From f8aa18cab066bf72a0f3cbbcc16f3b336bb5c1d3 Mon Sep 17 00:00:00 2001
From: tomDev5 <addr.toml@gmail.com>
Date: Fri, 27 Dec 2024 20:19:59 +0100
Subject: [PATCH] tcp: add retransmission exponential backoff test.

---
 src/socket/tcp.rs | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/src/socket/tcp.rs b/src/socket/tcp.rs
index fd23f6e36..a37dbe32d 100644
--- a/src/socket/tcp.rs
+++ b/src/socket/tcp.rs
@@ -6411,6 +6411,38 @@ mod test {
         recv_nothing!(s);
     }
 
+    #[test]
+    fn test_retransmit_exponential_backoff() {
+        let mut s = socket_established();
+        s.send_slice(b"abcdef").unwrap();
+        recv!(s, time 0, Ok(TcpRepr {
+            seq_number: LOCAL_SEQ + 1,
+            ack_number: Some(REMOTE_SEQ + 1),
+            payload:    &b"abcdef"[..],
+            ..RECV_TEMPL
+        }));
+
+        let expected_retransmission_instant = s.rtte.retransmission_timeout().total_millis() as i64;
+        recv_nothing!(s, time expected_retransmission_instant - 1);
+        recv!(s, time expected_retransmission_instant, Ok(TcpRepr {
+            seq_number: LOCAL_SEQ + 1,
+            ack_number: Some(REMOTE_SEQ + 1),
+            payload:    &b"abcdef"[..],
+            ..RECV_TEMPL
+        }));
+
+        // "current time" is expected_retransmission_instant, and we want to wait 2 * retransmission timeout
+        let expected_retransmission_instant = 3 * expected_retransmission_instant;
+
+        recv_nothing!(s, time expected_retransmission_instant - 1);
+        recv!(s, time expected_retransmission_instant, Ok(TcpRepr {
+            seq_number: LOCAL_SEQ + 1,
+            ack_number: Some(REMOTE_SEQ + 1),
+            payload:    &b"abcdef"[..],
+            ..RECV_TEMPL
+        }));
+    }
+
     // =========================================================================================//
     // Tests for window management.
     // =========================================================================================//