dhcp: Support RedHat dhcp rfc3442 lease format for option 121 (#76)

RedHat dhcp client writes out rfc3442 classless-static-routes in a different format[1]
than what is found in isc-dhcp clients.  This patch adds support for the RedHat format.

1. Background details on the format
 https://bugzilla.redhat.com/show_bug.cgi?id=516325
 https://github.com/vaijab/fedora-dhcp/blob/e83fb19c51765442d77fa60596bfdb2b3b9fbe2e/dhcp-rfc3442-classless-static-routes.patch#L252 
 https://github.com/heftig/NetworkManager/blob/f56c82d86122fc45304fc829b5f1e4766ed51589/src/dhcp-manager/nm-dhcp-client.c#L978

LP: #1850642

2 files changed, 100 insertions, 7 deletions

diff --git a/cloudinit/net/dhcp.py b/cloudinit/net/dhcp.py
index 17379918..c033cc8e 100644
--- a/cloudinit/net/dhcp.py
+++ b/cloudinit/net/dhcp.py
@@ -92,9 +92,12 @@ class EphemeralDHCPv4(object):
         nmap = {'interface': 'interface', 'ip': 'fixed-address',
                 'prefix_or_mask': 'subnet-mask',
                 'broadcast': 'broadcast-address',
-                'static_routes': 'rfc3442-classless-static-routes',
+                'static_routes': [
+                    'rfc3442-classless-static-routes',
+                    'classless-static-routes'
+                ],
                 'router': 'routers'}
-        kwargs = dict([(k, self.lease.get(v)) for k, v in nmap.items()])
+        kwargs = self.extract_dhcp_options_mapping(nmap)
         if not kwargs['broadcast']:
             kwargs['broadcast'] = bcip(kwargs['prefix_or_mask'], kwargs['ip'])
         if kwargs['static_routes']:
@@ -107,6 +110,25 @@ class EphemeralDHCPv4(object):
         self._ephipv4 = ephipv4
         return self.lease
 
+    def extract_dhcp_options_mapping(self, nmap):
+        result = {}
+        for internal_reference, lease_option_names in nmap.items():
+            if isinstance(lease_option_names, list):
+                self.get_first_option_value(
+                    internal_reference,
+                    lease_option_names,
+                    result
+                )
+            else:
+                result[internal_reference] = self.lease.get(lease_option_names)
+        return result
+
+    def get_first_option_value(self, internal_mapping,
+                               lease_option_names, result):
+        for different_names in lease_option_names:
+            if not result.get(internal_mapping):
+                result[internal_mapping] = self.lease.get(different_names)
+
 
 def maybe_perform_dhcp_discovery(nic=None):
     """Perform dhcp discovery if nic valid and dhclient command exists.
@@ -281,24 +303,30 @@ def parse_static_routes(rfc3442):
     """ parse rfc3442 format and return a list containing tuple of strings.
 
     The tuple is composed of the network_address (including net length) and
-    gateway for a parsed static route.
+    gateway for a parsed static route.  It can parse two formats of rfc3442,
+    one from dhcpcd and one from dhclient (isc).
 
-    @param rfc3442: string in rfc3442 format
+    @param rfc3442: string in rfc3442 format (isc or dhcpd)
     @returns: list of tuple(str, str) for all valid parsed routes until the
               first parsing error.
 
     E.g.
-    sr = parse_state_routes("32,169,254,169,254,130,56,248,255,0,130,56,240,1")
-    sr = [
+    sr=parse_static_routes("32,169,254,169,254,130,56,248,255,0,130,56,240,1")
+    sr=[
         ("169.254.169.254/32", "130.56.248.255"), ("0.0.0.0/0", "130.56.240.1")
     ]
 
+    sr2 = parse_static_routes("24.191.168.128 192.168.128.1,0 192.168.128.1")
+    sr2 = [
+        ("191.168.128.0/24", "192.168.128.1"), ("0.0.0.0/0", "192.168.128.1")
+    ]
+
     Python version of isc-dhclient's hooks:
        /etc/dhcp/dhclient-exit-hooks.d/rfc3442-classless-routes
     """
     # raw strings from dhcp lease may end in semi-colon
     rfc3442 = rfc3442.rstrip(";")
-    tokens = rfc3442.split(',')
+    tokens = [tok for tok in re.split(r"[, .]", rfc3442) if tok]
     static_routes = []
 
     def _trunc_error(cidr, required, remain):
diff --git a/cloudinit/net/tests/test_dhcp.py b/cloudinit/net/tests/test_dhcp.py
index 91f503c9..c3fa1e04 100644
--- a/cloudinit/net/tests/test_dhcp.py
+++ b/cloudinit/net/tests/test_dhcp.py
@@ -90,6 +90,32 @@ class TestDHCPRFC3442(CiTestCase):
         write_file(lease_file, content)
         self.assertItemsEqual(expected, parse_dhcp_lease_file(lease_file))
 
+    def test_parse_lease_finds_classless_static_routes(self):
+        """
+        parse_dhcp_lease_file returns classless-static-routes
+        for Centos lease format.
+        """
+        lease_file = self.tmp_path('leases')
+        content = dedent("""
+            lease {
+              interface "wlp3s0";
+              fixed-address 192.168.2.74;
+              option subnet-mask 255.255.255.0;
+              option routers 192.168.2.1;
+              option classless-static-routes 0 130.56.240.1;
+              renew 4 2017/07/27 18:02:30;
+              expire 5 2017/07/28 07:08:15;
+            }
+        """)
+        expected = [
+            {'interface': 'wlp3s0', 'fixed-address': '192.168.2.74',
+             'subnet-mask': '255.255.255.0', 'routers': '192.168.2.1',
+             'classless-static-routes': '0 130.56.240.1',
+             'renew': '4 2017/07/27 18:02:30',
+             'expire': '5 2017/07/28 07:08:15'}]
+        write_file(lease_file, content)
+        self.assertItemsEqual(expected, parse_dhcp_lease_file(lease_file))
+
     @mock.patch('cloudinit.net.dhcp.EphemeralIPv4Network')
     @mock.patch('cloudinit.net.dhcp.maybe_perform_dhcp_discovery')
     def test_obtain_lease_parses_static_routes(self, m_maybe, m_ipv4):
@@ -112,6 +138,31 @@ class TestDHCPRFC3442(CiTestCase):
             'router': '192.168.2.1'}
         m_ipv4.assert_called_with(**expected_kwargs)
 
+    @mock.patch('cloudinit.net.dhcp.EphemeralIPv4Network')
+    @mock.patch('cloudinit.net.dhcp.maybe_perform_dhcp_discovery')
+    def test_obtain_centos_lease_parses_static_routes(self, m_maybe, m_ipv4):
+        """
+        EphemeralDHPCv4 parses rfc3442 routes for EphemeralIPv4Network
+        for Centos Lease format
+        """
+        lease = [
+            {'interface': 'wlp3s0', 'fixed-address': '192.168.2.74',
+             'subnet-mask': '255.255.255.0', 'routers': '192.168.2.1',
+             'classless-static-routes': '0 130.56.240.1',
+             'renew': '4 2017/07/27 18:02:30',
+             'expire': '5 2017/07/28 07:08:15'}]
+        m_maybe.return_value = lease
+        eph = net.dhcp.EphemeralDHCPv4()
+        eph.obtain_lease()
+        expected_kwargs = {
+            'interface': 'wlp3s0',
+            'ip': '192.168.2.74',
+            'prefix_or_mask': '255.255.255.0',
+            'broadcast': '192.168.2.255',
+            'static_routes': [('0.0.0.0/0', '130.56.240.1')],
+            'router': '192.168.2.1'}
+        m_ipv4.assert_called_with(**expected_kwargs)
+
 
 class TestDHCPParseStaticRoutes(CiTestCase):
 
@@ -181,6 +232,20 @@ class TestDHCPParseStaticRoutes(CiTestCase):
         logs = self.logs.getvalue()
         self.assertIn(rfc3442, logs.splitlines()[0])
 
+    def test_redhat_format(self):
+        redhat_format = "24.191.168.128 192.168.128.1,0 192.168.128.1"
+        self.assertEqual(sorted([
+            ("191.168.128.0/24", "192.168.128.1"),
+            ("0.0.0.0/0", "192.168.128.1")
+        ]), sorted(parse_static_routes(redhat_format)))
+
+    def test_redhat_format_with_a_space_too_much_after_comma(self):
+        redhat_format = "24.191.168.128 192.168.128.1, 0 192.168.128.1"
+        self.assertEqual(sorted([
+            ("191.168.128.0/24", "192.168.128.1"),
+            ("0.0.0.0/0", "192.168.128.1")
+        ]), sorted(parse_static_routes(redhat_format)))
+
 
 class TestDHCPDiscoveryClean(CiTestCase):
     with_logs = True