refactor: prepare client init for upstream DoH servers (#10851)

In order to support multiple different protocols of upstream DNS
resolvers, we deprecate the `upstream_dns` field in the client's `init`
message and introduce two new fields:

- `upstream_do53`
- `upstream_doh`

For now, only `upstream_do53` is populated and `upstream_doh` is always
empty.

On the client-side, we for now only introduce the `upstream_do53` field
but fall-back to `upstream_dns` if that one is empty. This makes this PR
backwards-compatible with the portal version that is currently deployed
in production. Thus, this PR can be merged even prior to deploying the
portal.

Internally, we prepare connlib's abstractions to deal with different
kinds of upstreams by renaming all existing "upstream DNS" references to
`upstream_do53`: DNS over port 53. That includes UDP as well as TCP DNS
resolution.

Resolves: #10791

---------

Co-authored-by: Jamil Bou Kheir <jamilbk@users.noreply.github.com>

elixir/apps/api/lib/api/client/views/interface.ex

@@ -1,20 +1,36 @@
 defmodule API.Client.Views.Interface do
-  alias Domain.{Accounts, Clients}
+  alias Domain.Clients
 
   def render(%Clients.Client{} = client) do
+    clients_upstream_dns = Map.get(client.account.config, :clients_upstream_dns, [])
+
+    # TODO: DOH RESOLVERS
+    # Remove this old field once clients are upgraded.
+    # old field - append normalized port
     upstream_dns =
-      client.account.config
-      |> Map.get(:clients_upstream_dns, [])
-      |> Enum.map(fn dns_config ->
-        address = Accounts.Config.Changeset.normalize_dns_address(dns_config)
-        Map.from_struct(%{dns_config | address: address})
+      clients_upstream_dns
+      |> Enum.map(fn %{address: address} = dns_config ->
+        ip = URI.parse("//" <> address).host
+        Map.from_struct(%{dns_config | address: "#{ip}:53"})
+      end)
+
+    # new field - no port
+    upstream_do53 =
+      clients_upstream_dns
+      |> Enum.map(fn %{address: address} ->
+        %{ip: URI.parse("//" <> address).host}
       end)
 
     %{
       search_domain: client.account.config.search_domain,
-      upstream_dns: upstream_dns,
+      upstream_do53: upstream_do53,
+      # Populate from DB once present.
+      upstream_doh: [],
       ipv4: client.ipv4,
-      ipv6: client.ipv6
+      ipv6: client.ipv6,
+
+      # Legacy field
+      upstream_dns: upstream_dns
     }
   end
 end

elixir/apps/api/test/api/client/channel_test.exs

@@ -351,6 +351,11 @@ defmodule API.Client.ChannelTest do
                  %{protocol: :ip_port, address: "1.1.1.1:53"},
                  %{protocol: :ip_port, address: "8.8.8.8:53"}
                ],
+               upstream_do53: [
+                 %{ip: "1.1.1.1"},
+                 %{ip: "8.8.8.8"}
+               ],
+               upstream_doh: [],
                search_domain: "example.com"
              }
     end
@@ -909,7 +914,12 @@ defmodule API.Client.ChannelTest do
                  upstream_dns: [
                    %{address: "1.1.1.1:53", protocol: :ip_port},
                    %{address: "8.8.8.8:53", protocol: :ip_port}
-                 ]
+                 ],
+                 upstream_do53: [
+                   %{ip: "1.1.1.1"},
+                   %{ip: "8.8.8.8"}
+                 ],
+                 upstream_doh: []
                }
              }
     end

elixir/apps/domain/lib/domain/accounts/config/changeset.ex

@@ -64,22 +64,6 @@ defmodule Domain.Accounts.Config.Changeset do
     end
   end
 
-  def normalize_dns_address(%Config.ClientsUpstreamDNS{protocol: :ip_port, address: address}) do
-    case IPPort.cast(address) do
-      {:ok, address} ->
-        address
-        |> IPPort.put_default_port(@default_dns_port)
-        |> to_string()
-
-      _ ->
-        address
-    end
-  end
-
-  def normalize_dns_address(%Config.ClientsUpstreamDNS{address: address}) do
-    address
-  end
-
   def client_upstream_dns_changeset(client_upstream_dns \\ %Config.ClientsUpstreamDNS{}, attrs) do
     client_upstream_dns
     |> cast(attrs, [:protocol, :address])
@@ -130,4 +114,20 @@ defmodule Domain.Accounts.Config.Changeset do
     |> cast_embed(:outdated_gateway, with: &Config.Notifications.Email.Changeset.changeset/2)
     |> cast_embed(:idp_sync_error, with: &Config.Notifications.Email.Changeset.changeset/2)
   end
+
+  defp normalize_dns_address(%Config.ClientsUpstreamDNS{protocol: :ip_port, address: address}) do
+    case IPPort.cast(address) do
+      {:ok, address} ->
+        address
+        |> IPPort.put_default_port(@default_dns_port)
+        |> to_string()
+
+      _ ->
+        address
+    end
+  end
+
+  defp normalize_dns_address(%Config.ClientsUpstreamDNS{address: address}) do
+    address
+  end
 end