Add support for multiple connection hops in create channel command

crates/relayer-cli/src/commands/tx/channel.rs

@@ -116,6 +116,17 @@ pub struct TxChanOpenInitCmd {
     )]
     order: Ordering,
 
+    // --connection-hops receives a list of ConnectionId of intermediate connections between two chains
+    // if they are to be connected via a multihop channel. The list of connection identifiers passed to
+    // `--connection-hops` starts with the identifier of the connection that comes after `--dst-connection`
+    // in the channel path from `--dst-chain` towards `--src-chain`. For example, given the following
+    // channel path, where `--src-chain` is Chain-A and `--dst-chain` is Chain-D:
+    //
+    //  +---------+    connection-3   +---------+    connection-2   +---------+    connection-1   +---------+
+    //  | Chain-A | <---------------- | Chain-B | <---------------- | Chain-C | <---------------- | Chain-D |
+    //  +---------+                   +---------+                   +---------+                   +---------+
+    //
+    // The --connection-hops parameter should receive 'connection-2/connection-3' as argument.
     #[clap(
         long = "connection-hops",
         value_name = "CONNECTION_HOPS",
@@ -182,9 +193,9 @@ impl Runnable for TxChanOpenInitCmd {
         // possible ramifications.
 
         // Check if connection IDs were provided via --connection-hops, indicating a multi-hop channel
-        if let Some(connnection_ids) = &self.conn_hop_ids {
+        if let Some(connection_ids) = &self.conn_hop_ids {
             // Retrieve information for each of the remaining hops until the other end of the channel is reached
-            for connection_id in connnection_ids.as_slice().iter() {
+            for connection_id in connection_ids.as_slice().iter() {
                 // Retrieve the ChainId of the chain to which the last hop pointed to
                 let chain_id = &b_side_hops
                     .last()

crates/relayer-cli/src/error.rs

@@ -7,7 +7,7 @@ use tendermint::Error as TendermintError;
 
 use ibc_relayer_types::applications::ics29_fee::error::Error as FeeError;
 use ibc_relayer_types::core::ics04_channel::channel::IdentifiedChannelEnd;
-use ibc_relayer_types::core::ics24_host::identifier::ChainId;
+use ibc_relayer_types::core::ics24_host::identifier::{ChainId, ConnectionIds};
 use ibc_relayer_types::signer::SignerError;
 
 use ibc_relayer::channel::ChannelError;
@@ -131,5 +131,14 @@ define_error! {
                  but the received connection identifier(s) lead to chain '{}' ", e.dst_chain, e.src_chain,
                  e.reference_chain)
             },
+
+        Ics33HopsReturnToSource
+            {
+                channel_path: ConnectionIds,
+                src_chain: ChainId,
+            }
+            | e | {
+                format_args!("the connection hops '{}' form a channel path that starts and ends on the same chain ('{}')", e.channel_path, e.src_chain)
+            },
     }
 }

crates/relayer/src/channel.rs

@@ -5,6 +5,7 @@ pub use error::ChannelError;
 use ibc_proto::google::protobuf::Any;
 use ibc_proto::ibc::core::channel::v1::{MsgMultihopProofs, MultihopProof};
 use ibc_proto::Protobuf;
+use ibc_relayer_types::core::ics03_connection::connection::IdentifiedConnectionEnd;
 use ibc_relayer_types::core::ics04_channel::channel::{
     ChannelEnd, Counterparty, IdentifiedChannelEnd, Ordering, State,
 };
@@ -225,7 +226,7 @@ impl<ChainA: ChainHandle, ChainB: ChainHandle> Channel<ChainA, ChainB> {
             a_side: ChannelSide::new(
                 connection.src_chain(),
                 connection.src_client_id().clone(),
-                src_connection_id.clone(),
+                src_connection_id.clone(), // FIXME: We may want to remove this in favor of using only a_side_hops
                 a_side_hops,
                 a_port,
                 Default::default(),
@@ -234,7 +235,7 @@ impl<ChainA: ChainHandle, ChainB: ChainHandle> Channel<ChainA, ChainB> {
             b_side: ChannelSide::new(
                 connection.dst_chain(),
                 connection.dst_client_id().clone(),
-                dst_connection_id.clone(),
+                dst_connection_id.clone(), // FIXME: We may want to remove this in favor of using only b_side_hops
                 b_side_hops,
                 b_port,
                 Default::default(),
@@ -248,6 +249,47 @@ impl<ChainA: ChainHandle, ChainB: ChainHandle> Channel<ChainA, ChainB> {
         Ok(channel)
     }
 
+    pub fn new_multihop(
+        a_chain: ChainA,
+        b_chain: ChainB,
+        a_side_connection: IdentifiedConnectionEnd,
+        b_side_connection: IdentifiedConnectionEnd,
+        ordering: Ordering,
+        a_port: PortId,
+        b_port: PortId,
+        a_side_hops: Option<ConnectionHops>,
+        b_side_hops: Option<ConnectionHops>,
+        version: Option<Version>,
+        connection_delay: Duration,
+    ) -> Result<Self, ChannelError> {
+        let mut channel = Self {
+            ordering,
+            a_side: ChannelSide::new(
+                a_chain,
+                a_side_connection.end().client_id().clone(),
+                a_side_connection.id().clone(), // FIXME: We may want to remove this in favor of using only a_side_hops
+                a_side_hops,
+                a_port,
+                Default::default(),
+                version.clone(),
+            ),
+            b_side: ChannelSide::new(
+                b_chain,
+                b_side_connection.end().client_id().clone(),
+                b_side_connection.id().clone(), // FIXME: We may want to remove this in favor of using only b_side_hops
+                b_side_hops,
+                b_port,
+                Default::default(),
+                version,
+            ),
+            connection_delay,
+        };
+
+        channel.handshake()?;
+
+        Ok(channel)
+    }
+
     pub fn restore_from_event(
         chain: ChainA,
         counterparty_chain: ChainB,

guide/src/templates/commands/hermes/create/channel_3.md

@@ -0,0 +1 @@
+[[#BINARY hermes]][[#GLOBALOPTIONS]] create channel[[#OPTIONS]] --a-chain [[#A_CHAIN_ID]] --a-connection [[#A_CONNECTION_ID]] --connection-hops [[#CONNECTION_HOP_IDS]] --a-port [[#A_PORT_ID]] --b-port [[#B_PORT_ID]]

guide/src/templates/commands/hermes/create/channel_4.md

@@ -0,0 +1 @@
+NOTE: The `--new-client-connection` option does not support connection hops. To open a multi-hop channel, please provide existing connections or initialize them manually before invoking this command.

guide/src/templates/help_templates/create/channel.md

@@ -9,6 +9,10 @@ USAGE:
 
     hermes create channel [OPTIONS] --a-chain <A_CHAIN_ID> --b-chain <B_CHAIN_ID> --a-port <A_PORT_ID> --b-port <B_PORT_ID> --new-client-connection
 
+    hermes create channel [OPTIONS] --a-chain <A_CHAIN_ID> --a-connection <A_CONNECTION_ID> --connection-hops <CONNECTION_HOP_IDS> --a-port <A_PORT_ID> --b-port <B_PORT_ID>
+
+    NOTE: The `--new-client-connection` option does not support connection hops. To open a multi-hop channel, please provide existing connections or initialize them manually before invoking this command.
+
 OPTIONS:
         --channel-version <VERSION>
             The version for the new channel
@@ -48,3 +52,9 @@ FLAGS:
 
         --b-port <B_PORT_ID>
             Identifier of the side `b` port for the new channel
+
+        --connection-hops <CONNECTION_IDS>
+            A list of identifiers of the intermediate connections between side `a` and side `b` for
+            a multi-hop channel, separated by slashes, e.g, 'connection-1/connection-0' (optional).
+
+            [aliases: conn-hops]