Subversion Repositories udp_ip_stack

----------------------------------------------------------------------------------

-- Company: 

-- Engineer:            Peter Fall

-- 

-- Create Date:    16:20:42 06/01/2011 

-- Design Name: 

-- Module Name:    IPv4_TX - Behavioral 

-- Project Name: 

-- Target Devices: 

-- Tool versions: 

-- Description: 

--              handle simple IP TX

--              doesnt handle segmentation

--              dest MAC addr resolution through ARP layer

--              Handle IPv4 protocol

-- Dependencies: 

--

-- Revision: 

-- Revision 0.01 - File Created

-- Revision 0.02 - fixed up setting of tx_result control defaults

-- Revision 0.03 - Added data_out_first

-- Revision 0.04 - Added handling of broadcast address

-- Additional Comments: 

--

----------------------------------------------------------------------------------

library IEEE;

use IEEE.STD_LOGIC_1164.all;

use IEEE.NUMERIC_STD.all;

use work.axi.all;

use work.ipv4_types.all;

use work.arp_types.all;

entity IPv4_TX is

  port (

    -- IP Layer signals

    ip_tx_start          : in  std_logic;

    ip_tx                : in  ipv4_tx_type;                   -- IP tx cxns

    ip_tx_result         : out std_logic_vector (1 downto 0);  -- tx status (changes during transmission)

    ip_tx_data_out_ready : out std_logic;  -- indicates IP TX is ready to take data

    -- system signals

    clk                : in  std_logic;  -- same clock used to clock mac data and ip data

    reset              : in  std_logic;

    our_ip_address     : in  std_logic_vector (31 downto 0);

    our_mac_address    : in  std_logic_vector (47 downto 0);

    -- ARP lookup signals

    arp_req_req        : out arp_req_req_type;

    arp_req_rslt       : in  arp_req_rslt_type;

    -- MAC layer TX signals

    mac_tx_req         : out std_logic;  -- indicates that ip wants access to channel (stays up for as long as tx)

    mac_tx_granted     : in  std_logic;  -- indicates that access to channel has been granted            

    mac_data_out_ready : in  std_logic;  -- indicates system ready to consume data

    mac_data_out_valid : out std_logic;  -- indicates data out is valid

    mac_data_out_first : out std_logic;  -- with data out valid indicates the first byte of a frame

    mac_data_out_last  : out std_logic;  -- with data out valid indicates the last byte of a frame

    mac_data_out       : out std_logic_vector (7 downto 0)  -- ethernet frame (from dst mac addr through to last byte of frame)      

    );

end IPv4_TX;

architecture Behavioral of IPv4_TX is

  type tx_state_type is (

    IDLE,

    WAIT_MAC,                           -- waiting for response from ARP for mac lookup

    WAIT_CHN,                           -- waiting for tx access to MAC channel

    SEND_ETH_HDR,                       -- sending the ethernet header

    SEND_IP_HDR,                        -- sending the IP header

    SEND_USER_DATA                      -- sending the users data

    );

  type crc_state_type is (IDLE, TOT_LEN, ID, FLAGS, TTL, CKS, SAH, SAL, DAH, DAL, FINAL, WAIT_END);

  type count_mode_type is (RST, INCR, HOLD);

  type settable_cnt_type is (RST, SET, INCR, HOLD);

  type set_clr_type is (SET, CLR, HOLD);

  -- Configuration

  constant IP_TTL : std_logic_vector (7 downto 0) := x"80";

  -- TX state variables

  signal tx_state               : tx_state_type;

  signal tx_count               : unsigned (11 downto 0);

  signal tx_result_reg          : std_logic_vector (1 downto 0);

  signal tx_mac                 : std_logic_vector (47 downto 0);

  signal tx_mac_chn_reqd        : std_logic;

  signal tx_hdr_cks             : std_logic_vector (23 downto 0);

  signal mac_lookup_req         : std_logic;

  signal crc_state              : crc_state_type;

  signal arp_req_ip_reg         : std_logic_vector (31 downto 0);

  signal mac_data_out_ready_reg : std_logic;

  -- tx control signals

  signal next_tx_state   : tx_state_type;

  signal set_tx_state    : std_logic;

  signal next_tx_result  : std_logic_vector (1 downto 0);

  signal set_tx_result   : std_logic;

  signal tx_mac_value    : std_logic_vector (47 downto 0);

  signal set_tx_mac      : std_logic;

  signal tx_count_val    : unsigned (11 downto 0);

  signal tx_count_mode   : settable_cnt_type;

  signal tx_data         : std_logic_vector (7 downto 0);

  signal set_last        : std_logic;

  signal set_chn_reqd    : set_clr_type;

  signal set_mac_lku_req : set_clr_type;

  signal tx_data_valid   : std_logic;   -- indicates whether data is valid to tx or not

  -- tx temp signals

  signal total_length : std_logic_vector (15 downto 0);  -- computed combinatorially from header size

  function inv_if_one(s1 : std_logic_vector; en : std_logic) return std_logic_vector is

    --this function inverts all the bits of a vector if

    --'en' is '1'.

    variable Z : std_logic_vector(s1'high downto s1'low);

  begin

    for i in (s1'low) to s1'high loop

      Z(i) := en xor s1(i);

    end loop;

    return Z;

  end inv_if_one;  -- end function

-- IP datagram header format

--

--      0          4          8                      16      19             24                    31

--      --------------------------------------------------------------------------------------------

--      | Version  | *Header  |    Service Type      |        Total Length including header        |

--      |   (4)    |  Length  |     (ignored)        |                 (in bytes)                  |

--      --------------------------------------------------------------------------------------------

--      |           Identification                   | Flags |       Fragment Offset               |

--      |                                            |       |      (in 32 bit words)              |

--      --------------------------------------------------------------------------------------------

--      |    Time To Live     |       Protocol       |             Header Checksum                 |

--      |     (ignored)       |                      |                                             |

--      --------------------------------------------------------------------------------------------

--      |                                   Source IP Address                                      |

--      |                                                                                          |

--      --------------------------------------------------------------------------------------------

--      |                                 Destination IP Address                                   |

--      |                                                                                          |

--      --------------------------------------------------------------------------------------------

--      |                          Options (if any - ignored)               |       Padding        |

--      |                                                                   |      (if needed)     |

--      --------------------------------------------------------------------------------------------

--      |                                          Data                                            |

--      |                                                                                          |

--      --------------------------------------------------------------------------------------------

--      |                                          ....                                            |

--      |                                                                                          |

--      --------------------------------------------------------------------------------------------

--

-- * - in 32 bit words 

begin

  -----------------------------------------------------------------------

  -- combinatorial process to implement FSM and determine control signals

  -----------------------------------------------------------------------

  tx_combinatorial : process(

    -- input signals

    ip_tx_start, ip_tx, our_ip_address, our_mac_address, arp_req_rslt,  --clk, 

    mac_tx_granted, mac_data_out_ready,

    -- state variables

    tx_state, tx_count, tx_result_reg, tx_mac, tx_mac_chn_reqd,

    mac_lookup_req, tx_hdr_cks, arp_req_ip_reg, mac_data_out_ready_reg,

    -- control signals

    next_tx_state, set_tx_state, next_tx_result, set_tx_result, tx_mac_value, set_tx_mac, tx_count_mode,

    tx_data, set_last, set_chn_reqd, set_mac_lku_req, total_length,

    tx_data_valid, tx_count_val

    )

  begin

    -- set output followers

    ip_tx_result           <= tx_result_reg;

    mac_tx_req             <= tx_mac_chn_reqd;

    arp_req_req.lookup_req <= mac_lookup_req;

    arp_req_req.ip         <= arp_req_ip_reg;

    -- set initial values for combinatorial outputs

    mac_data_out_first <= '0';

    case tx_state is

      when SEND_ETH_HDR | SEND_IP_HDR =>

        mac_data_out      <= tx_data;

        tx_data_valid     <= mac_data_out_ready;  -- generated internally

        mac_data_out_last <= set_last;

      when SEND_USER_DATA =>

        mac_data_out      <= ip_tx.data.data_out;

        tx_data_valid     <= ip_tx.data.data_out_valid;

        mac_data_out_last <= ip_tx.data.data_out_last;

      when others =>

        mac_data_out      <= (others => '0');

        tx_data_valid     <= '0';       -- not transmitting during this phase

        mac_data_out_last <= '0';

    end case;

    mac_data_out_valid <= tx_data_valid and mac_data_out_ready;

    -- set signal defaults

    next_tx_state   <= IDLE;

    set_tx_state    <= '0';

    tx_count_mode   <= HOLD;

    tx_data         <= x"00";

    set_last        <= '0';

    set_tx_mac      <= '0';

    set_chn_reqd    <= HOLD;

    set_mac_lku_req <= HOLD;

    next_tx_result  <= IPTX_RESULT_NONE;

    set_tx_result   <= '0';

    tx_count_val    <= (others => '0');

    tx_mac_value    <= (others => '0');

    -- set temp signals

    total_length <= std_logic_vector(unsigned(ip_tx.hdr.data_length) + 20);  -- total length = user data length + header length (bytes)

    -- TX FSM

    case tx_state is

      when IDLE =>

        ip_tx_data_out_ready <= '0';  -- in this state, we are unable to accept user data for tx

        tx_count_mode        <= RST;

        set_chn_reqd         <= CLR;

        if ip_tx_start = '1' then

                                        -- check header count for error if too high

          if unsigned(ip_tx.hdr.data_length) > 1480 then

            next_tx_result <= IPTX_RESULT_ERR;

            set_tx_result  <= '1';

          else

            next_tx_result <= IPTX_RESULT_SENDING;

            set_tx_result  <= '1';

                                        -- TODO - check if we already have the mac addr for this ip, if so, bypass the WAIT_MAC state

            if ip_tx.hdr.dst_ip_addr = IP_BC_ADDR then

                                        -- for IP broadcast, dont need to look up the MAC addr

              tx_mac_value  <= MAC_BC_ADDR;

              set_tx_mac    <= '1';

              next_tx_state <= WAIT_CHN;

              set_tx_state  <= '1';

            else

                                        -- need to req the mac address for this ip

              set_mac_lku_req <= SET;

              next_tx_state   <= WAIT_MAC;

              set_tx_state    <= '1';

            end if;

          end if;

        else

          set_mac_lku_req <= CLR;

        end if;

      when WAIT_MAC =>

        ip_tx_data_out_ready <= '0';  -- in this state, we are unable to accept user data for tx

        set_mac_lku_req      <= CLR;  -- clear the request - will have been latched in the ARP layer

        if arp_req_rslt.got_mac = '1' then

                                        -- save the MAC we got back from the ARP lookup

          tx_mac_value <= arp_req_rslt.mac;

          set_tx_mac   <= '1';

          set_chn_reqd <= SET;

                                        -- check for optimise when already have the channel

          if mac_tx_granted = '1' then

                                        -- ready to send data

            next_tx_state <= SEND_ETH_HDR;

            set_tx_state  <= '1';

          else

            next_tx_state <= WAIT_CHN;

            set_tx_state  <= '1';

          end if;

        elsif arp_req_rslt.got_err = '1' then

          set_mac_lku_req <= CLR;

          next_tx_result  <= IPTX_RESULT_ERR;

          set_tx_result   <= '1';

          next_tx_state   <= IDLE;

          set_tx_state    <= '1';

        end if;

      when WAIT_CHN =>

        ip_tx_data_out_ready <= '0';  -- in this state, we are unable to accept user data for tx

        if mac_tx_granted = '1' then

                                        -- ready to send data

          next_tx_state <= SEND_ETH_HDR;

          set_tx_state  <= '1';

        end if;

        -- probably should handle a timeout here

      when SEND_ETH_HDR =>

        ip_tx_data_out_ready <= '0';  -- in this state, we are unable to accept user data for tx

        if mac_data_out_ready = '1' then

          if tx_count = x"00d" then

            tx_count_mode <= RST;

            next_tx_state <= SEND_IP_HDR;

            set_tx_state  <= '1';

          else

            tx_count_mode <= INCR;

          end if;

          case tx_count is

            when x"000" =>

              mac_data_out_first <= mac_data_out_ready;

              tx_data            <= tx_mac (47 downto 40);  -- trg = mac from ARP lookup                                            

            when x"001" => tx_data <= tx_mac (39 downto 32);

            when x"002" => tx_data <= tx_mac (31 downto 24);

            when x"003" => tx_data <= tx_mac (23 downto 16);

            when x"004" => tx_data <= tx_mac (15 downto 8);

            when x"005" => tx_data <= tx_mac (7 downto 0);

            when x"006" => tx_data <= our_mac_address (47 downto 40);  -- src = our mac

            when x"007" => tx_data <= our_mac_address (39 downto 32);

            when x"008" => tx_data <= our_mac_address (31 downto 24);

            when x"009" => tx_data <= our_mac_address (23 downto 16);

            when x"00a" => tx_data <= our_mac_address (15 downto 8);

            when x"00b" => tx_data <= our_mac_address (7 downto 0);

            when x"00c" => tx_data <= x"08";  -- pkt type = 0800 : IP                                         

            when x"00d" => tx_data <= x"00";

            when others =>

                                        -- shouldnt get here - handle as error

              next_tx_result <= IPTX_RESULT_ERR;

              set_tx_result  <= '1';

              next_tx_state  <= IDLE;

              set_tx_state   <= '1';

          end case;

        end if;

      when SEND_IP_HDR =>

        ip_tx_data_out_ready <= '0';  -- in this state, we are unable to accept user data for tx

        if mac_data_out_ready = '1' then

          if tx_count = x"013" then

            tx_count_val  <= x"001";

            tx_count_mode <= SET;

            next_tx_state <= SEND_USER_DATA;

            set_tx_state  <= '1';

          else

            tx_count_mode <= INCR;

          end if;

          case tx_count is

            when x"000" => tx_data <= x"45";  -- v4, 5 words in hdr

            when x"001" => tx_data <= x"00";  -- service type

            when x"002" => tx_data <= total_length (15 downto 8);            -- total length

            when x"003" => tx_data <= total_length (7 downto 0);

            when x"004" => tx_data <= x"00";  -- identification

            when x"005" => tx_data <= x"00";

            when x"006" => tx_data <= x"00";  -- flags and fragment offset

            when x"007" => tx_data <= x"00";

            when x"008" => tx_data <= IP_TTL;                                -- TTL

            when x"009" => tx_data <= ip_tx.hdr.protocol;                    -- protocol

            when x"00a" => tx_data <= tx_hdr_cks (15 downto 8);              -- HDR checksum

            when x"00b" => tx_data <= tx_hdr_cks (7 downto 0);               -- HDR checksum

            when x"00c" => tx_data <= our_ip_address (31 downto 24);         -- src ip

            when x"00d" => tx_data <= our_ip_address (23 downto 16);

            when x"00e" => tx_data <= our_ip_address (15 downto 8);

            when x"00f" => tx_data <= our_ip_address (7 downto 0);

            when x"010" => tx_data <= ip_tx.hdr.dst_ip_addr (31 downto 24);  -- dst ip

            when x"011" => tx_data <= ip_tx.hdr.dst_ip_addr (23 downto 16);

            when x"012" => tx_data <= ip_tx.hdr.dst_ip_addr (15 downto 8);

            when x"013" => tx_data <= ip_tx.hdr.dst_ip_addr (7 downto 0);

            when others =>

                                        -- shouldnt get here - handle as error

              next_tx_result <= IPTX_RESULT_ERR;

              set_tx_result  <= '1';

              next_tx_state  <= IDLE;

              set_tx_state   <= '1';

          end case;

        end if;

      when SEND_USER_DATA =>

        ip_tx_data_out_ready <= mac_data_out_ready;-- and mac_data_out_ready_reg;  -- in this state, we are always ready to accept user data for tx

        if mac_data_out_ready = '1' then

          if ip_tx.data.data_out_valid = '1' or tx_count = x"000" then

                                                                                -- only increment if ready and valid has been subsequently established, otherwise data count moves on too fast

            if unsigned(tx_count) = unsigned(ip_tx.hdr.data_length) then

                                        -- TX terminated due to count - end normally

              set_last       <= '1';

              set_chn_reqd   <= CLR;

              tx_data        <= ip_tx.data.data_out;

              next_tx_result <= IPTX_RESULT_SENT;

              set_tx_result  <= '1';

              next_tx_state  <= IDLE;

              set_tx_state   <= '1';

              if ip_tx.data.data_out_last = '0' then

                next_tx_result <= IPTX_RESULT_ERR;

              end if;

            elsif ip_tx.data.data_out_last = '1' then

                                                                                -- TX terminated due to receiving last indication from upstream - end with error

              set_last       <= '1';

              set_chn_reqd   <= CLR;

              tx_data        <= ip_tx.data.data_out;

              next_tx_result <= IPTX_RESULT_ERR;

              set_tx_result  <= '1';

              next_tx_state  <= IDLE;

              set_tx_state   <= '1';

            else

                                        -- TX continues

              tx_count_mode <= INCR;

              tx_data       <= ip_tx.data.data_out;

            end if;

          end if;

        end if;

    end case;

  end process;

  -----------------------------------------------------------------------------

  -- sequential process to action control signals and change states and outputs

  -----------------------------------------------------------------------------

  tx_sequential : process (clk)--, reset, mac_data_out_ready_reg)

  begin

--    if rising_edge(clk) then

--      mac_data_out_ready_reg <= mac_data_out_ready;

--    else

--      mac_data_out_ready_reg <= mac_data_out_ready_reg;

--    end if;

    if rising_edge(clk) then

      if reset = '1' then

        -- reset state variables

        tx_state        <= IDLE;

        tx_count        <= x"000";

        tx_result_reg   <= IPTX_RESULT_NONE;

        tx_mac          <= (others => '0');

        tx_mac_chn_reqd <= '0';

        mac_lookup_req  <= '0';

      else

        -- Next tx_state processing

        if set_tx_state = '1' then

          tx_state <= next_tx_state;

        else

          tx_state <= tx_state;

        end if;

        -- tx result processing

        if set_tx_result = '1' then

          tx_result_reg <= next_tx_result;

        else

          tx_result_reg <= tx_result_reg;

        end if;

        -- control arp lookup request

        case set_mac_lku_req is

          when SET =>

            arp_req_ip_reg <= ip_tx.hdr.dst_ip_addr;

            mac_lookup_req <= '1';

          when CLR =>

            mac_lookup_req <= '0';

            arp_req_ip_reg <= arp_req_ip_reg;

          when HOLD =>

            mac_lookup_req <= mac_lookup_req;

            arp_req_ip_reg <= arp_req_ip_reg;

        end case;

        -- save MAC

        if set_tx_mac = '1' then

          tx_mac <= tx_mac_value;

        else

          tx_mac <= tx_mac;

        end if;

        -- control access request to mac tx chn

        case set_chn_reqd is

          when SET  => tx_mac_chn_reqd <= '1';

          when CLR  => tx_mac_chn_reqd <= '0';

          when HOLD => tx_mac_chn_reqd <= tx_mac_chn_reqd;

        end case;

        -- tx_count processing

        case tx_count_mode is

          when RST  => tx_count <= x"000";

          when SET  => tx_count <= tx_count_val;

          when INCR => tx_count <= tx_count + 1;

          when HOLD => tx_count <= tx_count;

        end case;

      end if;

    end if;

  end process;

  -----------------------------------------------------------------------------

  -- Process to calculate CRC in parallel with pkt out processing

  -- this process must yield a valid CRC before it is required to be used in the hdr

  -----------------------------------------------------------------------------

  crc : process (clk)--, reset)

  begin

    if rising_edge(clk) then

      case crc_state is

        when IDLE =>

          if ip_tx_start = '1' then

            tx_hdr_cks <= x"004500";    -- vers & hdr len & service

            crc_state  <= TOT_LEN;

          end if;

        when TOT_LEN =>

          tx_hdr_cks <= std_logic_vector (unsigned(tx_hdr_cks) + unsigned(total_length));

          crc_state  <= ID;

        when ID =>

          tx_hdr_cks <= tx_hdr_cks;

          crc_state  <= FLAGS;

        when FLAGS =>

          tx_hdr_cks <= tx_hdr_cks;

          crc_state  <= TTL;

        when TTL =>

          tx_hdr_cks <= std_logic_vector (unsigned(tx_hdr_cks) + unsigned(IP_TTL & ip_tx.hdr.protocol));

          crc_state  <= CKS;

        when CKS =>

          tx_hdr_cks <= tx_hdr_cks;

          crc_state  <= SAH;

        when SAH =>

          tx_hdr_cks <= std_logic_vector (unsigned(tx_hdr_cks) + unsigned(our_ip_address(31 downto 16)));

          crc_state  <= SAL;

        when SAL =>

          tx_hdr_cks <= std_logic_vector (unsigned(tx_hdr_cks) + unsigned(our_ip_address(15 downto 0)));

          crc_state  <= DAH;

        when DAH =>

          tx_hdr_cks <= std_logic_vector (unsigned(tx_hdr_cks) + unsigned(ip_tx.hdr.dst_ip_addr(31 downto 16)));

          crc_state  <= DAL;

        when DAL =>

          tx_hdr_cks <= std_logic_vector (unsigned(tx_hdr_cks) + unsigned(ip_tx.hdr.dst_ip_addr(15 downto 0)));

          crc_state  <= FINAL;

        when FINAL =>

          tx_hdr_cks <= inv_if_one(std_logic_vector (unsigned(tx_hdr_cks) + unsigned(tx_hdr_cks(23 downto 16))), '1');

          crc_state  <= WAIT_END;

        when WAIT_END =>

          tx_hdr_cks <= tx_hdr_cks;

          if ip_tx_start = '0' then

            crc_state <= IDLE;

          else

            crc_state <= WAIT_END;

          end if;

      end case;

    end if;

  end process;

end Behavioral;