn_opts()
+    |> maybe_add_transport_opts()
+  end
+
   defp maybe_add_pools(opts) do
     if Keyword.has_key?(opts, :pools) do
       opts
@@ -96,11 +105,15 @@ defmodule Pleroma.HTTP.AdapterHelper do
   defp maybe_add_transport_opts(opts) do
     transport_opts = get_in(opts, [:pools, :default, :conn_opts, :transport_opts])
 
-    unless is_nil(transport_opts) do
-      opts
-    else
-      put_in(opts, [:pools, :default, :conn_opts, :transport_opts], [])
-    end
+    opts =
+      unless is_nil(transport_opts) do
+        opts
+      else
+        put_in(opts, [:pools, :default, :conn_opts, :transport_opts], [])
+      end
+
+    # IPv6 is disabled and IPv4 enabled by default; ensure we can use both
+    put_in(opts, [:pools, :default, :conn_opts, :transport_opts, :inet6], true)
   end
 
   @doc """