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Advertize known compression algorithms
Add a tlv field in `init` to list supported compression algorithms. This compression will be used in several places, currently in extended gossip queries. Fixes #811
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‎01-messaging.md‎

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@@ -258,10 +258,20 @@ The `features` field MUST be padded to bytes with 0s.
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1. type: 1 (`networks`)
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2. data:
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* [`...*chain_hash`:`chains`]
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1. type: 3 (`compression_algorithms`)
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2. data:
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* [`...*byte`:`supported_algorithms`]
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The optional `networks` indicates the chains the node is interested in.
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The optional `compression_algorithms` is a bitfield indicating what compression
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algorithms the node supports for [gossip queries](07-routing-gossip.md#query-messages).
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| Bit Position | Algorithm |
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| ------------- | ---------------------------------------------------- |
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| 0 | Uncompressed |
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| 1 | [zlib_deflate](https://www.ietf.org/rfc/rfc1950.txt) |
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#### Requirements
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The sending node:
@@ -271,6 +281,8 @@ The sending node:
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- SHOULD NOT set features greater than 13 in `globalfeatures`.
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- SHOULD use the minimum length required to represent the `features` field.
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- SHOULD set `networks` to all chains it will gossip or open channels for.
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- if it sets the `option_compression` feature bit:
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- MUST set the `compression_algorithms` field
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The receiving node:
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- MUST wait to receive `init` before sending any other messages.
@@ -284,6 +296,9 @@ The receiving node:
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- MAY fail the connection.
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- if the feature vector does not set all known, transitive dependencies:
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- MUST fail the connection.
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- if it has no `compression_algorithms` in common with the sending node:
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- MUST NOT exchange messages that require compression (e.g. gossip queries).
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- MAY fail the connection.
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#### Rationale
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@@ -453,6 +468,7 @@ multi-byte values with big-endian.
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Values encoded with BigSize will produce an encoding of either 1, 3, 5, or 9
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bytes depending on the size of the integer. The encoding is a piece-wise
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function that takes a `uint64` value `x` and produces:
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```
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uint8(x) if x < 0xfd
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0xfd + be16(uint16(x)) if x < 0x10000
@@ -471,6 +487,7 @@ decoded with BigSize should be checked to ensure they are minimally encoded.
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### BigSize Decoding Tests
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The following is an example of how to execute the BigSize decoding tests.
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```golang
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func testReadBigSize(t *testing.T, test bigSizeTest) {
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var buf [8]byte
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```
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A correct implementation should pass against these test vectors:
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```json
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[
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{
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### BigSize Encoding Tests
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The following is an example of how to execute the BigSize encoding tests.
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```golang
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func testWriteBigSize(t *testing.T, test bigSizeTest) {
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var (
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```
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A correct implementation should pass against the following test vectors:
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```json
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[
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{

‎07-routing-gossip.md‎

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@@ -568,9 +568,12 @@ request what gossip should be received.
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There are several messages which contain a long array of
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`short_channel_id`s (called `encoded_short_ids`) so we utilize a
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simple compression scheme: the first byte indicates the encoding, the
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rest contains the data.
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rest contains the data. The compression algorithms supported by each
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node are advertised in the `init` message's `compression_algorithms`
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tlv field.
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Encoding types:
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* `0`: uncompressed array of `short_channel_id` types, in ascending order.
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* `1`: array of `short_channel_id` types, in ascending order, compressed with zlib deflate<sup>[1](#reference-1)</sup>
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@@ -636,6 +639,7 @@ The sender:
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- MUST set `chain_hash` to the 32-byte hash that uniquely identifies the chain
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that the `short_channel_id`s refer to.
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- MUST set the first byte of `encoded_short_ids` to the encoding type.
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- MUST NOT use an encoding not supported by the remote peer.
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- MUST encode a whole number of `short_channel_id`s to `encoded_short_ids`
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- MAY send this if it receives a `channel_update` for a
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`short_channel_id` for which it has no `channel_announcement`.

‎09-features.md‎

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@@ -19,40 +19,43 @@ for use of the channel, so the presentation of those features depends
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on the feature itself.
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The Context column decodes as follows:
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* `I`: presented in the `init` message.
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* `N`: presented in the `node_announcement` messages
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* `C`: presented in the `channel_announcement` message.
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* `C-`: presented in the `channel_announcement` message, but always odd (optional).
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* `C+`: presented in the `channel_announcement` message, but always even (required).
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* `9`: presented in [BOLT 11](11-payment-encoding.md) invoices.
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| Bits | Name | Description | Context | Dependencies | Link |
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|-------|----------------------------------|-----------------------------------------------------------|----------|-------------------|---------------------------------------|
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| 0/1 | `option_data_loss_protect` | Requires or supports extra `channel_reestablish` fields | IN | | [BOLT #2][bolt02-retransmit] |
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| 3 | `initial_routing_sync` | Sending node needs a complete routing information dump | I | | [BOLT #7][bolt07-sync] |
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| 4/5 | `option_upfront_shutdown_script` | Commits to a shutdown scriptpubkey when opening channel | IN | | [BOLT #2][bolt02-open] |
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| 6/7 | `gossip_queries` | More sophisticated gossip control | IN | | [BOLT #7][bolt07-query] |
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| 8/9 | `var_onion_optin` | Requires/supports variable-length routing onion payloads | IN9 | | [Routing Onion Specification][bolt04] |
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| 10/11 | `gossip_queries_ex` | Gossip queries can include additional information | IN | `gossip_queries` | [BOLT #7][bolt07-query] |
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| 12/13 | `option_static_remotekey` | Static key for remote output | IN | | [BOLT #3](03-transactions.md) |
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| 14/15 | `payment_secret` | Node supports `payment_secret` field | IN9 | `var_onion_optin` | [Routing Onion Specification][bolt04] |
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| 16/17 | `basic_mpp` | Node can receive basic multi-part payments | IN9 | `payment_secret` | [BOLT #4][bolt04-mpp] |
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| 18/19 | `option_support_large_channel` | Can create large channels | IN | | [BOLT #2](02-peer-protocol.md#the-open_channel-message) |
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| 20/21 | `option_anchor_outputs` | Anchor outputs | IN | `option_static_remotekey` | [BOLT #3](03-transactions.md) |
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| 22/23 | `option_anchors_zero_fee_htlc_tx` | Anchor commitment type with zero fee HTLC transactions | IN | | [BOLT #3][bolt03-htlc-tx], [lightning-dev][ml-sighash-single-harmful]|
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| Bits | Name | Description | Context | Dependencies | Link |
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|-------|-----------------------------------|----------------------------------------------------------|----------|---------------------------|----------------------------------------------------------------------|
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| 0/1 | `option_data_loss_protect` | Requires or supports extra `channel_reestablish` fields | IN | | [BOLT #2][bolt02-retransmit] |
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| 3 | `initial_routing_sync` | Sending node needs a complete routing information dump | I | | [BOLT #7][bolt07-sync] |
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| 4/5 | `option_upfront_shutdown_script` | Commits to a shutdown scriptpubkey when opening channel | IN | | [BOLT #2][bolt02-open] |
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| 6/7 | `gossip_queries` | More sophisticated gossip control | IN | | [BOLT #7][bolt07-query] |
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| 8/9 | `var_onion_optin` | Requires/supports variable-length routing onion payloads | IN9 | | [Routing Onion Specification][bolt04] |
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| 10/11 | `gossip_queries_ex` | Gossip queries can include additional information | IN | `gossip_queries` | [BOLT #7][bolt07-query] |
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| 12/13 | `option_static_remotekey` | Static key for remote output | IN | | [BOLT #3](03-transactions.md) |
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| 14/15 | `payment_secret` | Node supports `payment_secret` field | IN9 | `var_onion_optin` | [Routing Onion Specification][bolt04] |
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| 16/17 | `basic_mpp` | Node can receive basic multi-part payments | IN9 | `payment_secret` | [BOLT #4][bolt04-mpp] |
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| 18/19 | `option_support_large_channel` | Can create large channels | IN | | [BOLT #2](02-peer-protocol.md#the-open_channel-message) |
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| 20/21 | `option_anchor_outputs` | Anchor outputs | IN | `option_static_remotekey` | [BOLT #3](03-transactions.md) |
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| 22/23 | `option_anchors_zero_fee_htlc_tx` | Anchor commitment type with zero fee HTLC transactions | IN | | [BOLT #3][bolt03-htlc-tx], [lightning-dev][ml-sighash-single-harmful]|
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| 24/25 | `option_compression` | Compression algorithms advertised in `init` | IN | | [BOLT #1](01-messaging.md#the-init-message) |
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## Requirements
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The origin node:
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* If it supports a feature above, SHOULD set the corresponding odd
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bit in all feature fields indicated by the Context column unless
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indicated that it must set the even feature bit instead.
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* If it requires a feature above, MUST set the corresponding even
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feature bit in all feature fields indicated by the Context column,
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unless indicated that it must set the odd feature bit instead.
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* MUST NOT set feature bits it does not support.
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* MUST NOT set feature bits in fields not specified by the table above.
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* MUST set all transitive feature dependencies.
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* If it supports a feature above, SHOULD set the corresponding odd
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bit in all feature fields indicated by the Context column unless
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indicated that it must set the even feature bit instead.
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* If it requires a feature above, MUST set the corresponding even
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feature bit in all feature fields indicated by the Context column,
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unless indicated that it must set the odd feature bit instead.
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* MUST NOT set feature bits it does not support.
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* MUST NOT set feature bits in fields not specified by the table above.
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* MUST set all transitive feature dependencies.
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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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