NOC: Send an ACK up-front since NOC operations take longer time

Ack the other end while we are processing stuff, so it doesn't bombard us
with retransmissions

matter/src/data_model/sdm/noc.rs

@@ -30,7 +30,7 @@ use crate::interaction_model::messages::ib;
 use crate::tlv::{FromTLV, OctetStr, TLVElement, TLVWriter, TagType, ToTLV, UtfStr};
 use crate::transport::session::SessionMode;
 use crate::utils::writebuf::WriteBuf;
-use crate::{cmd_enter, error::*};
+use crate::{cmd_enter, error::*, secure_channel};
 use log::{error, info};
 use num_derive::FromPrimitive;
 
@@ -177,6 +177,15 @@ impl NocCluster {
             return Err(NocStatus::InsufficientPrivlege);
         }
 
+        // This command's processing may take longer, send a stand alone ACK to the peer to avoid any retranmissions
+        let ack_send = secure_channel::common::send_mrp_standalone_ack(
+            cmd_req.trans.exch,
+            cmd_req.trans.session,
+        );
+        if ack_send.is_err() {
+            error!("Error sending Standalone ACK, falling back to piggybacked ACK");
+        }
+
         let r = AddNocReq::from_tlv(&cmd_req.data).map_err(|_| NocStatus::InvalidNOC)?;
 
         let noc_value = Cert::new(r.noc_value.0).map_err(|_| NocStatus::InvalidNOC)?;
@@ -188,7 +197,6 @@ impl NocCluster {
         } else {
             None
         };
-
         let fabric = Fabric::new(
             noc_data.key_pair,
             noc_data.root_ca,

matter/src/interaction_model/command.rs

@@ -37,11 +37,11 @@ macro_rules! cmd_enter {
     }};
 }
 
-pub struct CommandReq<'a, 'b, 'c, 'd> {
+pub struct CommandReq<'a, 'b, 'c, 'd, 'e> {
     pub cmd: ib::CmdPath,
     pub data: TLVElement<'a>,
     pub resp: &'a mut TLVWriter<'b, 'c>,
-    pub trans: &'a mut Transaction<'d>,
+    pub trans: &'a mut Transaction<'d, 'e>,
 }
 
 impl InteractionModel {

matter/src/interaction_model/core.rs

@@ -25,7 +25,7 @@ use crate::{
         exchange::Exchange,
         packet::Packet,
         proto_demux::{self, ProtoCtx, ResponseRequired},
-        session::Session,
+        session::SessionHandle,
     },
 };
 use colored::Colorize;
@@ -59,8 +59,8 @@ pub enum OpCode {
     TimedRequest = 10,
 }
 
-impl<'a> Transaction<'a> {
-    pub fn new(session: &'a mut Session, exch: &'a mut Exchange) -> Self {
+impl<'a, 'b> Transaction<'a, 'b> {
+    pub fn new(session: &'a mut SessionHandle<'b>, exch: &'a mut Exchange) -> Self {
         Self {
             state: TransactionState::Ongoing,
             session,

matter/src/interaction_model/mod.rs

@@ -18,7 +18,7 @@
 use crate::{
     error::Error,
     tlv::TLVWriter,
-    transport::{exchange::Exchange, proto_demux::ResponseRequired, session::Session},
+    transport::{exchange::Exchange, proto_demux::ResponseRequired, session::SessionHandle},
 };
 
 use self::{
@@ -32,9 +32,9 @@ pub enum TransactionState {
     Complete,
     Terminate,
 }
-pub struct Transaction<'a> {
+pub struct Transaction<'a, 'b> {
     pub state: TransactionState,
-    pub session: &'a mut Session,
+    pub session: &'a mut SessionHandle<'b>,
     pub exch: &'a mut Exchange,
 }
 

matter/src/secure_channel/common.rs

@@ -15,9 +15,18 @@
  *    limitations under the License.
  */
 
+use boxslab::Slab;
+use log::info;
 use num_derive::FromPrimitive;
 
-use crate::{error::Error, transport::packet::Packet};
+use crate::{
+    error::Error,
+    transport::{
+        exchange::Exchange,
+        packet::{Packet, PacketPool},
+        session::SessionHandle,
+    },
+};
 
 use super::status_report::{create_status_report, GeneralCode};
 
@@ -83,3 +92,10 @@ pub fn create_mrp_standalone_ack(proto_tx: &mut Packet) {
     proto_tx.set_proto_opcode(OpCode::MRPStandAloneAck as u8);
     proto_tx.unset_reliable();
 }
+
+pub fn send_mrp_standalone_ack(exch: &mut Exchange, sess: &mut SessionHandle) -> Result<(), Error> {
+    info!("Sending standalone ACK");
+    let mut ack_packet = Slab::<PacketPool>::try_new(Packet::new_tx()?).ok_or(Error::NoMemory)?;
+    create_mrp_standalone_ack(&mut ack_packet);
+    exch.send(ack_packet, sess)
+}

matter/src/transport/exchange.rs

@@ -175,7 +175,7 @@ impl Exchange {
         }
     }
 
-    fn send(
+    pub fn send(
         &mut self,
         mut proto_tx: BoxSlab<PacketPool>,
         session: &mut SessionHandle,