arp: Implement ARP replies

design/top_hwitl.vhd

@@ -186,6 +186,9 @@ architecture eth of top_hwitl is
 	constant ETH_CONFIG : configuration_t    := (
 		mac_address => (x"00", x"ff", x"ff", x"11", x"22", x"33")
 	);
+	constant IP_CONFIG  : ip_configuration_t := (
+		ip_address => (x"C0", x"A8", x"02", x"02")
+	);
 
 	signal rst          : std_logic;
 	signal clk_phy      : std_logic;
@@ -199,12 +202,30 @@ architecture eth of top_hwitl is
 
 	constant PROT_ARP              : integer                     := 0;
 	constant PROT_IP               : integer                     := 1;
-	constant ETHERNET_II_PROTOCOLS : ethernet_ii_protocol_vector := (PROT_ARP => ETHERNET_II_PROTOCOL_ARP, PROT_IP => ETHERNET_II_PROTOCOL_IP);
+	constant ETHERNET_II_PROTOCOLS : ethernet_ii_protocol_vector := (
+		PROT_ARP => ETHERNET_II_PROTOCOL_ARP,
+		PROT_IP  => ETHERNET_II_PROTOCOL_IP
+	);
 	signal ethernet_i_out          : ethernet_i_out_t;
 	signal ethernet_i_in           : ethernet_i_in_t;
 	signal ethernet_ii_out         : ethernet_ii_out_vector(ETHERNET_II_PROTOCOLS'range);
 	signal ethernet_ii_in          : ethernet_ii_in_vector(ETHERNET_II_PROTOCOLS'range);
+
+	signal arp_out : arp_out_t;
+	signal arp_in  : arp_in_t;
 begin
+	trashernet_arp_inst : entity trashernet.trashernet_arp
+		port map(
+			clk             => clk,
+			rst             => rst,
+			mac_config      => ETH_CONFIG,
+			ip_config       => IP_CONFIG,
+			arp_out         => arp_out,
+			arp_in          => arp_in,
+			ethernet_ii_out => ethernet_ii_out(PROT_ARP),
+			ethernet_ii_in  => ethernet_ii_in(PROT_ARP)
+		);
+
 	trashernet_eth_inst : entity trashernet.trashernet_eth
 		generic map(
 			ETHERNET_II_PROTOCOLS => ETHERNET_II_PROTOCOLS

trashernet/trashernet_arp.vhd

@@ -0,0 +1,210 @@
+-- -------------------------------------------------------------------------- --
+--               TRASHERNET - A Trashy Ethernet Stack for FPGAs               --
+-- -------------------------------------------------------------------------- --
+-- trashernet_arp.vhd : Address Resolution Protocol
+--   Implements simple single-entry cache ARP.
+-- -------------------------------------------------------------------------- --
+-- Author       : Markus Koch <markus@notsyncing.net>
+-- Contributors : None
+-- License      : Mozilla Public License (MPL) Version 2
+-- -------------------------------------------------------------------------- --
+
+library ieee;
+use ieee.std_logic_1164.all;
+use ieee.numeric_std.all;
+
+use work.trashernet_pkg.all;
+
+entity trashernet_arp is
+	port(
+		-- Global
+		clk             : in  std_logic; -- Global clock
+		rst             : in  std_logic; -- Asynchronous reset
+
+		-- Configuration
+		mac_config      : in  configuration_t; -- Trashernet MAC configuration
+		ip_config       : in  ip_configuration_t; -- Trashernet IP configuration
+
+		-- ARP application interface
+		arp_out         : out arp_out_t; -- ARP IF (out from ARP)
+		arp_in          : in  arp_in_t; -- ARP IF (into ARP)
+
+		-- Ethernet II application interface
+		ethernet_ii_out : in  ethernet_ii_out_t; -- Ethernet II IF (out from MAC)
+		ethernet_ii_in  : out ethernet_ii_in_t -- Ethernet II IF (into MAC)
+	);
+end entity trashernet_arp;
+
+architecture rtl of trashernet_arp is
+	constant HTYPE        : byte_vector := (x"00", x"01");
+	constant PTYPE        : byte_vector := (x"08", x"00");
+	constant HLEN         : byte        := x"06";
+	constant PLEN         : byte        := x"04";
+	constant OPER_REQUEST : byte_vector := (x"00", x"01");
+	constant OPER_REPLY   : byte_vector := (x"00", x"02");
+
+	signal arp_reply_rq  : std_logic; -- Request to transmit an ARP reply
+	signal arp_reply_tha : mac_addr_t; -- Target MAC to use in reply (SHA in received packet)
+	signal arp_reply_tpa : ip_addr_t; -- Target IP to use in reply (SPA in received packet)
+	signal arp_reply_ack : std_logic; -- ARP reply has been latched and is being sent
+begin
+	rx : block
+		constant BYTECOUNT_HEAD      : integer := 8; -- HTYPE -> OPER
+		constant BYTECOUNT_ADDRESSES : integer := 20; -- SHA -> TPA
+
+		signal sr : byte_vector(0 to BYTECOUNT_ADDRESSES - 1);
+
+		constant SR_HEAD_OFFSET : integer := BYTECOUNT_ADDRESSES - BYTECOUNT_HEAD;
+		alias sr_head_htype is sr(SR_HEAD_OFFSET + 0 to SR_HEAD_OFFSET + 1);
+		alias sr_head_ptype is sr(SR_HEAD_OFFSET + 2 to SR_HEAD_OFFSET + 3);
+		alias sr_head_hlen is sr(SR_HEAD_OFFSET + 4);
+		alias sr_head_plen is sr(SR_HEAD_OFFSET + 5);
+		alias sr_head_oper is sr(SR_HEAD_OFFSET + 6 to SR_HEAD_OFFSET + 7);
+
+		constant SR_ADDRESSES_OFFSET : integer := -8;
+		alias sr_addresses_sha is sr(8 + SR_ADDRESSES_OFFSET to 13 + SR_ADDRESSES_OFFSET);
+		alias sr_addresses_spa is sr(14 + SR_ADDRESSES_OFFSET to 17 + SR_ADDRESSES_OFFSET);
+		alias sr_addresses_tha is sr(18 + SR_ADDRESSES_OFFSET to 23 + SR_ADDRESSES_OFFSET);
+		alias sr_addresses_tpa is sr(24 + SR_ADDRESSES_OFFSET to 27 + SR_ADDRESSES_OFFSET);
+
+		type state_t is (HEAD, ADDRESSES, WAITCRC, SENDREPLY, IGNORE);
+		signal state     : state_t;
+		signal bytecount : integer range 0 to BYTECOUNT_ADDRESSES;
+		signal shifted   : std_logic;
+
+		signal block_done : std_logic;
+
+		signal header_ok    : std_logic;
+		signal we_are_asked : std_logic;
+
+		signal is_request : std_logic;
+	begin
+
+		block_done <= '1' when shifted = '1' and bytecount = 0 else '0';
+
+		header_ok <= '1' when           --
+		             sr_head_htype = HTYPE and --
+		             sr_head_ptype = PTYPE and --
+		             sr_head_hlen = HLEN and sr_head_plen = PLEN --
+		             else
+		             '0';
+
+		we_are_asked <= '1' when        --
+		                sr_addresses_tpa = ip_config.ip_address else
+		                '0';
+
+		rx_fsm : process(clk, rst) is
+		begin
+			if rst then
+				state     <= HEAD;
+				shifted   <= '0';
+				bytecount <= BYTECOUNT_HEAD;
+
+			elsif rising_edge(clk) then
+				if (ethernet_ii_out.rx_crc_ok or ethernet_ii_out.rx_crc_error) then
+					state     <= HEAD;  -- Safe return from any state, may be overridden below
+					bytecount <= BYTECOUNT_HEAD;
+				end if;
+				shifted <= ethernet_ii_out.rx_data_valid;
+				if (ethernet_ii_out.rx_data_valid = '1') and (bytecount > 0) then
+					sr        <= sr(sr'low + 1 to sr'high) & ethernet_ii_out.rx_data;
+					bytecount <= bytecount - 1;
+				end if;
+				case state is
+					when HEAD =>
+						if block_done then
+							if header_ok then
+								bytecount  <= BYTECOUNT_ADDRESSES;
+								state      <= ADDRESSES;
+								is_request <= '1' when (sr_head_oper = OPER_REQUEST) else '0';
+							else
+								state <= IGNORE;
+							end if;
+						end if;
+
+					when ADDRESSES =>
+						if block_done then
+							if (we_are_asked) then
+								state <= WAITCRC;
+							else
+								state <= IGNORE;
+							end if;
+						end if;
+
+					when WAITCRC =>
+						if ethernet_ii_out.rx_crc_ok then
+							if is_request then
+								state <= SENDREPLY;
+							else
+								report "reply";
+								null;   -- TODO: process response
+							end if;
+						end if;
+
+					when SENDREPLY =>
+						if arp_reply_ack then
+							bytecount <= BYTECOUNT_HEAD;
+							state     <= HEAD;
+						end if;
+
+					when IGNORE =>
+						null;
+				end case;
+			end if;
+		end process rx_fsm;
+		arp_reply_rq  <= '1' when state = SENDREPLY else '0';
+		arp_reply_tha <= sr_addresses_sha;
+		arp_reply_tpa <= sr_addresses_spa;
+	end block rx;
+
+	tx : block
+		signal sr                : byte_vector(0 to 27);
+		signal arp_reply_preload : byte_vector(sr'range);
+		constant BYTECOUNT_MAX   : integer := sr'length + 1;
+		signal bytecount         : integer range 0 to BYTECOUNT_MAX;
+
+		type state_t is (IDLE, TRANSMIT);
+		signal state : state_t;
+	begin
+
+		arp_reply_preload <= HTYPE & PTYPE & HLEN & PLEN & OPER_REPLY & -- Header
+		                     mac_config.mac_address & ip_config.ip_address & -- Sender
+		                     arp_reply_tha & arp_reply_tpa; -- Target
+
+		tx_fsm : process(clk, rst) is
+		begin
+			if rst then
+				arp_reply_ack <= '0';
+
+			elsif rising_edge(clk) then
+				arp_reply_ack <= '0';
+
+				if (ethernet_ii_out.tx_data_ack = '1') and (bytecount > 0) then
+					sr        <= sr(sr'low + 1 to sr'high) & x"00";
+					bytecount <= bytecount - 1;
+				end if;
+
+				case state is
+					when IDLE =>
+						if arp_reply_rq then
+							state         <= TRANSMIT;
+							arp_reply_ack <= '1';
+							sr            <= arp_reply_preload;
+						end if;
+
+						bytecount <= BYTECOUNT_MAX;
+
+					when TRANSMIT =>
+						if bytecount = 0 then
+							state <= IDLE;
+						end if;
+				end case;
+			end if;
+		end process tx_fsm;
+
+		ethernet_ii_in.tx_mac_address <= arp_reply_tha;
+		ethernet_ii_in.tx_en          <= '1' when state = TRANSMIT else '0';
+		ethernet_ii_in.tx_data        <= sr(0);
+
+	end block tx;
+end architecture rtl;

trashernet/trashernet_pkg.vhd

@@ -34,6 +34,9 @@ package trashernet_pkg is
 	type configuration_t is record
 		mac_address : mac_addr_t;       -- MAC address of this node
 	end record configuration_t;
+	type ip_configuration_t is record
+		ip_address : ip_addr_t;         -- IP address of this node
+	end record ip_configuration_t;
 
 	-- PHY interface
 	type phy_in_t is record