Kernel: Migrate TCP socket tables locking to ProtectedValue

Note: TCPSocket::create_client() has a dubious locking process where
the sockets by tuple table is first shared lock to check if the socket
exists and bail out if it does, then unlocks, then exclusively locks to
add the tuple. There could be a race condition where two client
creation requests for the same tuple happen at the same time and both
cleared the shared lock check. When in doubt, lock exclusively the
whole time.

1 files changed, 82 insertions, 76 deletions

diff --git a/Kernel/Net/TCPSocket.cpp b/Kernel/Net/TCPSocket.cpp
index e555899169..faf3352a41 100644
--- a/Kernel/Net/TCPSocket.cpp
+++ b/Kernel/Net/TCPSocket.cpp
@@ -9,7 +9,7 @@
 #include <Kernel/Debug.h>
 #include <Kernel/Devices/RandomDevice.h>
 #include <Kernel/FileSystem/FileDescription.h>
-#include <Kernel/Locking/Lockable.h>
+#include <Kernel/Locking/ProtectedValue.h>
 #include <Kernel/Net/EthernetFrameHeader.h>
 #include <Kernel/Net/IPv4.h>
 #include <Kernel/Net/NetworkAdapter.h>
@@ -24,9 +24,9 @@ namespace Kernel {
 
 void TCPSocket::for_each(Function<void(const TCPSocket&)> callback)
 {
-    MutexLocker locker(sockets_by_tuple().lock(), Mutex::Mode::Shared);
-    for (auto& it : sockets_by_tuple().resource())
+    sockets_by_tuple().for_each_shared([&](const auto& it) {
         callback(*it.value);
+    });
 }
 
 void TCPSocket::set_state(State new_state)
@@ -42,8 +42,9 @@ void TCPSocket::set_state(State new_state)
         m_role = Role::Connected;
 
     if (new_state == State::Closed) {
-        MutexLocker locker(closing_sockets().lock());
-        closing_sockets().resource().remove(tuple());
+        closing_sockets().with_exclusive([&](auto& table) {
+            table.remove(tuple());
+        });
 
         if (m_originator)
             release_to_originator();
@@ -53,71 +54,68 @@ void TCPSocket::set_state(State new_state)
         evaluate_block_conditions();
 }
 
-static AK::Singleton<Lockable<HashMap<IPv4SocketTuple, RefPtr<TCPSocket>>>> s_socket_closing;
+static AK::Singleton<ProtectedValue<HashMap<IPv4SocketTuple, RefPtr<TCPSocket>>>> s_socket_closing;
 
-Lockable<HashMap<IPv4SocketTuple, RefPtr<TCPSocket>>>& TCPSocket::closing_sockets()
+ProtectedValue<HashMap<IPv4SocketTuple, RefPtr<TCPSocket>>>& TCPSocket::closing_sockets()
 {
     return *s_socket_closing;
 }
 
-static AK::Singleton<Lockable<HashMap<IPv4SocketTuple, TCPSocket*>>> s_socket_tuples;
+static AK::Singleton<ProtectedValue<HashMap<IPv4SocketTuple, TCPSocket*>>> s_socket_tuples;
 
-Lockable<HashMap<IPv4SocketTuple, TCPSocket*>>& TCPSocket::sockets_by_tuple()
+ProtectedValue<HashMap<IPv4SocketTuple, TCPSocket*>>& TCPSocket::sockets_by_tuple()
 {
     return *s_socket_tuples;
 }
 
 RefPtr<TCPSocket> TCPSocket::from_tuple(const IPv4SocketTuple& tuple)
 {
-    MutexLocker locker(sockets_by_tuple().lock(), Mutex::Mode::Shared);
+    return sockets_by_tuple().with_shared([&](const auto& table) -> RefPtr<TCPSocket> {
+        auto exact_match = table.get(tuple);
+        if (exact_match.has_value())
+            return { *exact_match.value() };
 
-    auto exact_match = sockets_by_tuple().resource().get(tuple);
-    if (exact_match.has_value())
-        return { *exact_match.value() };
+        auto address_tuple = IPv4SocketTuple(tuple.local_address(), tuple.local_port(), IPv4Address(), 0);
+        auto address_match = table.get(address_tuple);
+        if (address_match.has_value())
+            return { *address_match.value() };
 
-    auto address_tuple = IPv4SocketTuple(tuple.local_address(), tuple.local_port(), IPv4Address(), 0);
-    auto address_match = sockets_by_tuple().resource().get(address_tuple);
-    if (address_match.has_value())
-        return { *address_match.value() };
+        auto wildcard_tuple = IPv4SocketTuple(IPv4Address(), tuple.local_port(), IPv4Address(), 0);
+        auto wildcard_match = table.get(wildcard_tuple);
+        if (wildcard_match.has_value())
+            return { *wildcard_match.value() };
 
-    auto wildcard_tuple = IPv4SocketTuple(IPv4Address(), tuple.local_port(), IPv4Address(), 0);
-    auto wildcard_match = sockets_by_tuple().resource().get(wildcard_tuple);
-    if (wildcard_match.has_value())
-        return { *wildcard_match.value() };
-
-    return {};
+        return {};
+    });
 }
 RefPtr<TCPSocket> TCPSocket::create_client(const IPv4Address& new_local_address, u16 new_local_port, const IPv4Address& new_peer_address, u16 new_peer_port)
 {
     auto tuple = IPv4SocketTuple(new_local_address, new_local_port, new_peer_address, new_peer_port);
-
-    {
-        MutexLocker locker(sockets_by_tuple().lock(), Mutex::Mode::Shared);
-        if (sockets_by_tuple().resource().contains(tuple))
+    return sockets_by_tuple().with_exclusive([&](auto& table) -> RefPtr<TCPSocket> {
+        if (table.contains(tuple))
             return {};
-    }
 
-    auto receive_buffer = create_receive_buffer();
-    if (!receive_buffer)
-        return {};
-    auto result = TCPSocket::create(protocol(), receive_buffer.release_nonnull());
-    if (result.is_error())
-        return {};
+        auto receive_buffer = create_receive_buffer();
+        if (!receive_buffer)
+            return {};
+        auto result = TCPSocket::create(protocol(), receive_buffer.release_nonnull());
+        if (result.is_error())
+            return {};
 
-    auto client = result.release_value();
-    client->set_setup_state(SetupState::InProgress);
-    client->set_local_address(new_local_address);
-    client->set_local_port(new_local_port);
-    client->set_peer_address(new_peer_address);
-    client->set_peer_port(new_peer_port);
-    client->set_direction(Direction::Incoming);
-    client->set_originator(*this);
+        auto client = result.release_value();
+        client->set_setup_state(SetupState::InProgress);
+        client->set_local_address(new_local_address);
+        client->set_local_port(new_local_port);
+        client->set_peer_address(new_peer_address);
+        client->set_peer_port(new_peer_port);
+        client->set_direction(Direction::Incoming);
+        client->set_originator(*this);
 
-    MutexLocker locker(sockets_by_tuple().lock());
-    m_pending_release_for_accept.set(tuple, client);
-    sockets_by_tuple().resource().set(tuple, client);
+        m_pending_release_for_accept.set(tuple, client);
+        table.set(tuple, client);
 
-    return client;
+        return { move(client) };
+    });
 }
 
 void TCPSocket::release_to_originator()
@@ -143,8 +141,9 @@ TCPSocket::TCPSocket(int protocol, NonnullOwnPtr<DoubleBuffer> receive_buffer, O
 
 TCPSocket::~TCPSocket()
 {
-    MutexLocker locker(sockets_by_tuple().lock());
-    sockets_by_tuple().resource().remove(tuple());
+    sockets_by_tuple().with_exclusive([&](auto& table) {
+        table.remove(tuple());
+    });
 
     dequeue_for_retransmit();
 
@@ -378,10 +377,14 @@ KResult TCPSocket::protocol_bind()
 KResult TCPSocket::protocol_listen(bool did_allocate_port)
 {
     if (!did_allocate_port) {
-        MutexLocker socket_locker(sockets_by_tuple().lock());
-        if (sockets_by_tuple().resource().contains(tuple()))
+        bool ok = sockets_by_tuple().with_exclusive([&](auto& table) -> bool {
+            if (table.contains(tuple()))
+                return false;
+            table.set(tuple(), this);
+            return true;
+        });
+        if (!ok)
             return EADDRINUSE;
-        sockets_by_tuple().resource().set(tuple(), this);
     }
 
     set_direction(Direction::Passive);
@@ -443,23 +446,24 @@ KResultOr<u16> TCPSocket::protocol_allocate_local_port()
     constexpr u16 ephemeral_port_range_size = last_ephemeral_port - first_ephemeral_port;
     u16 first_scan_port = first_ephemeral_port + get_good_random<u16>() % ephemeral_port_range_size;
 
-    MutexLocker locker(sockets_by_tuple().lock());
-    for (u16 port = first_scan_port;;) {
-        IPv4SocketTuple proposed_tuple(local_address(), port, peer_address(), peer_port());
+    return sockets_by_tuple().with_exclusive([&](auto& table) -> KResultOr<u16> {
+        for (u16 port = first_scan_port;;) {
+            IPv4SocketTuple proposed_tuple(local_address(), port, peer_address(), peer_port());
 
-        auto it = sockets_by_tuple().resource().find(proposed_tuple);
-        if (it == sockets_by_tuple().resource().end()) {
-            set_local_port(port);
-            sockets_by_tuple().resource().set(proposed_tuple, this);
-            return port;
+            auto it = table.find(proposed_tuple);
+            if (it == table.end()) {
+                set_local_port(port);
+                table.set(proposed_tuple, this);
+                return port;
+            }
+            ++port;
+            if (port > last_ephemeral_port)
+                port = first_ephemeral_port;
+            if (port == first_scan_port)
+                break;
         }
-        ++port;
-        if (port > last_ephemeral_port)
-            port = first_ephemeral_port;
-        if (port == first_scan_port)
-            break;
-    }
-    return EADDRINUSE;
+        return EADDRINUSE;
+    });
 }
 
 bool TCPSocket::protocol_is_disconnected() const
@@ -499,30 +503,32 @@ KResult TCPSocket::close()
         set_state(State::LastAck);
     }
 
-    if (state() != State::Closed && state() != State::Listen) {
-        MutexLocker locker(closing_sockets().lock());
-        closing_sockets().resource().set(tuple(), *this);
-    }
+    if (state() != State::Closed && state() != State::Listen)
+        closing_sockets().with_exclusive([&](auto& table) {
+            table.set(tuple(), *this);
+        });
     return result;
 }
 
-static AK::Singleton<Lockable<HashTable<TCPSocket*>>> s_sockets_for_retransmit;
+static AK::Singleton<ProtectedValue<HashTable<TCPSocket*>>> s_sockets_for_retransmit;
 
-Lockable<HashTable<TCPSocket*>>& TCPSocket::sockets_for_retransmit()
+ProtectedValue<HashTable<TCPSocket*>>& TCPSocket::sockets_for_retransmit()
 {
     return *s_sockets_for_retransmit;
 }
 
 void TCPSocket::enqueue_for_retransmit()
 {
-    MutexLocker locker(sockets_for_retransmit().lock());
-    sockets_for_retransmit().resource().set(this);
+    sockets_for_retransmit().with_exclusive([&](auto& table) {
+        table.set(this);
+    });
 }
 
 void TCPSocket::dequeue_for_retransmit()
 {
-    MutexLocker locker(sockets_for_retransmit().lock());
-    sockets_for_retransmit().resource().remove(this);
+    sockets_for_retransmit().with_exclusive([&](auto& table) {
+        table.remove(this);
+    });
 }
 
 void TCPSocket::retransmit_packets()