Ignore socket files in utils.tar

Signed-off-by: Joffrey F <joffrey@docker.com>

docker/utils/utils.py

@@ -4,7 +4,6 @@ import os
 import os.path
 import json
 import shlex
-import sys
 import tarfile
 import tempfile
 import warnings
@@ -15,6 +14,7 @@ from fnmatch import fnmatch
 import requests
 import six
 
+from .. import constants
 from .. import errors
 from .. import tls
 
@@ -90,7 +90,12 @@ def tar(path, exclude=None, dockerfile=None, fileobj=None, gzip=False):
     for path in sorted(exclude_paths(root, exclude, dockerfile=dockerfile)):
         i = t.gettarinfo(os.path.join(root, path), arcname=path)
 
-        if sys.platform == 'win32':
+        if i is None:
+            # This happens when we encounter a socket file. We can safely
+            # ignore it and proceed.
+            continue
+
+        if constants.IS_WINDOWS_PLATFORM:
             # Windows doesn't keep track of the execute bit, so we make files
             # and directories executable by default.
             i.mode = i.mode & 0o755 | 0o111

tests/unit/utils_test.py

@@ -5,6 +5,7 @@ import json
 import os
 import os.path
 import shutil
+import socket
 import sys
 import tarfile
 import tempfile
@@ -894,6 +895,20 @@ class TarTest(unittest.TestCase):
                 sorted(tar_data.getnames()), ['bar', 'bar/foo', 'foo']
             )
 
+    def test_tar_socket_file(self):
+        base = tempfile.mkdtemp()
+        self.addCleanup(shutil.rmtree, base)
+        for d in ['foo', 'bar']:
+            os.makedirs(os.path.join(base, d))
+        sock = socket.socket(socket.AF_UNIX)
+        self.addCleanup(sock.close)
+        sock.bind(os.path.join(base, 'test.sock'))
+        with tar(base) as archive:
+            tar_data = tarfile.open(fileobj=archive)
+            self.assertEqual(
+                sorted(tar_data.getnames()), ['bar', 'foo']
+            )
+
 
 class ShouldCheckDirectoryTest(unittest.TestCase):
     exclude_patterns = [