mirror of
https://github.com/lightning/bolts.git
synced 2024-11-19 01:50:03 +01:00
60 lines
3.5 KiB
Markdown
60 lines
3.5 KiB
Markdown
# BOLT #9: Assigned Feature Flags
|
|
|
|
This document tracks the assignment of `localfeatures` and `globalfeatures`
|
|
flags in the `init` message ([BOLT #1](01-messaging.md)) along with the
|
|
`features` flag 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.
|
|
|
|
The `features` flags in the routing messages are a subset of the
|
|
`globalfeatures` flags, as `localfeatures`, by definition, are only of interest
|
|
to direct peers.
|
|
|
|
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(_even_ bits), which will be refused by outdated nodes: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).
|
|
|
|
## Assigned `localfeatures` flags
|
|
|
|
These flags may only be used in the `init` message:
|
|
|
|
| Bits | Name | Description | Link |
|
|
|-------|----------------------------------|---------------------------------------------------------------------------|------------------------------|
|
|
| 0/1 | `option_data_loss_protect` | Requires or supports extra `channel_reestablish` fields | [BOLT #2][bolt02-retransmit] |
|
|
| 3 | `initial_routing_sync` | Indicates that the sending node needs a complete routing information dump | [BOLT #7][bolt07-sync] |
|
|
| 4/5 | `option_upfront_shutdown_script` | Commits to a shutdown scriptpubkey when opening channel | [BOLT #2][bolt02-open] |
|
|
| 6/7 | `gossip_queries` | More sophisticated gossip control | [BOLT #7][bolt07-query] |
|
|
| 10/11 | `gossip_queries_ex` | Gossip queries can include additional information | [BOLT #7][bolt07-query] |
|
|
|
|
## Assigned `globalfeatures` flags
|
|
|
|
The following `globalfeatures` bits are currently assigned by this specification:
|
|
|
|
| Bits | Name | Description | Link |
|
|
|------|-------------------|--------------------------------------------------------------------|---------------------------------------|
|
|
| 8/9 | `var_onion_optin` | This node requires/supports variable-length routing onion payloads | [Routing Onion Specification][bolt04] |
|
|
|
|
## Requirements
|
|
|
|
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
|