Gun and HTTP2: HEADER and DATA frames in different packets

[Luke Bakken]

Hi Stefano,

I may be mistaken, but this might be due to how Wireshark is decoding
the data and presenting it to you. I see that the IP and TCP
information for both "packets" is the same. Most importantly, the Seq
and Ack numbers.

If they were distinct TCP packets I would expect to see different
numbers (https://packetlife.net/blog/2010/jun/7/understanding-tcp-sequence-acknowledgment-numbers/).

Also, your code is making a connection to port 8088 but the Wireshark
output shows port 80.

Thanks,
Luke

On Sun, Sep 13, 2020 at 6:07 AM Stefano Bertuola
<stefano.bertuola@REDACTED> wrote:
>
> Hi all.
>
> When sending an HTTP2 request using Gun:
>
>   {ok, ConnPid} = gun:open({127,0,0,1}, 8088, #{protocols => [http2]}).
>   gun:post(ConnPid, "/test", [ {<<"content-type">>, <<"application/json">>} ], <<"{\"test\": \"test\" }">>).
>
> the HEADER and DATA frames are sent in different HTTPs packets:
>
>   Internet Protocol Version 4, Src: 127.0.0.1 (127.0.0.1), Dst: 127.0.0.1 (127.0.0.1)
>   Transmission Control Protocol, Src Port: 1299, Dst Port: 80, Seq: 266, Ack: 229, Len: 46
>   HyperText Transfer Protocol 2
>       Stream: HEADERS, Stream ID: 1, Length 37, POST /test
>           Length: 37
>           Type: HEADERS (1)
>           Flags: 0x04
>           0... .... .... .... .... .... .... .... = Reserved: 0x0
>           .000 0000 0000 0000 0000 0000 0000 0001 = Stream Identifier: 1
>           [Pad Length: 0]
>           Header Block Fragment: 8644846125427f83418a089d5c0b8170dc780f3d5f8b1d75…
>           [Header Length: 148]
>           [Header Count: 6]
>           Header: :scheme: http
>           Header: :path: /test
>           Header: :method: POST
>           Header: :authority: 127.0.0.1:8088
>           Header: content-type: application/json
>          Header: content-length: 17
>
>   Internet Protocol Version 4, Src: 127.0.0.1 (127.0.0.1), Dst: 127.0.0.1 (127.0.0.1)
>   Transmission Control Protocol, Src Port: 1299, Dst Port: 80, Seq: 266, Ack: 229, Len: 46
>   HyperText Transfer Protocol 2
>       Stream: DATA, Stream ID: 1, Length 17
>           Length: 17
>           Type: DATA (0)
>           Flags: 0x01
>           0... .... .... .... .... .... .... .... = Reserved: 0x0
>           .000 0000 0000 0000 0000 0000 0000 0001 = Stream Identifier: 1
>           [Pad Length: 0]
>           Data: 7b2274657374223a20227465737422207d
>       JavaScript Object Notation: application/json
>           JSON compact form: {...}
>               test: "test"
>           Object
>               Member Key: test
>                   String value: test
>                   Key: test
>
> Why Gun is acting in this way? How to get both HEADER and DATA in the same HTTP2 request?
>
> I did the test with both 1.3.3 and 2.0.0-pre.2 releases.
>
> Br. Stefano