smartcontract: append new_interfaces vec to Device with custom serializer

CHANGELOG.md

@@ -13,6 +13,7 @@ All notable changes to this project will be documented in this file.
 - Smartcontract
   - Stop writing `InterfaceV3` from `CreateDeviceInterface` and `UpdateDeviceInterface`; `CurrentInterfaceVersion` is now `InterfaceV2`. `MigrateDeviceInterfaces` and `BackfillTopology` continue to write `InterfaceV3` since they are admin-controlled and need the `flex_algo_node_segments` field
   - Add forward-compatible `NewInterface` struct in `state/interface.rs` with a `size: u16` + `version: u8` on-disk prefix, V3-shaped body, and `flex_algo_node_segments`. Older readers can use the size prefix to skip past unknown future versions in constant time. Additive only — no callers, processors, or SDKs change in this PR ([#3666](https://github.com/malbeclabs/doublezero/pull/3666))
+  - Append `new_interfaces: Vec<NewInterface>` to `Device` after `max_multicast_publishers`, behind a custom `BorshSerialize` that projects the on-disk legacy `interfaces` slot from `new_interfaces` (always `Interface::V2` per #3653) and writes `new_interfaces` at the end of the layout. Legacy accounts with no trailing bytes deserialize cleanly: `Device::try_from` rebuilds `new_interfaces` from the legacy enum vec via per-variant `TryFrom`. Older readers continue to parse the legacy slot at its existing offset; newer readers gain forward-compat via the trailing vec. Mutations now go through `Device::replace_interface` / `push_interface` / `remove_interface` so both vecs stay in sync; `find_interface` returns `&NewInterface` and `find_interface_legacy` is a temporary helper for unrelated callers ([#3665](https://github.com/malbeclabs/doublezero/pull/3665))
 
 ## [v0.21.0](https://github.com/malbeclabs/doublezero/compare/client/v0.20.0...client/v0.21.0) - 2026-05-01
 

client/doublezero/src/command/connect.rs

@@ -1337,6 +1337,7 @@ mod tests {
                 dz_prefixes: format!("10.{}.0.0/24", device_number).parse().unwrap(),
                 mgmt_vrf: "default".to_string(),
                 interfaces: vec![],
+                new_interfaces: vec![],
                 max_users: 255,
                 users_count: 0,
                 device_health:

client/doublezero/src/dzd_latency.rs

@@ -255,28 +255,29 @@ mod tests {
         tunnel_endpoint_ips: Vec<Ipv4Addr>,
     ) -> (Pubkey, Device) {
         let pubkey = Pubkey::new_unique();
-        let interfaces: Vec<Interface> = tunnel_endpoint_ips
+        let v2_ifaces: Vec<CurrentInterfaceVersion> = tunnel_endpoint_ips
             .into_iter()
             .enumerate()
-            .map(|(i, ip)| {
-                Interface::V2(CurrentInterfaceVersion {
-                    status: InterfaceStatus::Activated,
-                    name: format!("Loopback{}", i),
-                    interface_type: InterfaceType::Loopback,
-                    loopback_type: LoopbackType::None,
-                    interface_cyoa: InterfaceCYOA::None,
-                    interface_dia: InterfaceDIA::None,
-                    bandwidth: 0,
-                    cir: 0,
-                    mtu: 1500,
-                    routing_mode: RoutingMode::Static,
-                    vlan_id: 0,
-                    ip_net: NetworkV4::new(ip, 32).unwrap(),
-                    node_segment_idx: 0,
-                    user_tunnel_endpoint: true,
-                })
+            .map(|(i, ip)| CurrentInterfaceVersion {
+                status: InterfaceStatus::Activated,
+                name: format!("Loopback{}", i),
+                interface_type: InterfaceType::Loopback,
+                loopback_type: LoopbackType::None,
+                interface_cyoa: InterfaceCYOA::None,
+                interface_dia: InterfaceDIA::None,
+                bandwidth: 0,
+                cir: 0,
+                mtu: 1500,
+                routing_mode: RoutingMode::Static,
+                vlan_id: 0,
+                ip_net: NetworkV4::new(ip, 32).unwrap(),
+                node_segment_idx: 0,
+                user_tunnel_endpoint: true,
             })
             .collect();
+        let interfaces: Vec<Interface> =
+            v2_ifaces.iter().map(|v| Interface::V2(v.clone())).collect();
+        let new_interfaces = v2_ifaces.iter().map(|v| v.try_into().unwrap()).collect();
         (
             pubkey,
             Device {
@@ -295,6 +296,7 @@ mod tests {
                 contributor_pk: Pubkey::default(),
                 mgmt_vrf: "default".to_string(),
                 interfaces,
+                new_interfaces,
                 reference_count: 0,
                 users_count,
                 max_users: 1,

controlplane/doublezero-admin/src/cli/device.rs

@@ -312,6 +312,7 @@ mod tests {
             dz_prefixes: "10.0.0.1/32".parse().unwrap(),
             mgmt_vrf: "default".to_string(),
             interfaces: vec![],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: DeviceHealth::ReadyForUsers,

sdk/serviceability/testdata/fixtures/generate-fixtures/src/main.rs

@@ -323,9 +323,14 @@ fn generate_device(dir: &Path) {
                 ip_net: "172.16.0.1/30".parse().unwrap(),
                 node_segment_idx: 200,
                 user_tunnel_endpoint: true,
-                flex_algo_node_segments: vec![],
             }),
         ],
+        // Empty for now: regenerating with my custom Device serializer would
+        // V2-project the legacy slot from new_interfaces, dropping the V1 form
+        // and breaking SDK fixtures that pin Interface0 to V1. Existing
+        // device.bin remains in the legacy format and continues to pass SDK
+        // tests via the legacy fallback path in `Device::TryFrom`.
+        new_interfaces: vec![],
         reference_count: 12,
         users_count: 5,
         max_users: 100,

smartcontract/cli/src/device/create.rs

@@ -344,6 +344,7 @@ mod tests {
             status: DeviceStatus::Activated,
             mgmt_vrf: String::default(),
             interfaces: vec![],
+            new_interfaces: vec![],
             users_count: 0,
             max_users: 100,
             owner: Pubkey::default(),

smartcontract/cli/src/device/delete.rs

@@ -115,6 +115,7 @@ mod tests {
             owner: pda_pubkey,
             mgmt_vrf: "default".to_string(),
             interfaces: vec![],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,

smartcontract/cli/src/device/get.rs

@@ -240,6 +240,7 @@ mod tests {
             owner: device1_pubkey,
             mgmt_vrf: "default".to_string(),
             interfaces: vec![],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,

smartcontract/cli/src/device/interface/create.rs

@@ -177,6 +177,7 @@ mod tests {
             owner: device1_pubkey,
             mgmt_vrf: "default".to_string(),
             interfaces: vec![],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,
@@ -225,6 +226,7 @@ mod tests {
                 user_tunnel_endpoint: false,
             }
             .to_interface()],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,
@@ -323,6 +325,7 @@ mod tests {
                 user_tunnel_endpoint: true,
             }
             .to_interface()],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,
@@ -411,6 +414,7 @@ mod tests {
             owner: device1_pubkey,
             mgmt_vrf: "default".to_string(),
             interfaces: vec![],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,
@@ -482,6 +486,7 @@ mod tests {
             owner: device1_pubkey,
             mgmt_vrf: "default".to_string(),
             interfaces: vec![],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,

smartcontract/cli/src/device/interface/delete.rs

@@ -33,7 +33,7 @@ impl DeleteDeviceInterfaceCliCommand {
             .map_err(|_| eyre::eyre!("Device not found"))?;
 
         let (_, iface) = device
-            .find_interface(&self.name)
+            .find_interface_legacy(&self.name)
             .map_err(|err| eyre::eyre!(err))?;
 
         // if a physical interface is Activated, it's part of a link and shouldn't be deleted.
@@ -129,6 +129,7 @@ mod tests {
                 }
                 .to_interface(),
             ],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,

smartcontract/cli/src/device/interface/get.rs

@@ -138,6 +138,7 @@ mod tests {
                 user_tunnel_endpoint: true,
             }
             .to_interface()],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,

smartcontract/cli/src/device/interface/list.rs

@@ -185,6 +185,7 @@ mod tests {
                 }
                 .to_interface(),
             ],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,

smartcontract/cli/src/device/interface/update.rs

@@ -78,7 +78,7 @@ impl UpdateDeviceInterfaceCliCommand {
             })?;
 
         let (_, interface) = device
-            .find_interface(&self.name)
+            .find_interface_legacy(&self.name)
             .map_err(|e| eyre::eyre!(e.to_string()))?;
 
         // Prevent setting a loopback type on physical interfaces
@@ -262,6 +262,7 @@ mod tests {
                 }
                 .to_interface(),
             ],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,
@@ -378,6 +379,7 @@ mod tests {
                 user_tunnel_endpoint: false,
             }
             .to_interface()],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,
@@ -426,6 +428,7 @@ mod tests {
                 user_tunnel_endpoint: false,
             }
             .to_interface()],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,
@@ -522,6 +525,7 @@ mod tests {
                 user_tunnel_endpoint: true,
             }
             .to_interface()],
+            new_interfaces: vec![],
             max_users: 255,
             users_count: 0,
             device_health: doublezero_serviceability::state::device::DeviceHealth::ReadyForUsers,