The main responsibility of this new function is to mark a payment
process as terminated and set a reasonable error message, that will be
displayed to the caller. We also skip the remaining modifiers since
they might end up clobbering the message.
When we support bolt12, this won't exist. We only need min_final_cltv_expiry,
routes and features, so put them into struct payment explicitly.
We move the default final ctlv out to the caller, too, which is clearer.
e.g. keysend was using this value, but it was hard to tell.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This adds a new state `PAYMENT_STEP_RETRY_GETROUTE` which is used to
retry just that one step, without spawning a completely new
attempt. It's a new state so that modifiers do not act on it twice.
Changelog-Fixed: pay: Improved the performance of the `pay` command considerably by avoiding conflicting changes to our local network view.
This is a fairly direct translation. Even so, it should be faster in
most cases, and and we can do more sophisticated things if we want.
This also handles disabled channels better.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Changed: plugins: `pay` will now try disabled channels as a last resort.
Fixes: #3926
(probably)
Changelog-Fixed: pay: Also limit the number of splits if the payee seems to have a low number of channels that can enter it, given the max-concurrent-htlcs limit.
As revealed by the failure of tests in #3936, where we ended up trying
to send a partial payment using legacy style, we are not handling
style properly.
1. BOLT9 has features, so we can *know* that the destination supports
MPP. We may not have seen a node_announcement.
2. We can't assume that nodes inside routehints support TLV.
3. We can't assume direct peers support TLV.
The keysend code tried to fix this up, so I'm not sure that this caused
the issue in #3968, though.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Fixed: `pay` will now make reliable multi-part payments to nodes it doesn't have a node_announcement for.
This avoids overwriting the ones in git, and generally makes things neater.
We have convenience headers wire/peer_wire.h and wire/onion_wire.h to
avoid most #ifdefs: simply include those.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Arguably a low-priority bug since no current node ever generates routehints longer
than one hop.
However, it is possible as an edge case, if the destination is directly accessible
*and* supports multiple channels, that we route through the destination, one of the
*other* channels it has not in the routehint, to the entry point, and then through
the routehint.
This change removes the risk of the above edge case.
Changelog-None: arguably a low-priority bug.
The shortcut in the retry_mod that we can skip retrying if getroute fails or
we have no result is only valid if the parameters don't change. As we iterate
through the routehints the parameters change, and so we must signal to the
retry_mod that it can retry even in those cases.
This uses @cdecker's idea of excluding the routehinted channel from the route,
and also consumes the route hints as it goes so that it makes progress.
I don't know if this is correct, but it reliably passes tests/test_pay.py::test_tlv_or_legacy
now.
We store an offset of the current routehint in the modifier data. It gets
incremented on retry, and it gets reset to 0 on split. This is because once we
split we have a different amount and a previously unusable routehint becomes
usable again.
This does two things: it checks if the destination of the payment is at all
reachable without routehints, and if it is it adds a direct attempt as option
to the routehints in the form of a NULL routehint. It also simplifies the
selection of the routehint since the direct case is no longer special, instead
we just return a NULL routehint as if it were a normal routehint.
There is little point in trying to split if the resulting HTLCs exceed the
maximum number of HTLCs we can add to our channels. So abort if a split would
result in more HTLCs than our channels can support.
It turns out that by aggressively splitting payments we may end up exhausting
the number of HTLCs we can add to a channel quickly. By tracking the number of
HTLCs we can still add, and excluding the channels to which we cannot add any
more we increase the route diversity, and avoid quickly exhausting the HTLC
budget.
In the next commit we'll also implement an early abort if we've exhausted all
channels, so we don't end up splitting indefinitely and we can also optimize
the initial split to not run afoul of that limit.
This modifier splits a payment that has been attempted a number of times (by a
modifier earlier in the mod chain) and has failed consistently. It splits the
amount roughly in half, with a but if random fuzz, and then starts a new round
of attempts for the two smaller amounts.
With MPP we require that the sum of parts is equal to the `total_msat` amount
declared in the onion. Since that can't be changed once the first part arrives
we need a way to disable amount fuzzing for MPP.
These are primarily the fee and cltv constraints that we need to keep up to
date in order to give modifiers a correct view of what is and what isn't
allowed.
We're lucky that we can distinguish the severity of the failure based on the
failcode, so we bubble up the one with the maximum failcode, and let callers
inspect details if they need more information.
We can have quite detailed information about our local channels, so call
`listpeers` before the `getroute` call on the root payment, to seed that
information in the channel_hints.
We need to keep them around so we can inspect them later. We'll also need a
background cleanup every once in a while to free some memory. More on that in
a future commit.
Rusty Russell
Christian Decker
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