feat: Update consumer BTC light client (#112)

1. updates proto definitions
2. new btc_header ibc packet handler to ingest the headers sent from
babylon

contracts/babylon/src/ibc.rs

@@ -1,7 +1,7 @@
 use crate::error::ContractError;
 use babylon_bindings::BabylonMsg;
 use babylon_proto::babylon::zoneconcierge::v1::{
-    outbound_packet::Packet as OutboundPacketType, BtcTimestamp, OutboundPacket,
+    outbound_packet::Packet as OutboundPacketType, BtcTimestamp, OutboundPacket, BtcHeaders,
 };
 
 use crate::state::config::CONFIG;
@@ -138,6 +138,9 @@ pub fn ibc_packet_receive(
             OutboundPacketType::BtcStaking(btc_staking) => {
                 ibc_packet::handle_btc_staking(deps, caller, &btc_staking)
             }
+            OutboundPacketType::BtcHeaders(btc_headers) => {
+                ibc_packet::handle_btc_headers(deps, caller, &btc_headers)
+            }
         }
     })()
     .or_else(|e| {
@@ -252,6 +255,29 @@ pub(crate) mod ibc_packet {
         Ok(resp)
     }
 
+    pub fn handle_btc_headers(
+        deps: DepsMut,
+        _caller: String,
+        btc_headers: &BtcHeaders,
+    ) -> StdResult<IbcReceiveResponse<BabylonMsg>> {
+        let storage = deps.storage;
+        let cfg = CONFIG.load(storage)?;
+
+        let msg_option = crate::state::handle_btc_headers(storage, btc_headers)?;
+
+        let mut resp: IbcReceiveResponse<BabylonMsg> =
+            IbcReceiveResponse::new(StdAck::success(vec![])); // TODO: design response format
+        resp = resp.add_attribute("action", "receive_btc_headers");
+
+        if let Some(msg) = msg_option {
+            if cfg.notify_cosmos_zone {
+                resp = resp.add_message(msg);
+            }
+        }
+
+        Ok(resp)
+    }
+
     pub fn slashing_msg(
         env: &Env,
         channel: &IbcChannel,

contracts/babylon/src/state/mod.rs

@@ -1,8 +1,7 @@
 //! state is the module that manages smart contract's system state
 use cosmwasm_std::{StdError, Storage};
 
-use babylon_proto::babylon::zoneconcierge::v1::BtcTimestamp;
-
+use babylon_proto::babylon::zoneconcierge::v1::{BtcTimestamp, BtcHeaders};
 use crate::bindings::msg_btc_finalized_header;
 use babylon_bindings::BabylonMsg;
 
@@ -21,13 +20,15 @@ pub fn handle_btc_timestamp(
     btc_ts: &BtcTimestamp,
 ) -> Result<Option<BabylonMsg>, StdError> {
     // extract and init/handle BTC headers
-    let btc_headers = &btc_ts.btc_headers;
+    let btc_headers = btc_ts.btc_headers.as_ref()
+        .ok_or_else(|| StdError::generic_err("btc_headers is None"))?;
+
     if btc_light_client::is_initialized(storage) {
-        btc_light_client::handle_btc_headers_from_babylon(storage, btc_headers).map_err(|e| {
+        btc_light_client::handle_btc_headers_from_babylon(storage, &btc_headers.headers).map_err(|e| {
             StdError::generic_err(format!("failed to handle BTC headers from Babylon: {e}"))
         })?;
     } else {
-        btc_light_client::init(storage, btc_headers)
+        btc_light_client::init(storage, &btc_headers.headers)
             .map_err(|e| StdError::generic_err(format!("failed to initialize BTC headers: {e}")))?;
     }
 
@@ -76,3 +77,22 @@ pub fn handle_btc_timestamp(
 
     Ok(None)
 }
+
+pub fn handle_btc_headers(
+    storage: &mut dyn Storage,
+    btc_headers: &BtcHeaders,
+) -> Result<Option<BabylonMsg>, StdError> {
+    if btc_light_client::is_initialized(storage) {
+        btc_light_client::handle_btc_headers_from_babylon(storage, &btc_headers.headers)
+            .map_err(|e| StdError::generic_err(format!("failed to handle BTC headers: {e}")))?;
+    } else {
+        // TODO: Two issues to fix:
+        // 1. Remove init logic once BSN base BTC header is set during contract instantiation
+        // 2. Babylon to send headers from BSN base to tip instead of last w+1 headers
+        // See: https://github.com/babylonlabs-io/babylon-contract/issues/114
+        btc_light_client::init(storage, &btc_headers.headers)
+            .map_err(|e| StdError::generic_err(format!("failed to initialize BTC headers: {e}")))?;
+    }
+
+    Ok(None)
+}

packages/proto/src/gen/babylon.zoneconcierge.v1.rs

@@ -153,7 +153,7 @@ pub struct ProofFinalizedChainInfo {
 #[derive(Clone, PartialEq, ::prost::Message)]
 pub struct OutboundPacket {
     /// packet is the actual message carried in the IBC packet
-    #[prost(oneof="outbound_packet::Packet", tags="1, 2")]
+    #[prost(oneof="outbound_packet::Packet", tags="1, 2, 3")]
     pub packet: ::core::option::Option<outbound_packet::Packet>,
 }
 /// Nested message and enum types in `OutboundPacket`.
@@ -166,6 +166,8 @@ pub mod outbound_packet {
         BtcTimestamp(super::BtcTimestamp),
         #[prost(message, tag="2")]
         BtcStaking(super::super::super::btcstaking::v1::BtcStakingIbcPacket),
+        #[prost(message, tag="3")]
+        BtcHeaders(super::BtcHeaders),
     }
 }
 /// InboundPacket represents packets received by Babylon from other chains
@@ -186,6 +188,14 @@ pub mod inbound_packet {
         ConsumerSlashing(super::ConsumerSlashingIbcPacket),
     }
 }
+/// BTCHeaders contains BTC headers that have been verified and inserted into Babylon's BTC light client
+/// These headers are forwarded to consumer chains to keep their light clients in sync with Babylon
+#[allow(clippy::derive_partial_eq_without_eq)]
+#[derive(Clone, PartialEq, ::prost::Message)]
+pub struct BtcHeaders {
+    #[prost(message, repeated, tag="1")]
+    pub headers: ::prost::alloc::vec::Vec<super::super::btclightclient::v1::BtcHeaderInfo>,
+}
 /// BTCTimestamp is a BTC timestamp that carries information of a BTC-finalised epoch
 /// It includes a number of BTC headers, a raw checkpoint, an epoch metadata, and
 /// a CZ header if there exists CZ headers checkpointed to this epoch.
@@ -204,8 +214,8 @@ pub struct BtcTimestamp {
     /// - the block AFTER the common ancestor of BTC tip at epoch `lastFinalizedEpoch-1` and BTC tip at epoch `lastFinalizedEpoch`
     /// - BTC tip at epoch `lastFinalizedEpoch`
     /// where `lastFinalizedEpoch` is the last finalised epoch in Babylon
-    #[prost(message, repeated, tag="2")]
-    pub btc_headers: ::prost::alloc::vec::Vec<super::super::btclightclient::v1::BtcHeaderInfo>,
+    #[prost(message, optional, tag="2")]
+    pub btc_headers: ::core::option::Option<BtcHeaders>,
     //
     // Data for Babylon epoch chain