Don't relay buggy extra payments #2937
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If a payer is buggy and tries to pay the same invoice multiple times, it can lead to an edge case where the recipient accepted the first one and purchased liquidity for it, but didn't purchase additional liquidity and thus cannot receive the duplicate payments. In that case, the recipient may even have released the preimage, so the LSP (or any other node in the route) could steal the entire duplicate payment. To prevent that, we immediately fail such buggy duplicate payments. Note that if the first payment was fully completed, we don't fail the extra payments and the payer could get screwed, but they're buggy so it's their problem...
When replaying parts that were waiting for an on-the-fly funding, we explicitly set `commit = false` to all parts but the last one, in order to save us from signing multiple times. But this has side effects in the case where the last part is rejected for some reason, because previous parts stay stuck waiting for a `CMD_SIGN` that never arrives.
remyers
previously approved these changes
Nov 8, 2024
eclair-core/src/test/scala/fr/acinq/eclair/payment/relay/OnTheFlyFundingSpec.scala
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remyers
approved these changes
Nov 8, 2024
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If a payer is buggy and tries to pay the same invoice multiple times, it can lead to an edge case where the recipient accepted the first one and purchased liquidity for it, but didn't purchase additional liquidity and thus cannot receive the duplicate payments.
Also, when replaying parts that were waiting for an on-the-fly funding, we set
commit = falseto all parts, instead of just the last one. This optimization caused the payment to be stuck if the last part was unexpectedly rejected (which would for example happen in the buggy payer case described above, before we rejected those extra payments).