On Tue, Mar 14, 2017 at 12:21 PM, Tobias Klauser <tklau...@distanz.ch> wrote:
> On 2017-01-30 at 09:33:29 +0100, Vadim Kochan <vadi...@gmail.com> wrote:
>> Add trafgen_l7.c module with DNS proto header generation with
>> support of filling DNS query/answer/authority/additional sections
>> as sub headers.
>> Introcuded new concept as 'sub header' which is needed to easy handle
>> DNS sections which might be added on-demand, and to simplify using
>> sub-header as regular header with a fields, offset, etc. There is a
>> parent header which contains array of pointers of sub-headers, and the
>> array is ordered as they are located in the parent header. The
>> sub-headers mostly encapsulated by the parent header which 'knows'
>> the semantic of them. The new proto_hdr->push_sub_header(...) callback
>> was added to tell the parent header to push the sub-header's fields,
>> sub-header also may have proto_ops which must be filled by the parent.
>> This sub-header concept might be used in the future if it will be needed
>> to support DHCP, WLAN headers.
>> There are 4 kinds of DNS sub-headers - query, answer, authority,
>> additional. 'id' of each sub-header is used to only differentiate these
>> types of sections. These sections have strict order inside DNS header,
>> and there was added the proto_hdr_move_sub_header(...) to sort them in
>> required order.
> Might be a bit of a naive question: But wouldn't it be possible to
> enforce the sub-header order through the parser (i.e. only allow
> trafgen scripts which specify the respective sections in the right
> order? This would safe us from doing the whole header sorting/moving
> dance which looks a bit sacry to me (memmove of payload especially).

Well, I was thinking about this and decided to do so because:

    1) I really think that there might be in the future libtrafgen
which will handle sub-headers
         automatically (if it is needed by protocol header) both for
the application and trafgen tool (this
         reason might be not so strict).

    2) sub-headers might be a generic way for other protocol headers
like DHCP, WLAN.

Yes, the logic which does sub-headers moving is a bit scary as you
said, not sure if I can re-write it
to simplify it, will try.

Vadim Kochan

You received this message because you are subscribed to the Google Groups 
"netsniff-ng" group.
To unsubscribe from this group and stop receiving emails from it, send an email 
to netsniff-ng+unsubscr...@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

Reply via email to