Re: picotcp barebox integration

[Antony Pavlov <antonynpavlov@gmail.com>]

On Sun, 1 Mar 2015 01:29:56 +0100
DI PEDE Michele <michele.dipede@altran.com> wrote:

> On Sat 28 Feb 2015 21:01:01
...
> Please take a look at the application driven API.

> In order to integrate our stack you should use the application driven API. It 
> is documented in user manual in section 3.12 (TFTP). In order to receive a 
> file the sequence should be:
> session = pico_tftp_app_setup(&server_address, short_be(PICO_TFTP_PORT), 
> PICO_PROTO_IPV4, &synchro);
> ret = pico_tftp_app_start_rx(session, filename);
> ret = pico_tftp_get_file_size(session, &file_size);
> if (ret)
> printf("Information about file size has not been received"\n);
> 
> while (file_is_not_complete) {
>         len = pico_tftp_get(session, buf, PICO_TFTP_PAYLOAD_SIZE);
>         ....
> }
> 
> The example contained in test/test_tftp_app_client.c demonstrate how to use 
> the interface for application driven behaviour.

Hmm. I have tried pico_tftp_get() and now I have several questions:

1. pico_tftp_get() has 3rd argument 'int32_t len'.
This 'len' argument is actually unused. Can we just drop it?


2. here is pico_tftp_get() example fragment:

        len = pico_tftp_get(session, buf, PICO_TFTP_PAYLOAD_SIZE);
        if (len < 0) {
            fprintf(stderr, "Failure in pico_tftp_get\n");
            close(fd);
            countdown = 1;
            continue;
        }
        ret = write(fd, buf, len);

pico_tftp_get() copies data to pointer buf. But the first four bytes are not raw file
data but tftp header fields.
E.g. I receiving GPL text via pico_tftp_get():

first tftp data block:

00000000: 00 03 00 01 09 09 20 20 20 20 47 4e 55 20 47 45    ......    GNU GE
00000010: 4e 45 52 41 4c 20 50 55 42 4c 49 43 20 4c 49 43    NERAL PUBLIC LIC
00000020: 45 4e 53 45 0a 09 09 20 20 20 20 20 20 20 56 65    ENSE...       Ve
...
000001d0: 65 72 61 6c 20 50 75 62 6c 69 63 0a 4c 69 63 65    eral Public.Lice
000001e0: 6e 73 65 20 69 73 20 69 6e 74 65 6e 64 65 64 20    nse is intended
000001f0: 74 6f 20 67 75 61 72 61 6e 74 65 65                to guarantee

second tftp data block:

00000000: 00 03 00 02 65 65 64 6f 6d 20 74 6f 20 73 68 61    ....eedom to sha
00000010: 72 65 20 61 6e 64 20 63 68 61 6e 67 65 20 66 72    re and change fr
00000020: 65 65 0a 73 6f 66 74 77 61 72 65 2d 2d 74 6f 20    ee.software--to
00000030: 6d 61 6b 65 20 73 75 72 65 20 74 68 65 20 73 6f    make sure the so
00000040: 66 74 77 61 72 65 20 69 73 20 66 72 65 65 20 66    ftware is free f

Here is a original GPL file dump, you can see that substring ' your fr'
is missed in data received by pico_tftp_get():

000001d0:  20 50 75 62 6c 69 63 0a  4c 69 63 65 6e 73 65 20   Public.License 
000001e0:  69 73 20 69 6e 74 65 6e  64 65 64 20 74 6f 20 67  is intended to g
000001f0:  75 61 72 61 6e 74 65 65  20 79 6f 75 72 20 66 72  uarantee your fr <<<<<<
00000200:  65 65 64 6f 6d 20 74 6f  20 73 68 61 72 65 20 61  eedom to share a <<<<<<
00000210:  6e 64 20 63 68 61 6e 67  65 20 66 72 65 65 0a 73  nd change free.s
00000220:  6f 66 74 77 61 72 65 2d  2d 74 6f 20 6d 61 6b 65  oftware--to make
   
So data block written to file by
    ret = write(fd, buf, len);
is corrupted.

Could you please check this?


3. there is the find_session_by_socket() function. It uses special tftp_sessions list.
Can we simply use priv field in 'struct pico_socket' for this purpose?


4. How I can determine "End Of File reached" situation after pico_tftp_get() call?


-- 
Best regards,
  Antony Pavlov

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