Make zeroconf a channel type, and acceptance indicates trust.

Signed-off-by: Rusty Russell <[email protected]>

02-peer-protocol.md

@@ -215,6 +215,7 @@ The currently defined basic types are:
 
 Each basic type has the following variations allowed:
   - `option_scid_alias` (bit 46)
+  - `option_zeroconf` (bit 50)
 
 #### Requirements
 
@@ -281,7 +282,9 @@ are not valid secp256k1 pubkeys in compressed format.
   - the funder's amount for the initial commitment transaction is not sufficient for full [fee payment](03-transactions.md#fee-payment).
   - both `to_local` and `to_remote` amounts for the initial commitment transaction are less than or equal to `channel_reserve_satoshis` (see [BOLT 3](03-transactions.md#commitment-transaction-outputs)).
   - `funding_satoshis` is greater than or equal to 2^24 and the receiver does not support `option_support_large_channel`. 
-  - It supports `channel_type`, `channel_type` was set, and the `type` is not suitable.
+  - It supports `channel_type` and `channel_type` was set:
+    - if `type` is not suitable.
+    - if `type` includes `option_zeroconf` and it does not trust the sender to open an unconfirmed channel.
 
 The receiving node MUST NOT:
   - consider funds received, using `push_msat`, to be received until the funding transaction has reached sufficient depth.
@@ -349,9 +352,10 @@ The `temporary_channel_id` MUST be the same as the `temporary_channel_id` in
 the `open_channel` message.
 
 The sender:
-  - SHOULD set `minimum_depth` to a number of blocks it considers reasonable to
-avoid double-spending of the funding transaction.
-  - MAY set `minimum_depth` to zero if it trusts the peer.
+  - if `channel_type` includes `option_zeroconf`:
+    - MUST set `minimum_depth` to zero.
+  - otherwise:
+    - SHOULD set `minimum_depth` to a number of blocks it considers reasonable to avoid double-spending of the funding transaction.
   - MUST set `channel_reserve_satoshis` greater than or equal to `dust_limit_satoshis` from the `open_channel` message.
   - MUST set `dust_limit_satoshis` less than or equal to `channel_reserve_satoshis` from the `open_channel` message.
   - if it sets `channel_type`:

09-features.md

@@ -44,6 +44,7 @@ The Context column decodes as follows:
 | 44/45 | `option_channel_type`            | Node supports the `channel_type` field in open/accept     | IN       |                   | [BOLT #2](02-peer-protocol.md#the-open_channel-message) |
 | 46/47 | `option_scid_alias`              | Supply channel aliases for routing                        | IN       |                   | [BOLT #2][bolt02-funding-locked]   |
 | 48/49 | `option_payment_metadata` | Payment metadata in tlv record | 9 | | [BOLT #11](11-payment-encoding.md#tagged-fields)
+| 50/51 | `option_zeroconf`                | Understands zeroconf channel types                        | IN       | `option_scid_alias` | [BOLT #2][bolt02-funding-locked]   |
 
 ## Definitions