Support the `channel_type` feature bit.

Note that this feature bit does absolutely nothing. We signal it
(as we already support channel type negotiation), but do not bother
to look to see if peers support it, as we don't care - we simply
look for the TLV entry and deduce if a peer supports channel type
negotiation from that.

The only behavioral change at all here is that we don't barf if a
peer sets channel type negotiation to required via the feature bit
(instead of failing the channel at open-time), but of course no
implementations do this, and likely won't for some time (if ever -
you can simply fail channels with unknown types later, and there's
no reason to refuse connections, really).

As defined in https://github.com/lightning/bolts/pull/906

diff --git a/lightning/src/ln/features.rs b/lightning/src/ln/features.rs
index 07e1a3229443b312aceff86ae7cb270576257eba..dab841327802fc8ae3ee0c869395a7ce378c4148 100644 (file)
--- a/lightning/src/ln/features.rs
+++ b/lightning/src/ln/features.rs
@@ -126,6 +126,10 @@ mod sealed {
                        ,
                        // Byte 3
                        ,
+                       // Byte 4
+                       ,
+                       // Byte 5
+                       ,
                ],
                optional_features: [
                        // Byte 0
@@ -136,6 +140,10 @@ mod sealed {
                        BasicMPP,
                        // Byte 3
                        ShutdownAnySegwit,
+                       // Byte 4
+                       ,
+                       // Byte 5
+                       ChannelType,
                ],
        });
        define_context!(NodeContext {
@@ -167,7 +175,7 @@ mod sealed {
                        // Byte 4
                        ,
                        // Byte 5
-                       ,
+                       ChannelType,
                        // Byte 6
                        Keysend,
                ],
@@ -379,6 +387,9 @@ mod sealed {
        define_feature!(27, ShutdownAnySegwit, [InitContext, NodeContext],
                "Feature flags for `opt_shutdown_anysegwit`.", set_shutdown_any_segwit_optional,
                set_shutdown_any_segwit_required, supports_shutdown_anysegwit, requires_shutdown_anysegwit);
+       define_feature!(45, ChannelType, [InitContext, NodeContext],
+               "Feature flags for `option_channel_type`.", set_channel_type_optional,
+               set_channel_type_required, supports_channel_type, requires_channel_type);
        define_feature!(55, Keysend, [NodeContext],
                "Feature flags for keysend payments.", set_keysend_optional, set_keysend_required,
                supports_keysend, requires_keysend);
@@ -807,6 +818,11 @@ mod tests {
                assert!(!NodeFeatures::known().requires_basic_mpp());
                assert!(!InvoiceFeatures::known().requires_basic_mpp());
 
+               assert!(InitFeatures::known().supports_channel_type());
+               assert!(NodeFeatures::known().supports_channel_type());
+               assert!(!InitFeatures::known().requires_channel_type());
+               assert!(!NodeFeatures::known().requires_channel_type());
+
                assert!(InitFeatures::known().supports_shutdown_anysegwit());
                assert!(NodeFeatures::known().supports_shutdown_anysegwit());
 
@@ -845,11 +861,15 @@ mod tests {
                        // - var_onion_optin (req) | static_remote_key (req) | payment_secret(req)
                        // - basic_mpp
                        // - opt_shutdown_anysegwit
-                       assert_eq!(node_features.flags.len(), 4);
+                       // -
+                       // - option_channel_type
+                       assert_eq!(node_features.flags.len(), 6);
                        assert_eq!(node_features.flags[0], 0b00000010);
                        assert_eq!(node_features.flags[1], 0b01010001);
                        assert_eq!(node_features.flags[2], 0b00000010);
                        assert_eq!(node_features.flags[3], 0b00001000);
+                       assert_eq!(node_features.flags[4], 0b00000000);
+                       assert_eq!(node_features.flags[5], 0b00100000);
                }
 
                // Check that cleared flags are kept blank when converting back: