bLIP: 2
Title: Reserved values
Status: Active
Author: Bastien Teinturier <[email protected]>
Created: 2021-11-05
License: CC0
bLIPs may need to define messages and fields that need to be correctly parsed and interpreted throughout the network to ensure interoperability and guarantee backwards-compatibility.
The BOLTs already provide several mechanisms for that, which bLIPs should rely on:
- feature bits
- message format
- tlv fields
- an
extensiontlv stream for every message defined in the BOLTs
bLIP authors must edit the tables below to reserve values in these various namespaces to ensure there will be no conflict between unrelated bLIPs, which would otherwise potentially lead to a network split.
Feature bits are specified in Bolt 9.
They let nodes publicly advertise that they support or require a given feature.
Feature bits in the 0-255 range are reserved for BOLTs: bLIPs must use feature bits above that range.
Custom feature bits used in the I Bolt 11 context must be <= 5114 due to the size limitations on tagged fields.
bLIPs may reserve feature bits by adding them to the following table:
| Bits | Name | Description | Context | Dependencies | Link |
|---|---|---|---|---|---|
| 54/55 | keysend |
A form of spontaneous payment | N | var_onion_optin |
bLIP 3 |
| 256/257 | hosted_channels |
This node accepts requests for hosted channels | IN | bLIP 17 |
The BOLTs define a standard message format that every lightning implementation understands.
Message types in the 0-32767 range are reserved for BOLTs: bLIPs must use message types in the 32768-65535 range.
bLIPs may create new messages and reserve their type in the following table:
| Type | Name | Link |
|---|---|---|
| 65535 | invoke_hosted_channel |
bLIP 17 |
| 65533 | init_hosted_channel |
bLIP 17 |
| 65531 | last_cross_signed_state |
bLIP 17 |
| 65529 | state_update |
bLIP 17 |
| 65527 | state_override |
bLIP 17 |
| 65525 | hosted_channel_branding |
bLIP 17 |
| 65511 | ask_channel_branding |
bLIP 17 |
| 63505 | hc_update_add_htlc |
bLIP 17 |
| 63503 | hc_update_fulfill_htlc |
bLIP 17 |
| 63501 | hc_updated_fail_htlc |
bLIP 17 |
| 63499 | hc_update_fail_malformed_htlc |
bLIP 17 |
| 63497 | hc_error |
bLIP 17 |
Every BOLT message contains a trailing extension field, which is a tlv stream with tlv fields
specific to that BOLT message.
bLIPs may add new tlv fields to existing messages. bLIPs must carefully decide whether these new tlv fields should be even or odd, following the "it's ok to be odd" rule defined here.
When adding new tlv fields to existing BOLT messages, bLIPS must use types greater than 65536
and fill the table corresponding to the message they're modifying.
The following table contains extension tlv fields for the init message:
| Type | Name | Link |
|---|---|---|
| 65536 | tlv_field_name |
Link to the corresponding bLIP |
The following table contains extension tlv fields for the payment_onion_payload message:
| Type | Name | Link |
|---|---|---|
| 7629169 | podcasting_2_0 |
bLIP 10 |
| 5482373484 | keysend_preimage |
bLIP 3 |
The following table contains extension tlv fields for the ping message:
| Type | Name | Link |
|---|---|---|
| 65536 | tlv_field_name |
Link to the corresponding bLIP |
This bLIP is licensed under the CC0 license.