Follow BOLT1 handling for "no reply" pings: ignore, don't warn.#3278
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t-bast merged 2 commits intoACINQ:masterfrom Apr 2, 2026
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Follow BOLT1 handling for "no reply" pings: ignore, don't warn.#3278t-bast merged 2 commits intoACINQ:masterfrom
t-bast merged 2 commits intoACINQ:masterfrom
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These "oversize ping replies" are how we ask for no replies, such as when
we're sending dummy traffic. From the rationale:
This allows a convenient cutoff for `num_pong_bytes` to indicate that no reply should be sent.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
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I never noticed that the spec had this hook for pongless pings, thanks!
We previously tested that we were sending a `warning` back. We also add a comment to explain why we ignore those pings.
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BOLT1 says: ``` A node receiving a ping message: - if num_pong_bytes is less than 65532: - MUST respond by sending a pong message, with byteslen equal to num_pong_bytes. - otherwise (num_pong_bytes is not less than 65532): - MUST ignore the ping. ``` These reply-less pings are used to insert cover traffic to thwart network-level traffic analysis. We wanted to allow them in #3278 but we missed this ping flood protection that needed to be updated.
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BOLT1 says: ``` A node receiving a ping message: - if num_pong_bytes is less than 65532: - MUST respond by sending a pong message, with byteslen equal to num_pong_bytes. - otherwise (num_pong_bytes is not less than 65532): - MUST ignore the ping. ``` These reply-less pings are used to insert cover traffic to thwart network-level traffic analysis. We wanted to allow them in #3278 but we missed this ping flood protection that needed to be updated. We also had an off-by-one in the maximum pong length that is now fixed.
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These "oversize ping replies" are how we ask for no replies, such as when we're sending dummy traffic. From the rationale: