Hi Florin,
Sorry for the late response. In fact, you just confirmed what I expected, thank
you. I'll go with my own parser to include all options (even the reserved
ones), inspired by tcp_options_parse. I'll go with my own rewriter too,
inspired by tcp_options_write.
But, what about discarded options (the ones I just want to remove) ? How would
you free/allocate/resize the buffer containing data (..., ip header, tcp
header, payload...) ? I just found a function called tcp_buffer_discard_bytes
but I'm not sure it's what I really need. I'm looking for the cleanest vpp-way
to do this.
Thanks for your help !
Justin
> Hi Justin,
>
> The expectation until now has been that options are not parsed until hitting
> the
> tcp related nodes. If tcp_options_parse is enough, then make it public and use
> it. That function just expects a tcp_options_t struct for outputting the
> results so no need for a tcp_connection_t. Now, if you need your special
> function to both read, match and update in place the options, then I recommend
> you write your own options parser.
>
> Hope this helps,
> Florin
>
>> On Nov 14, 2017, at 5:13 AM, Justin Iurman <justin.iur...@uliege.be> wrote:
>>
>> Hi Dave,
>>
>> Thanks (again) for your reply.
>>
>>> Brief commercial: hopefully you added your node to the ip4 unicast feature
>>> arc,
>>> configured to grab pkts, pre-ip4/6-lookup.
>>
>> Indeed, I added my node to the ip4-unicast feature arc.
>>
>>> In feature-arc land, the following one-liner sets next0 so pkts will visit
>>> the
>>> next enabled feature. The last node in the ip4-unicast feature arc is
>>> ip4-lookup...
>>>
>>> /* Next node in unicast feature arc */
>>> vnet_get_config_data (em->config_main[table_index],
>>> &b0->current_config_index, &next0,
>>> /* # bytes of config data */ 0);
>>>
>>> Check the ip protocol and ignore any non-TCP pkts:
>>>
>>> ip40 = vlib_buffer_get_current (b0);
>>> if (ip40->protocol != IP_PROTOCOL_TCP)
>>> goto trace0;
>>>
>>> Then use ip4_next_header() to find the tcp layer, etc. etc.
>>
>> Actually, I'm already able to access L3 and L4 structures. But, when I have
>> the
>> following, for instance:
>>
>> ip40 = vlib_buffer_get_current (b0);
>> if (ip40->protocol == IP_PROTOCOL_TCP)
>> {
>> tcp_header_t *tcp = ip4_next_header(ip40);
>> // where are options (tcp_options_t) ?
>> }
>>
>> How am I able to access TCP options for each packet ? I mean, I could
>> directly
>> parse them by moving the data pointer but I've also seen a function called
>> tcp_options_parse (see my previous email) that already does this job. How
>> would
>> you proceed to do this ? The expected behavior is to match some options and
>> strip them.
>>
>> Thanks,
>>
>> Justin
>> _______________________________________________
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>> vpp-dev@lists.fd.io
> > https://lists.fd.io/mailman/listinfo/vpp-dev
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