mirror of
https://github.com/lightning/bolts.git
synced 2025-03-10 09:10:07 +01:00
8e69306e0a
A bit less dense, but avoids a separate feature space. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
69 lines
4.2 KiB
Markdown
69 lines
4.2 KiB
Markdown
# BOLT #9: Assigned Feature Flags
|
|
|
|
This document tracks the assignment of `features` flags in the `init`
|
|
message ([BOLT #1](01-messaging.md)), as well as `features` fields in
|
|
the `channel_announcement` and `node_announcement` messages ([BOLT
|
|
#7](07-routing-gossip.md)). The flags are tracked separately, since
|
|
new flags will likely be added over time.
|
|
|
|
Flags are numbered from the least-significant bit, at bit 0 (i.e. 0x1,
|
|
an _even_ bit). They are generally assigned in pairs so that features
|
|
can be introduced as optional (_odd_ bits) and later upgraded to be compulsory
|
|
(_even_ bits), which will be refused by outdated nodes:
|
|
see [BOLT #1: The `init` Message](01-messaging.md#the-init-message).
|
|
|
|
Some features don't make sense on a per-channels or per-node basis, so
|
|
each feature defines how it is presented in those contexts. Some
|
|
features may be required for opening a channel, but not a requirement
|
|
for use of the channel, so the presentation of those features depends
|
|
on the feature itself.
|
|
|
|
The Context column decodes as follows:
|
|
* `I`: presented in the `init` message.
|
|
* `N`: presented in the `node_announcement` messages
|
|
* `C`: presented in the `channel_announcement` message.
|
|
* `C-`: presented in the `channel_announcement` message, but always odd (optional).
|
|
* `C+`: presented in the `channel_announcement` message, but always even (required).
|
|
* `9`: presented in [BOLT 11](11-payment-encoding.md) invoices.
|
|
|
|
| Bits | Name | Description | Context | Link |
|
|
|-------|----------------------------------|-----------------------------------------------------------|----------|---------------------------------------|
|
|
| 0/1 | `option_data_loss_protect` | Requires or supports extra `channel_reestablish` fields | IN | [BOLT #2][bolt02-retransmit] |
|
|
| 3 | `initial_routing_sync` | Sending node needs a complete routing information dump | I | [BOLT #7][bolt07-sync] |
|
|
| 4/5 | `option_upfront_shutdown_script` | Commits to a shutdown scriptpubkey when opening channel | IN | [BOLT #2][bolt02-open] |
|
|
| 6/7 | `gossip_queries` | More sophisticated gossip control | IN | [BOLT #7][bolt07-query] |
|
|
| 8/9 | `var_onion_optin` | Requires/supports variable-length routing onion payloads | IN | [Routing Onion Specification][bolt04] |
|
|
| 10/11 | `gossip_queries_ex` | Gossip queries can include additional information | IN | [BOLT #7][bolt07-query] |
|
|
| 12/13| `option_static_remotekey` | Static key for remote output | IN | [BOLT #3](03-transactions.md) |
|
|
|
|
## Requirements
|
|
|
|
The origin node:
|
|
* If it supports a feature above, SHOULD set the corresponding odd
|
|
bit in all feature fields indicated by the Context column unless
|
|
indicated that it must set the even feature bit instead.
|
|
* If it requires a feature above, MUST set the corresponding even
|
|
feature bit in all feature fields indicated by the Context column,
|
|
unless indicated that it must set the odd feature bit instead.
|
|
* MUST NOT set feature bits it does not support.
|
|
* MUST NOT set feature bits in fields not specified by the table above.
|
|
|
|
The requirements for receiving specific bits are defined in the linked sections in the table above.
|
|
The requirements for feature bits that are not defined
|
|
above can be found in [BOLT #1: The `init` Message](01-messaging.md#the-init-message).
|
|
|
|
## Rationale
|
|
|
|
There is no _even_ bit for `initial_routing_sync`, as there would be little
|
|
point: a local node can't determine if a remote node complies, and it must
|
|
interpret the flag, as defined in the initial spec.
|
|
|
|
|
|
<br>
|
|
This work is licensed under a [Creative Commons Attribution 4.0 International License](http://creativecommons.org/licenses/by/4.0/).
|
|
|
|
[bolt02-retransmit]: 02-peer-protocol.md#message-retransmission
|
|
[bolt02-open]: 02-peer-protocol.md#the-open_channel-message
|
|
[bolt04]: 04-onion-routing.md
|
|
[bolt07-sync]: 07-routing-gossip.md#initial-sync
|
|
[bolt07-query]: 07-routing-gossip.md#query-messages
|