add -g option to specify TCP cc algorithm

This commit introduce SSH_OPTIONS_CCALGO option to the libssh patch
and add -g CONGESTION option to mscp.

test/test_e2e.py

@@ -3,6 +3,7 @@
 test_e2e.py: End-to-End test for mscp executable.
 """
 
+import platform
 import pytest
 import os
 
@@ -268,6 +269,21 @@ def test_compression(mscp, src_prefix, dst_prefix, compress):
     src.cleanup()
     dst.cleanup()
 
+@pytest.mark.parametrize("src_prefix, dst_prefix", param_remote_prefix)
+def test_ccalgo(mscp, src_prefix, dst_prefix):
+    src = File("src", size = 1024 * 1024).make()
+    dst = File("dst").make()
+    if platform.system() == "Darwin":
+        # Darwin does not support TCP_CONGESTION
+        algo = "cubic"
+        run = run2ng
+    elif platform.system() == "Linux":
+        # Linux supports TCP_CONGESTION
+        with open("/proc/sys/net/ipv4/tcp_allowed_congestion_control", r) as f:
+            algo = f.read().strip().split().pop()
+        run = run2ok
+    run([mscp, "-H", "-vvv", "-g", algo, src_prefix + src.path, dst_prefix + "dst"])
+
 
 testhost = "mscptestlocalhost"
 testhost_prefix = "{}:{}/".format(testhost, os.getcwd()) # use current dir

test/test_python.py

@@ -121,6 +121,7 @@ param_invalid_kwargs = [
     { "cipher": "invalid" },
     { "hmac": "invalid"},
     { "compress": "invalid"},
+    { "ccalgo": "invalid"},
 ]
 
 @pytest.mark.parametrize("kw", param_invalid_kwargs)