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/*
* ipv4.v
*
* Copyright (C) 2018, 2019 Mind Chasers Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* function: Receive State Machine and Logic for IPv4
*
*
* 0-7 8-15 16-23 24-31
* 0 Version/IHL TOS Total Length.............
* 4 Identification...... Flags/Frag Off...........
* 8 TTL Protocol Header Checksum..........
* 12 Source IP Address....................................
* 16 Dest IP Address......................................
* 20 Options / Padding....................................
*
*
* When pkt_start is detected, rx_data_m2 has the first byte
*/
`timescale 1ns /10ps
module ipv4_rx (
input rstn,
input clk,
// control
input phy_resetn,
input phy_up,
// packet data
input pkt_start, // assert for each new frame to start state machines
input rx_eop, // use as a synch reset
input[7:0] rx_data_m1,
input[7:0] rx_data_m2,
input[7:0] rx_data_m3, // first byte of packet appears here simultaneous with pkt_start
input[7:0] rx_data_m4,
// flags
output pkt_complete,
output reg trigger_src_addr,
output reg trigger_dst_addr,
output reg keep
);
/* Byte Address (when last byte of field is present on rx_data_m1 ) */
localparam IPV4_TOS=1, IPV4_LENGTH=3, IPV4_IP_ID=5, IPV4_PROTOCOL=9,
IPV4_HDR_CKSUM=11, IPV4_SRC_ADDR=15, IPV4_DST_ADDR=19;
localparam RX_ST_IDLE=4'h0, RX_ST_DATA=4'h1, RX_ST_DONE=4'h2, RX_ST_3=4'h3,
RX_ST_4=4'h4, RX_ST_5=4'h5, RX_ST_6=4'h6, RX_ST_7=4'h7,
RX_ST_8=4'h8, RX_ST_9=4'h9, RX_ST_A=4'ha, RX_ST_B=4'hb,
RX_ST_C=4'hc, RX_ST_D=4'hd, RX_ST_E=4'he, RX_ST_F=4'hf;
localparam IPV4_PROTO_ICMP = 1, IPV4_PROTO_IGMP = 2, IPV4_PROTO_TCP = 6, IPV4_PROTO_UDP = 17,
IPV4_PROTO_ENCAP = 41, IPV4_PROTO_OSPF = 89, IPV4_PROTO_SCTP = 132;
reg [3:0] rx_state;
reg [10:0] rx_byte_cnt;
reg [10:0] rx_pkt_length;
reg [7:0] protocol;
wire rx_error;
/*
* rx_state machine
* capture an IPv4 Packet
*
*/
always @(posedge clk, negedge rstn)
if (!rstn)
rx_state <= RX_ST_IDLE;
else if ( rx_eop || !phy_resetn ) // EOP will reset state machine
rx_state <= RX_ST_IDLE;
else if ( phy_up )
case ( rx_state )
RX_ST_IDLE: if ( pkt_start ) // Found /S/
rx_state <= RX_ST_DATA;
RX_ST_DATA: if (pkt_complete)
rx_state <= RX_ST_DONE;
RX_ST_DONE: rx_state <= RX_ST_IDLE;
endcase
else
rx_state <= RX_ST_IDLE;
/* rx_byte_cnt */
always @(posedge clk, negedge rstn)
if (!rstn)
rx_byte_cnt <= 0;
else if ( rx_state == RX_ST_IDLE && !pkt_start ) // synch reset
rx_byte_cnt <= 1;
else if ( rx_state != RX_ST_IDLE || pkt_start )
rx_byte_cnt <= rx_byte_cnt + 1;
/* protocol */
always @(posedge clk, negedge rstn)
if ( !rstn )
protocol <= 0;
else if ( rx_eop )
protocol <= 0;
else if ( rx_byte_cnt == IPV4_PROTOCOL )
protocol <= rx_data_m1;
/* rx_pkt_length */
always @(posedge clk, negedge rstn)
if ( !rstn )
rx_pkt_length <= 11'h7ff;
else if ( rx_eop )
rx_pkt_length <= 11'h7ff;
else if ( rx_state == RX_ST_DATA && rx_byte_cnt == IPV4_LENGTH )
rx_pkt_length <= { rx_data_m2[2:0], rx_data_m1 };
/*
* Packet Filter Trigger(s), assert the sample before the data appears
*
*/
always @(posedge clk, negedge rstn)
if (!rstn)
trigger_src_addr <= 1'b0;
else if ( rx_byte_cnt == IPV4_SRC_ADDR-1 )
trigger_src_addr <= 1'b1;
else
trigger_src_addr <= 1'b0;
always @(posedge clk, negedge rstn)
if (!rstn)
trigger_dst_addr <= 1'b0;
else if ( rx_byte_cnt == IPV4_DST_ADDR-1 )
trigger_dst_addr <= 1'b1;
else
trigger_dst_addr <= 1'b0;
assign pkt_complete = ( rx_state >= RX_ST_DATA && rx_pkt_length == rx_byte_cnt+1 ) ? 1 : 0;
assign rx_error = 0;
endmodule
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