net: teach an interface/device about hardware addresses

Since the interface must add its own hardware address when sending packets,
it better know about them.

net.cc

@@ -39,6 +39,10 @@ future<packet, ethernet_address> interface::receive(uint16_t proto_num) {
     return pr.get_future();
 }
 
+interface::interface(std::unique_ptr<device> dev)
+    : _dev(std::move(dev)), _hw_address(_dev->hw_address()) {
+}
+
 void interface::run() {
     _dev->receive().then([this] (packet p) {
         auto eh = p.get_header<eth_hdr>(0);

net.hh

@@ -132,11 +132,13 @@ private:
 class interface {
     std::unique_ptr<device> _dev;
     std::unordered_map<uint16_t, promise<packet, ethernet_address>> _proto_map;
+    ethernet_address _hw_address;
 private:
     future<packet, ethernet_address> receive(uint16_t proto_num);
     future<> send(uint16_t proto_num, ethernet_address to, packet p);
 public:
-    explicit interface(std::unique_ptr<device> dev) : _dev(std::move(dev)) {}
+    explicit interface(std::unique_ptr<device> dev);
+    ethernet_address hw_address() { return _hw_address; }
     void run();
     friend class l3_protocol;
 };
@@ -146,6 +148,7 @@ public:
     virtual ~device() {}
     virtual future<packet> receive() = 0;
     virtual future<> send(packet p) = 0;
+    virtual ethernet_address hw_address() = 0;
 };
 
 inline

virtio.cc

@@ -339,6 +339,7 @@ public:
     explicit virtio_net_device(sstring tap_device, init x = init());
     virtual future<packet> receive() override;
     virtual future<> send(packet p) override;
+    virtual ethernet_address hw_address() override;
 };
 
 virtio_net_device::txq::txq(virtio_net_device& dev, vring::config config,
@@ -514,6 +515,10 @@ void virtio_net_device::queue_rx_packet(packet p) {
     _rx_queue_length.signal(1);
 }
 
+ethernet_address virtio_net_device::hw_address() {
+    return { 0x12, 0x23, 0x34, 0x56, 0x67, 0x78 };
+}
+
 std::unique_ptr<net::device> create_virtio_net_device(sstring tap_device) {
     return std::make_unique<virtio_net_device>(tap_device);
 }