LWiP http POST - 缓冲区的大小与内容长度不同

Question

I'm writing a STM32 C function (using lwIP netconn) that accepts a HTTP Post Request with a file "attached". I've used a form to pick a file to transfer from the PC to the MCU. I use the following line to capture the request:

netbuf_data(inbuf, (void**)&buf, &buflen);

The buflen gets a value of 624 but the "Content-Length" header is 75093. Here is the buffer captured:

 POST /upload.cgi HTTP/1.1 Host: 192.168.0.10 Connection: keep-alive Content-Length: 75093 Cache-Control: max-age=0 Upgrade-Insecure-Requests: 1 Origin: http://192.168.0.10 Content-Type: multipart/form-data; boundary=----WebKitFormBoundary46gMrRDRRGlHEkwC User-Agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/85.0.4183.83 Safari/537.36 Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9 Referer: http://192.168.0.10/ Accept-Encoding: gzip, deflate Accept-Language: en-US,en;q=0.9

Why is the buflen different from the Content Length? The sample code I have searches for the string "octet-stream" to know when the binary data begins but with such a small header it doesn't find it.

Unfortunately I do now have Wireshark to know the exact size of the HTTP packet. Should I be using another method to capture the buffer that is safe with RTOS?

Thanks.

Answer 1

With netbuf_data you get slice of data from stream. And stream may have any data. Try any telnet client (Putty) to connect to your host and type something. You will see it in buffer.

And now you should parse such stream. This stream have format HTTP 1.1 and this stream have nothing with STM32 and TCP in common: different layer (see OSI model ) Read about HTTP headers . I see Content-Type: multipart/form-data Are you sure you want to parse this?

Why is the buflen different from the Content Length?

Because buflen is length of slice you captured, Content-Length: 75093 is about HTTP

Should I be using another method to capture the buffer that is safe with RTOS?

No, you do right way