BOLT 2: opt_shutdown_anysegwit

In bitcoin 0.19.0, standardness rules are going to be relaxed to allow future witness versions. Once this is widely deployed, it will be safe to accept them, smoothing use of future segwit versions. See: bitcoin/bitcoin#15846 Signed-off-by: Rusty Russell <[email protected]>
lightning · Feb 18, 2021 · 4f72856 · 4f72856
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diff --git a/.aspell.en.pws b/.aspell.en.pws
@@ -386,3 +386,4 @@ csv
 CHECKSIGVERIFY
 IFDUP
 sats
+anysegwit
diff --git a/02-peer-protocol.md b/02-peer-protocol.md
@@ -492,7 +492,10 @@ A sending node:
    (pay to pubkey hash), OR
     2. `OP_HASH160` `20` 20-bytes `OP_EQUAL` (pay to script hash), OR
     3. `OP_0` `20` 20-bytes (version 0 pay to witness pubkey hash), OR
-    4. `OP_0` `32` 32-bytes (version 0 pay to witness script hash)
+    4. `OP_0` `32` 32-bytes (version 0 pay to witness script hash), OR
+    5. if (and only if) `opt_shutdown_anysegwit` is negotiated:
+      * `OP_1` through `OP_16` inclusive, followed by a single push of 2 to 40 bytes
+	    (witness program versions 1 through 16)
 
 A receiving node:
   - if it hasn't received a `funding_signed` (if it is a funder) or a `funding_created` (if it is a fundee):

diff --git a/09-features.md b/09-features.md
@@ -40,6 +40,7 @@ The Context column decodes as follows:
 | 18/19 | `option_support_large_channel`   | Can create large channels                                 | IN       |                   | [BOLT #2](02-peer-protocol.md#the-open_channel-message) |
 | 20/21 | `option_anchor_outputs`          | Anchor outputs                                            | IN       | `option_static_remotekey` | [BOLT #3](03-transactions.md)         |
 | 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]|
+| 26/27 | `opt_shutdown_anysegwit`         | Future segwit versions allowed in `shutdown`              | IN       |                   | [BOLT #2][bolt02-shutdown]   |
 
 ## Requirements
 
@@ -82,6 +83,7 @@ This work is licensed under a [Creative Commons Attribution 4.0 International Li
 [bolt02-retransmit]: 02-peer-protocol.md#message-retransmission
 [bolt02-open]: 02-peer-protocol.md#the-open_channel-message
 [bolt03-htlc-tx]: 03-transactions.md#htlc-timeout-and-htlc-success-transactions
+[bolt02-shutdown]: 02-peer-protocol.md#closing-initiation-shutdown
 [bolt04]: 04-onion-routing.md
 [bolt07-sync]: 07-routing-gossip.md#initial-sync
 [bolt07-query]: 07-routing-gossip.md#query-messages
-Original file line number
+Diff line change
@@ Expand Up / @@ -386,3 +386,4 @@ csv @@
     CHECKSIGVERIFY
     IFDUP
     sats
+    anysegwit