chmod aix errors with 255 is not unreachable (#78249) (#78356)

* chmod aix errors with 255 is not unreachable

  fixes #78210

* added another 'aix chmod msg'
check stderr also

(cherry picked from commit c135a47f44fc6af816a5669499fa79b6cce69517)

2 files changed, 11 insertions, 4 deletions

diff --git a/changelogs/fragments/aix_chmod_255.yml b/changelogs/fragments/aix_chmod_255.yml
new file mode 100644
index 00000000000..b4b6aea2e14
--- /dev/null
+++ b/changelogs/fragments/aix_chmod_255.yml
@@ -0,0 +1,2 @@
+bugfixes:
+  - Avoid 'unreachable' error when chmod on AIX has 255 as return code.
diff --git a/lib/ansible/plugins/connection/ssh.py b/lib/ansible/plugins/connection/ssh.py
index d0c329ff487..e3b7cec68cd 100644
--- a/lib/ansible/plugins/connection/ssh.py
+++ b/lib/ansible/plugins/connection/ssh.py
@@ -22,6 +22,8 @@ DOCUMENTATION = '''
     notes:
         - Many options default to C(None) here but that only means we do not override the SSH tool's defaults and/or configuration.
           For example, if you specify the port in this plugin it will override any C(Port) entry in your C(.ssh/config).
+        - The ssh CLI tool uses return code 255 as a 'connection error', this can conflict with commands/tools that
+          also return 255 as an error code and will look like an 'unreachable' condition or 'connection error' to this plugin.
     options:
       host:
           description: Hostname/IP to connect to.
@@ -389,10 +391,12 @@ from ansible.utils.path import unfrackpath, makedirs_safe
 
 display = Display()
 
-
+# error messages that indicate 255 return code is not from ssh itself.
 b_NOT_SSH_ERRORS = (b'Traceback (most recent call last):',  # Python-2.6 when there's an exception
-                                                            # while invoking a script via -m
-                    b'PHP Parse error:',  # Php always returns error 255
+                                                            #   while invoking a script via -m
+                    b'PHP Parse error:',                    # Php always returns with error
+                    b'chmod: invalid mode',                 # chmod, but really only on AIX
+                    b'chmod: A flag or octal number is not correct.',    # chmod, other AIX
                     )
 
 SSHPASS_AVAILABLE = None
@@ -437,7 +441,8 @@ def _handle_error(remaining_retries, command, return_tuple, no_log, host, displa
     if return_tuple[0] == 255:
         SSH_ERROR = True
         for signature in b_NOT_SSH_ERRORS:
-            if signature in return_tuple[1]:
+            # 1 == stout, 2 == stderr
+            if signature in return_tuple[1] or signature in return_tuple[2]:
                 SSH_ERROR = False
                 break