From 2233bf95ed829488f020eabc2a921a31da1da0c6 Mon Sep 17 00:00:00 2001
From: Viktor Szakats <commit@vsz.me>
Date: Wed, 7 Oct 2026 14:46:45 +0200
Subject: [PATCH] tests: retry '(-43): Failed getting banner' flaky failures

Example:
```
1: libssh2_session_handshake failed (-43): Failed getting banner
1: ---- sshd log ----
1: No matching private key for certificate: /etc/ssh/ssh_host_mldsa44-ed25519_key-cert.pub
1: debug1: Set /proc/self/oom_score_adj from 0 to -1000
1: debug2: fd 6 setting O_NONBLOCK
1: debug1: Bind to port 22 on 0.0.0.0.
1: Server listening on 0.0.0.0 port 22.
1: debug2: fd 7 setting O_NONBLOCK
1: debug1: Bind to port 22 on ::.
1: Server listening on :: port 22.
1: ------------------
1: Command: docker image pull ghcr.io/libssh2/ci_tests_openssh_server:8d1fde1834077fddb9f9
1: Command: docker image tag ghcr.io/libssh2/ci_tests_openssh_server:8d1fde1834077fddb9f9 libssh2/openssh_server
1: Command: docker run --rm -d -p 22 libssh2/openssh_server
1: Command: docker inspect --format "{{ (index (index .NetworkSettings.Ports \"22/tcp\") 0).HostIp }}" a1f1a209001852fa7e3aba87c0f1198661c4fe07c34ddcbf2e76e264ef64b7b8
1: Command: docker inspect --format "{{ (index (index .NetworkSettings.Ports \"22/tcp\") 0).HostPort }}" a1f1a209001852fa7e3aba87c0f1198661c4fe07c34ddcbf2e76e264ef64b7b8
1: Command: docker logs a1f1a209001852fa7e3aba87c0f1198661c4fe07c34ddcbf2e76e264ef64b7b8
1: Command: docker stop a1f1a209001852fa7e3aba87c0f1198661c4fe07c34ddcbf2e76e264ef64b7b8
 1/61 Test  #1: test_aa_warmup .......................................***Failed    6.08 sec
libssh2_session_handshake failed (-43): Failed getting banner
```
Ref: https://github.com/libssh2/libssh2/actions/runs/37613324059/job/112765610280?pr=2659#step:25:133

Ref: 5bfa57446028b324430e8e8dedb7ee5838bb3207 #2603

Closes #2662
---
 tests/runner.c | 35 ++++++++++++++++++++++++++---------
 1 file changed, 26 insertions(+), 9 deletions(-)

diff --git a/tests/runner.c b/tests/runner.c
index e743a787..3077416f 100644
--- a/tests/runner.c
+++ b/tests/runner.c
@@ -34,15 +34,32 @@
 
 int main(void)
 {
-    int exit_code = 1;
-    int skipped, rc;
-    LIBSSH2_SESSION *session = start_session_fixture(&skipped, &rc);
-    if(session)
-        exit_code = (test(session) == 0) ? 0 : 1;
-    else if(skipped) {
-        fprintf(stderr, "Test skipped.\n");
-        exit_code = 0;
-    }
+    int exit_code;
+    /* Retry tests to mitigate flaky failures */
+    int retries = 2, retry = 0;
+
+    do {
+        int skipped, rc;
+        LIBSSH2_SESSION *session = start_session_fixture(&skipped, &rc);
+        if(session)
+            exit_code = (test(session) == 0) ? 0 : 1;
+        else if(skipped) {
+            fprintf(stderr, "Test skipped.\n");
+            exit_code = 0;
+        }
+        else
+            exit_code = 1;
+        stop_session_fixture(exit_code);
+        /* Retry:
+          'libssh2_session_handshake failed (-43): Failed getting banner' */
+        if(exit_code == 0 || rc != LIBSSH2_ERROR_SOCKET_RECV ||
+           ++retry > retries) {
+            break;
+        }
+        fprintf(stderr, "Test failed (%d). Retrying... %d / %d\n",
+                        rc, retry, retries);
+    } while(1);
+
     stop_session_fixture(exit_code);
     return exit_code;
 }