Kernel: Fix how socket closing works

Sockets are now closed only when they are not referenced any more. This
allows child process to close socket and still keep it open for the
parent.

kernel/kernel/Networking/TCPSocket.cpp

@@ -63,39 +63,6 @@ namespace Kernel
 	{
 		ASSERT(!is_bound());
 		ASSERT(m_process == nullptr);
-		dprintln_if(DEBUG_TCP, "socket destroyed");
-	}
-
-	void TCPSocket::on_close_impl()
-	{
-		LockGuard _(m_mutex);
-
-		if (!is_bound())
-			return;
-
-		switch (m_state)
-		{
-			case State::Established:
-				break;
-			case State::SynSent:
-				set_connection_as_closed();
-				// fall through
-			case State::SynReceived:
-			case State::FinWait1:
-			case State::FinWait2:
-			case State::CloseWait:
-			case State::Closing:
-			case State::TimeWait:
-			case State::LastAck:
-				return;
-			case State::Closed:		ASSERT_NOT_REACHED();
-			case State::Listen:		ASSERT_NOT_REACHED();
-		}
-
-		m_state = State::FinWait1;
-		m_should_ack = true;
-
-		dprintln_if(DEBUG_TCP, "Initiated close");
 	}
 
 	BAN::ErrorOr<void> TCPSocket::connect_impl(const sockaddr* address, socklen_t address_len)
@@ -407,6 +374,38 @@ namespace Kernel
 
 		m_semaphore.unblock();
 	}
+	
+	void TCPSocket::start_close_sequence()
+	{
+		LockGuard _(m_mutex);
+
+		if (!is_bound())
+			return;
+
+		switch (m_state)
+		{
+			case State::Established:
+				break;
+			case State::SynSent:
+				set_connection_as_closed();
+				return;
+			case State::SynReceived:
+			case State::FinWait1:
+			case State::FinWait2:
+			case State::CloseWait:
+			case State::Closing:
+			case State::TimeWait:
+			case State::LastAck:
+				return;
+			case State::Closed:		ASSERT_NOT_REACHED();
+			case State::Listen:		ASSERT_NOT_REACHED();
+		}
+
+		m_state = State::FinWait1;
+		m_should_ack = true;
+
+		dprintln_if(DEBUG_TCP, "Initiated close");
+	}
 
 	void TCPSocket::set_connection_as_closed()
 	{
@@ -427,13 +426,25 @@ namespace Kernel
 		static constexpr uint32_t retransmit_timeout_ms = 1000;
 
 		BAN::RefPtr<TCPSocket> keep_alive = this;
+		bool started_close_sequence = false;
 
 		while (m_process)
 		{
-			uint64_t current_ms = SystemTimer::get().ms_since_boot();
+			const uint64_t current_ms = SystemTimer::get().ms_since_boot();
 
 			if (m_state == State::TimeWait && current_ms >= m_time_wait_start_ms + 30'000)
+			{
 				set_connection_as_closed();
+				continue;
+			}
+
+			// This is the last instance
+			if (!started_close_sequence && ref_count() == 1)
+			{
+				start_close_sequence();
+				started_close_sequence = true;
+				continue;
+			}
 
 			{
 				LockGuard _(m_mutex);

kernel/kernel/Networking/UDPSocket.cpp

@@ -23,7 +23,7 @@ namespace Kernel
 		: NetworkSocket(network_layer, ino, inode_info)
 	{ }
 
-	void UDPSocket::on_close_impl()
+	UDPSocket::~UDPSocket()
 	{
 		if (is_bound())
 			m_network_layer.unbind_socket(this, m_port);

kernel/kernel/Networking/UNIX/Socket.cpp

@@ -47,7 +47,7 @@ namespace Kernel
 		}
 	}
 
-	void UnixDomainSocket::on_close_impl()
+	UnixDomainSocket::~UnixDomainSocket()
 	{
 		if (is_bound() && !is_bound_to_unused())
 		{