"spendable" is for a single HTLC: if we own the channel, this amount
decreases with every HTLC, as we have to pay fees. We have access to this since
we call listpeerchannels anyway, so we can calculate the additional costs and
use it in the refining phase.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is the root cause of the problem worked around in 50949b7b9c
"askrene: hack in some padding so we don't overflow capacities."
When adding fees to flows, we didn't recheck the boundary conditions: in
renepay this is done by routebuilder.
Fortunately, we can use our "reservations" infrastructure to temporarily
use capacity as we process flows, so we handle the cases where they are
not independent correclty.
My assumption is that the resulting errors are small, so we divide
them between the remaining flows based on highest-to-least
probability.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We had a workaround for channels added by "auto.local", but instead we
should make it work properly.
I didn't do this before because we can't manipulate the localmods while
they're applied, but it's simple to do it in two stages.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Not quite the same, as it doesn't have the "auto.local" layer, but it exhibits
the same problem if we revert the fix for test_live_spendable.
And it's much faster!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Of course, we still will, since spendable is for a single HTLC, but
this also shows why we should treat *minimum* as the incorrect answer
if they cross, too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Fixes: https://github.com/ElementsProject/lightning/issues/7563
Based on great test case from https://github.com/daywalker90
```
E AssertionError: assert {'107x2x0/1': 'Path total 285720859 > spendable 285718000', '108x1x0/1': 'Path total 384721849 > spendable 384718000'} == {}
E Left contains 2 more items:
E {'107x2x0/1': 'Path total 285720859 > spendable 285718000',
E '108x1x0/1': 'Path total 384721849 > spendable 384718000'}
E Full diff:
E {
E - ,
E + '107x2x0/1': 'Path total 285720859 > spendable 285718000',
E + '108x1x0/1': 'Path total 384721849 > spendable 384718000',
E }
```
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
You need to know it to make an onion, and in theory if we decided to
fuzz it could be different for different paths.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This populates information on both topology (i.e. unannounced channels) and capacity for the local node using `listpeerchannels`.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This marks all channels around the source node as free (no delay, no fee). This is normally what we want, if we are calculating a path for ourselves.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
