The fetchinvoice and offers plugins disable themselves if the option
isn't enabled (it's enabled by default on EXPERIMENTAL_FEATURES).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: `experimental-offers` enables fetch, payment and creation of (early draft) offers.
1. Hoist 7200 constant into the bolt12 heade2.
2. Make preimage the last createinvoice arg, so we could make it optional.
3. Check the validity of the preimage in createinvoice.
4. Always output used flag in listoffers.
5. Rename wallet offer iterators to offer_id iterators.
6. Fix paramter typos.
7. Rename `local_offer_id` parameter to `localofferid`.
8. Add reference constraints on local_offer_id db fields.
9. Remove cut/paste comment.
10. Clarify source of fatal() messages in wallet.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is for offers which have `send_invoice`: we need to associate the
payment with the original offer, in (the usual) case where it is a single
use offer. We mark it used when it's paid, to avoid a race.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Still asserts that it's the standard size, but makes it a dynamic
member. For simpliciy, changes the parse_onionpacket API (it must be
a tal object now, so we might as well allocate it here to catch all
the callers).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: delpay a new method to delete the payment completed or failed.
Signed-off-by: Vincenzo Palazzo <vincenzopalazzodev@gmail.com>
Suggested-by: Rusty Russell <@rustyrussell>
Changelog-Deprecated: JSON-RPC: `listsendpays` will no longer add `null` if we don't know the `amount_msat` for a payment.
While not directly necessary, it still feeds the `listpays` result, and so we
should pass it along if we can, so we don't have to rely solely on the
`amount_sent` field, which includes the fees.
Reported-by: Rusty Russell <@rustyrussell>
There were no channel updates in my log; because sendonion doesn't know the
actual node_ids or channel_ids, we can't tell gossipd what node/channel it was
so it can no longer remove them on PERM errors.
However, we can tell it the error message so it can apply the update.
Fixes: #3877
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
And document the partid arg.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `sendonion` has a new optional `bolt11` argument for when it's used to pay an invoice.
The test had part 1 and 2 backward, but still worked. When I copied that to
*after* the test had succeeded, it complained. It should always complain,
to catch bugs.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This wasn't important before, but now we have MPP it's good to enforce.
Reported-by: Christian Decker
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This happens to be an edge case with the way we use `sendonion` in
MPP. `sendonion` does not attempt to recover the route even if we supply the
shared secrets (it'd require us to map forwarding channels to the nodes etc),
so `failnode` will always be unset, unless it is the first hop, which gets
stored. This is not a problem if it weren't for the fact that we don't store
the partial route, consisting solely of the channel leading to the first hop,
therefore the assertion that either both are NULL or both aren't fails on the
first hop.
This went unnoticed since with MPP we have more concurrent payments in flight,
increasing the chances of a exhausted first hop considerably.
I noticed the following in logs for tests/test_connection.py::test_feerate_stress:
```
DEBUG 022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-chan#1: Failing HTLC 18446744073709551615 due to peer death
DEBUG 022d223620a359a47ff7f7ac447c85c46c923da53389221a0054c11c1e3ca31d59-chan#1: local_routing_failure: 8194 (WIRE_TEMPORARY_NODE_FAILURE)
```
This is because it reports the (transient) node_failure error, because
our channel_failure message is incomplete. Fix this wart up.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is what actually lets us pay blinded invoices.
Unfortunately, our internal logic assumes every hop in a path has a
next `short_channel_id`, so we have to use a dummy. This is
sufficient for testing, however.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Note that it's channeld which calculates the shared secret, too. This
minimizes the work that lightningd has to do, at cost of passing this
through.
We also don't yet save the blinding field(s) to the database.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
It's almost always "their_features" and "our_features" respectively, so
make those names clear.
Suggested-by: @cdecker
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Turns out that unnecessary: all callers can access the feature_set,
so make it much more like a normal primitive.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Instead of saving a stripped_update, we use the new
local_fail_in_htlc_needs_update.
One minor change: we return the more correct
towire_temporary_channel_failure when the node is still syncing.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is a common thing to do, so create a macro.
Unfortunately, it still needs the type arg, because the paramter may
be const, and the return cannot be, and C doesn't have a general
"(-const)" cast.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This cleans up the "local failure" callers for incoming HTLCs to hand
an onionreply instead of making us generate it from the code inside
make_failmsg.
(The db path still needs make_failmsg, so that's next).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-deprecated: Plugins: htlc_accepted_hook "failure_code" only handles simple cases now, use "failure_message".
At the moment, we store e.g. WIRE_TEMPORARY_CHANNEL_FAILURE, and then
lightningd has a large demux function which turns that into the correct
error message.
Such an enum demuxer is an anti-pattern.
Instead, store the message directly for output HTLCs; channeld now
sends us an error message rather than an error code.
For input HTLCs we will still need the failure code if the onion was
bad (since we need to prompt channeld to send a completely different
message than normal), though we can (and will!) eliminate its use in
non-BADONION failure cases.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Using it with a different value to the amount sent causes a crash in 0.8.0,
which is effectively deprecating it, so let's disallow it now.
Changelog-Changed: If the optional `msatoshi` param to sendpay for non-MPP is set, it must be the exact amount sent to the final recipient.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We tag them with specific versions when they're experimental,
but do a poor job of cleaning them up (and thus ensuring they're
checked!) afterwards.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Before this patch we used `int` for error codes. The problem with
`int` is that we try to pass it to/from wire and the size of `int` is
not defined by the standard. So a sender with 4-byte `int` would write
4 bytes to the wire and a receiver with 2-byte `int` (for example) would
read just 2 bytes from the wire.
To resolve this:
* Introduce an error code type with a known size:
`typedef s32 errcode_t`.
* Change all error code macros to constants of type `errcode_t`.
Constants also play better with gdb - it would visualize the name of
the constant instead of the numeric value.
* Change all functions that take error codes to take the new type
`errcode_t` instead of `int`.
* Introduce towire / fromwire functions to send / receive the newly added
type `errcode_t` and use it instead of `towire_int()`.
In addition:
* Remove the now unneeded `towire_int()`.
* Replace a hardcoded error code `-2` with a new constant
`INVOICE_EXPIRED_DURING_WAIT` (903).
Changelog-Changed: The waitinvoice command would now return error code 903 to designate that the invoice expired during wait, instead of the previous -2
1. We asserted that there wouldn't be a raw failcode.
2. We didn't pass the failure information via JSON in this case.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This makes it clear we're dealing with a message which is a wrapped error
reply (needing unwrap_onionreply), not an already-wrapped one.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
`wallet_payment_store` would free the `wallet_payment` instance which would
then cause us to reload it from the DB. Instead of doing the store->free->load
dance we now tell `wallet_payment_store` whether it should take ownership and
leave it alone if not.
Passing the payment around instead of referencing it through payment_hash and
partid is a nice side-effect.
`wallet_payment_store` frees the unstored payment after it has stored it, but
we still need that instance for our notifications. This is the smallest
possible fix, but I plan to refactor this out.
Changelog-Changed: plugin: `notify_sendpay_success` and `notify_sendpay_failure` are now always called, even if there is no command waiting on the result.
Thanks to @t-bast, who made this possible by interop testing with Eclair!
Changelog-Added: Protocol: can now send and receive TLV-style onion messages.
Changelog-Added: Protocol: can now send and receive BOLT11 payment_secrets.
Changelog-Added: Protocol: can now receive basic multi-part payments.
Changelog-Added: RPC: low-level commands sendpay and waitsendpay can now be used to manually send multi-part payments.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Bastien TEINTURIER <bastien@acinq.fr> writes:
> One thing I noticed but didn't investigate much: after sending the two
> payments, I tried using `waitsendpay` and it reported an error *208*
> (*"Never attempted payment for
> '98ee736d29d860948e436546a88b0cc84f267de8818531b0fdbe6ce3d080f22a'"*).
>
> I was expecting the result to be something like: "payment succeeded for
> that payment hash" (the HTLCs were correctly settled).
Indeed, if you waitsendpay without specifying a partid, you are waiting
for 0, which may not exist. Clarify the error msg.
Reported-by: @t-bast
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Bastien TEINTURIER <bastien@acinq.fr> writes:
> It looks like the split on c-lightning side is quite limited at the moment:
> the only option is to split a payment in exactly its two halves,
> otherwise I get rejected because of the rule of overpaying more than
> twice the amount?
We only tested exactly two equal-size payments; indeed, our finalhop
test was backwards. We only complain if the final hop pays more than
twice msat (technically, this test is still too loose for mpp: the
spec says we should sum to the exact amount).
Reported-by: @t-bast
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Explicit #if EXPERIMENTAL_FEATURES check in case we enable them at different
times, but it requires a payment_secret since we put them in the same field.
This incidently stops it working on legacy nodes.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
msatoshi was used to indicate the amount the invoice asked for, but
for parallel sendpay it's required, as it allows our sanity check of
limiting the total payments in flight, ie. it becomes
'total_msat'.
There's a special case for sendonion, which always tells us the value is 0.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We currently refuse a payment if one is already in flight. For parallel
payments, it's a bit more subtle: we want to refuse if it we already have
the total-amount-of-invoice in flight.
So we get all the current payments, and sum the pending ones.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
In particular, we're about to do surgery on the detection-of-previous-payments
logic, and we should not do this in two places.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is in preparation for partial payments. For existing payments,
partid is 0 (to match the corresponding payment).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This is in preparation for partial payments. For existing payments,
partid is 0 (arbitrarity) and total_msat is msatoshi.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Now "raw_payload" is always the complete string (including realm or length
bytes at the front).
This has several effects:
1. We can receive an decrypt an onion which is grossly malformed.
2. We can still hand this to the htlc_accepted hook.
3. We then fail it unless the htlc_accepted accepts it manually.
4. The createonion API now takes the raw payload, and does not know
anything about "style".
The only caveat is that the sphinx code needs to know the payload
length: we have a call for that, which simply tells it to copy the
entire onion (and treat us as the final node) if it's invalid.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
If we initiated the payment using an externally generated onion we don't know
what the final hop gets, or even who it is, so we don't display the amount in
these cases. I chose to show `null` instead in order not to break dependees
that rely on the value being there.
If we can't decode the onion, because the onion got corrupted or we used
`sendonion` without specifying the `shared_secrets` used, the best we can do
is tell the caller instead.
This means that c-lightning can now internally decrypt an eventual error
message, and not force the caller to implement the decryption. The main
difficulty was that we now have a new state (channels and nodes not specified,
while shared_secrets are specified) which needed to be handled.
When using `sendonion` with `shared_secrets` we may be able to decode the
onioned error message but we cannot infer which node reported the failure
since we don't know which nodes where involved.
We are breaking with a couple of assumptions, namely that we have the
`path_secrets` to decode the error onion. If this happens we just want it to
error out.
These are useful for the `createonion` JSON-RPC we're going to build next. The
secret is used for the optional `session_key` while the hex-encoded binary is
used for the `assocdata` field to which the onion commits. The latter does not
have a constant size, hence the raw binary conversion.
Also pulls in a new onion error (mpp_timeout). We change our
route_step_decode_end() to always return the total_msat and optional
secret.
We check total_amount (to prohibit mpp), but we do nothing with
secret for now other than hand it to the htlc_accepted hook.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Default is legacy. If we have future styles, new strings can be defined,
but for now it's "tlv" or "legacy".
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
pPayment field includes the basic information of the payment, so the return valves of 'sendpay_success()' and 'sendpay_fail()' should include this field.
Note "immediate_routing_failure" is before payment creation, and for this case, return won't include payment fields.
`sendpay_success`
A notification for topic `sendpay_success` is sent every time a sendpay
success(with `complete` status). The json is same as the return value of
command `sendpay`/`waitsendpay` when these cammand succeeds.
```json
{
"sendpay_success": {
"id": 1,
"payment_hash": "5c85bf402b87d4860f4a728e2e58a2418bda92cd7aea0ce494f11670cfbfb206",
"destination": "035d2b1192dfba134e10e540875d366ebc8bc353d5aa766b80c090b39c3a5d885d",
"msatoshi": 100000000,
"amount_msat": "100000000msat",
"msatoshi_sent": 100001001,
"amount_sent_msat": "100001001msat",
"created_at": 1561390572,
"status": "complete",
"payment_preimage": "9540d98095fd7f37687ebb7759e733934234d4f934e34433d4998a37de3733ee"
}
}
```
`sendpay` doesn't wait for the result of sendpay and `waitsendpay`
returns the result of sendpay in specified time or timeout, but
`sendpay_success` will always return the result anytime when sendpay
successes if is was subscribed.
This is just taking the existing serialization code and repackaging it in a
more useful form.
Signed-off-by: Christian Decker <decker.christian@gmail.com>
Direct leak of 1024 byte(s) in 2 object(s) allocated from:
#0 0x7f4c84ce4448 in malloc (/lib/x86_64-linux-gnu/libasan.so.5+0x10c448)
#1 0x55d11b782c96 in timer_default_alloc ccan/ccan/timer/timer.c:16
#2 0x55d11b7832b7 in add_level ccan/ccan/timer/timer.c:166
#3 0x55d11b783864 in timer_fast_forward ccan/ccan/timer/timer.c:334
#4 0x55d11b78396a in timers_expire ccan/ccan/timer/timer.c:359
#5 0x55d11b774993 in io_loop ccan/ccan/io/poll.c:395
#6 0x55d11b72322f in plugins_init lightningd/plugin.c:1013
#7 0x55d11b7060ea in main lightningd/lightningd.c:664
#8 0x7f4c84696b6a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x26b6a)
To fix this, we actually make 'ld->timers' a pointer, so we can clean
it up last of all. We can't free it before ld, because that causes
timers to be destroyed.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
"result" should always be an object (so that we can add new fields),
so make that implicit in json_stream_success.
This makes our primitives well-formed: we previously used NULL as our
fieldname when calling the first json_object_start, which is a hack
since we're actually in an object and the fieldname is 'result' (which
was already written by json_object_start).
There were only two cases which didn't do this:
1. dev-memdump returned an array. No API guarantees on this.
2. shutdown returned a string.
I temporarily made shutdown return an empty object, which shouldn't
break anything, but I want to fix that later anyway.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
A new string field is added to the command structure and is specified at the creation of each native command, and in the JSON created by 'json_add_help_command()'.
New fields don't have to be spelled out twice.
The raw version are called _only, so we don't miss a call
accidentally. We can rename them when we finally deprecated old
fields.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
I tried to just do gossipd, but it was uncontainable, so this ended up being
a complete sweep.
We didn't get much space saving in gossipd, even though we should save
24 bytes per node.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
New name is less confusing, and most people should be transitioning to
listpays rather than this anyway.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This field was used by `pay` to hold the bolt11 description if the bolt11
string used `h` to hash the description (which nobody ever did). If the
`h` field wasn't present, it could contain anything, as it wasn't checked.
It's really useful to have a label for payments (eg. '1 Cuban'), but adding
yet-another option would be painful, so we simply rename 'description'
to 'label' except inside the db.
This means we need to do some tricky parameter parsing to handle array
and keyword JSON arguments, but only until we remove the old name.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Without this, there's no proof of payment, since it is the signed invoice
that make the receipt valid.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We need to do it in various places, but we shouldn't do it lightly:
the primitives are there to help us get overflow handling correct.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
As a side-effect of using amount_msat in gossipd/routing.c, we explicitly
handle overflows and don't need to pre-prune ridiculous-fee channels.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We're about to add 'amount_msat' to getroute, but it's common to feed
'getroute' back into 'sendpay', so sendpay should allow it.
If both are specified, make sure they're the same!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
I got a spurious failure because the final node gave a CLTV error and
so it decided to use a different channel. It should probably handle
this corner case better, but meanwhile make the test robust.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
List the final one instead; if there's an error from the node it
may actually make sense to blame that channel (ie. previous node
did something wrong).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We no longer need a 'sendpay_result' structure, we can pass
appropriate parameter directly now they're simple calls.
Every waitsendpay command ends in tell_waiters_failed or
tell_waiters_success, which call sendpay_success or sendpay_fail on
all matching waiters. These all return 'struct command_result *'.
In cases where the result is immediately known, we call
sendpay_success/sendpay_fail directly for the command.
This also adds a helpful 'failcodename' field to the JSON output.
[ This was four separate cleanup patches, but that contained much
redundancy and was even worse to review ]
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
With only one caller, we don't need a callback pointer any more; we can simply
call the function.
This required some code shuffling, and I changed the callback function
arguments to be in a more natural order, now they're not used as
callbacks.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Now we don't have a second caller for these routines, we can move
them back into pay.c and make the functions static.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
As a general rule, lightningd shouldn't parse user packets. We move the
parsing into gossipd, and have it respond only to permanent failures.
Note that we should *not* unconditionally remove a channel on
WIRE_INVALID_ONION_HMAC, as this can be triggered (and we do!) by
feeding sendpay a route with an incorrect pubkey.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Christian points out that we can iterate by ->size rather than calling
json_next() to find the end (which traverses the entire object!).
Now ->size is reliable (since previous patch), this is OK.
Reported-by: @cdecker
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Fortunately, we can calculate the sha256 ourselves, so the
outgoing channeld doesn't need to tell us.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
The node which sent the error is doing so because the following
one sent WIRE_UPDATE_FAIL_MALFORMED_HTLC.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Obviously the Facebook relationship status joke was a bit subtle, but I've
continued it anyway because I'm especially susceptible to Dad jokes.
Suggested-by: @niftynei
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This causes a compiler warning if we don't do something with the
result (hopefully return immediately!).
We use was_pending() to ignore the result in the case where we
complete a command in a callback (thus really do want to ignore
the result).
This actually fixes one bug: we didn't return after command_fail
in json_getroute with a bad seed value.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Usually, this means they return 'command_param_failed()' if param()
fails, and changing 'command_success(); return;' to 'return
command_success()'.
Occasionally, it's more complex: there's a command_its_complicated()
for the case where we can't exactly determine what the status is,
but it should be considered a last resort.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Handers of a specific form are both designed to be used as callbacks
for param(), and also dispose of the command if something goes wrong.
Make them return the 'struct command_result *' from command_failed(),
or NULL.
Renaming them just makes sense: json_tok_XXX is used for non-command-freeing
parsers too.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
json_escaped.[ch], param.[ch] and jsonrpc_errors.h move from lightningd/
to common/. Tests moved too.
We add a new 'common/json_tok.[ch]' for the common parameter parsing
routines which a plugin might want, taking them out of
lightningd/json.c (which now only contains the lightningd-specific
ones).
The rest is mainly fixing up includes.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This (will) avoid the plugin having to walk back from the params object
as it currently does.
No code changes; I removed UNUSED and UNNEEDED labels from the other
parameters though (as *every* json_rpc callback needs to call param()
these days, they're *always* used).
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Such an API is required for when we stream it directly. Almost all our
handlers fit this pattern already, or nearly do.
We remove new_json_result() in favor of explicit json_stream_success()
and json_stream_fail(), but still allowing command_fail() if you just
want a simple all-in-one fail wrapper.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We don't expect payment or payment->route_channels to be NULL without an
old db, but putting an assert there reveals that we try to fail an HTLC
which has already succeeded in 'test_onchain_unwatch'.
Obviously we only want to fail an HTLC which goes onchain if we don't
already have the preimage!
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Note: Unlike before, this will now accept positional parameters.
Note: In case of error we no longer report the hop number. Is this acceptable?
We still report the name of the bad param and its value.
One option is to log the hop number if param() returns false. This would require
a change to command_fail so it doesn't delete the cmd, so we can still
access cmd->ld->log.
Signed-off-by: Mark Beckwith <wythe@intrig.com>
This was a very simple change and allowed us to remove the special
`json_opt_tok` macro.
Moved the callback out of `common/json.c` to `lightningd/json.c` because the new
callbacks are dependent on `struct command` etc.
(I already started on `json_tok_number`)
My plan is to:
1. upgrade json_tok_X one a time, maybe a PR for each one.
2. When done, rename macros (i.e, remove "_tal").
3. Remove all vestiges of the old callbacks
4. Add new callbacks so that we no longer need json_tok_tok!
(e.g., json_tok_label, json_tok_str, json_tok_msat)
Signed-off-by: Mark Beckwith <wythe@intrig.com>
This adds one line with the onion and the channel_update we extract from
it. This in turn allows us to check that the channel_update in the onion is not
type prefixed, and that we patch it correctly before passing it to gossipd.
As was pointed out by @robtex we have underspecified the format of the nested
`channel_update` in the onionreply: lnd and eclair inserted the raw
channel_update without the type prefix, while we went for the full wire format,
including the type prefix. While we agreed that with the type it is more
flexible, and consistent, we decided to adapt to the majority and at least be
compatibly broken.
This commit takes care of being able to interpret either format correctly. It's
not perfect since signatures can happen to start with 0x0102 (the channel_update
type) but that'll happen only once ever 65k failures.
