From 6a20733fcd2dabebc0e5954bb1971628a3c3ef6e Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 15 Aug 2021 16:37:45 +0200
Subject: [PATCH] Kernel: Convert TCP retransmit queue from HashTable to
 IntrusiveList

---
 Kernel/Net/NetworkTask.cpp |  2 +-
 Kernel/Net/TCPSocket.cpp   | 12 ++++++------
 Kernel/Net/TCPSocket.h     |  7 ++++++-
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/Kernel/Net/NetworkTask.cpp b/Kernel/Net/NetworkTask.cpp
index d1184e329b..0a8933a902 100644
--- a/Kernel/Net/NetworkTask.cpp
+++ b/Kernel/Net/NetworkTask.cpp
@@ -642,7 +642,7 @@ void retransmit_tcp_packets()
     // in case retransmit_packets() realizes that it wants to close the socket.
     NonnullRefPtrVector<TCPSocket, 16> sockets;
     TCPSocket::sockets_for_retransmit().for_each_shared([&](const auto& socket) {
-        sockets.append(*socket);
+        sockets.append(socket);
     });
 
     for (auto& socket : sockets) {
diff --git a/Kernel/Net/TCPSocket.cpp b/Kernel/Net/TCPSocket.cpp
index b55982b9a4..87ec059409 100644
--- a/Kernel/Net/TCPSocket.cpp
+++ b/Kernel/Net/TCPSocket.cpp
@@ -512,24 +512,24 @@ KResult TCPSocket::close()
     return result;
 }
 
-static Singleton<ProtectedValue<HashTable<TCPSocket*>>> s_sockets_for_retransmit;
+static Singleton<ProtectedValue<TCPSocket::RetransmitList>> s_sockets_for_retransmit;
 
-ProtectedValue<HashTable<TCPSocket*>>& TCPSocket::sockets_for_retransmit()
+ProtectedValue<TCPSocket::RetransmitList>& TCPSocket::sockets_for_retransmit()
 {
     return *s_sockets_for_retransmit;
 }
 
 void TCPSocket::enqueue_for_retransmit()
 {
-    sockets_for_retransmit().with_exclusive([&](auto& table) {
-        table.set(this);
+    sockets_for_retransmit().with_exclusive([&](auto& list) {
+        list.append(*this);
     });
 }
 
 void TCPSocket::dequeue_for_retransmit()
 {
-    sockets_for_retransmit().with_exclusive([&](auto& table) {
-        table.remove(this);
+    sockets_for_retransmit().with_exclusive([&](auto& list) {
+        list.remove(*this);
     });
 }
 
diff --git a/Kernel/Net/TCPSocket.h b/Kernel/Net/TCPSocket.h
index a85145db4b..9d491e4db9 100644
--- a/Kernel/Net/TCPSocket.h
+++ b/Kernel/Net/TCPSocket.h
@@ -153,7 +153,6 @@ public:
     void release_to_originator();
     void release_for_accept(RefPtr<TCPSocket>);
 
-    static ProtectedValue<HashTable<TCPSocket*>>& sockets_for_retransmit();
     void retransmit_packets();
 
     virtual KResult close() override;
@@ -222,6 +221,12 @@ private:
 
     // FIXME: Parse window size TCP option from the peer
     u32 m_send_window_size { 64 * KiB };
+
+    IntrusiveListNode<TCPSocket> m_retransmit_list_node;
+
+public:
+    using RetransmitList = IntrusiveList<TCPSocket, RawPtr<TCPSocket>, &TCPSocket::m_retransmit_list_node>;
+    static ProtectedValue<TCPSocket::RetransmitList>& sockets_for_retransmit();
 };
 
 }