Fetch block from a peer if we don't have it #7240
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This allows us to intercept getblock on a non 0 exit when the block was not found. We fill this with something meaningull in future commits. Signed-off-by: Peter Neuroth <[email protected]>
We move the `geblock` call into a separate function. This allows us to call if from various places in the future. Signed-off-by: Peter Neuroth <[email protected]>
We introduce the peers array that contains the known set of connected peers for future reference in case that we couldn't find the block we are looking for. Signed-off-by: Peter Neuroth <[email protected]>
In the case that we have peers left in the peers array and that we could not find the block yet, we ask the next peer for the desired block. Signed-off-by: Peter Neuroth <[email protected]>
`getblockfrompeer` was introduced in v23.0.0, we want to skip this path if the version of bitcoind used is below that. Signed-off-by: Peter Neuroth <[email protected]>
Changelog-Changed: Plugins: bcli: Add a path that tries to fetch blocks from a peer if we can not find them locally. Signed-off-by: Peter Neuroth <[email protected]>
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I would also really like some tests! This can be done using our inbuilt mocks for bitcoind; you can give a made-up blockhash, let it fail (since there are no peers), but also can fake up some peers and check it does indeed iterate through them. |
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@rustyrussell I am a bit confused about the tests. There are already a few tests using a mocked bitcoind that test the peer iteration in |
Using `getblockfrompeer` requires a version equal or above 23.0.0 Signed-off-by: Peter Neuroth <[email protected]>
It is simpler to just iterate through the peerlist backwards. Signed-off-by: Peter Neuroth <[email protected]>
Hmm, how did I miss that commit? Sorry, these look good! |
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This PR adds a path in the
bcliplugin that utilizesgetblockfrompeerto try to fetch a block from a peer in case that we don't know about the block. This is something that happens when core lightning tries to fetch a block from bitcoind that has already been pruned by bitcoind.getblockfrompeerhas been introduced inv23.0.0. The call asks a given peer for a block that the local node does not know about. Even thoughgetblockfrompeerdoes not make any guarantees about whether the block will be fetched (or pruned again right away), the success probabilities are really high if we just try long enough.Here is a brief description about what happens now if core lightning asks for a block
a) get blockhash for height x
b) try to get block from bitcoind:
resolves #7201