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42 lines
2.5 KiB
Markdown
42 lines
2.5 KiB
Markdown
# BOLT #9: Assigned Feature Flags
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This document tracks the assignment of `localfeatures` and `globalfeatures` flags in the `init` message ([BOLT #1](01-messaging.md)), as well as the `features` field in the `channel_announcement` message and `node_announcement` message ([BOLT #7](07-routing-gossip.md)).
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They are tracked separately since new flags will likely be added over time.
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The `features` flags in the routing messages are a subset of the `globalfeatures` flags, since the `localfeatures` are by definition only of interest to direct peers.
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Flags are numbered from the least-significant bit, at bit 0 (i.e. 0x1,
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an even bit). They are generally assigned in pairs so that features
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can be introduced as optional (odd bits) and later upgraded to be compulsory, refusing
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old nodes (even bits). See [BOLT #1: The `init` Message](01-messaging.md#the-init-message).
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## Assigned `localfeatures` flags
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These flags may only be used in the `init` message:
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| Bits | Name |Description | Link |
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|------|------------------|------------------------------------------------|---------------------------------------------------------------------|
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| 0/1 | `option_data_loss_protect` | Requires or supports extra `channel_reestablish` fields | [BOLT #2](02-peer-protocol.md#message-retransmission) |
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| 3 | `initial_routing_sync` | Indicates that the sending node needs a complete routing information dump | [BOLT #7](07-routing-gossip.md#initial-sync) |
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| 4/5 | `option_upfront_shutdown_script` | Commits to a shutdown scriptpubkey when opening | [BOLT #2](02-peer-protocol.md#the-open_channel-message) |
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## Assigned `globalfeatures` flags
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There are currently no `globalfeatures` flags.
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## Requirements
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The requirements for receiving specific bits are defined in the linked sections in the table above.
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The requirements for feature bits that are not defined
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above can be found in [BOLT #1: The `init` Message](01-messaging.md#the-init-message).
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## Rationale
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There's little point in insisting on an `initial_routing_sync`. You can't
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tell if the remote node complies, and it has to know what the flag means as
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it's defined in the initial spec. So, there's no even bit for this.
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<br>
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This work is licensed under a [Creative Commons Attribution 4.0 International License](http://creativecommons.org/licenses/by/4.0/).
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