From 8cf076bf5f4c2c3f4a12c22e97a75e337d5fa08a Mon Sep 17 00:00:00 2001
From: Alain Zscheile <zseri.devel@ytrizja.de>
Date: Sat, 26 Nov 2022 00:54:03 +0100
Subject: [PATCH] Floof.serve should be always tail-recursive

---
 lib/floof.ex | 109 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 61 insertions(+), 48 deletions(-)

diff --git a/lib/floof.ex b/lib/floof.ex
index c21398c..43bfccd 100644
--- a/lib/floof.ex
+++ b/lib/floof.ex
@@ -17,9 +17,12 @@ defmodule Floof do
         ] ++ opts
       )
 
-    Logger.info("Accepting connections on #{port}")
-    loop_acceptor(socket)
-    :ok = :gen_tcp.close(socket)
+    try do
+      Logger.info("Accepting connections on #{port}")
+      loop_acceptor(socket)
+    after
+      :ok = :gen_tcp.close(socket)
+    end
   end
 
   defp loop_acceptor(socket) do
@@ -45,60 +48,70 @@ defmodule Floof do
         active: true
       )
 
-    Floof.Distributor.register(self())
-    Logger.info("Established connection to #{inspect(host)}:#{port}")
+    try do
+      Floof.Distributor.register(self())
+      Logger.info("Established connection to #{inspect(host)}:#{port}")
 
-    if sesskey != nil do
-      {:ok, encd} = :FloofProtocol.encode(:ProtoMessage, {:session, {:attach, sesskey}})
-      :ok = :gen_tcp.send(socket, encd)
+      if sesskey != nil do
+        {:ok, encd} = :FloofProtocol.encode(:ProtoMessage, {:session, {:attach, sesskey}})
+        :ok = :gen_tcp.send(socket, encd)
+      end
+
+      serve(socket, %{}, nil)
+    after
+      :ok = :gen_tcp.close(socket)
     end
-
-    serve(socket, %{}, nil)
-    :ok = :gen_tcp.close(socket)
   end
 
   defp serve(client, backlog, sesskey) do
-    receive do
-      {:tcp, _, message} ->
-        message =
-          if :erlang.is_binary(message) do
-            message
-          else
-            :erlang.list_to_binary(message)
+    {backlog, sesskey} =
+      receive do
+        {:tcp, _, message} ->
+          message =
+            if :erlang.is_binary(message) do
+              message
+            else
+              :erlang.list_to_binary(message)
+            end
+
+          {:ok, dcd} = :FloofProtocol.decode(:ProtoMessage, message)
+          backlog = handle_incoming(client, backlog, sesskey, dcd)
+          {backlog, sesskey}
+
+        {:fwdxfer, {dcdhash, dcd}} ->
+          backlog =
+            if sesskey != nil do
+              # make sure that stuff gets handled uniformly
+              Floof.SessionManager.set(sesskey, dcdhash, dcd)
+            else
+              :ok = send_summary(client, :requestpull, [dcdhash])
+              Map.put(backlog, dcdhash, dcd)
+            end
+
+          {backlog, sesskey}
+
+        {:SessionPushed, sesskey} ->
+          :ok = send_summary(client, :requestpull, Floof.SessionManager.peek(sesskey))
+          {backlog, sesskey}
+
+        {:SessionDetached, _} ->
+          {backlog, nil}
+
+        {:tcp_closed, _} ->
+          # put all the backlogged stuff back if possible
+          if sesskey != nil do
+            Floof.SessionManager.set_multi(sesskey, backlog)
+            Floof.SessionManager.detach(sesskey, self())
           end
 
-        {:ok, dcd} = :FloofProtocol.decode(:ProtoMessage, message)
-        backlog = handle_incoming(client, backlog, sesskey, dcd)
-        serve(client, backlog, sesskey)
+          :erlang.exit(:normal)
 
-      {:fwdxfer, {dcdhash, dcd}} ->
-        if sesskey != nil do
-          # make sure that stuff gets handled uniformly
-          Floof.SessionManager.set(sesskey, dcdhash, dcd)
-          serve(client, backlog, sesskey)
-        else
-          :ok = send_summary(client, :requestpull, [dcdhash])
-          serve(client, Map.put(backlog, dcdhash, dcd), sesskey)
-        end
+        x ->
+          Logger.warn("unable to handle request: #{inspect(x)}")
+          {backlog, sesskey}
+      end
 
-      {:SessionPushed, sesskey} ->
-        :ok = send_summary(client, :requestpull, Floof.SessionManager.peek(sesskey))
-        serve(client, backlog, sesskey)
-
-      {:SessionDetached, _} ->
-        serve(client, backlog, nil)
-
-      {:tcp_closed, _} ->
-        # put all the backlogged stuff back if possible
-        if sesskey != nil do
-          Floof.SessionManager.set_multi(sesskey, backlog)
-          Floof.SessionManager.detach(sesskey, self())
-        end
-
-      x ->
-        Logger.warn("unable to handle request: #{inspect(x)}")
-        serve(client, backlog, sesskey)
-    end
+    serve(client, backlog, sesskey)
   end
 
   defp handle_incoming(client, backlog, sesskey, dcd) do