Re: Handling weight for PRIORITY and HEADERS frames for HTTP2 with lua

[Alexis La Goutte <alexis.lagoutte () gmail com>]

Hi Alexander,

No problem, you can push a fix with this enhance !

Cheers

On Fri, Dec 22, 2017 at 1:19 AM, Alexander Gryanko <xpahos () gmail com> wrote:

> Hello,
>
> When I try to dissect HTTP2 messages, I found one confusing thing. Here is
> a definition of fields:
>
> { &hf_http2_weight,
>     { "Weight", "http2.headers.weight",
>        FT_UINT8, BASE_DEC, NULL, 0x0,
>       "An 8-bit weight for the identified priority", HFILL }
> },
> { &hf_http2_weight_real,
>     { "Weight real", "http2.headers.weight_real",
>        FT_UINT8, BASE_DEC, NULL, 0x0,
>       "Real Weight value (Add one to value)", HFILL }
> },
>
> Function to fill this fields:
>
> /* helper function to get the priority dependence for the frames that
> feature them:
>    HEADERS and PRIORITY */
> static guint
> dissect_frame_prio(tvbuff_t *tvb, proto_tree *http2_tree, guint offset,
> guint8 flags)
> {
>     proto_tree *ti;
>     guint8 weight;
>
>     if(flags & HTTP2_FLAGS_PRIORITY)
>     {
>         proto_tree_add_item(http2_tree, hf_http2_excl_dependency, tvb,
> offset, 4, ENC_NA);
>         proto_tree_add_item(http2_tree, hf_http2_stream_dependency, tvb,
> offset, 4, ENC_BIG_ENDIAN);
>         offset += 4;
>         proto_tree_add_item(http2_tree, hf_http2_weight, tvb, offset, 1,
> ENC_BIG_ENDIAN);
>         weight = tvb_get_guint8(tvb, offset);
>         /* 6.2: Weight:  An 8-bit weight for the stream; Add one to the
> value to obtain a weight between 1 and 256 */
>         ti = proto_tree_add_uint(http2_tree, hf_http2_weight_real, tvb,
> offset, 1, weight+1);
>         PROTO_ITEM_SET_GENERATED(ti);
>         offset++;
>     }
>
>     return offset;
> }
>
> So, when we try to access weights for PRIORITY, we need to create a field
> with Field.new("http2.headers.weight"). Maybe it will be better to split
> weights for PRIORITY and HEADERS to two different fields
> http2.priority.weight* and http2.headers.weight*?
>
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