非黑色字體均為我自己添加

圖均為原文所有

原文放在文章末尾

加入TCP/IP棧

????????從我們的part14-spi-ethernet 中的以太網(wǎng)模塊達成了達成了"證明生活"的成就,你毫無疑問會好奇如何從這里出發(fā)到服務(wù)器上的網(wǎng)頁,在推特上發(fā)推(可惜現(xiàn)在叫X.com了)或者只是相應(yīng)一個ping!

????????這就是你需要成熟的TCP/IP棧的地方,它超越了手工的ARP,實現(xiàn)了許多協(xié)議來達成高效的雙向通信.

????????在這個部分里我們利用一些?tuxgraphics.org中Guido Socher的代碼.它被設(shè)置為具有輕量級的針對嵌入式設(shè)備的TCP/IP棧.我選擇這個是因為使它運轉(zhuǎn)(或者"移植")起來非常的簡單,但你可能想要看看LwIP(https://en.wikipedia.org/wiki/LwIP)如果你希望一些高級功能.

代碼

????????大多數(shù)代碼在??tcpip/ 子文件夾里.我實際上在這個tarball(http://tuxgraphics.org/common/src2/article09051/eth_tcp_client_server-dhcp-5.10.tar.gz)里面遇到了它,再次做了一些不重要的改動( diff 是你的好朋友!).

????????它確實要求我暴露我在 lib/fb.c 中實現(xiàn)的strlen()函數(shù),所以它被添加到?include/fb.h 中.類似的,我們暴露在 kernel/kernel.c 中實現(xiàn)的?memcpy() 函數(shù),所以它被添加到?kernel/kernel.h 中.

????????我同樣需要一個單獨的函數(shù)來告訴ENC發(fā)送一個包.沒有什么新東西,只是不同的封裝:

void enc28j60PacketSend(unsigned short buflen, void *buffer) {

? ?if (ENC_RestoreTXBuffer(&handle, buflen) == 0) {

? ? ? ENC_WriteBuffer((unsigned char *) buffer, buflen);

? ? ? handle.transmitLength = buflen;

? ? ? ENC_Transmit(&handle);

? ?}

}

????????它同樣被添加到?kernel/kernel.h 中了.

arp.c發(fā)生了什么?

????????你會注意到我合并了 arp.c 和 kernel.c.我也沒有使用多核或IRQ定時器，以保持內(nèi)核的簡單性.我們?nèi)匀挥猛瑯拥姆椒ǔ跏蓟W(wǎng)卡,但是當我們完成時我們調(diào)用?Guido 中的代碼:

init_udp_or_www_server(myMAC, deviceIP);

????????它告訴TCP/IP庫我們是誰,所以我們在同一頁!

????????最后,除了清理之外(比如移動 HAL/系統(tǒng) 時鐘到 lib/io.c,同時 include/io.h 也對應(yīng)改變),主要的變化是新的?serve()? 函數(shù):

void serve(void)

{

? ?while (1) {

? ? ? while (!ENC_GetReceivedFrame(&handle));

? ? ? uint8_t *buf = (uint8_t *)handle.RxFrameInfos.buffer;

? ? ? uint16_t len = handle.RxFrameInfos.length;

? ? ? uint16_t dat_p = packetloop_arp_icmp_tcp(buf, len);

? ? ? if (dat_p != 0) {

? ? ? ? ?debugstr("Incoming web request... ");

? ? ? ? ?if (strncmp("GET ", (char *)&(buf[dat_p]), 4) != 0) {

? ? ? ? ? ? debugstr("not GET");

? ? ? ? ? ? dat_p = fill_tcp_data(buf, 0, "HTTP/1.0 401 Unauthorized\r\nContent-Type: text/html\r\n\r\n<h1>ERROR</h1>");

? ? ? ? ?} else {

? ? ? ? ? ? if (strncmp("/ ", (char *)&(buf[dat_p+4]), 2) == 0) {

? ? ? ? ? ? ? ?// just one web page in the "root directory" of the web server

? ? ? ? ? ? ? ?debugstr("GET root");

? ? ? ? ? ? ? ?dat_p = fill_tcp_data(buf, 0, "HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n<h1>Hello world!</h1>");

? ? ? ? ? ? } else {

? ? ? ? ? ? ? ?// just one web page not in the "root directory" of the web server

? ? ? ? ? ? ? ?debugstr("GET not root");

? ? ? ? ? ? ? ?dat_p = fill_tcp_data(buf, 0, "HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n<h1>Goodbye cruel world.</h1>");

? ? ? ? ? ? }

? ? ? ? ?}

? ? ? ? ?www_server_reply(buf, dat_p); // send web page data

? ? ? ? ?debugcrlf();

? ? ? }

? ?}

}

????????這是一個無限循環(huán),它等待將要到來的包然后首先把它傳遞到?Guido 的?packetloop_arp_icmp_tcp() 函數(shù).這個函數(shù)實現(xiàn)了一些有用的東西,比如應(yīng)答ping.我修改這個例程當它發(fā)送"pong"的時候把信息打印到屏幕上(看到?tcpip/ip_arp_udp_tcp.c 的第 1371 行),所以當它行動時我們可以看到!

????????檢查?packetloop_arp_icmp_tcp() 的返回值,然后允許我們檢查它是否是一個到來的網(wǎng)絡(luò)請求,因為我們已經(jīng)使用 #define WWW_server 在?tcpip/ip_config.h中設(shè)置TCP/IP 庫為一個網(wǎng)絡(luò)服務(wù)器.

????????我們基于三中可能的情況做出服務(wù)應(yīng)答:

• 到來的請求不是一個GET請求(比如它可能是一個HEAD請求) -- 你可以使用 curl 工具模擬這個:curl -I 192.168.0.66

• 到來的請求是一個要求網(wǎng)頁根目錄的GET請求??/ -- curl 192.168.0.66/

• 到來的請求是任何一個非根網(wǎng)頁目錄請求 -- 比如?curl 192.168.0.66/isometimes/monkey

????????我推薦閱讀這一頁(http://tuxgraphics.org/electronics/200905/embedded-tcp-ip-stack.shtml)來得到完全的解釋.我移植的代碼與這里你看到的非常相似.

????????想象一下，當我構(gòu)建、運行并ping到192.168.0.66的RPi4，并在我的筆記本電腦和iPhone上的瀏覽器上獲得web響應(yīng)時，我有多興奮!

原文如下

Adding a TCP/IP stack

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

Having achieved "proof of life" from our Ethernet module in _part14-spi-ethernet_, you're doubtless wondering how to go from there to serving web pages, posting tweets on Twitter or perhaps even just simply responding to a ping!

This is where you'll need a fully-fledged TCP/IP stack that goes way beyond handcrafted ARPs, implementing many more protocols to achieve efficient bi-directional communication.

In this part we make use of some code from Guido Socher of [tuxgraphics.org](http://tuxgraphics.org/), designed to be a lightweight TCP/IP stack for embedded devices. I chose this because it was super simple to get working (or "port"), but you might want to look at [LwIP](https://en.wikipedia.org/wiki/LwIP) if you need something more advanced.

The code

--------

Most of the new code is in the _tcpip/_ subdirectory. I actually came across it in [this tarball](http://tuxgraphics.org/common/src2/article09051/eth_tcp_client_server-dhcp-5.10.tar.gz) and, again, made only a very few cosmetic changes (`diff` is your friend!).

It did require me to expose the `strlen()` function we implemented in _lib/fb.c_, so that's added to _include/fb.h_. Similarly, we expose the `memcpy()` function we implemented in _kernel/kernel.c_, so that's added to _kernel/kernel.h_.

I also needed a single function that tells the ENC to send a packet. Nothing new here, just different packaging:

```c

void enc28j60PacketSend(unsigned short buflen, void *buffer) {

? ?if (ENC_RestoreTXBuffer(&handle, buflen) == 0) {

? ? ? ENC_WriteBuffer((unsigned char *) buffer, buflen);

? ? ? handle.transmitLength = buflen;

? ? ? ENC_Transmit(&handle);

? ?}

}

```

This was also added to _kernel/kernel.h_.

What happened to _arp.c_?

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

You'll notice that I've merged _arp.c_ and _kernel.c_. I have also gone away from doing anything wih multicore or IRQ timers to keep this kernel simple. We still initialise the network card in exactly the same way but, when we're done, we call this function in Guido's code:

```c

init_udp_or_www_server(myMAC, deviceIP);

```

This tells the TCP/IP library who we are, so we're all on the same page!

Finally, and aside from a little cleanup (eg. moving the HAL/system timer functions to _lib/io.c_ with the commensurate changes to _include/io.h_), the major change is the new `serve()` function:

```c

void serve(void)

{

? ?while (1) {

? ? ? while (!ENC_GetReceivedFrame(&handle));

? ? ? uint8_t *buf = (uint8_t *)handle.RxFrameInfos.buffer;

? ? ? uint16_t len = handle.RxFrameInfos.length;

? ? ? uint16_t dat_p = packetloop_arp_icmp_tcp(buf, len);

? ? ? if (dat_p != 0) {

? ? ? ? ?debugstr("Incoming web request... ");

? ? ? ? ?if (strncmp("GET ", (char *)&(buf[dat_p]), 4) != 0) {

? ? ? ? ? ? debugstr("not GET");

? ? ? ? ? ? dat_p = fill_tcp_data(buf, 0, "HTTP/1.0 401 Unauthorized\r\nContent-Type: text/html\r\n\r\n<h1>ERROR</h1>");

? ? ? ? ?} else {

? ? ? ? ? ? if (strncmp("/ ", (char *)&(buf[dat_p+4]), 2) == 0) {

? ? ? ? ? ? ? ?// just one web page in the "root directory" of the web server

? ? ? ? ? ? ? ?debugstr("GET root");

? ? ? ? ? ? ? ?dat_p = fill_tcp_data(buf, 0, "HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n<h1>Hello world!</h1>");

? ? ? ? ? ? } else {

? ? ? ? ? ? ? ?// just one web page not in the "root directory" of the web server

? ? ? ? ? ? ? ?debugstr("GET not root");

? ? ? ? ? ? ? ?dat_p = fill_tcp_data(buf, 0, "HTTP/1.0 200 OK\r\nContent-Type: text/html\r\n\r\n<h1>Goodbye cruel world.</h1>");

? ? ? ? ? ? }

? ? ? ? ?}

? ? ? ? ?www_server_reply(buf, dat_p); // send web page data

? ? ? ? ?debugcrlf();

? ? ? }

? ?}

}

```

This is an infinite loop which waits for an incoming packet and then firstly passes it to Guido's `packetloop_arp_icmp_tcp()` function. This function implements some useful things, like responding to pings. I modified the routine to print a message to the screen when it sends a "pong" (look from line 1371 of _tcpip/ip_arp_udp_tcp.c_), so we can see when it's in action!

Examining the return value of `packetloop_arp_icmp_tcp()` then allows us to check whether there is an incoming web request, since we've configured the TCP/IP library to be a web server in _tcpip/ip_config.h_ with `#define WWW_server`.

We then serve responses based on three possible cases:

?* The incoming request is not a GET request (eg. maybe it's a HEAD request) - you can simulate this using the `curl` tool: `curl -I 192.168.0.66`

?* The incoming request is a GET request for the root web page `/` - `curl 192.168.0.66/`

?* The incoming request is a GET request for any non-root web page - eg. `curl 192.168.0.66/isometimes/monkey`

I recommend reading [this page](http://tuxgraphics.org/electronics/200905/embedded-tcp-ip-stack.shtml) for a full explanation. The code I have ported is very similar to what you see there.

_Imagine my excitement when I built, ran and could ping my RPi4 at 192.168.0.66 and get a web response to my browser on both my laptop and my iPhone!_