Gate uniform message padding behind --dev-uniform-padding#8997
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sangbida wants to merge 4 commits intoElementsProject:masterfrom
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Gate uniform message padding behind --dev-uniform-padding#8997sangbida wants to merge 4 commits intoElementsProject:masterfrom
sangbida wants to merge 4 commits intoElementsProject:masterfrom
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Lagrang3
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Mar 27, 2026
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sangbida
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26.04 bug
This boolean allows lightningd and connectd to be on the same page on whether the uniform padding experimental flag is enabled.
Uniform padding (sending all messages as 1460-byte chunks) breaks peers running LND-based nodes: LND disconnects on receiving a ping(num_pong_bytes=65535) with "pong bytes exceeded" instead of ignoring it as required by BOLT ElementsProject#1. Gate the feature behind --dev-uniform-padding so it is opt-in rather than forced on all connections. Nodes that only peer with CLN can enable it for the traffic analysis defence. Changelog-Changed: uniform message padding is now opt-in via the --dev-uniform-padding flag.
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CLN 26.04rc1 introduced uniform message padding, which pads outgoing pings to prevent traffic analysis. Per BOLT #1, a num_pong_bytes >= 65532 means the recipient must not reply with a pong — it is a valid no-reply ping. However, LND does not comply with this part of the spec (they have very recently fixed this though) so to maintain interoperability between lightning implementations this feature is being gated behind an experimental flag for now.
Fixes #8978
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tools/lightning-downgrade