Fix unknown handling in `impl_writeable_tlv_based_enum_upgradable`

[rust-lightning] / lightning / src / util / ser_macros.rs

diff --git a/lightning/src/util/ser_macros.rs b/lightning/src/util/ser_macros.rs
index 84d9f7a180bb301a1c18a136530a04ce75589a9e..5d6988ba1f193585c0d325c49fa679e52b4553c5 100644 (file)
--- a/lightning/src/util/ser_macros.rs
+++ b/lightning/src/util/ser_macros.rs
@@ -1065,6 +1065,10 @@ macro_rules! impl_writeable_tlv_based_enum {
 /// when [`MaybeReadable`] is practical instead of just [`Readable`] as it provides an upgrade path for
 /// new variants to be added which are simply ignored by existing clients.
 ///
+/// Note that only struct and unit variants (not tuple variants) will support downgrading, thus any
+/// new odd variants MUST be non-tuple (i.e. described using `$variant_id` and `$variant_name` not
+/// `$tuple_variant_id` and `$tuple_variant_name`).
+///
 /// [`MaybeReadable`]: crate::util::ser::MaybeReadable
 /// [`Writeable`]: crate::util::ser::Writeable
 /// [`DecodeError::UnknownRequiredFeature`]: crate::ln::msgs::DecodeError::UnknownRequiredFeature
@@ -1102,7 +1106,14 @@ macro_rules! impl_writeable_tlv_based_enum_upgradable {
                                        $($($tuple_variant_id => {
                                                Ok(Some($st::$tuple_variant_name(Readable::read(reader)?)))
                                        }),*)*
-                                       _ if id % 2 == 1 => Ok(None),
+                                       _ if id % 2 == 1 => {
+                                               // Assume that a $variant_id was written, not a $tuple_variant_id, and read
+                                               // the length prefix and discard the correct number of bytes.
+                                               let tlv_len: $crate::util::ser::BigSize = $crate::util::ser::Readable::read(reader)?;
+                                               let mut rd = $crate::util::ser::FixedLengthReader::new(reader, tlv_len.0);
+                                               rd.eat_remaining().map_err(|_| $crate::ln::msgs::DecodeError::ShortRead)?;
+                                               Ok(None)
+                                       },
                                        _ => Err($crate::ln::msgs::DecodeError::UnknownRequiredFeature),
                                }
                        }