Kernel/Net: Iron out the locking mechanism across the subsystem

There is a big mix of LockRefPtrs all over the Networking subsystem, as
well as lots of room for improvements with our locking patterns, which
this commit will not pursue, but will give a good start for such work.

To deal with this situation, we change the following things:
- Creating instances of NetworkAdapter should always yield a non-locking
  NonnullRefPtr. Acquiring an instance from the NetworkingManagement
  should give a simple RefPtr,as giving LockRefPtr does not really
  protect from concurrency problems in such case.
- Since NetworkingManagement works with normal RefPtrs we should
  protect all instances of RefPtr<NetworkAdapter> with SpinlockProtected
  to ensure references are gone unexpectedly.
- Protect the so_error class member with a proper spinlock. This happens
  to be important because the clear_so_error() method lacked any proper
  locking measures. It also helps preventing a possible TOCTOU when we
  might do a more fine-grained locking in the Socket code, so this could
  be definitely a start for this.
- Change unnecessary LockRefPtr<PacketWithTimestamp> in the structure
  of OutgoingPacket to a simple RefPtr<PacketWithTimestamp> as the whole
  list should be MutexProtected.

Kernel/Net/IPv4Socket.cpp

@@ -212,7 +212,8 @@ ErrorOr<size_t> IPv4Socket::sendto(OpenFileDescription&, UserOrKernelBuffer cons
         return set_so_error(EPIPE);
 
     auto allow_using_gateway = ((flags & MSG_DONTROUTE) || m_routing_disabled) ? AllowUsingGateway::No : AllowUsingGateway::Yes;
-    auto routing_decision = route_to(m_peer_address, m_local_address, bound_interface(), allow_using_gateway);
+    auto adapter = bound_interface().with([](auto& bound_device) -> RefPtr<NetworkAdapter> { return bound_device; });
+    auto routing_decision = route_to(m_peer_address, m_local_address, adapter, allow_using_gateway);
     if (routing_decision.is_zero())
         return set_so_error(EHOSTUNREACH);
 

Kernel/Net/NetworkAdapter.cpp

@@ -111,9 +111,9 @@ size_t NetworkAdapter::dequeue_packet(u8* buffer, size_t buffer_size, Time& pack
     return packet_size;
 }
 
-LockRefPtr<PacketWithTimestamp> NetworkAdapter::acquire_packet_buffer(size_t size)
+RefPtr<PacketWithTimestamp> NetworkAdapter::acquire_packet_buffer(size_t size)
 {
-    auto packet = m_unused_packets.with([size](auto& unused_packets) -> LockRefPtr<PacketWithTimestamp> {
+    auto packet = m_unused_packets.with([size](auto& unused_packets) -> RefPtr<PacketWithTimestamp> {
         if (unused_packets.is_empty())
             return nullptr;
 
@@ -135,7 +135,7 @@ LockRefPtr<PacketWithTimestamp> NetworkAdapter::acquire_packet_buffer(size_t siz
     auto buffer_or_error = KBuffer::try_create_with_size("NetworkAdapter: Packet buffer"sv, size, Memory::Region::Access::ReadWrite, AllocationStrategy::AllocateNow);
     if (buffer_or_error.is_error())
         return {};
-    packet = adopt_lock_ref_if_nonnull(new (nothrow) PacketWithTimestamp { buffer_or_error.release_value(), kgettimeofday() });
+    packet = adopt_ref_if_nonnull(new (nothrow) PacketWithTimestamp { buffer_or_error.release_value(), kgettimeofday() });
     if (!packet)
         return {};
     packet->buffer->set_size(size);

Kernel/Net/NetworkAdapter.h

@@ -39,7 +39,7 @@ struct PacketWithTimestamp final : public AtomicRefCounted<PacketWithTimestamp>
 
     NonnullOwnPtr<KBuffer> buffer;
     Time timestamp;
-    IntrusiveListNode<PacketWithTimestamp, LockRefPtr<PacketWithTimestamp>> packet_node;
+    IntrusiveListNode<PacketWithTimestamp, RefPtr<PacketWithTimestamp>> packet_node;
 };
 
 class NetworkingManagement;
@@ -91,7 +91,7 @@ public:
     u32 packets_out() const { return m_packets_out; }
     u32 bytes_out() const { return m_bytes_out; }
 
-    LockRefPtr<PacketWithTimestamp> acquire_packet_buffer(size_t);
+    RefPtr<PacketWithTimestamp> acquire_packet_buffer(size_t);
     void release_packet_buffer(PacketWithTimestamp&);
 
     constexpr size_t layer3_payload_offset() const { return sizeof(EthernetFrameHeader); }

Kernel/Net/NetworkTask.cpp

@@ -31,7 +31,7 @@ static void handle_icmp(EthernetFrameHeader const&, IPv4Packet const&, Time cons
 static void handle_udp(IPv4Packet const&, Time const& packet_timestamp);
 static void handle_tcp(IPv4Packet const&, Time const& packet_timestamp);
 static void send_delayed_tcp_ack(TCPSocket& socket);
-static void send_tcp_rst(IPv4Packet const& ipv4_packet, TCPPacket const& tcp_packet, LockRefPtr<NetworkAdapter> adapter);
+static void send_tcp_rst(IPv4Packet const& ipv4_packet, TCPPacket const& tcp_packet, RefPtr<NetworkAdapter> adapter);
 static void flush_delayed_tcp_acks();
 static void retransmit_tcp_packets();
 
@@ -333,7 +333,7 @@ void flush_delayed_tcp_acks()
     }
 }
 
-void send_tcp_rst(IPv4Packet const& ipv4_packet, TCPPacket const& tcp_packet, LockRefPtr<NetworkAdapter> adapter)
+void send_tcp_rst(IPv4Packet const& ipv4_packet, TCPPacket const& tcp_packet, RefPtr<NetworkAdapter> adapter)
 {
     auto routing_decision = route_to(ipv4_packet.source(), ipv4_packet.destination(), adapter);
     if (routing_decision.is_zero())

Kernel/Net/NetworkingManagement.cpp

@@ -35,7 +35,7 @@ UNMAP_AFTER_INIT NetworkingManagement::NetworkingManagement()
 {
 }
 
-NonnullLockRefPtr<NetworkAdapter> NetworkingManagement::loopback_adapter() const
+NonnullRefPtr<NetworkAdapter> NetworkingManagement::loopback_adapter() const
 {
     return *m_loopback_adapter;
 }
@@ -56,13 +56,13 @@ ErrorOr<void> NetworkingManagement::try_for_each(Function<ErrorOr<void>(NetworkA
     });
 }
 
-LockRefPtr<NetworkAdapter> NetworkingManagement::from_ipv4_address(IPv4Address const& address) const
+RefPtr<NetworkAdapter> NetworkingManagement::from_ipv4_address(IPv4Address const& address) const
 {
     if (address[0] == 0 && address[1] == 0 && address[2] == 0 && address[3] == 0)
         return m_loopback_adapter;
     if (address[0] == 127)
         return m_loopback_adapter;
-    return m_adapters.with([&](auto& adapters) -> LockRefPtr<NetworkAdapter> {
+    return m_adapters.with([&](auto& adapters) -> RefPtr<NetworkAdapter> {
         for (auto& adapter : adapters) {
             if (adapter->ipv4_address() == address || adapter->ipv4_broadcast() == address)
                 return adapter;
@@ -71,9 +71,9 @@ LockRefPtr<NetworkAdapter> NetworkingManagement::from_ipv4_address(IPv4Address c
     });
 }
 
-LockRefPtr<NetworkAdapter> NetworkingManagement::lookup_by_name(StringView name) const
+RefPtr<NetworkAdapter> NetworkingManagement::lookup_by_name(StringView name) const
 {
-    return m_adapters.with([&](auto& adapters) -> LockRefPtr<NetworkAdapter> {
+    return m_adapters.with([&](auto& adapters) -> RefPtr<NetworkAdapter> {
         for (auto& adapter : adapters) {
             if (adapter->name() == name)
                 return adapter;

Kernel/Net/NetworkingManagement.h

@@ -8,9 +8,9 @@
 
 #include <AK/Function.h>
 #include <AK/NonnullOwnPtr.h>
+#include <AK/RefPtr.h>
 #include <AK/Types.h>
 #include <Kernel/Bus/PCI/Definitions.h>
-#include <Kernel/Library/NonnullLockRefPtr.h>
 #include <Kernel/Locking/SpinlockProtected.h>
 #include <Kernel/Memory/Region.h>
 #include <Kernel/Net/NetworkAdapter.h>
@@ -33,16 +33,16 @@ public:
     void for_each(Function<void(NetworkAdapter&)>);
     ErrorOr<void> try_for_each(Function<ErrorOr<void>(NetworkAdapter&)>);
 
-    LockRefPtr<NetworkAdapter> from_ipv4_address(IPv4Address const&) const;
-    LockRefPtr<NetworkAdapter> lookup_by_name(StringView) const;
+    RefPtr<NetworkAdapter> from_ipv4_address(IPv4Address const&) const;
+    RefPtr<NetworkAdapter> lookup_by_name(StringView) const;
 
-    NonnullLockRefPtr<NetworkAdapter> loopback_adapter() const;
+    NonnullRefPtr<NetworkAdapter> loopback_adapter() const;
 
 private:
     ErrorOr<NonnullRefPtr<NetworkAdapter>> determine_network_device(PCI::DeviceIdentifier const&) const;
 
-    SpinlockProtected<Vector<NonnullLockRefPtr<NetworkAdapter>>, LockRank::None> m_adapters {};
-    LockRefPtr<NetworkAdapter> m_loopback_adapter;
+    SpinlockProtected<Vector<NonnullRefPtr<NetworkAdapter>>, LockRank::None> m_adapters {};
+    RefPtr<NetworkAdapter> m_loopback_adapter;
 };
 
 }

Kernel/Net/Routing.cpp

@@ -135,11 +135,11 @@ SpinlockProtected<Route::RouteList, LockRank::None>& routing_table()
     return *s_routing_table;
 }
 
-ErrorOr<void> update_routing_table(IPv4Address const& destination, IPv4Address const& gateway, IPv4Address const& netmask, u16 flags, LockRefPtr<NetworkAdapter> adapter, UpdateTable update)
+ErrorOr<void> update_routing_table(IPv4Address const& destination, IPv4Address const& gateway, IPv4Address const& netmask, u16 flags, RefPtr<NetworkAdapter> adapter, UpdateTable update)
 {
     dbgln_if(ROUTING_DEBUG, "update_routing_table {} {} {} {} {} {}", destination, gateway, netmask, flags, adapter, update == UpdateTable::Set ? "Set" : "Delete");
 
-    auto route_entry = adopt_lock_ref_if_nonnull(new (nothrow) Route { destination, gateway, netmask, flags, adapter.release_nonnull() });
+    auto route_entry = adopt_ref_if_nonnull(new (nothrow) Route { destination, gateway, netmask, flags, adapter.release_nonnull() });
     if (!route_entry)
         return ENOMEM;
 
@@ -178,7 +178,7 @@ static MACAddress multicast_ethernet_address(IPv4Address const& address)
     return MACAddress { 0x01, 0x00, 0x5e, (u8)(address[1] & 0x7f), address[2], address[3] };
 }
 
-RoutingDecision route_to(IPv4Address const& target, IPv4Address const& source, LockRefPtr<NetworkAdapter> const through, AllowUsingGateway allow_using_gateway)
+RoutingDecision route_to(IPv4Address const& target, IPv4Address const& source, RefPtr<NetworkAdapter> const through, AllowUsingGateway allow_using_gateway)
 {
     auto matches = [&](auto& adapter) {
         if (!through)
@@ -200,8 +200,8 @@ RoutingDecision route_to(IPv4Address const& target, IPv4Address const& source, L
     auto target_addr = target.to_u32();
     auto source_addr = source.to_u32();
 
-    LockRefPtr<NetworkAdapter> local_adapter = nullptr;
-    LockRefPtr<Route> chosen_route = nullptr;
+    RefPtr<NetworkAdapter> local_adapter = nullptr;
+    RefPtr<Route> chosen_route = nullptr;
 
     NetworkingManagement::the().for_each([source_addr, &target_addr, &local_adapter, &matches, &through](NetworkAdapter& adapter) {
         auto adapter_addr = adapter.ipv4_address().to_u32();
@@ -263,7 +263,7 @@ RoutingDecision route_to(IPv4Address const& target, IPv4Address const& source, L
         return { nullptr, {} };
     }
 
-    LockRefPtr<NetworkAdapter> adapter = nullptr;
+    RefPtr<NetworkAdapter> adapter = nullptr;
     IPv4Address next_hop_ip;
 
     if (local_adapter) {

Kernel/Net/Routing.h

@@ -7,7 +7,7 @@
 #pragma once
 
 #include <AK/IPv4Address.h>
-#include <Kernel/Library/NonnullLockRefPtr.h>
+#include <AK/RefPtr.h>
 #include <Kernel/Locking/MutexProtected.h>
 #include <Kernel/Net/NetworkAdapter.h>
 #include <Kernel/Thread.h>
@@ -15,7 +15,7 @@
 namespace Kernel {
 
 struct Route final : public AtomicRefCounted<Route> {
-    Route(IPv4Address const& destination, IPv4Address const& gateway, IPv4Address const& netmask, u16 flags, NonnullLockRefPtr<NetworkAdapter> adapter)
+    Route(IPv4Address const& destination, IPv4Address const& gateway, IPv4Address const& netmask, u16 flags, NonnullRefPtr<NetworkAdapter> adapter)
         : destination(destination)
         , gateway(gateway)
         , netmask(netmask)
@@ -38,14 +38,14 @@ struct Route final : public AtomicRefCounted<Route> {
     const IPv4Address gateway;
     const IPv4Address netmask;
     const u16 flags;
-    NonnullLockRefPtr<NetworkAdapter> adapter;
+    NonnullRefPtr<NetworkAdapter> const adapter;
 
-    IntrusiveListNode<Route, LockRefPtr<Route>> route_list_node {};
+    IntrusiveListNode<Route, RefPtr<Route>> route_list_node {};
     using RouteList = IntrusiveList<&Route::route_list_node>;
 };
 
 struct RoutingDecision {
-    LockRefPtr<NetworkAdapter> adapter;
+    RefPtr<NetworkAdapter> adapter;
     MACAddress next_hop;
 
     bool is_zero() const;
@@ -57,14 +57,14 @@ enum class UpdateTable {
 };
 
 void update_arp_table(IPv4Address const&, MACAddress const&, UpdateTable update);
-ErrorOr<void> update_routing_table(IPv4Address const& destination, IPv4Address const& gateway, IPv4Address const& netmask, u16 flags, LockRefPtr<NetworkAdapter> const adapter, UpdateTable update);
+ErrorOr<void> update_routing_table(IPv4Address const& destination, IPv4Address const& gateway, IPv4Address const& netmask, u16 flags, RefPtr<NetworkAdapter> const adapter, UpdateTable update);
 
 enum class AllowUsingGateway {
     Yes,
     No,
 };
 
-RoutingDecision route_to(IPv4Address const& target, IPv4Address const& source, LockRefPtr<NetworkAdapter> const through = nullptr, AllowUsingGateway = AllowUsingGateway::Yes);
+RoutingDecision route_to(IPv4Address const& target, IPv4Address const& source, RefPtr<NetworkAdapter> const through = nullptr, AllowUsingGateway = AllowUsingGateway::Yes);
 
 SpinlockProtected<HashMap<IPv4Address, MACAddress>, LockRank::None>& arp_table();
 SpinlockProtected<Route::RouteList, LockRank::None>& routing_table();

Kernel/Net/Socket.cpp

@@ -100,7 +100,9 @@ ErrorOr<void> Socket::setsockopt(int level, int option, Userspace<void const*> u
         auto device = NetworkingManagement::the().lookup_by_name(ifname->view());
         if (!device)
             return ENODEV;
-        m_bound_interface = move(device);
+        m_bound_interface.with([&device](auto& bound_device) {
+            bound_device = move(device);
+        });
         return {};
     }
     case SO_DEBUG:
@@ -169,31 +171,35 @@ ErrorOr<void> Socket::getsockopt(OpenFileDescription&, int level, int option, Us
     case SO_ERROR: {
         if (size < sizeof(int))
             return EINVAL;
-        int errno = 0;
-        if (auto const& error = so_error(); error.has_value())
-            errno = error.value();
-        TRY(copy_to_user(static_ptr_cast<int*>(value), &errno));
-        size = sizeof(int);
-        TRY(copy_to_user(value_size, &size));
-        clear_so_error();
-        return {};
+        return so_error().with([&size, value, value_size](auto& error) -> ErrorOr<void> {
+            int errno = 0;
+            if (error.has_value())
+                errno = error.value();
+            TRY(copy_to_user(static_ptr_cast<int*>(value), &errno));
+            size = sizeof(int);
+            TRY(copy_to_user(value_size, &size));
+            error = {};
+            return {};
+        });
     }
     case SO_BINDTODEVICE:
         if (size < IFNAMSIZ)
             return EINVAL;
-        if (m_bound_interface) {
-            auto name = m_bound_interface->name();
-            auto length = name.length() + 1;
-            auto characters = name.characters_without_null_termination();
-            TRY(copy_to_user(static_ptr_cast<char*>(value), characters, length));
-            size = length;
-            return copy_to_user(value_size, &size);
-        } else {
-            size = 0;
-            TRY(copy_to_user(value_size, &size));
-            // FIXME: This return value looks suspicious.
-            return EFAULT;
-        }
+        return m_bound_interface.with([&](auto& bound_device) -> ErrorOr<void> {
+            if (bound_device) {
+                auto name = bound_device->name();
+                auto length = name.length() + 1;
+                auto characters = name.characters_without_null_termination();
+                TRY(copy_to_user(static_ptr_cast<char*>(value), characters, length));
+                size = length;
+                return copy_to_user(value_size, &size);
+            } else {
+                size = 0;
+                TRY(copy_to_user(value_size, &size));
+                // FIXME: This return value looks suspicious.
+                return EFAULT;
+            }
+        });
     case SO_TIMESTAMP:
         if (size < sizeof(int))
             return EINVAL;

Kernel/Net/Socket.h

@@ -7,9 +7,9 @@
 #pragma once
 
 #include <AK/Error.h>
+#include <AK/RefPtr.h>
 #include <AK/Time.h>
 #include <Kernel/FileSystem/File.h>
-#include <Kernel/Library/LockRefPtr.h>
 #include <Kernel/Locking/Mutex.h>
 #include <Kernel/Net/NetworkAdapter.h>
 #include <Kernel/UnixTypes.h>
@@ -90,7 +90,7 @@ public:
     ProcessID acceptor_pid() const { return m_acceptor.pid; }
     UserID acceptor_uid() const { return m_acceptor.uid; }
     GroupID acceptor_gid() const { return m_acceptor.gid; }
-    LockRefPtr<NetworkAdapter> const bound_interface() const { return m_bound_interface; }
+    SpinlockProtected<RefPtr<NetworkAdapter>, LockRank::None> const& bound_interface() const { return m_bound_interface; }
 
     Mutex& mutex() { return m_mutex; }
 
@@ -123,31 +123,29 @@ protected:
 
     Role m_role { Role::None };
 
-    Optional<ErrnoCode> const& so_error() const
-    {
-        VERIFY(m_mutex.is_exclusively_locked_by_current_thread());
-        return m_so_error;
-    }
+    SpinlockProtected<Optional<ErrnoCode>, LockRank::None>& so_error() { return m_so_error; }
 
     Error set_so_error(ErrnoCode error_code)
     {
-        MutexLocker locker(mutex());
-        m_so_error = error_code;
-
+        m_so_error.with([&error_code](auto& so_error) {
+            so_error = error_code;
+        });
         return Error::from_errno(error_code);
     }
 
     Error set_so_error(Error error)
     {
-        MutexLocker locker(mutex());
-        m_so_error = static_cast<ErrnoCode>(error.code());
-
+        m_so_error.with([&error](auto& so_error) {
+            so_error = static_cast<ErrnoCode>(error.code());
+        });
         return error;
     }
 
     void clear_so_error()
     {
-        m_so_error = {};
+        m_so_error.with([](auto& so_error) {
+            so_error = {};
+        });
     }
 
     void set_origin(Process const&);
@@ -173,13 +171,13 @@ private:
     bool m_shut_down_for_reading { false };
     bool m_shut_down_for_writing { false };
 
-    LockRefPtr<NetworkAdapter> m_bound_interface { nullptr };
+    SpinlockProtected<RefPtr<NetworkAdapter>, LockRank::None> m_bound_interface;
 
     Time m_receive_timeout {};
     Time m_send_timeout {};
     int m_timestamp { 0 };
 
-    Optional<ErrnoCode> m_so_error;
+    SpinlockProtected<Optional<ErrnoCode>, LockRank::None> m_so_error;
 
     Vector<NonnullRefPtr<Socket>> m_pending;
 };

Kernel/Net/TCPSocket.cpp

@@ -202,7 +202,8 @@ ErrorOr<size_t> TCPSocket::protocol_receive(ReadonlyBytes raw_ipv4_packet, UserO
 
 ErrorOr<size_t> TCPSocket::protocol_send(UserOrKernelBuffer const& data, size_t data_length)
 {
-    RoutingDecision routing_decision = route_to(peer_address(), local_address(), bound_interface());
+    auto adapter = bound_interface().with([](auto& bound_device) -> RefPtr<NetworkAdapter> { return bound_device; });
+    RoutingDecision routing_decision = route_to(peer_address(), local_address(), adapter);
     if (routing_decision.is_zero())
         return set_so_error(EHOSTUNREACH);
     size_t mss = routing_decision.adapter->mtu() - sizeof(IPv4Packet) - sizeof(TCPPacket);
@@ -220,7 +221,8 @@ ErrorOr<void> TCPSocket::send_ack(bool allow_duplicate)
 
 ErrorOr<void> TCPSocket::send_tcp_packet(u16 flags, UserOrKernelBuffer const* payload, size_t payload_size, RoutingDecision* user_routing_decision)
 {
-    RoutingDecision routing_decision = user_routing_decision ? *user_routing_decision : route_to(peer_address(), local_address(), bound_interface());
+    auto adapter = bound_interface().with([](auto& bound_device) -> RefPtr<NetworkAdapter> { return bound_device; });
+    RoutingDecision routing_decision = user_routing_decision ? *user_routing_decision : route_to(peer_address(), local_address(), adapter);
     if (routing_decision.is_zero())
         return set_so_error(EHOSTUNREACH);
 
@@ -409,13 +411,14 @@ NetworkOrdered<u16> TCPSocket::compute_tcp_checksum(IPv4Address const& source, I
 
 ErrorOr<void> TCPSocket::protocol_bind()
 {
-    if (has_specific_local_address() && !m_adapter) {
-        m_adapter = NetworkingManagement::the().from_ipv4_address(local_address());
-        if (!m_adapter)
-            return set_so_error(EADDRNOTAVAIL);
-    }
-
-    return {};
+    return m_adapter.with([this](auto& adapter) -> ErrorOr<void> {
+        if (has_specific_local_address() && !adapter) {
+            adapter = NetworkingManagement::the().from_ipv4_address(local_address());
+            if (!adapter)
+                return set_so_error(EADDRNOTAVAIL);
+        }
+        return {};
+    });
 }
 
 ErrorOr<void> TCPSocket::protocol_listen(bool did_allocate_port)
@@ -598,7 +601,8 @@ void TCPSocket::retransmit_packets()
         return;
     }
 
-    auto routing_decision = route_to(peer_address(), local_address(), bound_interface());
+    auto adapter = bound_interface().with([](auto& bound_device) -> RefPtr<NetworkAdapter> { return bound_device; });
+    auto routing_decision = route_to(peer_address(), local_address(), adapter);
     if (routing_decision.is_zero())
         return;
 

Kernel/Net/TCPSocket.h

@@ -189,7 +189,7 @@ private:
     HashMap<IPv4SocketTuple, NonnullRefPtr<TCPSocket>> m_pending_release_for_accept;
     Direction m_direction { Direction::Unspecified };
     Error m_error { Error::None };
-    LockRefPtr<NetworkAdapter> m_adapter;
+    SpinlockProtected<RefPtr<NetworkAdapter>, LockRank::None> m_adapter;
     u32 m_sequence_number { 0 };
     u32 m_ack_number { 0 };
     State m_state { State::Closed };
@@ -200,7 +200,7 @@ private:
 
     struct OutgoingPacket {
         u32 ack_number { 0 };
-        LockRefPtr<PacketWithTimestamp> buffer;
+        RefPtr<PacketWithTimestamp> buffer;
         size_t ipv4_payload_offset;
         LockWeakPtr<NetworkAdapter> adapter;
         int tx_counter { 0 };

Kernel/Net/UDPSocket.cpp

@@ -84,7 +84,8 @@ ErrorOr<size_t> UDPSocket::protocol_receive(ReadonlyBytes raw_ipv4_packet, UserO
 
 ErrorOr<size_t> UDPSocket::protocol_send(UserOrKernelBuffer const& data, size_t data_length)
 {
-    auto routing_decision = route_to(peer_address(), local_address(), bound_interface());
+    auto adapter = bound_interface().with([](auto& bound_device) -> RefPtr<NetworkAdapter> { return bound_device; });
+    auto routing_decision = route_to(peer_address(), local_address(), adapter);
     if (routing_decision.is_zero())
         return set_so_error(EHOSTUNREACH);
     auto ipv4_payload_offset = routing_decision.adapter->ipv4_payload_offset();