driver/sshdriver: support selecting scp mode explicitly

OpenSSH >= 9.0 defaults to the SFTP protocol.
However, some older targets may only have scp installed.
OpenSSH allows to explicitly select scp by providing the -O flag.

As already done for the transition of SFTP, add a dedicated SSHDriver
attribute named 'explicit_scp_mode' which defaults to 'False'.

Signed-off-by: Enrico Jorns <[email protected]>

doc/configuration.rst

@@ -1573,6 +1573,8 @@ Arguments:
     target.
   - explicit_sftp_mode (bool, default=False): if set to True, `put()`, `get()`, and `scp()` will
     explicitly use the SFTP protocol for file transfers instead of scp's default protocol
+  - explicit_scp_mode (bool, default=False): if set to True, `put()`, `get()`, and `scp()` will
+    explicitly use the SCP protocol for file transfers instead of scp's default protocol
 
 UBootDriver
 ~~~~~~~~~~~

labgrid/driver/sshdriver.py

@@ -35,6 +35,7 @@ class SSHDriver(CommandMixin, Driver, CommandProtocol, FileTransferProtocol):
     stderr_merge = attr.ib(default=False, validator=attr.validators.instance_of(bool))
     connection_timeout = attr.ib(default=float(get_ssh_connect_timeout()), validator=attr.validators.instance_of(float))
     explicit_sftp_mode = attr.ib(default=False, validator=attr.validators.instance_of(bool))
+    explicit_scp_mode = attr.ib(default=False, validator=attr.validators.instance_of(bool))
 
     def __attrs_post_init__(self):
         super().__attrs_post_init__()
@@ -361,6 +362,8 @@ def scp(self, *, src, dst):
 
         if self.explicit_sftp_mode and self._scp_supports_explicit_sftp_mode():
             complete_cmd.insert(1, "-s")
+        if self.explicit_scp_mode and self._scp_supports_explicit_scp_mode():
+            complete_cmd.insert(1, "-O")
 
         self.logger.info("Running command: %s", complete_cmd)
         sub = subprocess.Popen(
@@ -450,6 +453,14 @@ def _scp_supports_explicit_sftp_mode(self):
             return False
         raise Exception(f"OpenSSH version {major}.{minor} does not support explicit SFTP mode")
 
+    def _scp_supports_explicit_scp_mode(self):
+        major, minor = self._ssh_version
+
+        # OpenSSH >= 9.0 default to the SFTP protocol
+        if major >= 9:
+            return True
+        raise Exception(f"OpenSSH version {major}.{minor} does not support explicit SCP mode")
+
     @Driver.check_active
     @step(args=['filename', 'remotepath'])
     def put(self, filename, remotepath=''):
@@ -464,6 +475,8 @@ def put(self, filename, remotepath=''):
 
         if self.explicit_sftp_mode and self._scp_supports_explicit_sftp_mode():
             transfer_cmd.insert(1, "-s")
+        if self.explicit_scp_mode and self._scp_supports_explicit_scp_mode():
+            transfer_cmd.insert(1, "-O")
 
         try:
             sub = subprocess.call(
@@ -492,6 +505,8 @@ def get(self, filename, destination="."):
 
         if self.explicit_sftp_mode and self._scp_supports_explicit_sftp_mode():
             transfer_cmd.insert(1, "-s")
+        if self.explicit_scp_mode and self._scp_supports_explicit_scp_mode():
+            transfer_cmd.insert(1, "-O")
 
         try:
             sub = subprocess.call(