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invoice: turn assert failure into more informative log_broken message.

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We had this assertion fail, and I can't see a clear reason why.  Remove it
(i.e. don't crash because we're having trouble with creating invoice routehints)
and add logging.

```
Assertion failed: a->c->rr_number < b->c->rr_number (lightningd/invoice.c: cmp_rr_number: 623)
lightningd: FATAL SIGNAL 6 (version v0.10.2-modded)
0x5654f1c40061 send_backtrace
        common/daemon.c:33
0x5654f1c400e9 crashdump
        common/daemon.c:46
0x7efd87da6c8a ???
        ???:0
```

There are several possible causes for this:

1. We have two channels with the same rr_number. A quick audit shows we always set that rr_number to a unique value (and 64 bits, so wrap is not possible between the release and now!).
2. It's theoretically possible that sort() could compare a value with itself, but that would be really dumb: it doesn't that I've ever seen, but then, we've never seen this assert() hit, either.
3. listincoming has given us the same channel twice. I don't see how that is possible: we had a race where channels could momentarily vanish, but never be duplicated (emailed crash.log shows no duplicates!).
4. General corruption/freed memory access. If a channel we've just looked up is gone but still in the hash table, this is possible but would cause lots of random behavior and crashes.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2022-07-10 16:16:37 +09:30 committed by neil saitug
parent 9d1b5a654e
commit 3a61e0e181
1 changed files with 9 additions and 5 deletions
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14
lightningd/invoice.c
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@ -617,13 +617,17 @@ static struct route_info **select_inchan(const tal_t *ctx,
static int cmp_rr_number(const struct routehint_candidate *a,
const struct routehint_candidate *b,
void *unused)
struct lightningd *ld)
{
/* They're unique, so can't be equal */
if (a->c->rr_number > b->c->rr_number)
return 1;
assert(a->c->rr_number < b->c->rr_number);
return -1;
if (a->c->rr_number < b->c->rr_number)
return -1;
/* They're unique, so can't be equal */
log_broken(ld->log, "Two equal candidates %p and %p, channels %p and %p, rr_number %"PRIu64" and %"PRIu64,
a, b, a->c, b->c, a->c->rr_number, b->c->rr_number);
return 0;
}
/** select_inchan_mpp
@ -650,7 +654,7 @@ static struct route_info **select_inchan_mpp(const tal_t *ctx,
routehints = tal_arr(ctx, struct route_info *, 0);
/* Sort by rr_number, so we get fresh channels. */
asort(candidates, tal_count(candidates), cmp_rr_number, NULL);
asort(candidates, tal_count(candidates), cmp_rr_number, ld);
for (size_t i = 0; i < tal_count(candidates); i++) {
if (amount_msat_greater_eq(gathered, amount_needed))
break;