remote_rom: implement ARP requests

src/lib/remote_rom/backend/nic_ip/base.cc

@@ -20,6 +20,28 @@ void Remote_rom::Backend_base::_handle_rx_packet()
 	}
 }
 
+void Remote_rom::Backend_base::_handle_arp_request(Ethernet_frame &eth,
+                                                   Size_guard     &guard,
+                                                   Arp_packet     &arp)
+{
+	/*
+	 * The ARP packet gets re-written, we interchange source
+	 * and destination MAC and IP addresses, and set the opcode
+	 * to reply, and then push the packet back to the NIC driver.
+	 */
+	Ipv4_address old_src_ip = arp.src_ip();
+	arp.opcode(Arp_packet::REPLY);
+	arp.dst_mac(arp.src_mac());
+	arp.src_mac(_mac_address);
+	arp.src_ip(arp.dst_ip());
+	arp.dst_ip(old_src_ip);
+	eth.dst(arp.dst_mac());
+
+	/* set our MAC as sender */
+	eth.src(_mac_address);
+	send(&eth, guard.total_size());
+}
+
 void Remote_rom::Backend_base::handle_ethernet(void* src, Genode::size_t size)
 {
 	try {
@@ -51,23 +73,17 @@ void Remote_rom::Backend_base::handle_arp(Ethernet_frame &eth,
 
 	/* look whether the IP address is our's */
 	if (arp.dst_ip() == _accept_ip) {
-		if (arp.opcode() == Arp_packet::REQUEST) {
+		switch (arp.opcode()) {
-			/*
+			case Arp_packet::REQUEST:
-			 * The ARP packet gets re-written, we interchange source
+				_handle_arp_request(eth, edguard, arp);
-			 * and destination MAC and IP addresses, and set the opcode
+				break;
-			 * to reply, and then push the packet back to the NIC driver.
+			case Arp_packet::REPLY:
-			 */
+				if (_arp_waiting && arp.src_ip() == _dst_ip) {
-			Ipv4_address old_src_ip = arp.src_ip();
+					_dst_mac = arp.src_mac();
-			arp.opcode(Arp_packet::REPLY);
+					_arp_waiting = false;
-			arp.dst_mac(arp.src_mac());
+				}
-			arp.src_mac(_mac_address);
+				break;
-			arp.src_ip(arp.dst_ip());
+			default: break;
-			arp.dst_ip(old_src_ip);
-			eth.dst(arp.dst_mac());
-
-			/* set our MAC as sender */
-			eth.src(_mac_address);
-			send(&eth, edguard.total_size());
 		}
 	}
 }
@@ -80,6 +96,9 @@ void Remote_rom::Backend_base::handle_ip(Ethernet_frame &eth,
 		 || _accept_ip == ip.dst()) {
 
 		if (ip.protocol() == Ipv4_packet::Protocol::UDP) {
+			if (_dst_mac == Ethernet_frame::broadcast() && ip.src() == _dst_ip) {
+				_dst_mac = eth.src();
+			}
 			/* remote_rom protocol is wrapped in UDP */
 			Udp_packet &udp = ip.data<Udp_packet>(edguard);
 			if (udp.dst_port() == _udp_port)

src/lib/remote_rom/backend/nic_ip/base.h

@@ -54,6 +54,10 @@ class Remote_rom::Backend_base : public Genode::Interface
 		/* rx packet handler */
 		void _handle_rx_packet();
 
+		void _handle_arp_request(Ethernet_frame &eth,
+		                         Size_guard     &guard,
+		                         Arp_packet     &arp);
+
 		void _handle_link_state()
 		{
 			Genode::log("link state changed");
@@ -79,6 +83,7 @@ class Remote_rom::Backend_base : public Genode::Interface
 		Timer::Connection     _timer;
 
 		const bool            _verbose = false;
+		bool                  _arp_waiting { false };
 		Nic::Packet_allocator _tx_block_alloc;
 		Nic::Connection       _nic;
 		Mac_address           _mac_address;
@@ -93,8 +98,41 @@ class Remote_rom::Backend_base : public Genode::Interface
 		 */
 		virtual void receive(Packet &packet, Size_guard &) = 0;
 
+		inline void arp_request()
+		{
+			if (_dst_mac == Ethernet_frame::broadcast() && !_arp_waiting) {
+				size_t const frame_size = sizeof(Ethernet_frame)
+			                           + sizeof(Arp_packet);
+				Nic::Packet_descriptor pd = alloc_tx_packet(frame_size);
+				Size_guard size_guard(pd.size());
+
+				char *content = _nic.tx()->packet_content(pd);
+				Ethernet_frame &eth = Ethernet_frame::construct_at(content,
+				                                                   size_guard);
+				eth.src(_mac_address);
+				eth.dst(Ethernet_frame::broadcast());
+				eth.type(Ethernet_frame::Type::ARP);
+
+				Arp_packet &arp = eth.construct_at_data<Arp_packet>(size_guard);
+				arp.hardware_address_type(Arp_packet::ETHERNET);
+				arp.protocol_address_type(Arp_packet::IPV4);
+				arp.hardware_address_size(sizeof(Mac_address));
+				arp.protocol_address_size(sizeof(Ipv4_address));
+				arp.opcode(Arp_packet::REQUEST);
+				arp.src_mac(_mac_address);
+				arp.src_ip(_src_ip);
+				arp.dst_mac(Ethernet_frame::broadcast());
+				arp.dst_ip(_dst_ip);
+
+				_arp_waiting = true;
+				submit_tx_packet(pd);
+			}
+		}
+
 		Ethernet_frame &prepare_eth(void *base, Size_guard &size_guard)
 		{
+			arp_request();
+
 			Ethernet_frame &eth = Ethernet_frame::construct_at(base, size_guard);
 			eth.src(_mac_address);
 			eth.dst(_dst_mac);