[PATCH v1] dts: only sniff inbound packets

[Andrew Bailey]

Tested-by: Andrew Bailey <abailey at iol.unh.edu>
Reviewed-by: Andrew Bailey <abailey at iol.unh.edu>

On Tue, Mar 10, 2026 at 1:13 PM Patrick Robb <probb at iol.unh.edu> wrote:

> Add a filter to the Scapy traffic generator sniffer which
> forces the sniffer to ignore outbound traffic, preventing
> double counting of packets. Without this change sniffing
> will double count packets when DTS is being run with a
> single link topology, because the Scapy packet transmission
> and Scapy sniffing is happening on the same port. The
> correct behavior is to only count inbound traffic which is
> being returned to the traffic generator by the DTS SUT.
>
> Fixes: dfb667368077 ("dts: add Scapy asynchronous sniffer")
>
> Signed-off-by: Patrick Robb <probb at iol.unh.edu>
> ---
>  dts/framework/testbed_model/traffic_generator/scapy.py | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/dts/framework/testbed_model/traffic_generator/scapy.py
> b/dts/framework/testbed_model/traffic_generator/scapy.py
> index 9e15a31c00..c6e9006205 100644
> --- a/dts/framework/testbed_model/traffic_generator/scapy.py
> +++ b/dts/framework/testbed_model/traffic_generator/scapy.py
> @@ -203,7 +203,7 @@ def _sniff(self, recv_port: Port) -> None:
>          ready_prompt = "Ready."
>          self.send_command(
>              "sniff("
> -            f'iface="{recv_port.logical_name}", quiet=True, store=False, '
> +            f'iface="{recv_port.logical_name}", filter="inbound",
> quiet=True, store=False, '
>              "prn=lambda p: bytes_base64(p.build()).decode(), "
>              f'started_callback=lambda: print("{ready_prompt}")'
>              ")",
> --
> 2.49.0
>
>
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