serenity/Kernel/Net/Routing.cpp

#include <Kernel/Net/LoopbackAdapter.h>
#include <Kernel/Net/Routing.h>
#include <Kernel/Thread.h>

//#define ROUTING_DEBUG

Lockable<HashMap<IPv4Address, MACAddress>>& arp_table()
{
    static Lockable<HashMap<IPv4Address, MACAddress>>* the;
    if (!the)
        the = new Lockable<HashMap<IPv4Address, MACAddress>>;
    return *the;
}

bool RoutingDecision::is_zero() const
{
    return adapter.is_null() || next_hop.is_zero();
}

RoutingDecision route_to(const IPv4Address& target, const IPv4Address& source)
{
    if (target[0] == 127)
        return { LoopbackAdapter::the().make_weak_ptr(), {} };

    auto target_addr = target.to_u32();
    auto source_addr = source.to_u32();

    WeakPtr<NetworkAdapter> local_adapter = nullptr;
    WeakPtr<NetworkAdapter> gateway_adapter = nullptr;

    NetworkAdapter::for_each([source_addr, &target_addr, &local_adapter, &gateway_adapter](auto& adapter) {
        auto adapter_addr = adapter.ipv4_address().to_u32();
        auto adapter_mask = adapter.ipv4_netmask().to_u32();

        if (source_addr != 0 && source_addr != adapter_addr)
            return;

        if ((target_addr & adapter_mask) == (adapter_addr & adapter_mask))
            local_adapter = adapter.make_weak_ptr();

        if (adapter.ipv4_gateway().to_u32() != 0)
            gateway_adapter = adapter.make_weak_ptr();
    });

    if (!local_adapter && !gateway_adapter) {
#ifdef ROUTING_DEBUG
        kprintf("Routing: Couldn't find a suitable adapter for route to %s\n",
            target.to_string().characters());
#endif
        return { nullptr, {} };
    }

    WeakPtr<NetworkAdapter> adapter = nullptr;
    IPv4Address next_hop_ip;

    if (local_adapter) {
#ifdef ROUTING_DEBUG
        kprintf("Routing: Got adapter for route (direct): %s (%s/%s) for %s\n",
            local_adapter->name().characters(),
            local_adapter->ipv4_address().to_string().characters(),
            local_adapter->ipv4_netmask().to_string().characters(),
            target.to_string().characters());
#endif
        adapter = local_adapter;
        next_hop_ip = target;
    } else if (gateway_adapter) {
#ifdef ROUTING_DEBUG
        kprintf("Routing: Got adapter for route (using gateway %s): %s (%s/%s) for %s\n",
            gateway_adapter->ipv4_gateway().to_string().characters(),
            gateway_adapter->name().characters(),
            gateway_adapter->ipv4_address().to_string().characters(),
            gateway_adapter->ipv4_netmask().to_string().characters(),
            target.to_string().characters());
#endif
        adapter = gateway_adapter;
        next_hop_ip = gateway_adapter->ipv4_gateway();
    } else {
        return { nullptr, {} };
    }

    {
        LOCKER(arp_table().lock());
        auto addr = arp_table().resource().get(next_hop_ip);
        if (addr.has_value()) {
#ifdef ROUTING_DEBUG
            kprintf("Routing: Using cached ARP entry for %s (%s)\n",
                next_hop_ip.to_string().characters(),
                addr.value().to_string().characters());
#endif
            return { adapter, addr.value() };
        }
    }

#ifdef ROUTING_DEBUG
    kprintf("Routing: Sending ARP request via adapter %s for IPv4 address %s\n",
        adapter->name().characters(),
        next_hop_ip.to_string().characters());
#endif

    ARPPacket request;
    request.set_operation(ARPOperation::Request);
    request.set_target_hardware_address({ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff });
    request.set_target_protocol_address(next_hop_ip);
    request.set_sender_hardware_address(adapter->mac_address());
    request.set_sender_protocol_address(adapter->ipv4_address());
    adapter->send({ 0xff, 0xff, 0xff, 0xff, 0xff, 0xff }, request);

    (void)current->block_until("Routing (ARP)", [next_hop_ip] {
        return arp_table().resource().get(next_hop_ip).has_value();
    });

    {
        LOCKER(arp_table().lock());
        auto addr = arp_table().resource().get(next_hop_ip);
        if (addr.has_value()) {
#ifdef ROUTING_DEBUG
            kprintf("Routing: Got ARP response using adapter %s for %s (%s)\n",
                adapter->name().characters(),
                next_hop_ip.to_string().characters(),
                addr.value().to_string().characters());
#endif
            return { adapter, addr.value() };
        }
    }

#ifdef ROUTING_DEBUG
    kprintf("Routing: Couldn't find route using adapter %s for %s\n",
        adapter->name().characters(),
        target.to_string().characters());
#endif

    return { nullptr, {} };
}