Move handle_sequence_number_too_low to inbound module

Author: davidsteiner

crates/hotfix/src/session.rs

@@ -596,8 +596,17 @@ where
                 actual,
                 possible_duplicate,
             } => {
-                self.handle_sequence_number_too_low(expected, actual, possible_duplicate)
+                if let Some(writer) = self.state.get_writer() {
+                    let result = inbound::handle_sequence_number_too_low(
+                        &mut self.ctx,
+                        writer,
+                        expected,
+                        actual,
+                        possible_duplicate,
+                    )
                     .await;
+                    self.apply_transition(result);
+                }
             }
             MessageVerificationError::SeqNumberTooHigh { expected, actual } => {
                 self.handle_sequence_number_too_high(expected, actual)
@@ -678,28 +687,6 @@ where
         Ok(())
     }
 
-    async fn handle_sequence_number_too_low(
-        &mut self,
-        expected: u64,
-        actual: u64,
-        possible_duplicate: bool,
-    ) {
-        if possible_duplicate {
-            warn!(
-                "sequence number too low (expected {expected}, actual {actual}, but counterparty indicated it's poss duplicate, ignoring"
-            );
-            return;
-        }
-        error!(
-            "we expected {expected} sequence number, but target sent lower ({actual}), terminating..."
-        );
-        let reason = format!("sequence number too low (actual {actual}, expected {expected})");
-        self.state
-            .logout_and_terminate(&mut self.ctx, &reason)
-            .await;
-        self.state = SessionState::new_disconnected(false, &reason);
-    }
-
     async fn handle_sequence_number_too_high(
         &mut self,
         expected: u64,

crates/hotfix/src/session/inbound.rs

@@ -92,6 +92,32 @@ pub(crate) async fn handle_incorrect_comp_id<A, S: MessageStore>(
     TransitionResult::TransitionTo(SessionState::new_disconnected(true, "incorrect comp ID"))
 }
 
+pub(crate) async fn handle_sequence_number_too_low<A, S: MessageStore>(
+    ctx: &mut SessionCtx<A, S>,
+    writer: &WriterRef,
+    expected: u64,
+    actual: u64,
+    possible_duplicate: bool,
+) -> TransitionResult {
+    if possible_duplicate {
+        warn!(
+            "sequence number too low (expected {expected}, actual {actual}, but counterparty indicated it's poss duplicate, ignoring"
+        );
+        return TransitionResult::Stay;
+    }
+    error!(
+        "we expected {expected} sequence number, but target sent lower ({actual}), terminating..."
+    );
+    let reason = format!("sequence number too low (actual {actual}, expected {expected})");
+    let logout = Logout::with_reason(reason.clone());
+    match ctx.prepare_message(logout).await {
+        Ok(prepared) => writer.send_raw_message(prepared.raw).await,
+        Err(err) => warn!("failed to send logout for sequence number too low: {err}"),
+    }
+    writer.disconnect().await;
+    TransitionResult::TransitionTo(SessionState::new_disconnected(false, &reason))
+}
+
 pub(crate) async fn handle_invalid_msg_type<A, S: MessageStore>(
     ctx: &mut SessionCtx<A, S>,
     writer: &WriterRef,