[米联客-安路飞龙DR1-FPSOC] UDP通信篇连载-05 ARP层程序设计

软件版本：Anlogic -TD5.9.1-DR1_ES1.1

操作系统：WIN10 64bit

硬件平台：适用安路(Anlogic)FPGA

实验平台：米联客-MLK-L1-CZ06-DR1M90G开发板

板卡获取平台：https://milianke.tmall.com/

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3.4 ARP层

该层具有接收ARP请求、发送ARP回复，和发送ARP请求、接收ARP回复的功能，并将接收到的对端的地址信息存入cache中。

3.4.1 ARP接收模块

该模块通过计数器接收28字节ARP信息字段。信息接收完成后，通过接收到的操作码判断接收到的数据包是ARP请求包还是ARP应答包。如果是应答包，将接收到的地址信息写入cache中；如果是请求包，判断目的IP地址与本地IP地址是否一致，若一致，将地址信息写入cache中，且发送至uiarp_rx模块，若不一致，则过滤该包。

if(OPER == ARP_REQUEST) begin//如果是ARP请求 ARP_REQUEST = 16'h0001（16’h01 ARP请求包； 16’h02 ARP应答）
if(TPA == I_ip_local_addr) begin //比较接收到的ARP包里面的IP地址是否和本地IP地址一致
O_arp_req_ip_addr <= SPA; //发送IP(远端源IP地址)
O_arp_req_mac_addr <= SHA; //发送方MAC(远端源地址MAC)
O_arp_req_valid <= 1'b1; //设置ARP请求有效(通知发送ARP发送模块发送一个ARP应答给远端主机),保存远端主机的IP地址和MAC地址到cache
O_arp_reply_done <= 1'b0;
end
else begin
O_arp_req_ip_addr <= 32'd0;
O_arp_req_mac_addr <= 48'd0;
O_arp_req_valid <= 1'b0;
O_arp_reply_done <= 1'b0;
end
end

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3.4.2 ARP发送模块

该模块对ARP应答和ARP请求同时进行处理，首先对这两种逻辑进行仲裁，以避免发送冲突。如果既没有ARP应答也没有ARP请求，且内部ARP包发送逻辑非忙，则处理缓存的有效信号；如果只有ARP应答，没有ARP请求，且发送逻辑非忙，则请求发送ARP应答包，若发送逻辑忙，则将发送ARP应答包的请求缓存至reply_buffer_valid中，等待非忙时发出；如果只有ARP请求，没有ARP应答，且发送逻辑非忙，则请求发送ARP请求包，若发送逻辑忙，则将发送ARP请求包的请求缓存至request_buffer_valid中，等待非忙时发出；若ARP应答和ARP请求同时为高，则优先发送ARP请求，缓存ARP应答。

case({I_arp_treq_en, I_arp_rreply_en})//本状态机实现了即便是同时有ARP应答或者ARP请求，都能确保完成发送
2'b00:begin
if((!O_arp_treq) && (!O_arp_tvalid)) begin//没有arp_treq请求，并且arp_tvalid为0 代表没有要发送的ARP数据
if(request_buffer_valid) begin//如果有未发送完的ARP请求，则继续发送
OPER <= ARP_REQUEST;
TPA <= ip_request_buffer;
THA <= 48'd0;
request_buffer_valid <= 1'b0;//清除request_buffer_valid
O_arp_treq <= 1'b1;
end
else if(reply_buffer_valid) begin//如果有未发送完的ARP应答，则继续发送
OPER <= ARP_REPLY;
TPA <= ip_reply_buffer;
THA <= mac_reply_buffer;
reply_buffer_valid <= 1'b0;//清除request_buffer_valid
O_arp_treq <= 1'b1;
end
end
end
2'b01:begin//发送ARP应答
if((!O_arp_treq) && (!O_arp_tvalid)) begin
OPER <= ARP_REPLY;
TPA <= I_arp_rreply_ip_addr;
THA <= I_arp_rreply_mac_addr;
O_arp_treq <= 1'b1;
end
else begin//需要arp应答
ip_reply_buffer <= I_arp_rreply_ip_addr;//寄存目的地址IP
mac_reply_buffer <= I_arp_rreply_mac_addr;//寄存目的地址MAC
reply_buffer_valid <= 1'b1;//需要发送ARP应答
end
end
2'b10:begin//发送ARP请求,当ip_arp_tx发送IP包查询MAC没有查询到，执行ARP请求，请求远程主机提供MAC
if((!O_arp_treq) && (!O_arp_tvalid)) begin
OPER <= ARP_REQUEST;
TPA <= I_arp_tip_addr;
THA <= 48'd0;
O_arp_treq <= 1'b1;//ARP 发送
end
else begin//arp请求包
ip_request_buffer <= I_arp_tip_addr;
request_buffer_valid <= 1'b1;//ARP 请求有效标志
end
end
2'b11:begin//既有ARP请求，又有ARP应答
if((!O_arp_treq) && (!O_arp_tvalid)) begin
OPER <= ARP_REQUEST;
TPA <= I_arp_tip_addr;
THA <= 48'd0;
O_arp_treq <= 1'b1;//ARP 发送
end
else begin
ip_request_buffer <= I_arp_tip_addr;
request_buffer_valid <= 1'b1;//ARP请求有效
end
ip_reply_buffer <= I_arp_rreply_ip_addr;
mac_reply_buffer <= I_arp_rreply_mac_addr;
reply_buffer_valid <= 1'b1; //ARP应答有效
end
endcase

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若O_arp_treq和uiip_arp_tx模块发送的I_arp_tbusy完成握手，则开始发送ARP包，并且通过判断ARP包的类型来确定发送的目的地址。通过计数器cnt发送28字节有效数据，再通过计数器pad_cnt在末尾补18个字节的0，即完成发送，开始等待下一次握手。

case(STATE)
WAIT_BUFFER_READY:begin
if(O_arp_treq && I_arp_tbusy) begin
O_arp_tdata <= HTYPE[15:8]; //硬件类型-以太网类型
O_arp_tvalid <= 1'b1; //ARP数据有效
cnt <= cnt + 1'b1;
if(OPER == ARP_REQUEST) begin //如果是ARP请求
O_arp_tdest_mac_addr <= 48'hff_ff_ff_ff_ff_ff; //ARP目的地址为广播地址
O_arp_ttype <= 1'b1; //通知ip_arp_tx ARP类型为ARP请求
end
else begin
O_arp_tdest_mac_addr <= THA;
O_arp_ttype <= 1'b0; //通知ip_arp_tx ARP类型为ARP应答
end
O_arp_treq <= 1'b0;
STATE <= SEND_ARP_PACKET;
end
else
STATE <= WAIT_BUFFER_READY;
end
SEND_ARP_PACKET:begin
case(cnt)
1: begin O_arp_tdata <= HTYPE[7:0]; cnt <= cnt + 1'b1;end
2: begin O_arp_tdata <= PTYPE[15:8]; cnt <= cnt + 1'b1;end
3: begin O_arp_tdata <= PTYPE[7:0]; cnt <= cnt + 1'b1;end
4: begin O_arp_tdata <= HLEN; cnt <= cnt + 1'b1;end
5: begin O_arp_tdata <= PLEN; cnt <= cnt + 1'b1;end
6: begin O_arp_tdata <= OPER[15:8]; cnt <= cnt + 1'b1;end
7: begin O_arp_tdata <= OPER[7:0]; cnt <= cnt + 1'b1;end
8: begin O_arp_tdata <= I_mac_local_addr[47:40]; cnt <= cnt + 1'b1;end
9: begin O_arp_tdata <= I_mac_local_addr[39:32]; cnt <= cnt + 1'b1;end
10: begin O_arp_tdata <= I_mac_local_addr[31:24]; cnt <= cnt + 1'b1;end
11: begin O_arp_tdata <= I_mac_local_addr[23:16]; cnt <= cnt + 1'b1;end
12: begin O_arp_tdata <= I_mac_local_addr[15:8]; cnt <= cnt + 1'b1;end
13: begin O_arp_tdata <= I_mac_local_addr[7:0]; cnt <= cnt + 1'b1;end
14: begin O_arp_tdata <= I_ip_local_addr[31:24]; cnt <= cnt + 1'b1;end
15: begin O_arp_tdata <= I_ip_local_addr[23:16]; cnt <= cnt + 1'b1;end
16: begin O_arp_tdata <= I_ip_local_addr[15:8]; cnt <= cnt + 1'b1;end
17: begin O_arp_tdata <= I_ip_local_addr[7:0]; cnt <= cnt + 1'b1;end
18: begin O_arp_tdata <= THA[47:40]; cnt <= cnt + 1'b1;end
19: begin O_arp_tdata <= THA[39:32]; cnt <= cnt + 1'b1;end
20: begin O_arp_tdata <= THA[31:24]; cnt <= cnt + 1'b1;end
21: begin O_arp_tdata <= THA[23:16]; cnt <= cnt + 1'b1;end
22: begin O_arp_tdata <= THA[15:8]; cnt <= cnt + 1'b1;end
23: begin O_arp_tdata <= THA[7:0]; cnt <= cnt + 1'b1;end
24: begin O_arp_tdata <= TPA[31:24]; cnt <= cnt + 1'b1;end
25: begin O_arp_tdata <= TPA[23:16]; cnt <= cnt + 1'b1;end
26: begin O_arp_tdata <= TPA[15:8]; cnt <= cnt + 1'b1;end
27: begin O_arp_tdata <= TPA[7:0]; cnt <= cnt + 1'b1;end
28: begin
O_arp_tdata <= 8'd0;
if(pad_cnt == 5'd17) begin //通过在末尾添加0以确保数据长度为46
cnt <= cnt + 1'b1;
pad_cnt <= 5'd0;
end
else begin
cnt <= cnt;
pad_cnt <= pad_cnt + 1'b1;
end
end
29: begin
O_arp_tdata <= 8'd0;
O_arp_tvalid <= 1'b0;
O_arp_tdest_mac_addr <= 48'd0;
O_arp_ttype <= 1'b0;
cnt <= 5'd0;
STATE <= WAIT_BUFFER_READY;
end
default:begin
O_arp_tdata <= 8'd0;
O_arp_tvalid <= 1'b0;
cnt <= 5'd0;
STATE <= WAIT_BUFFER_READY;
end
endcase
end
endcase
end
end

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3.4.3 CACHE模块

mac_cache模块相当于一个RAM，通过IP作为地址，写入或读出MAC地址。写入mac_cache模块的地址信息远程主机发送的ARP应答包或ARP请求包中的地址，在IP层发送UDP数据报文时，需要在mac_cache中读出和IP地址对应的MAC地址。

`timescale 1ns/1ps
module mac_cache
(
input wire I_wclk,
input wire I_reset,
input wire I_wen,
input wire [31:0] I_wip_addr,
input wire [47:0] I_wmac_addr,
input wire I_rclk,
input wire I_ren,
input wire [31:0] I_rip_addr,
output reg [47:0] O_rmac_addr,
output reg O_rmac_done
);
reg mac_cache_flag [0:3];
reg [31:0] ip_address_cache [0:3];
reg [47:0] mac_address_cache [0:3];
reg [1:0] index;
always@(posedge I_wclk or posedge I_reset) begin
if(I_reset) begin
mac_cache_flag[0] <= 1'b0;
ip_address_cache[0] <= 32'd0;
mac_address_cache[0] <= 48'd0;
mac_cache_flag[1] <= 1'b0;
ip_address_cache[1] <= 32'd0;
mac_address_cache[1] <= 48'd0;
mac_cache_flag[2] <= 1'b0;
ip_address_cache[2] <= 32'd0;
mac_address_cache[2] <= 48'd0;
mac_cache_flag[3] <= 1'b0;
ip_address_cache[3] <= 32'd0;
mac_address_cache[3] <= 48'd0;
index <= 2'd0;
end
else begin
if(I_wen) begin
if(mac_cache_flag[0] && ip_address_cache[0] == I_wip_addr)
mac_address_cache[0] <= I_wmac_addr;
else if(mac_cache_flag[1] && ip_address_cache[1] == I_wip_addr)
mac_address_cache[1] <= I_wmac_addr;
else if(mac_cache_flag[2] && ip_address_cache[2] == I_wip_addr)
mac_address_cache[2] <= I_wmac_addr;
else if(mac_cache_flag[3] && ip_address_cache[3] == I_wip_addr)
mac_address_cache[3] <= I_wmac_addr;
else begin
mac_cache_flag[index] <= 1'b1;
ip_address_cache[index] <= I_wip_addr;
mac_address_cache[index] <= I_wmac_addr;
index <= index + 1'b1;
end
end
else begin
mac_cache_flag[0] <= mac_cache_flag[0];
ip_address_cache[0] <= ip_address_cache[0];
mac_address_cache[0] <= mac_address_cache[0];
mac_cache_flag[1] <= mac_cache_flag[1];
ip_address_cache[1] <= ip_address_cache[1];
mac_address_cache[1] <= mac_address_cache[1];
mac_cache_flag[2] <= mac_cache_flag[2];
ip_address_cache[2] <= ip_address_cache[2];
mac_address_cache[2] <= mac_address_cache[2];
mac_cache_flag[3] <= mac_cache_flag[3];
ip_address_cache[3] <= ip_address_cache[3];
mac_address_cache[3] <= mac_address_cache[3];
end
end
end
always@(posedge I_rclk or posedge I_reset) begin
if(I_reset) begin
O_rmac_addr <= 48'd0;
O_rmac_done <= 1'b0;
end
else begin
if(I_ren) begin
O_rmac_done <= 1'b1;
if(mac_cache_flag[0] && I_rip_addr == ip_address_cache[0])
O_rmac_addr <= mac_address_cache[0];
else if(mac_cache_flag[1] && I_rip_addr == ip_address_cache[1])
O_rmac_addr <= mac_address_cache[1];
else if(mac_cache_flag[2] && I_rip_addr == ip_address_cache[2])
O_rmac_addr <= mac_address_cache[2];
else if(mac_cache_flag[3] && I_rip_addr == ip_address_cache[3])
O_rmac_addr <= mac_address_cache[3];
else
O_rmac_addr <= 48'd0;
end
else begin
O_rmac_addr <= O_rmac_addr;
O_rmac_done <= 1'b0;
end
end
end
endmodule

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