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bLIP: 2
Title: Reserved values
Status: Active
Author: Bastien Teinturier <bastien@acinq.fr>
Created: 2021-11-05
License: CC0

Abstract

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:

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.

Reserved values

Table of Contents

Feature bits

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

Messages

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

TLV fields in BOLT messages

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.

init

The following table contains extension tlv fields for the init message:

Type Name Link
65536 tlv_field_name Link to the corresponding bLIP

payment_onion_payload

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

ping

The following table contains extension tlv fields for the ping message:

Type Name Link
65536 tlv_field_name Link to the corresponding bLIP

Copyright

This bLIP is licensed under the CC0 license.