arp: manage the case when the target is unreacheable

liteeth/core/arp.py

@@ -134,7 +134,7 @@ class LiteEthARPRX(Module):
 		)
 
 class LiteEthARPTable(Module):
-	def __init__(self, clk_freq):
+	def __init__(self, clk_freq, max_requests=8):
 		self.sink = sink = Sink(_arp_table_layout) 			# from arp_rx
 		self.source = source = Source(_arp_table_layout) 	# to arp_tx
 
@@ -143,9 +143,10 @@ class LiteEthARPTable(Module):
 		self.response = response = Source(arp_table_response_layout)
 		###
 		request_timeout = Timeout(clk_freq//10)
+		request_counter = Counter(max=max_requests)
 		request_pending = FlipFlop()
-		request_ip_address = FlipFlop(32, reset=0xffffffff)
-		self.submodules += request_timeout, request_pending, request_ip_address
+		request_ip_address = FlipFlop(32)
+		self.submodules += request_timeout, request_counter, request_pending, request_ip_address
 		self.comb += [
 			request_timeout.ce.eq(request_pending.q),
 			request_pending.d.eq(1),
@@ -165,11 +166,13 @@ class LiteEthARPTable(Module):
 		self.submodules.fsm = fsm = FSM(reset_state="IDLE")
 		fsm.act("IDLE",
 			# Note: for simplicicy, if APR table is busy response from arp_rx
-			# is lost. This is compensated by the protocol (retrys)
+			# is lost. This is compensated by the protocol (retry)
 			If(sink.stb & sink.request,
 				NextState("SEND_REPLY")
 			).Elif(sink.stb & sink.reply & request_pending.q,
 				NextState("UPDATE_TABLE"),
+			).Elif(request_counter.value == max_requests-1,
+				NextState("PRESENT_RESPONSE")
 			).Elif(request.stb | (request_pending.q & request_timeout.reached),
 				NextState("CHECK_TABLE")
 			)
@@ -224,15 +227,23 @@ class LiteEthARPTable(Module):
 			source.ip_address.eq(request_ip_address.q),
 			If(source.ack,
 				request_timeout.reset.eq(1),
+				request_counter.reset.eq(request.stb),
+				request_counter.ce.eq(1),
 				request_pending.ce.eq(1),
 				request.ack.eq(1),
 				NextState("IDLE")
 			)
 		)
+		self.comb += [
+			If(request_counter == max_requests-1,
+				response.failed.eq(1),
+				request_counter.reset.eq(1),
+				request_pending.reset.eq(1)
+			),
+			response.mac_address.eq(cached_mac_address)
+		]
 		fsm.act("PRESENT_RESPONSE",
 			response.stb.eq(1),
-			response.failed.eq(0), # XXX add timeout to trigger failed
-			response.mac_address.eq(cached_mac_address),
 			If(response.ack,
 				NextState("IDLE")
 			)

liteeth/core/ip.py

@@ -42,6 +42,7 @@ class LiteEthIPTX(Module):
 	def __init__(self, mac_address, ip_address, arp_table):
 		self.sink = Sink(eth_ipv4_user_description(8))
 		self.source = Source(eth_mac_description(8))
+		self.target_unreachable = Signal()
 		###
 		packetizer = LiteEthIPV4Packetizer()
 		self.submodules += packetizer
@@ -87,11 +88,14 @@ class LiteEthIPTX(Module):
 			)
 		)
 		fsm.act("WAIT_MAC_ADDRESS_RESPONSE",
-			# XXX add timeout
 			If(arp_table.response.stb,
 				arp_table.response.ack.eq(1),
-				# XXX manage failed
-				NextState("SEND")
+				If(arp_table.response.failed,
+					self.target_unreachable.eq(1),
+					NextState("DROP"),
+				).Else(
+					NextState("SEND")
+				)
 			)
 		)
 		self.sync += If(arp_table.response.stb, target_mac.eq(arp_table.response.mac_address))
@@ -101,7 +105,12 @@ class LiteEthIPTX(Module):
 			self.source.target_mac.eq(target_mac),
 			self.source.sender_mac.eq(mac_address),
 			If(self.source.stb & self.source.eop & self.source.ack,
-				# XXX manage failed
+				NextState("IDLE")
+			)
+		)
+		fsm.act("DROP",
+			packetizer.source.ack.eq(1),
+			If(packetizer.source.stb & packetizer.source.eop & packetizer.source.ack,
 				NextState("IDLE")
 			)
 		)