Bounded WEB HTTP conveyor with replay-safe streaming downlink added

Co-Authored-By: brekotis <93345790+brekotis@users.noreply.github.com>

src/web/manager/budget.rs

@@ -337,6 +337,11 @@ impl Drop for WebSocketBudgetLease {
 }
 
 impl WebProcessRuntime {
+    /// Reserves a parked future uplink without consuming the head request's capacity.
+    pub(crate) fn try_conveyor_waiter(&self) -> Option<OwnedSemaphorePermit> {
+        Arc::clone(&self.conveyor_waiters).try_acquire_owned().ok()
+    }
+
     /// Reserves one body reader and its declared bounded body allocation.
     pub(crate) fn try_body_budget(
         &self,

src/web/manager/lifecycle.rs

@@ -136,6 +136,7 @@ impl WebProcessRuntime {
         self.lane_aux_polls.close();
         self.body_readers.close();
         self.body_bytes.close();
+        self.conveyor_waiters.close();
         self.stream_handshakes.close();
         self.websocket_connections.close();
         let sessions = {

src/web/manager/negotiation.rs

@@ -130,6 +130,7 @@ pub(crate) struct CarrierRequest {
     attempt: Option<u8>,
     failure: Option<CarrierFailure>,
     user_agent_hash: [u8; 32],
+    up_window: Option<u8>,
 }
 
 impl CarrierRequest {
@@ -141,6 +142,7 @@ impl CarrierRequest {
             attempt: None,
             failure: None,
             user_agent_hash,
+            up_window: None,
         }
     }
 
@@ -152,6 +154,7 @@ impl CarrierRequest {
             attempt: None,
             failure: None,
             user_agent_hash,
+            up_window: None,
         }
     }
 
@@ -169,9 +172,21 @@ impl CarrierRequest {
             attempt: Some(attempt),
             failure,
             user_agent_hash,
+            up_window: None,
         }
     }
 
+    /// Attaches the separately validated HTTP conveyor capability.
+    pub(crate) const fn with_up_window(mut self, window: Option<u8>) -> Self {
+        self.up_window = window;
+        self
+    }
+
+    /// Returns the separately advertised HTTP conveyor capability.
+    pub(crate) const fn up_window(self) -> Option<u8> {
+        self.up_window
+    }
+
     /// Returns whether this request participates in server-side negotiation.
     pub(crate) const fn is_automatic(self) -> bool {
         self.capabilities.is_some()
@@ -215,6 +230,7 @@ impl CarrierRequest {
         self.class == other.class
             && self.capabilities_bits() == other.capabilities_bits()
             && self.user_agent_hash == other.user_agent_hash
+            && self.up_window == other.up_window
     }
 
     /// Checks the complete idempotent identity of one exact attempt request.

src/web/manager/session_creation.rs

@@ -125,6 +125,7 @@ impl WebProcessRuntime {
                     entry.carrier_phase.as_str()
                 };
                 let result = CreateResult {
+                    up_window: carrier_request.up_window().map(|_| session.up_window()),
                     token: entry.session_token.as_str().to_owned(),
                     carrier: session.carrier(),
                     attempt: carrier_request.attempt(),
@@ -357,6 +358,11 @@ impl WebProcessRuntime {
             issued_timeouts.clone(),
             Some(user_registration),
         );
+        session.configure_conveyor(if config.web.conveyor {
+            carrier_request.up_window().unwrap_or(1)
+        } else {
+            1
+        });
         state.sessions.insert(session_hash, Arc::clone(&session));
         *state.sessions_per_ip.entry(client_ip).or_insert(0) += 1;
         *state.sessions_per_profile.entry(profile_key).or_insert(0) += 1;
@@ -399,6 +405,7 @@ impl WebProcessRuntime {
         }
         let identity = session.trace_identity();
         let result = CreateResult {
+            up_window: carrier_request.up_window().map(|_| session.up_window()),
             token: session_token,
             carrier,
             attempt: carrier_request.attempt(),

src/web/manager/session_creation/replacement.rs

@@ -104,6 +104,7 @@ impl WebProcessRuntime {
             replacement.old_session.timeouts().clone(),
             Some(user_registration),
         );
+        session.configure_conveyor(replacement.old_session.conveyor_offer());
         let Some(supersede) = replacement.old_session.prepare_carrier_supersede() else {
             drop(user_publication);
             drop(state);
@@ -149,6 +150,7 @@ impl WebProcessRuntime {
             crate::web::session::SessionCloseReason::CarrierSuperseded,
         );
         let result = CreateResult {
+            up_window: replacement.request.up_window().map(|_| session.up_window()),
             token: session_token,
             carrier: replacement.carrier,
             attempt: Some(replacement.attempt),