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 <rusty@rustcorp.com.au>
lightning · Dec 22, 2020 · 75c02f9 · 75c02f9
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diff --git a/.aspell.en.pws b/.aspell.en.pws
@@ -385,3 +385,4 @@ 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), 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
@@ -39,6 +39,7 @@ The Context column decodes as follows:
 | 16/17 | `basic_mpp`                      | Node can receive basic multi-part payments                | IN9      | `payment_secret`  | [BOLT #4][bolt04-mpp]                 |
 | 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 | `opt_shutdown_anysegwit`         | Future segwit versions allowed in `shutdown`              | IN       |                   | [BOLT #2][bolt02-shutdown]   |
 
 ## Requirements
 
@@ -80,6 +81,7 @@ 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
+[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