Kernel: Add a LoopbackAdapter for talking to yourself via 127.0.0.1.

Choosing adapter for transmit is done by adapter_for_route_to(IPv4Address).
This is just hard-coded logic right now but can be expanded to support a
proper routing table.

Also start moving kernel networking code into Kernel/Net/.

Kernel/IPv4Socket.cpp

@@ -9,6 +9,7 @@
 #include <Kernel/TCP.h>
 #include <Kernel/UDP.h>
 #include <Kernel/ARP.h>
+#include <Kernel/Net/Routing.h>
 #include <LibC/errno_numbers.h>
 
 #define IPV4_SOCKET_DEBUG
@@ -128,12 +129,6 @@ ssize_t IPv4Socket::sendto(const void* data, size_t data_length, int flags, cons
     (void)flags;
     if (addr && addr_length != sizeof(sockaddr_in))
         return -EINVAL;
-    // FIXME: Find the adapter some better way!
-    auto* adapter = NetworkAdapter::from_ipv4_address(IPv4Address(192, 168, 5, 2));
-    if (!adapter) {
-        // FIXME: Figure out which error code to return.
-        ASSERT_NOT_REACHED();
-    }
 
     if (addr) {
         if (addr->sa_family != AF_INET) {
@@ -146,6 +141,10 @@ ssize_t IPv4Socket::sendto(const void* data, size_t data_length, int flags, cons
         m_destination_port = ntohs(ia.sin_port);
     }
 
+    auto* adapter = adapter_for_route_to(m_destination_address);
+    if (!adapter)
+        return -EHOSTUNREACH;
+
     int rc = allocate_source_port_if_needed();
     if (rc < 0)
         return rc;

Kernel/Makefile

@@ -39,6 +39,8 @@ KERNEL_OBJS = \
        UDPSocket.o \
        NetworkAdapter.o \
        E1000NetworkAdapter.o \
+       Net/LoopbackAdapter.o \
+       Net/Routing.o \
        NetworkTask.o
 
 VFS_OBJS = \

Kernel/Net/.gitignore

@@ -0,0 +1,2 @@
+*.o
+*.d

Kernel/Net/LoopbackAdapter.cpp

@@ -0,0 +1,24 @@
+#include <Kernel/Net/LoopbackAdapter.h>
+
+LoopbackAdapter& LoopbackAdapter::the()
+{
+    static LoopbackAdapter* the;
+    if (!the)
+        the = new LoopbackAdapter;
+    return *the;
+}
+
+LoopbackAdapter::LoopbackAdapter()
+{
+    set_ipv4_address({ 127, 0, 0, 1 });
+}
+
+LoopbackAdapter::~LoopbackAdapter()
+{
+}
+
+void LoopbackAdapter::send_raw(const byte* data, int size)
+{
+    dbgprintf("LoopbackAdapter: Sending %d byte(s) to myself.\n", size);
+    did_receive(data, size);
+}

Kernel/Net/LoopbackAdapter.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include <Kernel/NetworkAdapter.h>
+
+class LoopbackAdapter final : public NetworkAdapter {
+public:
+    static LoopbackAdapter& the();
+
+    virtual ~LoopbackAdapter() override;
+
+    virtual void send_raw(const byte*, int) override;
+    virtual const char* class_name() const override { return "LoopbackAdapter"; }
+
+private:
+    LoopbackAdapter();
+};

Kernel/Net/Routing.cpp

@@ -0,0 +1,10 @@
+#include <Kernel/Net/Routing.h>
+#include <Kernel/Net/LoopbackAdapter.h>
+
+NetworkAdapter* adapter_for_route_to(const IPv4Address& ipv4_address)
+{
+    // FIXME: Have an actual routing table.
+    if (ipv4_address == IPv4Address(127, 0, 0, 1))
+        return &LoopbackAdapter::the();
+    return NetworkAdapter::from_ipv4_address(IPv4Address(192, 168, 5, 2));
+}

Kernel/Net/Routing.h

@@ -0,0 +1,5 @@
+#pragma once
+
+#include <Kernel/NetworkAdapter.h>
+
+NetworkAdapter* adapter_for_route_to(const IPv4Address&);

Kernel/NetworkAdapter.cpp

@@ -28,14 +28,12 @@ NetworkAdapter::NetworkAdapter()
     : m_packet_queue_alarm(*this)
 {
     // FIXME: I wanna lock :(
-    ASSERT_INTERRUPTS_DISABLED();
     all_adapters().resource().set(this);
 }
 
 NetworkAdapter::~NetworkAdapter()
 {
     // FIXME: I wanna lock :(
-    ASSERT_INTERRUPTS_DISABLED();
     all_adapters().resource().remove(this);
 }
 

Kernel/NetworkTask.cpp

@@ -11,6 +11,7 @@
 #include <Kernel/Process.h>
 #include <Kernel/EtherType.h>
 #include <Kernel/Lock.h>
+#include <Kernel/Net/LoopbackAdapter.h>
 
 //#define ETHERNET_DEBUG
 #define IPV4_DEBUG
@@ -34,16 +35,27 @@ Lockable<HashMap<IPv4Address, MACAddress>>& arp_table()
 
 void NetworkTask_main()
 {
+    LoopbackAdapter::the();
+
     auto* adapter_ptr = E1000NetworkAdapter::the();
     ASSERT(adapter_ptr);
     auto& adapter = *adapter_ptr;
     adapter.set_ipv4_address(IPv4Address(192, 168, 5, 2));
 
+    auto dequeue_packet = [&] () -> ByteBuffer {
+        if (LoopbackAdapter::the().has_queued_packets())
+            return LoopbackAdapter::the().dequeue_packet();
+        if (adapter.has_queued_packets())
+            return adapter.dequeue_packet();
+        return { };
+    };
+
     kprintf("NetworkTask: Enter main loop.\n");
     for (;;) {
-        auto packet = adapter.dequeue_packet();
+        auto packet = dequeue_packet();
         if (packet.is_null()) {
-            current->snooze_until(adapter.packet_queue_alarm());
+            // FIXME: Wake up when one of the adapters has packets.
+            current->sleep(1);
             continue;
         }
         if (packet.size() < (int)(sizeof(EthernetFrameHeader))) {

Kernel/TCPSocket.cpp

@@ -2,6 +2,7 @@
 #include <Kernel/TCP.h>
 #include <Kernel/NetworkAdapter.h>
 #include <Kernel/Process.h>
+#include <Kernel/Net/Routing.h>
 #include <Kernel/RandomDevice.h>
 
 Lockable<HashMap<word, TCPSocket*>>& TCPSocket::sockets_by_port()
@@ -63,18 +64,18 @@ int TCPSocket::protocol_receive(const ByteBuffer& packet_buffer, void* buffer, s
 
 int TCPSocket::protocol_send(const void* data, int data_length)
 {
-    // FIXME: Figure out the adapter somehow differently.
-    auto* adapter = NetworkAdapter::from_ipv4_address(IPv4Address(192, 168, 5, 2));
+    auto* adapter = adapter_for_route_to(destination_address());
     if (!adapter)
-        ASSERT_NOT_REACHED();
+        return -EHOSTUNREACH;
     send_tcp_packet(TCPFlags::PUSH | TCPFlags::ACK, data, data_length);
     return data_length;
 }
 
 void TCPSocket::send_tcp_packet(word flags, const void* payload, int payload_size)
 {
-    // FIXME: Figure out the adapter somehow differently.
-    auto& adapter = *NetworkAdapter::from_ipv4_address(IPv4Address(192, 168, 5, 2));
+    // FIXME: Maybe the socket should be bound to an adapter instead of looking it up every time?
+    auto* adapter = adapter_for_route_to(destination_address());
+    ASSERT(adapter);
 
     auto buffer = ByteBuffer::create_zeroed(sizeof(TCPPacket) + payload_size);
     auto& tcp_packet = *(TCPPacket*)(buffer.pointer());
@@ -96,9 +97,9 @@ void TCPSocket::send_tcp_packet(word flags, const void* payload, int payload_siz
     }
 
     memcpy(tcp_packet.payload(), payload, payload_size);
-    tcp_packet.set_checksum(compute_tcp_checksum(adapter.ipv4_address(), destination_address(), tcp_packet, payload_size));
+    tcp_packet.set_checksum(compute_tcp_checksum(adapter->ipv4_address(), destination_address(), tcp_packet, payload_size));
     kprintf("sending tcp packet from %s:%u to %s:%u with (%s %s) seq_no=%u, ack_no=%u\n",
-        adapter.ipv4_address().to_string().characters(),
+        adapter->ipv4_address().to_string().characters(),
         source_port(),
         destination_address().to_string().characters(),
         destination_port(),
@@ -107,7 +108,7 @@ void TCPSocket::send_tcp_packet(word flags, const void* payload, int payload_siz
         tcp_packet.sequence_number(),
         tcp_packet.ack_number()
     );
-    adapter.send_ipv4(MACAddress(), destination_address(), IPv4Protocol::TCP, move(buffer));
+    adapter->send_ipv4(MACAddress(), destination_address(), IPv4Protocol::TCP, move(buffer));
 }
 
 NetworkOrdered<word> TCPSocket::compute_tcp_checksum(const IPv4Address& source, const IPv4Address& destination, const TCPPacket& packet, word payload_size)
@@ -153,10 +154,9 @@ NetworkOrdered<word> TCPSocket::compute_tcp_checksum(const IPv4Address& source,
 
 KResult TCPSocket::protocol_connect()
 {
-    // FIXME: Figure out the adapter somehow differently.
-    auto* adapter = NetworkAdapter::from_ipv4_address(IPv4Address(192, 168, 5, 2));
+    auto* adapter = adapter_for_route_to(destination_address());
     if (!adapter)
-        ASSERT_NOT_REACHED();
+        return KResult(-EHOSTUNREACH);
 
     allocate_source_port_if_needed();
 

Kernel/UDPSocket.cpp

@@ -3,6 +3,7 @@
 #include <Kernel/NetworkAdapter.h>
 #include <Kernel/Process.h>
 #include <Kernel/RandomDevice.h>
+#include <Kernel/Net/Routing.h>
 
 Lockable<HashMap<word, UDPSocket*>>& UDPSocket::sockets_by_port()
 {
@@ -62,8 +63,9 @@ int UDPSocket::protocol_receive(const ByteBuffer& packet_buffer, void* buffer, s
 
 int UDPSocket::protocol_send(const void* data, int data_length)
 {
-    // FIXME: Figure out the adapter somehow differently.
-    auto& adapter = *NetworkAdapter::from_ipv4_address(IPv4Address(192, 168, 5, 2));
+    auto* adapter = adapter_for_route_to(destination_address());
+    if (!adapter)
+        return -EHOSTUNREACH;
     auto buffer = ByteBuffer::create_zeroed(sizeof(UDPPacket) + data_length);
     auto& udp_packet = *(UDPPacket*)(buffer.pointer());
     udp_packet.set_source_port(source_port());
@@ -71,11 +73,11 @@ int UDPSocket::protocol_send(const void* data, int data_length)
     udp_packet.set_length(sizeof(UDPPacket) + data_length);
     memcpy(udp_packet.payload(), data, data_length);
     kprintf("sending as udp packet from %s:%u to %s:%u!\n",
-        adapter.ipv4_address().to_string().characters(),
+        adapter->ipv4_address().to_string().characters(),
         source_port(),
         destination_address().to_string().characters(),
         destination_port());
-    adapter.send_ipv4(MACAddress(), destination_address(), IPv4Protocol::UDP, move(buffer));
+    adapter->send_ipv4(MACAddress(), destination_address(), IPv4Protocol::UDP, move(buffer));
     return data_length;
 }