Tapping a Tx port to access all the packets being Txed

[Stephen Hemminger]

On Thu, 11 Jan 2024 05:55:53 +0000
Nicolson Ken (ニコルソン ケン) <ken.nicolson at jp.panasonic.com> wrote:

> Hi all,
> 
> I'm wanting to basically tap a DPDK stream and for instance save all packets being Txed by a PMD to a separate file.
> 
> I know I could relatively easily modify an existing PMD to have two output ports, but is there either an existing PMD that does this, or a programmatic way to graft a second port onto an arbitrary PMD, or is there another simpler way that I haven't realised yet. As mbufs are already reference counted, I would hope, and require, that such a solution would be zero copy. RSS-friendly would also be a plus.
> 
> Thanks,
> Ken

I started doing this with mirror support but decided it was adding more complexity.
The main use of taps was for debugging and pdump/dumpcap handle that.