feat(registry): add merge_subnets endpoint

rs/nns/governance/api/src/types.rs

@@ -4334,6 +4334,11 @@ pub enum NnsFunction {
     /// `SetupInitialDKG` requests without an explicit subnet id are routed to the
     /// calling subnet (NNS).
     SetDefaultInitialDkgSubnet = 58,
+    /// Merge a subnet into another subnet: the canister ID ranges of the source
+    /// subnet are merged into the canister ID range set of the destination subnet,
+    /// so that all canisters that used to be hosted by the source subnet are routed
+    /// to the destination subnet.
+    MergeSubnets = 59,
 }
 impl NnsFunction {
     /// String value of the enum field names used in the ProtoBuf definition.
@@ -4422,6 +4427,7 @@ impl NnsFunction {
             NnsFunction::SetDefaultInitialDkgSubnet => {
                 "NNS_FUNCTION_SET_DEFAULT_INITIAL_DKG_SUBNET"
             }
+            NnsFunction::MergeSubnets => "NNS_FUNCTION_MERGE_SUBNETS",
         }
     }
     /// Creates an enum from field names used in the ProtoBuf definition.
@@ -4505,6 +4511,7 @@ impl NnsFunction {
             "NNS_FUNCTION_SPLIT_SUBNET" => Some(Self::SplitSubnet),
             "NNS_FUNCTION_DELETE_SUBNET" => Some(Self::DeleteSubnet),
             "NNS_FUNCTION_SET_DEFAULT_INITIAL_DKG_SUBNET" => Some(Self::SetDefaultInitialDkgSubnet),
+            "NNS_FUNCTION_MERGE_SUBNETS" => Some(Self::MergeSubnets),
             _ => None,
         }
     }

rs/nns/governance/proto/ic_nns_governance/pb/v1/governance.proto

@@ -513,6 +513,12 @@ enum NnsFunction {
   // `SetupInitialDKG` requests without an explicit subnet id are routed to the
   // calling subnet (NNS).
   NNS_FUNCTION_SET_DEFAULT_INITIAL_DKG_SUBNET = 58;
+
+  // Merge a subnet into another subnet: the canister ID ranges of the source
+  // subnet are merged into the canister ID range set of the destination subnet,
+  // so that all canisters that used to be hosted by the source subnet are routed
+  // to the destination subnet.
+  NNS_FUNCTION_MERGE_SUBNETS = 59;
 }
 
 // Payload of a proposal that calls a function on another NNS

rs/nns/governance/src/gen/ic_nns_governance.pb.v1.rs

@@ -5548,6 +5548,11 @@ pub enum NnsFunction {
     /// `SetupInitialDKG` requests without an explicit subnet id are routed to the
     /// calling subnet (NNS).
     SetDefaultInitialDkgSubnet = 58,
+    /// Merge a subnet into another subnet: the canister ID ranges of the source
+    /// subnet are merged into the canister ID range set of the destination subnet,
+    /// so that all canisters that used to be hosted by the source subnet are routed
+    /// to the destination subnet.
+    MergeSubnets = 59,
 }
 impl NnsFunction {
     /// String value of the enum field names used in the ProtoBuf definition.
@@ -5624,6 +5629,7 @@ impl NnsFunction {
             Self::SplitSubnet => "NNS_FUNCTION_SPLIT_SUBNET",
             Self::DeleteSubnet => "NNS_FUNCTION_DELETE_SUBNET",
             Self::SetDefaultInitialDkgSubnet => "NNS_FUNCTION_SET_DEFAULT_INITIAL_DKG_SUBNET",
+            Self::MergeSubnets => "NNS_FUNCTION_MERGE_SUBNETS",
         }
     }
     /// Creates an enum from field names used in the ProtoBuf definition.
@@ -5707,6 +5713,7 @@ impl NnsFunction {
             "NNS_FUNCTION_SPLIT_SUBNET" => Some(Self::SplitSubnet),
             "NNS_FUNCTION_DELETE_SUBNET" => Some(Self::DeleteSubnet),
             "NNS_FUNCTION_SET_DEFAULT_INITIAL_DKG_SUBNET" => Some(Self::SetDefaultInitialDkgSubnet),
+            "NNS_FUNCTION_MERGE_SUBNETS" => Some(Self::MergeSubnets),
             _ => None,
         }
     }

rs/nns/governance/src/pb/conversions/mod.rs

@@ -3940,6 +3940,7 @@ impl From<pb::NnsFunction> for api::NnsFunction {
                 api::NnsFunction::SetSubnetOperationalLevel
             }
             pb::NnsFunction::SplitSubnet => api::NnsFunction::SplitSubnet,
+            pb::NnsFunction::MergeSubnets => api::NnsFunction::MergeSubnets,
             pb::NnsFunction::DeleteSubnet => api::NnsFunction::DeleteSubnet,
             pb::NnsFunction::SetDefaultInitialDkgSubnet => {
                 api::NnsFunction::SetDefaultInitialDkgSubnet
@@ -4040,6 +4041,7 @@ impl From<api::NnsFunction> for pb::NnsFunction {
                 pb::NnsFunction::SetSubnetOperationalLevel
             }
             api::NnsFunction::SplitSubnet => pb::NnsFunction::SplitSubnet,
+            api::NnsFunction::MergeSubnets => pb::NnsFunction::MergeSubnets,
             api::NnsFunction::DeleteSubnet => pb::NnsFunction::DeleteSubnet,
             api::NnsFunction::SetDefaultInitialDkgSubnet => {
                 pb::NnsFunction::SetDefaultInitialDkgSubnet

rs/nns/governance/src/proposals/execute_nns_function.rs

@@ -459,6 +459,7 @@ pub enum ValidNnsFunction {
     SplitSubnet,
     DeleteSubnet,
     SetDefaultInitialDkgSubnet,
+    MergeSubnets,
 }
 
 impl ValidNnsFunction {
@@ -592,6 +593,7 @@ impl ValidNnsFunction {
             ValidNnsFunction::SetDefaultInitialDkgSubnet => {
                 (REGISTRY_CANISTER_ID, "set_default_initial_dkg_subnet")
             }
+            ValidNnsFunction::MergeSubnets => (REGISTRY_CANISTER_ID, "merge_subnets"),
         }
     }
 
@@ -623,7 +625,8 @@ impl ValidNnsFunction {
             | ValidNnsFunction::SetSubnetOperationalLevel
             | ValidNnsFunction::SplitSubnet
             | ValidNnsFunction::DeleteSubnet
-            | ValidNnsFunction::SetDefaultInitialDkgSubnet => Topic::SubnetManagement,
+            | ValidNnsFunction::SetDefaultInitialDkgSubnet
+            | ValidNnsFunction::MergeSubnets => Topic::SubnetManagement,
 
             ValidNnsFunction::ReviseElectedGuestosVersions
             | ValidNnsFunction::ReviseElectedHostosVersions => Topic::IcOsVersionElection,
@@ -714,6 +717,7 @@ impl ValidNnsFunction {
             ValidNnsFunction::SplitSubnet => "Split subnet",
             ValidNnsFunction::DeleteSubnet => "Delete Subnet",
             ValidNnsFunction::SetDefaultInitialDkgSubnet => "Set Default Initial DKG Subnet",
+            ValidNnsFunction::MergeSubnets => "Merge subnets",
         }
     }
 
@@ -944,6 +948,13 @@ impl ValidNnsFunction {
                 calls are routed when no subnet is specified explicitly in the request. If unset, \
                 such requests are routed to the calling subnet (NNS)."
             }
+            ValidNnsFunction::MergeSubnets => {
+                "Merge a subnet into another subnet. The canister ID ranges of the source subnet \
+                are merged into the canister ID range set of the destination subnet, so that all \
+                canisters that used to be hosted by the source subnet are routed to the \
+                destination subnet. Only the routing table is updated: neither subnet record is \
+                modified and the source subnet is not deleted."
+            }
         }
     }
 }
@@ -1033,6 +1044,7 @@ impl TryFrom<NnsFunction> for ValidNnsFunction {
                 Ok(ValidNnsFunction::SetSubnetOperationalLevel)
             }
             NnsFunction::SplitSubnet => Ok(ValidNnsFunction::SplitSubnet),
+            NnsFunction::MergeSubnets => Ok(ValidNnsFunction::MergeSubnets),
             NnsFunction::DeleteSubnet => Ok(ValidNnsFunction::DeleteSubnet),
             NnsFunction::SetDefaultInitialDkgSubnet => {
                 Ok(ValidNnsFunction::SetDefaultInitialDkgSubnet)

rs/nns/governance/unreleased_changelog.md

@@ -9,6 +9,13 @@ on the process that this file is part of, see
 
 ## Added
 
+* Added a new `NnsFunction` variant `MergeSubnets`, which proposes to merge a
+  subnet into another subnet: the canister ID ranges of the source subnet are
+  merged into the canister ID range set of the destination subnet, so that all
+  canisters that used to be hosted by the source subnet are routed to the
+  destination subnet. Only the routing table is updated: neither subnet record
+  is modified and the source subnet is not deleted.
+
 ## Changed
 
 ## Deprecated

rs/registry/canister/canister/canister.rs

@@ -79,6 +79,7 @@ use registry_canister::{
         firewall::{
             AddFirewallRulesPayload, RemoveFirewallRulesPayload, UpdateFirewallRulesPayload,
         },
+        merge_subnets::MergeSubnetsPayload,
         node_management::{
             do_remove_node_directly::RemoveNodeDirectlyPayload,
             do_remove_nodes::RemoveNodesPayload,
@@ -1085,6 +1086,24 @@ fn reroute_canister_ranges_(payload: RerouteCanisterRangesPayload) {
     recertify_registry();
 }
 
+#[unsafe(export_name = "canister_update merge_subnets")]
+fn merge_subnets() {
+    check_caller_is_governance_and_log("merge_subnets");
+    over(candid_one, merge_subnets_);
+}
+
+#[candid_method(update, rename = "merge_subnets")]
+fn merge_subnets_(payload: MergeSubnetsPayload) {
+    registry_mut()
+        .merge_subnets(payload)
+        .unwrap_or_else(|error_message| {
+            trap_with(&format!(
+                "{LOG_PREFIX} Merge subnets failed: {error_message}"
+            ))
+        });
+    recertify_registry();
+}
+
 #[unsafe(export_name = "canister_update split_subnet")]
 fn split_subnet() {
     check_caller_is_governance_and_log("split_subnet");

rs/registry/canister/canister/registry.did

@@ -308,6 +308,11 @@ type IPv4Config = record {
   ip_addr : text;
 };
 
+type MergeSubnetsPayload = record {
+  source_subnet : principal;
+  destination_subnet : principal;
+};
+
 type MigrateCanistersPayload = record {
   canister_ids : vec principal;
   target_subnet_id : principal;
@@ -646,6 +651,7 @@ service : {
   get_node_providers_monthly_xdr_rewards : (opt GetNodeProvidersMonthlyXdrRewardsRequest) -> (GetNodeProvidersMonthlyXdrRewardsResponse) query;
   get_subnet : (GetSubnetRequest) -> (GetSubnetResponse) query;
   get_subnet_for_canister : (GetSubnetForCanisterRequest) -> (GetSubnetForCanisterResponse) query;
+  merge_subnets : (MergeSubnetsPayload) -> ();
   migrate_canisters: (MigrateCanistersPayload) -> (MigrateCanistersResponse);
   migrate_node_operator_directly : (MigrateNodeOperatorPayload) -> ();
   prepare_canister_migration : (PrepareCanisterMigrationPayload) -> ();

rs/registry/canister/canister/registry_test.did

@@ -308,6 +308,11 @@ type IPv4Config = record {
   ip_addr : text;
 };
 
+type MergeSubnetsPayload = record {
+  source_subnet : principal;
+  destination_subnet : principal;
+};
+
 type MigrateCanistersPayload = record {
   canister_ids : vec principal;
   target_subnet_id : principal;
@@ -646,6 +651,7 @@ service : {
   get_node_providers_monthly_xdr_rewards : (opt GetNodeProvidersMonthlyXdrRewardsRequest) -> (GetNodeProvidersMonthlyXdrRewardsResponse) query;
   get_subnet : (GetSubnetRequest) -> (GetSubnetResponse) query;
   get_subnet_for_canister : (GetSubnetForCanisterRequest) -> (GetSubnetForCanisterResponse) query;
+  merge_subnets : (MergeSubnetsPayload) -> ();
   migrate_canisters: (MigrateCanistersPayload) -> (MigrateCanistersResponse);
   migrate_node_operator_directly : (MigrateNodeOperatorPayload) -> ();
   prepare_canister_migration : (PrepareCanisterMigrationPayload) -> ();