Is there something like this already present in the firmware to reduce traffic?

[RichieFrame]

When 2 nodes are in close proximity, and one sends a message, it is received by the 2nd, which determines if it shall be rebroadcasted. The 2nd may not know where the first is.

If the RSSI is very high, say -35dBm or stronger, and the SNR is similarly high at say 6dB or stronger, the receiving node should infer that the sender is in very close proximity and choose not to rebroadcast.

If this were to be an added feature, it would be best if those thresholds were configurable within a reasonable range, and probably not available on router role.

[GUVWAF]

Why should it not rebroadcast in this case? For example, when you send a packet from a node inside the house, it would be good if the node on your roof would rebroadcast, even though its received signal is strong. If another node received it with worse signal quality, it will rebroadcast first and then the node on the roof will not anymore.

[RichieFrame]

A roof node would not be close to that level of signal quality, RSSI would be closer to -60dBm as the antennas are not on the same horizontal plane, and you need to go through the roof and probably at least 1 ceiling. I did a test going through just 1 ceiling, I got a very good SNR of 7dB, but RSSI was -52dBm. The solid wood roof with asphalt shingles will surely drop the signal noticeably more, as would the additional distance.

That is not to say you make an excellent point, this should be something can be tuned to a users environment and use case, or allowed to be disabled, though I would suggest client type modes have this enabled with a sane default, it could reduce airtime substantially in crowded areas, which is extremely important when there are airtime/duty cycle limitations imposed.